Journal articles on the topic 'Futile redox cycling'
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Bhatia, Muskan, Jyotika Thakur, Shradha Suyal, Ruchika Oniel, Rahul Chakraborty, Shalini Pradhan, Monika Sharma, et al. "Allosteric inhibition of MTHFR prevents futile SAM cycling and maintains nucleotide pools in one-carbon metabolism." Journal of Biological Chemistry 295, no. 47 (September 15, 2020): 16037–57. http://dx.doi.org/10.1074/jbc.ra120.015129.
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Methylenetetrahydrofolate reductase (MTHFR) links the folate cycle to the methionine cycle in one-carbon metabolism. The enzyme is known to be allosterically inhibited by SAM for decades, but the importance of this regulatory control to one-carbon metabolism has never been adequately understood. To shed light on this issue, we exchanged selected amino acid residues in a highly conserved stretch within the regulatory region of yeast MTHFR to create a series of feedback-insensitive, deregulated mutants. These were exploited to investigate the impact of defective allosteric regulation on one-carbon metabolism. We observed a strong growth defect in the presence of methionine. Biochemical and metabolite analysis revealed that both the folate and methionine cycles were affected in these mutants, as was the transsulfuration pathway, leading also to a disruption in redox homeostasis. The major consequences, however, appeared to be in the depletion of nucleotides. 13C isotope labeling and metabolic studies revealed that the deregulated MTHFR cells undergo continuous transmethylation of homocysteine by methyltetrahydrofolate (CH3THF) to form methionine. This reaction also drives SAM formation and further depletes ATP reserves. SAM was then cycled back to methionine, leading to futile cycles of SAM synthesis and recycling and explaining the necessity for MTHFR to be regulated by SAM. The study has yielded valuable new insights into the regulation of one-carbon metabolism, and the mutants appear as powerful new tools to further dissect out the intersection of one-carbon metabolism with various pathways both in yeasts and in humans.
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Gherasim, Carmen, Markus Ruetz, Zhu Li, Stephanie Hudolin, and Ruma Banerjee. "Pathogenic Mutations Differentially Affect the Catalytic Activities of the Human B12-processing Chaperone CblC and Increase Futile Redox Cycling." Journal of Biological Chemistry 290, no. 18 (March 25, 2015): 11393–402. http://dx.doi.org/10.1074/jbc.m115.637132.
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Wei Shen and Betty-ann Hoener. "Mitigation of nitrofurantoin-induced toxicity in the perfused rat liver." Human & Experimental Toxicology 15, no. 5 (May 1996): 428–34. http://dx.doi.org/10.1177/096032719601500511.
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1 Nitrofurantoin is an antimicrobial agent which pro duces hepatotoxicity caused by the redox cycling of the nitro group and its radical anion. This futile cycling triggers a complex series of events known collectively as oxidative stress. 2 Our goal was to determine treatment strategies which could mitigate nitrofurantoin-induced toxicity in the isolated perfused rat liver. We co-infused various agents which blocked early or late events in the progression to toxicity. Tissue levels of glutathione and protein thiols were measured as indicators of the progression to toxicity and lactate dehydrogenase leakage into the perfusate was used as a marker of irreversible cell death. 3 Five treatments significantly ( P < 0.05) decreased LDH leakage (reported as thousands of units accumulated in perfusate at 300 min, mean ± standard error, n=3- 4) when compared to nitrofurantoin alone (274 ±37). These treatments were adenosine-2'-monophosphate (120 ± 53), penicillamine (90 ± 29), N-(2-mercaptopro pionyl)-glycine (120 ± 49) and bromosulfophthalein with (80 ± 29) or without 5,5'-difluro-1,2-bis(O-amino phenoxy)ethane-N,N,N'N'-tetraacetic acid (101 ± 46). Two other treatments, N-acetylcysteine (183 ± 7) and dithiothreitol (166 ± 59) delayed the onset of toxicity. Finally, calpeptin (319 ± 34) which blocks activation of nonlysosomal proteases was ineffective. 4 We concluded that early intervention on the pathway to toxicity was most effective. The strategies detailed here may prove beneficial in treating hepatotoxicity seen following nitrofurantoin therapy.
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Bernard, Craig E., Amani A. Magid, TS Benedict Yen, and Betty-ann Hoener. "Mitigation of nitrofurantoin-induced toxicity in the perfused rat lung." Human & Experimental Toxicology 16, no. 12 (December 1997): 727–32. http://dx.doi.org/10.1177/096032719701601206.
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1 Nitrofurantoin is an antimicrobial agent which pro duces pulmonary toxicity via the redox cycling of the nitro group and its radical anion. This futile cycling triggers a complex series of events known collectively as oxidative stress. 2 In the isolated perfused rat lung, nitrofurantoin induced a decrease in tissue levels of glutathione but not protein thiols by the end of the 180 min experi ment. There was no decline in tissue levels of angiotensin converting enzyme (a marker of cell disruption). However, edema was extensive as mon itored in real time by weight gain (2.71 ± 0.56 g vs 0.63 ± 0.53 g in control, P<0.05, n=4) and lung mechanical functioning. The edema was matched by an increase in lavage proteins (85 ± 15 mg vs 16 ± 9 mg in controls, P<0.05, n=4). Electron microscopic examination of tissue indicated that the endothelial cells were detached from the basement membrane which would account for the edema. 3 Co-infusion of penicillamine, N-acetylcysteine or N- (2-mercaptopropionyl)-glycine which can protect tissue from oxidative stress failed to mitigate NFT induced edema. Allopurinol, an inhibitor of xanthine oxidase and a metal chelator, significantly decreased weight gain but did not prevent the loss of glutathione. These results suggested that allopurinol was not blocking metabolic activation of NFT by xanthine oxidase but scavenging metal cations which can initiate and/or propagate the oxidative stress cascade. 4 We concluded that, in the isolated perfused rat lung, the classic pathway of oxidative stress induced by NFT is interrupted at the stage of GSH loss. These experiments demonstrated that organ function was compromised more than the individual cells. They also suggested that allopurinol may prove beneficial in modulating NFT pulmonary toxicity.
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Dai, Shaodong, Cristina Schwendtmayer, Kenth Johansson, S. Ramaswamy, Peter Schürmann, and Hans Eklund. "How does light regulate chloroplast enzymes? Structure–function studies of the ferredoxin/thioredoxin system." Quarterly Reviews of Biophysics 33, no. 1 (February 2000): 67–108. http://dx.doi.org/10.1017/s0033583500003607.
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1. Introduction 682. Ferredoxin reduction by photosystem I 723. Ferredoxins 734. Ferredoxin[ratio ]thioredoxin reductase 734.1 Spectroscopic investigations of FTR 764.2 The three-dimensional structure of FTR from the cyanobacterium Synechocystis sp. PCC6803 774.2.1 The variable subunit 774.2.2 The catalytic subunit 814.2.3 The iron–sulfur center and active site disulfide bridge 824.2.4 The dimer 844.3 Thioredoxin f and m 854.4 Ferredoxin and thioredoxin interactions 864.5 Mechanism of action 884.6 Comparison with other chloroplast FTRs 925. Target enzymes 955.1 NADP-dependent malate dehydrogenase 955.1.1 Regulatory role of the N-terminal extension 975.1.2 Regulatory role of the C-terminal extension 995.1.3 Thioredoxin interactions 1015.2 Fructose-1,6-bisphosphatase 1015.3 Redox regulation of chloroplast target enzymes 1036. Conclusion 1037. Acknowledgements 1048. References 104A pre-requisite for life on earth is the conversion of solar energy into chemical energy by photosynthetic organisms. Plants and photosynthetic oxygenic microorganisms trap the energy from sunlight with their photosynthetic machinery and use it to produce reducing equivalents, NADPH, and ATP, both necessary for the reduction of carbon dioxide to carbohydrates, which are then further used in the cellular metabolism as building blocks and energy source. Thus, plants can satisfy their energy needs directly via the light reactions of photosynthesis during light periods. The situation is quite different in the dark, when these organisms must use normal catabolic processes like non-photosynthetic organisms to obtain the necessary energy by degrading carbohydrates, like starch, accumulated in the chloroplasts during daylight. The chloroplast stroma contains both assimilatory enzymes of the Calvin cycle and dissimilatory enzymes of the pentose phosphate cycle and glycolysis. This necessitates a strict, light-sensitive control that switches between assimilatory and dissimilatory pathways to avoid futile cycling (Buchanan, 1980, 1991; Buchanan et al. 1994; Jacquot et al. 1997; Schürmann & Buchanan, 2000).
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O'Malley, Yunxia Q., Maher Y. Abdalla, Michael L. McCormick, Krzysztof J. Reszka, Gerene M. Denning, and Bradley E. Britigan. "Subcellular localization ofPseudomonaspyocyanin cytotoxicity in human lung epithelial cells." American Journal of Physiology-Lung Cellular and Molecular Physiology 284, no. 2 (February 1, 2003): L420—L430. http://dx.doi.org/10.1152/ajplung.00316.2002.
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The Pseudomonas aeruginosa secretory product pyocyanin damages lung epithelium, likely due to redox cycling of pyocyanin and resultant superoxide and H2O2generation. Subcellular site(s) of pyocyanin redox cycling and toxicity have not been well studied. Therefore, pyocyanin's effects on subcellular parameters in the A549 human type II alveolar epithelial cell line were examined. Confocal and electron microscopy studies suggested mitochondrial redox cycling of pyocyanin and extracellular H2O2release, respectively. Pyocyanin decreased mitochondrial and cytoplasmic aconitase activity, ATP levels, cellular reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide, and mitochondrial membrane potential. These effects were transient at low pyocyanin concentrations and were linked to apparent cell-mediated metabolism of pyocyanin. Overexpression of MnSOD, but not CuZnSOD or catalase, protected cellular aconitase, but not ATP, from pyocyanin-mediated depletion. This suggests that loss of aconitase activity is not responsible for ATP depletion. How pyocyanin leads to ATP depletion, the mechanism of cellular metabolism of pyocyanin, and the impact of mitochondrial pyocyanin redox cycling on other cellular events are important areas for future study.
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Hwang, Ye Yeong, Ji Hyun Han, Sol Hui Park, Ji Eun Jung, Nam Kyeong Lee, and Yun Jung Lee. "Understanding anion-redox reactions in cathode materials of lithium-ion batteries through in situ characterization techniques: a review." Nanotechnology 33, no. 18 (February 10, 2022): 182003. http://dx.doi.org/10.1088/1361-6528/ac4c60.
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Abstract As the demand for rechargeable lithium-ion batteries (LIBs) with higher energy density increases, the interest in lithium-rich oxide (LRO) with extraordinarily high capacities is surging. The capacity of LRO cathodes exceeds that of conventional layered oxides. This has been attributed to the redox contribution from both cations and anions, either sequentially or simultaneously. However, LROs with notable anion redox suffer from capacity loss and voltage decay during cycling. Therefore, a fundamental understanding of their electrochemical behaviors and related structural evolution is a prerequisite for the successful development of high-capacity LRO cathodes with anion redox activity. However, there is still controversy over their electrochemical behavior and principles of operation. In addition, complicated redox mechanisms and the lack of sufficient analytical tools render the basic study difficult. In this review, we aim to introduce theoretical insights into the anion redox mechanism and in situ analytical instruments that can be used to prove the mechanism and behavior of cathodes with anion redox activity. We summarized the anion redox phenomenon, suggested mechanisms, and discussed the history of development for anion redox in cathode materials of LIBs. Finally, we review the recent progress in identification of reaction mechanisms in LROs and validation of engineering strategies to improve cathode performance based on anion redox through various analytical tools, particularly, in situ characterization techniques. Because unexpected phenomena may occur during cycling, it is crucial to study the kinetic properties of materials in situ under operating conditions, especially for this newly investigated anion redox phenomenon. This review provides a comprehensive perspective on the future direction of studies on materials with anion redox activity.
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Wu, Jinpeng, Qinghao Li, Shawn Sallis, Zengqing Zhuo, William E. Gent, William C. Chueh, Shishen Yan, Yi-de Chuang, and Wanli Yang. "Fingerprint Oxygen Redox Reactions in Batteries through High-Efficiency Mapping of Resonant Inelastic X-ray Scattering." Condensed Matter 4, no. 1 (January 5, 2019): 5. http://dx.doi.org/10.3390/condmat4010005.
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Realizing reversible reduction-oxidation (redox) reactions of lattice oxygen in batteries is a promising way to improve the energy and power density. However, conventional oxygen absorption spectroscopy fails to distinguish the critical oxygen chemistry in oxide-based battery electrodes. Therefore, high-efficiency full-range mapping of resonant inelastic X-ray scattering (mRIXS) has been developed as a reliable probe of oxygen redox reactions. Here, based on mRIXS results collected from a series of Li1.17Ni0.21Co0.08Mn0.54O2 electrodes at different electrochemical states and its comparison with peroxides, we provide a comprehensive analysis of five components observed in the mRIXS results. While all the five components evolve upon electrochemical cycling, only two of them correspond to the critical states associated with oxygen redox reactions. One is a specific feature at 531.0 eV excitation and 523.7 eV emission energy, the other is a low-energy loss feature. We show that both features evolve with electrochemical cycling of Li1.17Ni0.21Co0.08Mn0.54O2 electrodes, and could be used for characterizing oxidized oxygen states in the lattice of battery electrodes. This work provides an important benchmark for a complete assignment of all mRIXS features collected from battery materials, which sets a general foundation for future studies in characterization, analysis, and theoretical calculation for probing and understanding oxygen redox reactions.
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Farag, Nadia L., Rajesh Jethwa, Alice E. Beardmore, Clare P. Grey, and Dominic S. Wright. "Triarylamines: Promising Candidates As Aqueous Organic Redox Flow Catholytes." ECS Meeting Abstracts MA2022-01, no. 48 (July 7, 2022): 2046. http://dx.doi.org/10.1149/ma2022-01482046mtgabs.
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Redox flow batteries (RFBs) have significant potential in grid-level electrical energy storage, generated by renewable sources such as wind or solar power. Of particular interest in this research are aqueous organic electrolyte systems due to their safety, cost, fast kinetics and greater sustainability compared to the use of conventional inorganic electrolytes or organic solvents. To date this area has been limited by both the solubility and long term cycling stability of organic electrolytes.1 The most difficult challenge in this field is the development of stable organic catholytes that have high redox potentials, high energy density, and high battery efficiency. Triarylamines (TAAs) have the potential to meet these criteria because of the ease of functional group modification allowing for variation of the redox potential, and the low reorganisation energy between the neutral and radical states.2,3 TAAs have previously been explored as catholyte materials in organic non-aqueous RFBs, with studies showing that the redox properties of these easily prepared compounds can be tuned by judicious choice of functional groups at the para positions.4 It was also shown that TAAs have high cycling stability compared to other popular catholytes such as TEMPOL.5 However, TAAs have not previously been used as catholytes in aqueous RFBs. In this work, a number of TAAs were explored with various substituents in the para-positions of their aromatic rings, with the aim of promoting good aqueous solubility and cycling stability (two of the main selection criteria for any RFB electrolyte). Tris-4-amino-phenyl amine was found to be the most promising candidate, with reversible redox at high positive potentials, ease of synthesis, and reasonable aqueous solubility. Extensive electrochemical investigations using cyclic voltammetry (CV), impedance and full cell cycling were carried out which provide clues as to how the TAA framework can be modified to improve the redox properties for future catholyte applications. Figure 1: Triarylamine framework containing various substituents and CV of 1mM Tris-4-amino-phenyl amine with a scan rate of 20 mV/s in 1 M HCl with a Ag/AgCl reference electrode, glassy carbon working electrode and platinum counter electrode 1 R. M. Darling, K. G. Gallagher, J. A. Kowalski, S. Ha and F. R. Brushett, Energy Environ. Sci., 2014, 7, 3459–3477. 2 Tohru Nishinaga, Organic Redox Systems, Synthesis, Properties and Applications, Wiley, 2016. 3 J. Wang, K. Liu, L. Ma and X. Zhan, Chem. Rev., 2016, 116, 14675–14725. 4 I. A. V. Romadina, Elena I., K. J. Stevensona and P. A. Troshin, Mater. Chem. A, 2021, 9, 8303–8307. 5 G. Kwon, K. Lee, J. Yoo, S. Lee, J. Kim, Y. Kim, J. E. Kwon, S. Y. Park and K. Kang, Energy Storage Mater., 2021, 42, 185–192. Figure 1
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Daub, Nicolas. "A Critical Approach to Multi-Electron Materials for High Energy Density Non-Aqueous Redox Flow Batteries." ECS Meeting Abstracts MA2022-01, no. 48 (July 7, 2022): 2030. http://dx.doi.org/10.1149/ma2022-01482030mtgabs.
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Redox flow batteries (RFBs) are very promising storage systems in the transition towards renewable energy sources. They can be broadly classified in aqueous and non-aqueous systems. Last-named operate with organic solvents, which allow for a much broader potential window (up to three times higher) compared to water. Combination of organic solvents with organic redox active materials could pave the way for all carbon-based RFBs with superior energy densities compared to aqueous systems. In this contribution, newly developed organic electrolytes will be presented, focusing on their performance as RFB materials in acetonitrile with quaternary ammonium electrolyte salts. To push the limits of energy density, we investigated multi-electron reduction and oxidation reactions on a single molecule. As catholyte, tetrathiafulvalene (TTF) as a core structure was used. The unsubstituted TTF exhibits two reversible oxidation events (-0.04 and +0.34 V vs Fc/Fc+) but a poor solubility in acetonitrile. To optimize this and to achieve a higher oxidation potential a series of molecules with different side chains was synthesized. The resulting solubilities led to volumetric capacities of up to 71 Ah/L for the newly designed compounds. Electrochemical cycling stability was evaluated in bulk electrolysis, UV-Vis-NIR and flow cycling experiments. Current state-of-the-art anolytes based on N-methylphthalimide compounds exhibit one reversible reduction pair at a desirable low reduction potential (-1.87 V vs Fc/Fc+) and good cycling stability in bulk electrolysis experiments.[1] Expanding on this structure, new derivatives with one or two additional functional imide groups per phthalimide core were synthesized. Consequently, molecules with a single (-1.87 V vs Fc/Fc+), double (-1.26 and -1.88 V vs Fc/Fc+) and triple reduction event (-1.02, -1.65 and -2.37 V vs Fc/Fc+) can be obtained. To optimize their solubility in acetonitrile, a series of molecules with different side chains was synthesized for each of the three core structures. Determination of the solubility led to volumetric capacities of up to 66 Ah/L for the newly developed compounds. Additionally, we tested the electrochemical cycling stability in bulk electrolysis, UV-Vis-NIR, coin cell and flow cycling experiments. In the final flow battery, a high energy density of 24 Wh/L was achieved (at 1 M of transferred electrons).[2] All of this led to a critical comparison between the different molecular designs, cumulating in design rules that will influence future designs of the organic redox active compounds for organic RFBs. [1] Wei, X.; Duan, W.; Huang, J.; Zhang, L.; Li, B.; Reed, D.; Xu, W.; Sprenkle, V.; Wang, W. A High-Current, Stable Nonaqueous Organic Redox Flow Battery. ACS Energy Lett. 2016, 1, 705−711 [2] Daub, N.; Janssen, R. A. J.; Hendriks, K. H. Imide-Based Multielectron Anolytes as High-Performance Materials in Nonaqueous Redox Flow Batteries. ACS Appl. Energy Mater. 2021, 4, 9, 9248–9257
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Si, Lin, Brian A. Branfireun, and Jessica Fierro. "Chemical Oxidation and Reduction Pathways of Mercury Relevant to Natural Waters: A Review." Water 14, no. 12 (June 12, 2022): 1891. http://dx.doi.org/10.3390/w14121891.
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Mercury (Hg) pollution in the environment is a global issue and the toxicity of mercury depends on its speciation. Chemical redox reactions of mercury in an aquatic environment greatly impact on Hg evasion to the atmosphere and the methylation of mercury in natural waters. Identifying the abiotic redox pathways of mercury relevant to natural waters is important for predicting the transport and fate of Hg in the environment. The objective of this review is to summarize the current state of knowledge on specific redox reactions of mercury relevant to natural waters at a molecular level. The rate constants and factors affecting them, as well as the mechanistic information of these redox pathways, are discussed in detail. Increasing experimental evidence also implied that the structure of natural organic matter (NOM) play an important role in dark Hg(II) reduction, dark Hg(0) oxidation and Hg(II) photoreduction in the aquatic environment. Significant photooxidation pathways of Hg(0) identified are Hg(0) photooxidation by hydroxyl radical (OH•) and by carbonate radical (CO3−•). Future research needs on improving the understanding of Hg redox cycling in natural waters are also proposed.
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Wilmoth, Jared L. "Redox Heterogeneity Entangles Soil and Climate Interactions." Sustainability 13, no. 18 (September 9, 2021): 10084. http://dx.doi.org/10.3390/su131810084.
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Interactions between soils and climate impact wider environmental sustainability. Soil heterogeneity intricately regulates these interactions over short spatiotemporal scales and therefore needs to be more finely examined. This paper examines how redox heterogeneity at the level of minerals, microbial cells, organic matter, and the rhizosphere entangles biogeochemical cycles in soil with climate change. Redox heterogeneity is used to develop a conceptual framework that encompasses soil microsites (anaerobic and aerobic) and cryptic biogeochemical cycling, helping to explain poorly understood processes such as methanogenesis in oxygenated soils. This framework is further shown to disentangle global carbon (C) and nitrogen (N) pathways that include CO2, CH4, and N2O. Climate-driven redox perturbations are discussed using wetlands and tropical forests as model systems. Powerful analytical methods are proposed to be combined and used more extensively to study coupled abiotic and biotic reactions that are affected by redox heterogeneity. A core view is that emerging and future research will benefit substantially from developing multifaceted analyses of redox heterogeneity over short spatiotemporal scales in soil. Taking a leap in our understanding of soil and climate interactions and their evolving influence on environmental sustainability then depends on greater collaborative efforts to comprehensively investigate redox heterogeneity spanning the domain of microscopic soil interfaces.
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Oudejans, Daphne, Michele Offidani, Achilleas Constantinou, Stefania Albonetti, Nikolaos Dimitratos, and Atul Bansode. "A Comprehensive Review on Two-Step Thermochemical Water Splitting for Hydrogen Production in a Redox Cycle." Energies 15, no. 9 (April 21, 2022): 3044. http://dx.doi.org/10.3390/en15093044.
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The interest in and need for carbon-free fuels that do not rely on fossil fuels are constantly growing from both environmental and energetic perspectives. Green hydrogen production is at the core of the transition away from conventional fuels. Along with popularly investigated pathways for hydrogen production, thermochemical water splitting using redox materials is an interesting option for utilizing thermal energy, as this approach makes use of temperature looping over the material to produce hydrogen from water. Herein, two-step thermochemical water splitting processes are discussed and the key aspects are analyzed using the most relevant information present in the literature. Redox materials and their compositions, which have been proven to be efficient for this reaction, are reported. Attention is focused on non-volatile redox oxides, as the quenching step required for volatile redox materials is unnecessary. Reactors that could be used to conduct the reduction and oxidation reaction are discussed. The most promising materials are compared to each other using a multi-criteria analysis, providing a direction for future research. As evident, ferrite supported on yttrium-stabilized zirconia, ceria doped with zirconia or samarium and ferrite doped with nickel as the core and an yttrium (III) oxide shell are promising choices. Isothermal cycling and lowering of the reduction temperature are outlined as future directions towards increasing hydrogen yields and improving the cyclability.
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Chen, Hui, Zhongjie Wang, Shirui Zhang, Ming Cheng, Fuyu Chen, Ying Xu, and Juhua Luo. "A Low-Cost Neutral Aqueous Redox Flow Battery with Dendrite-Free Tin Anode." Journal of The Electrochemical Society 168, no. 11 (November 1, 2021): 110547. http://dx.doi.org/10.1149/1945-7111/ac39db.
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A neutral aqueous tin-based flow battery is proposed by employing Sn2+/Sn as active materials for the negative side, [Fe(CN)6]3−/ Fe(CN)6]4− as active materials for the positive side, and potassium chloride as the supporting electrolyte, and its overall performances and cost for capacity unit are investigated. Cyclic voltammetry is performed and shows that the Sn2+/Sn has outstanding electrochemical behavior. The charging-discharging tests are conducted with the optimized electrolyte composition of 0.2 M [Fe(CN)6]3− and 3 M KCl. It is shown that the flow cell can reach a high energy efficiency of 80% at 10 mA cm−2 and be stably operated at 40 mA cm−2. The 120-cycling test shows that the flow cell can be of superior cycling performances, benefitting from the dendrite-free property of tin. Finally, cost analysis further confirms its competitiveness in price, offering a promising future for commercial application. This work not only forms a promising energy storage device with dendrite-free and low-cost benefits, but also provide a deep insight into its overall behavior, which is highly beneficial to the full understanding and further advancement of the proposed neutral tin-iron flow battery.
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Leonard, Jeffrey, Nichole Reyes, Kyle M. Allen, Kelvin Randhir, Like Li, Nick AuYeung, Jeremy Grunewald, Nathan Rhodes, Michael Bobek, and James F. Klausner. "Effects of Dopant Metal Variation and Material Synthesis Method on the Material Properties of Mixed Metal Ferrites in Yttria Stabilized Zirconia for Solar Thermochemical Fuel Production." International Journal of Photoenergy 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/856385.
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Mixed metal ferrites have shown much promise in two-step solar-thermochemical fuel production. Previous work has typically focused on evaluating a particular metal ferrite produced by a particular synthesis process, which makes comparisons between studies performed by independent researchers difficult. A comparative study was undertaken to explore the effects different synthesis methods have on the performance of a particular material during redox cycling using thermogravimetry. This study revealed that materials made via wet chemistry methods and extended periods of high temperature calcination yield better redox performance. Differences in redox performance between materials made via wet chemistry methods were minimal and these demonstrated much better performance than those synthesized via the solid state method. Subsequently, various metal ferrite samples (NiFe2O4, MgFe2O4, CoFe2O4, and MnFe2O4) in yttria stabilized zirconia (8YSZ) were synthesized via coprecipitation and tested to determine the most promising metal ferrite combination. It was determined that 10 wt.% CoFe2O4in 8YSZ produced the highest and most consistent yields of O2and CO. By testing the effects of synthesis methods and dopants in a consistent fashion, those aspects of ferrite preparation which are most significant can be revealed. More importantly, these insights can guide future efforts in developing the next generation of thermochemical fuel production materials.
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Wang, Guixiang, Haitao Zou, Xiaobo Zhu, Mei Ding, and Chuankun Jia. "Recent progress in zinc-based redox flow batteries: a review." Journal of Physics D: Applied Physics 55, no. 16 (December 20, 2021): 163001. http://dx.doi.org/10.1088/1361-6463/ac4182.
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Abstract Zinc-based redox flow batteries (ZRFBs) have been considered as ones of the most promising large-scale energy storage technologies owing to their low cost, high safety, and environmental friendliness. However, their commercial application is still hindered by a few key problems. First, the hydrogen evolution and zinc dendrite formation cause poor cycling life, of which needs to ameliorated or overcome by finding suitable anolytes. Second, the stability and energy density of catholytes are unsatisfactory due to oxidation, corrosion, and low electrolyte concentration. Meanwhile, highly catalytic electrode materials remain to be explored and the ion selectivity and cost efficiency of membrane materials demands further improvement. In this review, we summarize different types of ZRFBs according to their electrolyte environments including ZRFBs using neutral, acidic, and alkaline electrolytes, then highlight the advances of key materials including electrode and membrane materials for ZRFBs, and finally discuss the challenges and perspectives for the future development of high-performance ZRFBs.
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Zhang, Chuanlun, Hongyue Dang, Farooq Azam, Ronald Benner, Louis Legendre, Uta Passow, Luca Polimene, Carol Robinson, Curtis A. Suttle, and Nianzhi Jiao. "Evolving paradigms in biological carbon cycling in the ocean." National Science Review 5, no. 4 (July 1, 2018): 481–99. http://dx.doi.org/10.1093/nsr/nwy074.
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ABSTRACT Carbon is a keystone element in global biogeochemical cycles. It plays a fundamental role in biotic and abiotic processes in the ocean, which intertwine to mediate the chemistry and redox status of carbon in the ocean and the atmosphere. The interactions between abiotic and biogenic carbon (e.g. CO2, CaCO3, organic matter) in the ocean are complex, and there is a half-century-old enigma about the existence of a huge reservoir of recalcitrant dissolved organic carbon (RDOC) that equates to the magnitude of the pool of atmospheric CO2. The concepts of the biological carbon pump (BCP) and the microbial loop (ML) shaped our understanding of the marine carbon cycle. The more recent concept of the microbial carbon pump (MCP), which is closely connected to those of the BCP and the ML, explicitly considers the significance of the ocean's RDOC reservoir and provides a mechanistic framework for the exploration of its formation and persistence. Understanding of the MCP has benefited from advanced ‘omics’ and novel research in biological oceanography and microbial biogeochemistry. The need to predict the ocean's response to climate change makes an integrative understanding of the BCP, ML and MCP a high priority. In this review, we summarize and discuss progress since the proposal of the MCP in 2010 and formulate research questions for the future.
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Ahn, Juhyeon, and Guoying Chen. "(Invited) High-Energy Mn-Rich Disordered Rocksalt Cathodes." ECS Meeting Abstracts MA2022-02, no. 1 (October 9, 2022): 35. http://dx.doi.org/10.1149/ma2022-02135mtgabs.
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In recent years, cation-disordered Li-excess rocksalts (DRX) have emerged as a promising new class of high-energy cathode materials for lithium-ion batteries. [1] Aside from the desirable Co-free chemistry, these compounds offer exceptionally large charge storage capacities by utilizing the redox reactions of both cationic transition-metals and anionic oxygen in the lattice. While early research focused on DRX oxides, which met with significant challenges in voltage stability and capacity retention upon cycling [2-3], recent studies shifted towards oxyfluorides with a substantial level of F substitution. It was found that incorporating F into the anionic sublattice can reduce oxygen gas release, impedance rise and capacity fade, consequently improving cathode cycling stability. [4-5] To this end, developing synthesis methods to incorporate large F content in the lattice as well as designing and optimizing oxyfluoride chemistry for both high energy density and cycling stability are imperative. While high F substitution levels (up to 30-40 at.%) in DRX have been achieved through mechanochemical synthesis, the method has limitations in industrial application due to poor scalability. Solid-state synthesis, on the other hand, are readily scalable and often offers drop-in replacement in materials processing. In this presentation, we show our recent effort in developing calcination-based fluorination approach to achieve high-level fluorination of Mn-redox-active DRX materials. [6] The unique behavior of capacity rise upon cycling of a new class of Mn-rich DRX oxyfluoride cathodes will be reported. Our understanding in how chemistry can impact local and long-range structures and their evolution during electrochemical cycling will also be presented, as well as perspectives on future directions in DRX development. References Lee, J.; Urban, A.; Li, X.; Su, D.; Hautier, G.; Ceder, G. Unlocking the Potential of Cation-Disordered Oxides for Rechargeable Lithium Batteries. Science 2014, 343, 519. Yabuuchi, N.; Takeuchi, M.; Nakayama, M.; Shiiba, H.; Ogawa, M.; Nakayama, K.; Ohta, T.; Endo, D.; Ozaki, T.; Inamasu, T.; Sato, K.; Komaba, S., High-Capacity Electrode Materials for Rechargeable Lithium Batteries: Li3NbO4-based System with Cation-Disordered Rocksalt Structure. Natl. Acad. Sci. 2015, 112, 7650. Chen, D.; Kan, W. H.; Chen, G. Understanding Performance Degradation in Cation-Disordered Rock-Salt Oxide Cathodes. Energy Mater. 2019, 9, 1901255. Lee, J.; Papp, J. K.; Clément, R. J.; Sallis, S.; Kwon, D.-H.; Shi, T.; Yang, W.; McCloskey, B. D.; Ceder, G. Mitigating oxygen loss to improve the cycling performance of high capacity cation-disordered cathode materials. Commun. 2017, 8, 981. Lun, Z.; Ouyang, B.; Kitchaev, D. A.; Clément, R. J.; Papp, J. K.; Balasubramanian, M.; Tian, Y.; Lei, T.; Shi, T.; McCloskey, B. D.; Lee, J.; Ceder, G. Improved Cycling Performance of Li-Excess Cation-Disordered Cathode Materials upon Fluorine Substitution. Energy Mater. 2018, 9,1802959. Ahn, J.; Chen, D.; Chen, G.. A Fluorination Method for Improving Cation-Disordered Rocksalt Cathode Performance. Energy Mater. 2020, 10, 2001671.
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van de Velde, Sebastiaan J., Dominik Hülse, Christopher T. Reinhard, and Andy Ridgwell. "Iron and sulfur cycling in the cGENIE.muffin Earth system model (v0.9.21)." Geoscientific Model Development 14, no. 5 (May 18, 2021): 2713–45. http://dx.doi.org/10.5194/gmd-14-2713-2021.
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Abstract. The coupled biogeochemical cycles of iron and sulfur are central to the long-term biogeochemical evolution of Earth's oceans. For instance, before the development of a persistently oxygenated deep ocean, the ocean interior likely alternated between states buffered by reduced sulfur (“euxinic”) and buffered by reduced iron (“ferruginous”), with important implications for the cycles and hence bioavailability of dissolved iron (and phosphate). Even after atmospheric oxygen concentrations rose to modern-like values, the ocean episodically continued to develop regions of euxinic or ferruginous conditions, such as those associated with past key intervals of organic carbon deposition (e.g. during the Cretaceous) and extinction events (e.g. at the Permian–Triassic boundary). A better understanding of the cycling of iron and sulfur in an anoxic ocean, how geochemical patterns in the ocean relate to the available spatially heterogeneous geological observations, and quantification of the feedback strengths between nutrient cycling, biological productivity, and ocean redox requires a spatially resolved representation of ocean circulation together with an extended set of (bio)geochemical reactions. Here, we extend the “muffin” release of the intermediate-complexity Earth system model cGENIE to now include an anoxic iron and sulfur cycle (expanding the existing oxic iron and sulfur cycles), enabling the model to simulate ferruginous and euxinic redox states as well as the precipitation of reduced iron and sulfur minerals (pyrite, siderite, greenalite) and attendant iron and sulfur isotope signatures, which we describe in full. Because tests against present-day (oxic) ocean iron cycling exercises only a small part of the new code, we use an idealized ocean configuration to explore model sensitivity across a selection of key parameters. We also present the spatial patterns of concentrations and δ56Fe and δ34S isotope signatures of both dissolved and solid-phase Fe and S species in an anoxic ocean as an example application. Our sensitivity analyses show that the first-order results of the model are relatively robust against the choice of kinetic parameter values within the Fe–S system and that simulated concentrations and reaction rates are comparable to those observed in process analogues for ancient oceans (i.e. anoxic lakes). Future model developments will address sedimentary recycling and benthic iron fluxes back to the water column, together with the coupling of nutrient (in particular phosphate) cycling to the iron cycle.
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Odijk, Mathieu, and Albert van den Berg. "Nanoscale Electrochemical Sensing and Processing in Microreactors." Annual Review of Analytical Chemistry 11, no. 1 (June 12, 2018): 421–40. http://dx.doi.org/10.1146/annurev-anchem-061417-125642.
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In this review, we summarize recent advances in nanoscale electrochemistry, including the use of nanoparticles, carbon nanomaterials, and nanowires. Exciting developments are reported for nanoscale redox cycling devices, which can chemically amplify signal readout. We also discuss promising high-frequency techniques such as nanocapacitive CMOS sensor arrays or heterodyning. In addition, we review electrochemical microreactors for use in (drug) synthesis, biocatalysis, water treatment, or to electrochemically degrade urea for use in a portable artificial kidney. Electrochemical microreactors are also used in combination with mass spectrometry, e.g., to study the mimicry of drug metabolism or to allow electrochemical protein digestion. The review concludes with an outlook on future perspectives in both nanoscale electrochemical sensing and electrochemical microreactors. For sensors, we see a future in wearables and the Internet of Things. In microreactors, a future goal is to monitor the electrochemical conversions more precisely or ultimately in situ by combining other spectroscopic techniques.
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Leaf, David E., and Dorine W. Swinkels. "Catalytic iron and acute kidney injury." American Journal of Physiology-Renal Physiology 311, no. 5 (November 1, 2016): F871—F876. http://dx.doi.org/10.1152/ajprenal.00388.2016.
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Acute kidney injury (AKI) is a common and often devastating condition among hospitalized patients and is associated with markedly increased hospital length of stay, mortality, and cost. The pathogenesis of AKI is complex, but animal models support an important role for catalytic iron in causing AKI. Catalytic iron, also known as labile iron, is a transitional pool of non-transferrin-bound iron that is readily available to participate in redox cycling. Initial findings related to catalytic iron and animal models of kidney injury have only recently been extended to human AKI. In this review, we discuss the role of catalytic iron in human AKI, focusing on recent translational studies in humans, assay considerations, and potential therapeutic targets for future interventional studies.
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Hamal, Dambar, Osama Awadallah, and Bilal El-Zahab. "Catalysis in Lithium-Sulfur Cathodes for Improved Performance and Stability." ECS Meeting Abstracts MA2022-02, no. 4 (October 9, 2022): 535. http://dx.doi.org/10.1149/ma2022-024535mtgabs.
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Among next generation batteries, lithium-sulfur batteries are expected to be first battery to find a commercial route in the next few years. The sulfur cathodes in lithium-sulfur batteries provide both a lower cost and high capacity (1675 mAh/g) in comparison to intercalation cathode materials [1]. Despite these upsides, this conversion reaction type battery suffers from few problems that hinders their adoption. Some of these problems include the sluggish reaction kinetics, low sulfur utilization, rapid capacity loss due to various sulfur loss phenomena, and low Coulombic efficiency [2]. The use of electrocatalysts was shown to significantly boost the polysulfides redox reactions and improves the battery performance [3]. Transition metals, especially platinum group metal (PGM) based catalysts are proven to effectively boost the reaction rate of polysulfides conversion during cycling due to their high electrocatalytic activity [4], [5]. However, catalyst incorporation in conversion reaction batteries systems often would lead to side reactions and strategies on how to incorporate them into the battery system have to be developed. In this work, platinum group metal (PGM) nanocatalysts were implemented in lithium-sulfur cathodes using a process that is tailored to effectively improve catalyst dispersion and to provide controlled catalyst electrolyte contact. The nanocatalysts were loaded in carbon nanotube at variable low contents 0.1 – 5 wt% (Figure 1a) and were used in cathodes with sulfur loading up to 70 wt%. Using standard lithium-sulfur electrolyte based on 1 mol/kg LiTFSI in DOL:DME (v:v = 1:1) with lean electrolyte condition, batteries based on 2032 type coin cells and multilayer pouch cells were studied. The batteries' performance was studied for their impedance growth using electrochemical impedance spectroscopy, the redox performance using cycling voltammetry, and for their sulfur utilization/sulfur loss/Coulombic efficiency using galvanostatic charge-discharge cycling. These cathodes were shown to have improved redox performance in the batteries, improved sulfur utilization, and maintained stable capacity even at high sulfur loadings of 4-5 mg/cm2. Comparison of performance of nanocatalyst-containing batteries versus control batteries show improved first cycle capacity and stabilized capacity retention in the early cycling life of the battery (Figure 1b). Elucidating the underlying phenomena of the stabilization is studied in detail revealing reduced sulfur precipitation and shuttle effects. Higher C-rate performance of up to 1C revealed similar observations of stabilization. References [1] G. Li, Z. Chen, and J. Lu, “Lithium-Sulfur Batteries for Commercial Applications,” Chem, vol. 4, no. 1, pp. 3–7, Jan. 2018. [2] X. Tang et al., “Factors of Kinetics Processes in Lithium–Sulfur Reactions,” Energy Technology, vol. 7, no. 12, p. 1900574, Dec. 2019. [3] H. Chen et al., “Catalytic materials for lithium-sulfur batteries: mechanisms, design strategies and future perspective,” Materials Today, vol. 52, pp. 364–388, 2022. [4] Z. Shen et al., “Rational Design of a Ni3N0.85 Electrocatalyst to Accelerate Polysulfide Conversion in Lithium–Sulfur Batteries,” ACS Nano, vol. 14, no. 6, pp. 6673–6682, Jun. 2020. [5] Y. Qi et al., “Catalytic polysulfide conversion in lithium-sulfur batteries by platinum nanoparticles supported on carbonized microspheres,” Chemical Engineering Journal, vol. 435, p. 135112, 2022. Figure 1
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Rütting, T., P. Boeckx, C. Müller, and L. Klemedtsson. "Assessment of the importance of dissimilatory nitrate reduction to ammonium for the terrestrial nitrogen cycle." Biogeosciences Discussions 8, no. 1 (February 9, 2011): 1169–96. http://dx.doi.org/10.5194/bgd-8-1169-2011.
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Abstract. The nitrogen (N) cycle contains two different processes of dissimilatory nitrate (NO3−) reduction, denitrification and dissimilatory NO3− reduction to ammonium (DNRA). While there is general agreement that the denitrification process takes place in many soils, the occurrence and importance of DNRA is generally not considered. Two approaches have been used to investigate DNRA in soil, (1) microbiological techniques to identify soil microorganisms capable of DNRA and (2) 15N tracing to elucidate the occurrence of DNRA and to quantify gross DNRA rates. There is evidence that many soil bacteria and fungi have the ability to perform DNRA. Redox status and C/NO3− ratio have been identified as the most important factors regulating DNRA in soil. 15N tracing studies have shown that gross DNRA rates can be a significant or even a dominant NO3− consumption process in some ecosystems. Moreover, a link between heterotrophic nitrification and DNRA provides an alternative pathway of ammonium (NH4+) production to mineralisation. Numerical 15N tracing models can be particularly useful when investigating DNRA in the context of other N cycling processes. With this review we summarise the importance and current knowledge of this often overlooked NO3− consumption process within the terrestrial N cycle. We strongly encourage considering DNRA as a relevant soil N process in future N cycling investigations.
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Morozov, Anatolii V., Ivan A. Moiseev, Aleksandra A. Savina, and Artem M. Abakumov. "Impact of TM-O Bonding Covalency on the Structure and Performance of Li-Rich Layered Oxide Positive Electrodes for Li-Ion Batteries." ECS Meeting Abstracts MA2022-01, no. 2 (July 7, 2022): 340. http://dx.doi.org/10.1149/ma2022-012340mtgabs.
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The application of positive electrode (cathode) materials with anionic redox activity is hoped to improve the energy density of future Li-ion batteries, and thus facilitate the mileage issue in rapidly growing electric transport industry. Such positive expectations are dictated by promising application potential of the Li4/3-xNi2+ xMn4+ 2/3-xCo3+ xO2 layered oxides demonstrating outstanding reversible discharge capacity exceeding 250 mAh/g and specific energy density of > 1000 Wh/kg. Such outstanding values are the result of joint participance of cationic (Ni2+→Ni3+→Ni4+, Co3+→Co4+) redox transitions and processes of O2 n-/2O2- units formation in charge compensation mechanism upon Li (de)intercalation. Nevertheless, oxygen redox chemistry in battery materials is a «double-edged sword», since it`s associated with practical drawbacks like sluggish kinetics, voltage hysteresis, voltage fade and safety worries alongside greatly improved energy density. At the same time, the exact nature of partially oxidized oxygen species is still raising intensive debates as well as the role of TM-O bonding in oxygen oxidation reversibility and interplay between anionic redox and accompanying bulk and local structure transformations and their accumulation during prolonged cycling. In our work, we probed the anionic redox properties as a function of electronic structure and chemical bonding substituting a small fraction of 3d-metals with Ru in a parent Li1.2Ni0.2Mn0.6O2 according to xLi2RuO3-(1-x)Li1.2Ni0.2Mn0.6O2 solid solution system (x is up to 0.1). This approach allowed us to gently tune the ratio between the contributions of the cationic and anionic redox whereas employing the same mixed Ni-Mn carbonate precursor excludes the impact of different sample morphology on the electrochemical behavior, providing a legitimate justification to attribute all the observed effects solely to crystal structure and TM-O bonding character. Both experimental results and theoretical calculations demonstrated that gradual increasing of Ru content drastically changes electrochemical behavior of the Li-rich layered oxides improving the reversibility of the oxygen redox thus suppressing irreversible oxygen oxidation at the first charge. In turn, diminished gaseous O2 evolution led to the retardation of “structural densification” as well as concomitant mitigation of Mn redox activity and changes in spatial distribution of the reduced Mn species. Moreover, despite the discharge voltage fade did not differ much for compounds with different Ru concentration, Ru doping surely decreased the charge voltage fade and, surprisingly, total discharge capacity likely due to inhibited Mn4+/3+/2+ redox activity in the Ru-doped compounds. In our report we will present the whole set of observations on xLi2RuO3-(1-x)Li1.2Ni0.2Mn0.6O2 model system aimed to trace the whole chain of events from increasing the covalency of the TM-O bond, suppressing irreversible oxygen oxidation and appearance of the reduced Mn species to retarding the structure densification in the Li-rich layered oxides.
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Naafs, B. David A., Fanny M. Monteiro, Ann Pearson, Meytal B. Higgins, Richard D. Pancost, and Andy Ridgwell. "Fundamentally different global marine nitrogen cycling in response to severe ocean deoxygenation." Proceedings of the National Academy of Sciences 116, no. 50 (November 25, 2019): 24979–84. http://dx.doi.org/10.1073/pnas.1905553116.
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The present-day marine nitrogen (N) cycle is strongly regulated by biology. Deficiencies in the availability of fixed and readily bioavailable nitrogen relative to phosphate (P) in the surface ocean are largely corrected by the activity of diazotrophs. This feedback system, termed the “nitrostat,” is thought to have provided close regulation of fixed-N speciation and inventory relative to P since the Proterozoic. In contrast, during intervals of intense deoxygenation such as Cretaceous ocean anoxic event (OAE) 2, a few regional sedimentary δ15N records hint at the existence of a different mode of marine N cycling in which ammonium plays a major role in regulating export production. However, the global-scale dynamics during this time remain unknown. Here, using an Earth System model and taking the example of OAE 2, we provide insights into the global marine nitrogen cycle under severe ocean deoxygenation. Specifically, we find that the ocean can exhibit fundamental transitions in the species of nitrogen dominating the fixed-N inventory––from nitrate (NO3−) to ammonium (NH4+)––and that as this transition occurs, the inventory can partially collapse relative to P due to progressive spatial decoupling between the loci of NH4+ oxidation, NO3− reduction, and nitrogen fixation. This finding is relatively independent of the specific state of ocean circulation and is consistent with nitrogen isotope and redox proxy data. The substantive reduction in the ocean fixed-N inventory at an intermediate state of deoxygenation may represent a biogeochemical vulnerability with potential implications for past and future (warmer) oceans.
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McCammon, Catherine, Hélène Bureau, James H. Cleaves, Elizabeth Cottrell, Susannah M. Dorfman, Louise H. Kellogg, Jie Li, et al. "Deep Earth carbon reactions through time and space." American Mineralogist 105, no. 1 (January 1, 2020): 22–27. http://dx.doi.org/10.2138/am-2020-6888ccby.
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Abstract Reactions involving carbon in the deep Earth have limited manifestations on Earth's surface, yet they have played a critical role in the evolution of our planet. The metal-silicate partitioning reaction promoted carbon capture during Earth's accretion and may have sequestered substantial carbon in Earth's core. The freezing reaction involving iron-carbon liquid could have contributed to the growth of Earth's inner core and the geodynamo. The redox melting/freezing reaction largely controls the movement of carbon in the modern mantle, and reactions between carbonates and silicates in the deep mantle also promote carbon mobility. The 10-year activity of the Deep Carbon Observatory has made important contributions to our knowledge of how these reactions are involved in the cycling of carbon throughout our planet, both past and present, and has helped to identify gaps in our understanding that motivate and give direction to future studies.
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Xu, Juan, Zheng Lin, Xingrun Huang, Yuan Lei, Chao Chen, and Zhan Lin. "MOF-derived nanoporous carbon with embedded cobalt nanoparticles as interlayer for high-performance Li–S batteries." Applied Physics Letters 121, no. 12 (September 19, 2022): 123902. http://dx.doi.org/10.1063/5.0115364.
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Lithium–sulfur (Li–S) battery is one of the promising energy storage systems due to its high theoretical energy density with low cost. The main challenge at present for its commercialization is the polysulfides shuttling, leading to poor cycling performance. Here, we report a facilely prepared metal-organic framework (MOF)-derived nanoporous carbon with embedded cobalt nanoparticles (NPCo/C) for alleviating the polysulfides shuttling. The NPCo/C with large surface area and abundant Co nanoparticles is simply prepared by direct carbonization of a Co-based MOF material, which is combined with graphene to construct a robust membrane as the interlayer (NPCo/C@G) to modify the pristine separator. The NPCo/C@G-modified separator gives the battery good cycling stability (707 mAh g−1 after 300 cycles at 0.5 C) and rate performance (capacity decay rate of 0.18% in 300 cycles at 2 C). Excellent battery performance (620 mAh g−1 after 100 cycles at 0.5 C) is exhibited even under ultra-low loading of NPCo/C@G (0.08 mg cm−2). The superior electrochemical performance is mainly attributed to abundant exposed Co active sites in NPCo/C to immobilize polysulfides and accelerate sulfur redox kinetics as well as excellent electrical conductivity of NPCo/C@G for improved sulfur utilization. This study provides a guidance for designing functional separators for Li–S battery application in the near future.
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Zhang, Lifang, Yinghui Xia, Hao Yang, Sijie Xiao, Jinqiu Zhou, Yufeng Cao, and Tao Qian. "The current status of sodium metal anodes for improved sodium batteries and its future perspectives." APL Materials 10, no. 7 (July 1, 2022): 070901. http://dx.doi.org/10.1063/5.0097264.
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Sodium-ion batteries with evident merits in resource abundance and expenditure are emerging as a more suitable alternative to lithium-ion batteries for fulfilling the voracious energy demand of human activities. As the integral component of the battery, the exploration of anode materials suited to the electrochemical system during the last few decades has been never suspended, and the sodium metal anode successfully stands out with its high theoretical capacity and low redox potential. However, a huge gap exists between the direct usage of the sodium metal anode and the large-scale applications, as the uncontrollable sodium dendritic growth during cycling brings about serious concerns (i.e. infinite volume change, unstable solid electrolyte interphase, and safety issues) on battery performance losses. Although a few review articles on high-performance sodium metal anode have been already published, new research on solving the aforementioned challenges is still in progress. Therefore, we herein summarize the recent progress on the high-energy sodium metal anode from four aspects (protective layers, electrolyte additives, three-dimensional framework current collectors, and alloy materials) together with the detailed discussion and analysis in this Perspective. Furthermore, the potential directions and prospects of future research on constructing high-performance sodium metal anodes are also proposed.
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Llewellyn, Alice V., Alessia Matruglio, Dan J. L. Brett, Rhodri Jervis, and Paul R. Shearing. "Using In-Situ Laboratory and Synchrotron-Based X-ray Diffraction for Lithium-Ion Batteries Characterization: A Review on Recent Developments." Condensed Matter 5, no. 4 (November 16, 2020): 75. http://dx.doi.org/10.3390/condmat5040075.
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Renewable technologies, and in particular the electric vehicle revolution, have generated tremendous pressure for the improvement of lithium ion battery performance. To meet the increasingly high market demand, challenges include improving the energy density, extending cycle life and enhancing safety. In order to address these issues, a deep understanding of both the physical and chemical changes of battery materials under working conditions is crucial for linking degradation processes to their origins in material properties and their electrochemical signatures. In situ and operando synchrotron-based X-ray techniques provide powerful tools for battery materials research, allowing a deep understanding of structural evolution, redox processes and transport properties during cycling. In this review, in situ synchrotron-based X-ray diffraction methods are discussed in detail with an emphasis on recent advancements in improving the spatial and temporal resolution. The experimental approaches reviewed here include cell designs and materials, as well as beamline experimental setup details. Finally, future challenges and opportunities for battery technologies are discussed.
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Tagliabue, A., and C. Völker. "Towards accounting for dissolved iron speciation in global ocean models." Biogeosciences 8, no. 10 (October 31, 2011): 3025–39. http://dx.doi.org/10.5194/bg-8-3025-2011.
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Abstract. The trace metal iron (Fe) is now routinely included in state-of-the-art ocean general circulation and biogeochemistry models (OGCBMs) because of its key role as a limiting nutrient in regions of the world ocean important for carbon cycling and air-sea CO2 exchange. However, the complexities of the seawater Fe cycle, which impact its speciation and bioavailability, are simplified in such OGCBMs due to gaps in understanding and to avoid high computational costs. In a similar fashion to inorganic carbon speciation, we outline a means by which the complex speciation of Fe can be included in global OGCBMs in a reasonably cost-effective manner. We construct an Fe speciation model based on hypothesised relationships between rate constants and environmental variables (temperature, light, oxygen, pH, salinity) and assumptions regarding the binding strengths of Fe complexing organic ligands and test hypotheses regarding their distributions. As a result, we find that the global distribution of different Fe species is tightly controlled by spatio-temporal environmental variability and the distribution of Fe binding ligands. Impacts on bioavailable Fe are highly sensitive to assumptions regarding which Fe species are bioavailable and how those species vary in space and time. When forced by representations of future ocean circulation and climate we find large changes to the speciation of Fe governed by pH mediated changes to redox kinetics. We speculate that these changes may exert selective pressure on phytoplankton Fe uptake strategies in the future ocean. In future work, more information on the sources and sinks of ocean Fe ligands, their bioavailability, the cycling of colloidal Fe species and kinetics of Fe-surface coordination reactions would be invaluable. We hope our modeling approach can provide a means by which new observations of Fe speciation can be tested against hypotheses of the processes present in governing the ocean Fe cycle in an integrated sense
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Ussher, Simon J., Eric P. Achterberg, and Paul J. Worsfold. "Marine Biogeochemistry of Iron." Environmental Chemistry 1, no. 2 (2004): 67. http://dx.doi.org/10.1071/en04053.
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Environmental Context. Several trace elements are essential to the growth of microorganisms, iron being arguably the most important. Marine microorganisms, which affect the global carbon cycle and consequently indirectly influence the world’s climate, are therefore sensitive to the presence of iron. This link means iron-related oceanic processes are a significant ecological and political issue. Abstract. The importance of the role of iron as a limiting micronutrient for primary production in the World Ocean has become increasingly clear following large-scale in situ iron fertilization experiments in high-nutrient, low-chlorophyll (HNLC) regions.[1] This has led to intensive international research with the aim of understanding the marine biogeochemistry of iron and quantifying the spatial distribution and transport of the element in the oceans. Recent studies have benefited from improved trace metal handling protocols and sensitive analytical techniques, but uncertainties remain concerning fundamental processes such as redox transfer, solubility, adsorption, biological uptake, and remineralization. This review summarizes our present knowledge of iron biogeochemistry. It begins with a discussion of the effects of the physicochemical speciation of iron in seawater from a thermodynamic perspective, including important topics such as inorganic and organic complexation and redox chemistry. This is followed by an overview of the fluxes of iron to the ocean interface and a description of iron cycling within the open ocean water column. Current uncertainties of iron biogeochemistry are highlighted and suggestions of future work provided.
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Rütting, T., P. Boeckx, C. Müller, and L. Klemedtsson. "Assessment of the importance of dissimilatory nitrate reduction to ammonium for the terrestrial nitrogen cycle." Biogeosciences 8, no. 7 (July 8, 2011): 1779–91. http://dx.doi.org/10.5194/bg-8-1779-2011.
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Abstract. The nitrogen (N) cycle contains two different processes of dissimilatory nitrate (NO3−) reduction, denitrification and dissimilatory NO3− reduction to ammonium (DNRA). While there is general agreement that the denitrification process takes place in many soils, the occurrence and importance of DNRA is generally not considered. Two approaches have been used to investigate DNRA in soil, (1) microbiological techniques to identify soil microorganisms capable of DNRA and (2) 15N tracing to elucidate the occurrence of DNRA and to quantify gross DNRA rates. There is evidence that many soil bacteria and fungi have the ability to perform DNRA. Redox status and C/NO3− ratio have been identified as the most important factors regulating DNRA in soil. 15N tracing studies have shown that gross DNRA rates can be a significant or even a dominant NO3− consumption process in some ecosystems. Moreover, a link between heterotrophic nitrification and DNRA provides an alternative pathway of ammonium (NH4+) production to mineralisation. Numerical 15N tracing models are particularly useful when investigating DNRA in the context of other N cycling processes. The results of correlation and regression analyses show that highest gross DNRA rates can be expected in soils with high organic matter content in humid regions, while its relative importance is higher in temperate climates. With this review we summarise the importance and current knowledge of this often overlooked NO3− consumption process within the terrestrial N cycle. We strongly encourage considering DNRA as a relevant process in future soil N cycling investigations.
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Gorlin, Mikaela, Andrew J. Naylor, Dickson O. Ojwang, Yang Shao-Horn, and Mario Valvo. "(Digital Presentation) The Influence of Alkali Metal Cations on the Redox Processes of Copper Hexacyanoferrate in Rechargeable Aqueous Zinc-Ion Batteries." ECS Meeting Abstracts MA2022-02, no. 59 (October 9, 2022): 2214. http://dx.doi.org/10.1149/ma2022-02592214mtgabs.
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Rechargeable aqueous batteries are of high interest for future stationary grid-scale energy storage applications where high safety is needed (1). Copper hexacyanoferrate (CuHCF), a Prussian Blue Analogue (PBA) material, has recently gained interest as positive electrode for aqueous Zn-ion batteries (ZIBs) (2,3). Reversible Zn2+ ion insertion is facilitated by its open-framework with large channels that can host a variety of monovalent and divalent cations. Recent studies have shown that the charge compensation process takes place via Zn2+ ions swapping position between tunnel sites and vacancy sites (4). Among aqueous ZIBs, the Zn/CuHCF cell has attracted noticeable attention, as it can combine abundant and inexpensive materials with a good trade-off between capacity and performance. Zinc can supply a high capacity (820 mAh g-1), while CuHCF typically provides a moderate capacity of ca. 60-80 mAh g-1.However, it exhibits one of the highest operating voltages among PBA-type cathodes (1.7 V vs. Zn2+/Zn) and exhibits a cubic-type structure with wide channels. In comparison to many other materials, CuHCF undergoes minimal volume and structural changes during ion insertion/de-insertion, exhibits a high Coulombic efficiency of ca. 99%, and can be cycled at high rates without compromising the capacity, which makes it an interesting material for high-power applications. Nevertheless, CuHCF suffers from capacity fade owing to instabilities of Cu, which we have demonstrated in details in a recent investigation (5). In that study, we also highlighted that the characteristic aging effect, observed as a growth of a two-phase plateau in the charge/discharge profiles and associated with capacity loss (6), can be explained by Cu dissolution and thereby a displacement of the two Cu2+/Cu+ and Fe3+/Fe2+ redox-couples (5). Alkali metal cations (Li+, Na+, K+, Rb+, Cs+) have recently been shown to impact the capacity of the Zn/CuHCF cell along with a modulation of the characteristic redox-features in the voltammetric profiles (7). Cycling of large cations (Rb+, Cs+) was linked to a reduced capacity, while moderately sized cations (K+) resulted in optimal capacity and higher charge retention. This has motivated us to investigate the effect of the alkali metal cations on the charge compensation and redox processes in CuHCF in more detail in this study. By employing X-ray photoelectron spectroscopy (XPS), we show that small cations (Li+) have negligible impact on the Cu and Fe redox processes, while moderately sized cations (K+) suppress Cu redox and enhance Fe redox, which optimizes the capacity and improves the cycling stability, accordingly. Large cations (Cs+), on the other hand, prevent reversible redox and lock both metal centers in their most reduced states (Cu+, Fe2+), which impedes the charge compensation process and reduces the capacity. Our study unveils how alkali metal cations influence the performance of ZIBs by affecting the synergy of the Cu2+/Cu+ and Fe3+/Fe2+ redox couples in CuHCF and demonstrates how tailoring the electrolyte formulation can conveniently impact the capacity retention of this compound in PBA-type ZIBs. Figure 1. The aqueous Zn/CuHCF cell. (a) Schematic figures illustrating the structure of the CuHCF cathode and its wide channels that can host ions. (b) Cyclic voltammograms (CV) of the Zn/CuHCF cell in pure 1M ZnSO4 and in presence of 0.2 M alkali metal cation additives (Li+, K+, Cs+). (c) X-ray photoelectron spectroscopy (XPS) showing the Cu 2p3/2 and Fe 2p3/2 spectra of the same electrolytes as shown in (b). References J. Shin, and J. W. Choi, Advanced Energy Materials, 10, 2001386–2001386 (2020). R. Trócoli, and F. La Mantia, ChemSusChem, 8, 481–485 (2015). Z. Jia, B. Wang, and Y. Wang, Materials Chemistry and Physics, 149–150, 601–606 (2015). V. Renman, D. O. Ojwang, M. Valvo, C. P. Gómez, T. Gustafsson, G. Svensson, Journal of Power Sources, 369, 146–153 (2017). M. Görlin, D. O., Ojwang, M.-T. Lee, V. Renman, C.-W. Tai, and M. Valvo, ACS Applied Materials & Interfaces, 13, 59962–59974 (2021) R. Trócoli, G. Kasiri, and F. La Mantia, Journal of Power Sources, 400, 167–171 (2018). D. Phadke, R. Mysyk, and M. Anouti, Journal of Energy Chemistry 40, 31–38 (2020). Figure 1
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Pahari, Shyam Kumar, Benjoe Rey B. Visayas, Ross S. Brown, Tugba Ceren Gokoglan Barut, James A. Golen, Ertan Agar, Maricris L. Mayes, and Patrick J. Cappillino. "(Digital Presentation) Development of a Bio-Inspired Non-Aqueous Redox Flow Battery Utilizing Anionic Active Materials." ECS Meeting Abstracts MA2022-01, no. 3 (July 7, 2022): 481. http://dx.doi.org/10.1149/ma2022-013481mtgabs.
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Energy storage is an indispensable part of future electrical grids as they increasingly shift toward renewable energy sources.1 Although many other energy storage technologies have shown potential, redox flow batteries are especially promising because of advantages arising from their decoupled power and energy capacity, wide range of possible electroactive materials, wider potential window (in non-aqueous solvents) and safety. 2 However, the nascent non-aqueous redox flow battery (NRFB) technology currently faces key challenges that need to be addressed to ensure their reliability and widespread implementation. Low stability of active material during deep cycling is one such challenge that needs to be addressed while low solubility of active material in organic solvent is another main hurdle that greatly limits energy density. Herein, we present a cost-effective, experimental-theoretical approach 3 , 4 to improve the solubility of a vanadium-based, highly stable, anionic active material known as vanadium-bis-hydroxyiminodiacetate (VBH). This is accomplished by tuning the key thermodynamic quantities of free energy of solvation and free energy of the lattice. We also demonstrate that the lattice free energy, which has been largely ignored in theoretical solubility models, is vital to obtain a meaningful prediction of solubility, and cannot be overlooked. Finally, we report the full cell cycling of the highly soluble VBH, coupled with an anthraquinone, exhibiting excellent cyclability and a reliable spectroscopic method to characterize pre- and post-cycled electrolytes. References (1) IEA. Renewable Energy Market Update 2021 ; Paris, 2021. (2) Dunn, B.; Kamath, H.; Tarascon, J.-M. Electrical Energy Storage for the Grid: A Battery of Choices. Science 2011, 334 (6058), 928-935. DOI: 10.1126/science.1212741. (3) Pahari, S. K.; Gokoglan, T. C.; Visayas, B. R. B.; Woehl, J.; Golen, J. A.; Howland, R.; Mayes, M. L.; Agar, E.; Cappillino, P. J. Designing high energy density flow batteries by tuning active-material thermodynamics. RSC Advances 2021, 11 (10), 5432-5443, 10.1039/D0RA10913D. DOI: 10.1039/D0RA10913D. (4) Visayas, B. R. B.; Pahari, S. K.; Gokoglan, T. C.; Golen, J. A.; Agar, E.; Cappillino, P. J.; Mayes, M. L. Computational and experimental investigation of the effect of cation structure on the solubility of anionic flow battery active-materials. Chemical Science 2021, 12 (48), 15892-15907, 10.1039/D1SC04990A. DOI: 10.1039/D1SC04990A.
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Bao, Liying, Xinyu Zhu, Ning Li, Yongjian Li, Lifeng Xu, Lai Chen, Duanyun Cao, et al. "Modulating anionic activities in layered Li-rich cathode materials with inverse spinel MnFe2O4 coating." MATEC Web of Conferences 358 (2022): 01051. http://dx.doi.org/10.1051/matecconf/202235801051.
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Layered Li-rich cathode oxides can provide high specific capacity due to oxygen anion redox involving in charge compensation process during cycling, but there is a severe structural transition from layered to spinel accompanying with irreversible oxygen loss during cycling, which lead to electrochemical degradation. The current researches show that the irreversible oxygen evolution reaction of layered lithiumrich materials in the first cycle mainly comes from the surface lattice oxygen, so the surface modification by the materials with more stable structure is one of the effective ways to improve the electrochemical performance of layered lithium-rich materials. In this paper, we report a modified layered lithium-rich cathode material by surface coating of inverse spinel MnFe2O4. The inverse spinel has strong polarization effect on anion migration due to its different atoms occupying octahedral sites from layered structure and it can also modulate the Fermi level and stretching the O-O bond, thereby increasing the energy barrier for surface oxygen oxidization. Furthermore, the three-dimensional connected tunnel structure of the inverse spinel also makes the surface layer of the material have a faster lithium ion transferring rate, and a large number of lithium storable vacancies inside of it improved the Li+ intercalation efficiency, initial coulombic efficiency and rate performance. Compared with the unmodified sample, the modified material coated with 2% MnFe2O4 has superior cycle stability and outstanding rate performance. It is hoped our work would provide the knowledge for the future development of high-performance cathode materials for Li-ion batteries.
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Uxa, Daniel, Lars Dörrer, Michal Schulz, Nicole Knoblauch, Peter Fielitz, Martin Roeb, Martin Schmücker, and Günter Borchardt. "Investigation of CO2 Splitting on Ceria-Based Redox Materials for Low-Temperature Solar Thermochemical Cycling with Oxygen Isotope Exchange Experiments." Processes 11, no. 1 (December 30, 2022): 109. http://dx.doi.org/10.3390/pr11010109.
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The surface exchange and bulk transport of oxygen are highly relevant to ceria-based redox materials, which are envisaged for the solar thermochemical splitting of carbon dioxide in the future. Experimental investigations of oxygen isotope exchange on CeO2-δ, Ce0.9M3+0.1O1.95-δ (with M3+ = Y, Sm) and Ce0.9M4+0.1O2-δ (with M4+ = Zr) samples were carried out for the first time utilizing oxygen-isotope-enriched C18O2 gas atmospheres as the tracer source, followed by Secondary Ion Mass Spectrometry (SIMS), at the temperature range 300 ≤ T ≤ 800 °C. The experimental K˜O and D˜O data reveal promising results in terms of CO2 splitting when trivalent (especially Sm)-doped ceria is employed. The reaction temperatures are lower than previously proposed/reported due to the weak temperature dependency of the parameters K˜O and D˜O. The majority of isotope exchange experiments show higher values of K˜O and D˜O for Sm-doped cerium dioxide in comparison to Y-doped and Zr-doped ceria, as well as nominally undoped ceria. The apparent activation energies for both K˜O and D˜O are lowest for Sm-doped ceria. Using Zr-doped cerium oxide exhibits various negative aspects. The Zr-doping of ceria enhances the reducibility, but the possible Zr-based surface alteration effects and dopant-induced migration barrier enhancement in Zr-doped ceria are detrimental to surface exchange and oxygen diffusion at lower temperatures of T ≤ 800 °C.
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Tagliabue, A., and C. Völker. "Towards accounting for dissolved iron speciation in global ocean models." Biogeosciences Discussions 8, no. 2 (March 16, 2011): 2775–810. http://dx.doi.org/10.5194/bgd-8-2775-2011.
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Abstract. The trace metal iron (Fe) is now routinely included in state-of-the-art ocean general circulation and biogeochemistry models (OGCBMs) because of its key role as a limiting nutrient in regions of the world ocean important for carbon cycling and air-sea CO2 exchange. However, the complexities of the seawater Fe cycle, which impact its speciation and bioavailability, are highly simplified in such OGCBMs to avoid high computational costs. In a similar fashion to inorganic carbon speciation, we outline a means by which the complex speciation of Fe can be included in global OGCBMs in a reasonably cost-effective manner. We use our Fe speciation to suggest the global distribution of different Fe species is tightly controlled by environmental variability (temperature, light, oxygen and pH) and the assumptions regarding Fe binding ligands. Impacts on bioavailable Fe are highly sensitive to assumptions regarding which Fe species are bioavailable. When forced by representations of future ocean circulation and climate we find large changes to the speciation of Fe governed by pH mediated changes to redox kinetics. We speculate that these changes may exert selective pressure on phytoplankton Fe uptake strategies in the future ocean. We hope our modeling approach can also be used as a ''test bed'' for exploring our understanding of Fe speciation at the global scale.
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Rahman, Anis Ur, Nighat Zarshad, Wu Jianghua, Muslim Shah, Sana Ullah, Guigen Li, Muhammad Tariq, and Asad Ali. "Sodium Pre-Intercalation-Based Na3-δ-MnO2@CC for High-Performance Aqueous Asymmetric Supercapacitor: Joint Experimental and DFT Study." Nanomaterials 12, no. 16 (August 18, 2022): 2856. http://dx.doi.org/10.3390/nano12162856.
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Electrochemical energy storage devices are ubiquitous for personal electronics, electric vehicles, smart grids, and future clean energy demand. SCs are EES devices with excellent power density and superior cycling ability. Herein, we focused on the fabrication and DFT calculations of Na3-δ-MnO2 nanocomposite, which has layered MnO2 redox-active sites, supported on carbon cloth. MnO2 has two-dimensional diffusion channels and is not labile to structural changes during intercalation; therefore, it is considered the best substrate for intercalation. Cation pre-intercalation has proven to be an effective way of increasing inter-layered spacing, optimizing the crystal structure, and improving the relevant electrochemical behavior of asymmetric aqueous supercapacitors. We successfully established Na+ pre-intercalated δ-MnO2 nanosheets on carbon cloth via one-pot hydrothermal synthesis. As a cathode, our prepared material exhibited an extended potential window of 0–1.4 V with a remarkable specific capacitance of 546 F g−1(300 F g−1 at 50 A g−1). Moreover, when this cathode was accompanied by an N-AC anode in an asymmetric aqueous supercapacitor, it illustrated exceptional performance (64 Wh kg−1 at a power density of 1225 W kg−1) and incomparable potential window of 2.4 V and 83% capacitance retention over 10,000 cycles with a great Columbic efficiency.
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Romadina, Elena, and Keith J. Stevenson. "(Digital Presentation) Novel Organic Materials for Non-Aqueous Redox Flow Batteries: Implementation of Triarylamine and Phenazine Core Structures." ECS Meeting Abstracts MA2022-01, no. 48 (July 7, 2022): 2039. http://dx.doi.org/10.1149/ma2022-01482039mtgabs.
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The rapid growth of the role of renewable energy sources dictates new requirements for the efficiency, stability and scales of electrochemical energy storage devices for stationary applications [1]. Among the storage systems, redox flow batteries (RFBs) are regarded as a promising technology, since their advantages of excellent scalability, low cost, easy fabrication and operation, long lifetime, and safety. Today inorganic RFBs are penetrating the market, however, low specific capacity in conjunction with low electrochemical stability window of aqueous electrolytes (≈1.5 V) and safety issues, hinders their wide-scale commercialization. [2]. Replacing the inorganic materials with environment-friendly organic redox-active molecules may solve the capacity problems and safety issues. Moreover, the application of non-aqueous electrolytes provides a wide electrochemical stability window (e.g., up to 5 V for acetonitrile) enabling high-voltage batteries with increased energy density [3]. Within the framework of the current project, we implemented a comprehensive study for a large group of novel highly soluble organic materials based on aromatic amines with general formulas of NPh3RnBrm (M1-M4) and N2Ph5RnBrm (M5-M7) where R=-(OCH2CH2)2-OCH3 (Fig. 1a). All the compounds demonstrated high solubility in MeCN (from >2.2 M up to complete miscibility), which can potentially enable outstanding specific capacities of organic RFBs approaching 134 Ah L-1 [4]. Compounds demonstrated one or two quasi-reversible electron transition processes with redox potential up to 0.6 V vs. Ag/AgNO3 electrode, which makes them perspective for the investigation in the RFBs as catholyte materials. For the RFB investigation butylviologen perchlorate (-0.75V vs. Ag/AgNO3, ~1.15 V battery voltage) was chosen as the redox pair (Fig. 1b, d). On the first step, the selection of the most appropriate electrolyte was performed: it was shown that the usage of electrolytes that contained lithium cations (Li+) and hexafluorophosphate anions (PF6 -) leads to fast decreasing of all the parameters of the RFBs, whereas the usage of the tetrabutylammonium tetrafluoroborate (TBABF4) and NaClO4 produces the stable characteristics (Fig. 1e). Final RFB tests proved that the most promising systems are capable to exhibit 65% of maximum capacities and more than 95% coulombic efficiency after 50 cycles [4] (Fig. 1f). In the next step, we focused on the creation of low-voltage anolyte material: thus, we synthesized and investigated novel phenazine derivative with oligomeric ethylene glycol ether substituents as promising anolyte material for non-aqueous organic RFBs (Fig. 1c) [5]. The designed compound undergoes a reversible and stable reduction at -1.72 V vs. Ag/AgNO3 and demonstrates excellent (>2.5 M) solubility in MeCN. A non-aqueous organic redox flow battery assembled using novel phenazine derivative as anolyte and substituted triarylamine derivative as a catholyte exhibited high specific capacity (~93% from the theoretical value), >95% coulombic efficiency, 65% utilization of active materials and good charge-discharge cycling stability (Fig. 1g). To summarize, triarylamine-based and phenazine-based materials establish themselves attractive for future research: obtained redox potentials, high solubility, fast diffusion and kinetics opens promising future directions for their usage as organic cathodic and anodic materials for non-aqueous RFBs. References [1] Panwar N., Kaushik, S., Kothari S. Renewable and Sustainable Energy Reviews 2011, 15 (3), 1513-1524. [2] Placke T., Heckmann A., Schmuch, R., Meister P., Beltrop K., Winter, M. Joule 2018, 2 (12), 2528-2550. [3] Elgrishi N., Rountree K., McCarthy B., Rountree E., Eisenhart T., Dempsey J. J. Chem. Educ. 2018, 95 (2), 197-206 [4] (a) Romadina E., Volodin I., Stevenson K., Troshin P. JMC-A, 2021, 9, 8303-8307; (b) Romadina E., Troshin P., Stevenson K., Patent RU 2 752 762 C1 “Highly soluble triphenylamine-based catholyte and electrochemical current source based on it” [5] Romadina E., Komarov D., Stevenson K., Troshin P. ChemComm, 2021, 57, (24), 2986-2989 Acknowledgements Romadina Elena acknowledges the support provided by Haldor Topsøe A/S Scholarship 2021. Figure 1
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Hoang Huy, Vo Pham, Luong Trung Hieu, and Jaehyun Hur. "Zn Metal Anodes for Zn-Ion Batteries in Mild Aqueous Electrolytes: Challenges and Strategies." Nanomaterials 11, no. 10 (October 17, 2021): 2746. http://dx.doi.org/10.3390/nano11102746.
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Over the past few years, rechargeable aqueous Zn-ion batteries have garnered significant interest as potential alternatives for lithium-ion batteries because of their low cost, high theoretical capacity, low redox potential, and environmentally friendliness. However, several constraints associated with Zn metal anodes, such as the growth of Zn dendrites, occurrence of side reactions, and hydrogen evolution during repeated stripping/plating processes result in poor cycling life and low Coulombic efficiency, which severely impede further advancements in this technology. Despite recent efforts and impressive breakthroughs, the origin of these fundamental obstacles remains unclear and no successful strategy that can address these issues has been developed yet to realize the practical applications of rechargeable aqueous Zn-ion batteries. In this review, we have discussed various issues associated with the use of Zn metal anodes in mildly acidic aqueous electrolytes. Various strategies, including the shielding of the Zn surface, regulating the Zn deposition behavior, creating a uniform electric field, and controlling the surface energy of Zn metal anodes to repress the growth of Zn dendrites and the occurrence of side reactions, proposed to overcome the limitations of Zn metal anodes have also been discussed. Finally, the future perspectives of Zn anodes and possible design strategies for developing highly stable Zn anodes in mildly acidic aqueous environments have been discussed.
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Chen, Hsiang-Chun, Yang-Ru Lyu, Alex Fang, Gang-Juan Lee, Lakshmanan Karuppasamy, Jerry J. Wu, Chung-Kwei Lin, Sambandam Anandan, and Chin-Yi Chen. "The Design of ZnO Nanorod Arrays Coated with MnOx for High Electrochemical Stability of a Pseudocapacitor Electrode." Nanomaterials 10, no. 3 (March 6, 2020): 475. http://dx.doi.org/10.3390/nano10030475.
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Tremendous efforts have been made on the development of unique electrochemical capacitors or pseudocapacitors due to the overgrowing electrical energy demand. Here, the authors report a new and simple strategy for fabricating hybrid MnOx-coated ZnO nanorod arrays. First, the vertically aligned ZnO nanorods were prepared by chemical bath deposition (CBD) as a template providing a large surface area for active material deposition. The manganese oxide was subsequently coated onto the surface of the ZnO nanorods to form a hybrid MnOx-coated ZnO nanostructure by anodic deposition in a manganese acetate (MnA)-containing aqueous solution. The hybrid structure of MnOx-coated ZnO nanorod arrays exhibits a large surface area and high conductivity, essential for enhancing the faradaic processes across the interface and improving redox reactions at active MnOx sites. A certain concentration of the deposition solution was selected for the MnOx coating, which was studied as a function of deposition time. Cyclic voltammetry (CV) curves showed that the specific capacitance (SC) of the MnOx-coated ZnO nanostructure was 222 F/g for the deposition times at 10 s when the concentration of MnA solution was 0.25 M. The unique hybrid nanostructures also exhibit excellent cycling stability with >97.5% capacitance retention after 1200 CV cycles. The proposed simple and cost-effective method of fabricating hybrid nanostructures may pave the way for mass production of future intelligent and efficient electrochemical energy storage devices.
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Bigarella, Carolina L., Pauline Rimmele, Brigitte Izac, Valentina d'Escamard, and Saghi Ghaffari. "Foxo3-Mediated Redox Regulation Is Required for DNA Damage Response in Hematopoietic Stem Cells." Blood 120, no. 21 (November 16, 2012): 2295. http://dx.doi.org/10.1182/blood.v120.21.2295.2295.
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Abstract Abstract 2295 Stringent regulation of redox status is critical to the control of hematopoietic stem cell (HSC) quiescence and to the maintenance of HSC pool. However mechanisms by which oxidative stress controls HSC quiescence versus cycling remain unknown. Foxo3 transcription factor is required for the regulation of HSC quiescence and for the maintenance of hematopoietic and leukemic stem cell pool. Redox regulation is key to the Foxo3 control of HSC pool. ROS accumulation in Foxo3 null HSC mediates in vivo activation of p53, and increased p21 expression leading to an arrest in the G2/M phase of cell cycle associated with loss of quiescence. We hypothesized that ROS may regulate HSC quiescence versus cycling via control of DNA damage repair program. To address this question, we examined whether Foxo3 is involved in DNA damage response of HSC. We first evaluated by immunostaining phosphorylation of histone H2AX variant (γH2AX), a hallmark sensor of DNA strand break, in LSK (Lin−Sca-1+c-Kit+) cells freshly isolated from Foxo3−/− bone marrow. We found the number of cells with nuclear γH2AX foci significantly increased in Foxo3−/− LSK cells (n=100; >5 foci/nuclei) in comparison with wild type (WT)-LSK. We subsequently confirmed and quantified these data by flow cytometry analysis of γH2AX. Together these analyses showed that loss of Foxo3 leads to increased γH2AX levels in LSK cells at the steady state. We next evaluated the presence of DNA breaks, by submitting Foxo3−/− versus WT LSK FACS-sorted cells to single-cell gel electrophoresis (Comet Assay). These investigations confirmed that LSK cells from Foxo3−/− mice accumulate DNA breaks at the steady state, as the percentage of comet shape cells (4 fold) and comet length (3 fold) were all increased in Foxo3 mutant LSK. We then asked whether the increased ROS accumulation had any direct role in damaging DNA in Foxo3−/− LSK. Using a fluorescent probe specific for the most common oxidative DNA damage lesion, the 8-hydroxyguanine base (8-OxoG), we further showed that Foxo3−/− LSK cells exhibit oxidative DNA damage. To further investigate the potential function of ROS in the control of HSC DNA damage response, we treated Foxo3−/− and WT mice for 14 days with the ROS scavenger N-acetyl-cysteine (NAC; 100 mg/Kg/day) in vivo. NAC treatment reduced by four fold γH2AX in Foxo3−/− LSK cells to levels similar to that in WT-LSK cells. Similarly, comet assay analysis of FACS-sorted LSK cells from NAC-treated WT and Foxo3−/− mice showed a two fold reduction of DNA breaks. These results suggest that increase in ROS damage DNA and triggers DNA damage response in Foxo3−/− LSK cells at the steady state. Additionally, expression of a number of genes involved in DNA damage repair including Xrcc5 (Ku80) and Xrcc6 (Ku70) was highly downregulated in both long-term-HSC (LT-HSC, LSK-CD150+CD48−) and LSK populations as evidenced by Q-RT-PCR on the Fluidigm™ microfluidics array technology. Together these results strongly suggest that Foxo3-mediated redox regulation is required for protection of DNA from accumulating damage at the steady state in HSC. We further investigated whether ROS-mediated activation of p53 in Foxo3 null HSCs limits the extent of accumulation of DNA damage in HSC. To address this question we crossed p53+/−Foxo3+/− double heterozygous animals to generate p53-Foxo3 double knockout mice. Loss of p53 in Foxo3−/− mice led to significant rise in lymphocyte counts and decrease in neutrophil counts in comparison with Foxo3−/−, indicating a potential shift in lineage determination from HSC. To our surprise, loss of one allele of p53 in Foxo3-null mice significantly reduced gH2AX staining and DNA breaks, as analyzed respectively by flow cytometry and comet assay of sorted LSK cells. While the rescue of DNA damage in Foxo3−/− HSCs as result of loss of p53 was unexpected it is not clear whether it is related to the impact on the fate of HSC. The clarification of these questions in future studies will be important for understanding mechanisms that control the emergence of leukemic stem cells. Together these studies suggest that Foxo3 guards DNA from damage in HSC at the steady state. In addition they indicate an important function for ROS modulation in the in vivo regulation of DNA damage response in HSC. Altogether understanding mechanisms that control ROS modulation of DNA damage response are likely to advance our understanding of the regulation of normal hematopoietic and leukemic stem cell quiescence. Disclosures: No relevant conflicts of interest to declare.
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Llewellyn, Alice V., Andrew S. Leach, Isabella Mombrini, Alessia Matruglio, Jiecheng Diao, Chun Tan, Thomas M. M. Heenan, et al. "Understanding the Degradation Mechanisms of Lithium Ion Batteries Using in-Situ Multi-Scale Diffraction Techniques." ECS Meeting Abstracts MA2022-01, no. 2 (July 7, 2022): 177. http://dx.doi.org/10.1149/ma2022-012177mtgabs.
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Advanced Li-ion batteries adopting new cathode chemistries are required for the successful widespread transition to electric vehicles (EVs) and renewable energy sources, aiming for high energy density, long cycle life, and good rate capability. Commercial candidates for EV batteries include Ni-rich Li(NixMnyCo1−x-y)O2 (NMC) cathodes, with Ni:Mn:Co ratios of 8:1:1 (NMC811) and higher. These are favored because of their high specific capacity (~ 200 mAh g-1)and reduced cobalt content. Despite all of the advantages, these materials suffer from a range of degradation modes, many of which are associated with the redox and crystallographic behavior at high states of charge. In particular, Ni-rich cathodes suffer from several limitations, such as rapid capacity fade in comparison to NMC stoichiometries with lower Ni content. In addition, they also have a lower onset voltage for oxygen release and subsequent surface reconstruction leading to the formation of spinel and rock salt phases which impede (de)lithiation and therefore the achievable capacity of the cell.1 Crystallographic properties of electrode materials are intrinsically linked to the electrochemical performance of the cell. NMC materials suffer from anisotropic changes in the crystal structure during cycling which induces strain and leads to issues such as crack formation, expediting degradation. One method to tackle capacity fade is to switch to single-crystal morphologies (particle size 1-3 μm) which have better mechanical stability than conventional polycrystalline morphologies (secondary agglomerate particles ~ 10 μm made up of primary particles which are 100 nm – 1 μm in size) and have less propensity to form extensive rock-salt layers. It is thought that the single-crystal morphology helps to reduce stress in the material as the anisotropic stress in polycrystalline cathodes is concentrated at grain boundaries. However, there is still a limited understanding of the subtle mechanistic differences between the two materials during cycling.2 A multi-scale approach is required to gain a more comprehensive understanding of the degradation mechanisms at play and how they initiate and propagate. In this work, synchrotron diffraction methods were employed at the crystal, particle and cell scale using a variety of techniques including in-situ Bragg Coherent Diffraction Imaging (BCDI), 3D-XRD and operando high-resolution XRD. Intra-particle, inter-particle and electrode level heterogeneities were observed during cycling, both in pristine and aged samples. It is believed that these heterogeneities accelerate the loss of performance at the cell level by inducing crack formation which can then be observed in X-ray computed tomography data acquired in simultaneous lab studies. The overarching goal of these investigations is to add to the understanding of complex degradation mechanisms for Ni-rich layered transition metal oxide cathodes, ultimately aiding in the informed development of future battery electrode materials. References: 1] Xu, C. et al., Phase Behaviour during Electrochemical Cycling of Ni‐Rich Cathode Materials for Li‐Ion Batteries. Adv. Energy Mater. 2021, 11, 2003404. 2] Yin, S. et al., Fundamental and solutions of microcracks in Ni-rich layered oxide cathode materials of lithium-ion batteries. Nano Energy, 2021, 83, 105854.
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Yadav, Dharmendra K., Surendra Kumar, Mahesh K. Teli, Ravikant Yadav, and Sandeep Chaudhary. "Molecular Targets for Malarial Chemotherapy: A Review." Current Topics in Medicinal Chemistry 19, no. 10 (July 19, 2019): 861–73. http://dx.doi.org/10.2174/1568026619666190603080000.
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The malaria parasite resistance to the existing drugs is a serious problem to the currently used antimalarials and, thus, highlights the urgent need to develop new and effective anti-malarial molecules. This could be achieved either by the identification of the new drugs for the validated targets or by further refining/improving the existing antimalarials; or by combining previously effective agents with new/existing drugs to have a synergistic effect that counters parasite resistance; or by identifying novel targets for the malarial chemotherapy. In this review article, a comprehensive collection of some of the novel molecular targets has been enlisted for the antimalarial drugs. The targets which could be deliberated for developing new anti-malarial drugs could be: membrane biosynthesis, mitochondrial system, apicoplasts, parasite transporters, shikimate pathway, hematin crystals, parasite proteases, glycolysis, isoprenoid synthesis, cell cycle control/cycline dependent kinase, redox system, nucleic acid metabolism, methionine cycle and the polyamines, folate metabolism, the helicases, erythrocyte G-protein, and farnesyl transferases. Modern genomic tools approaches such as structural biology and combinatorial chemistry, novel targets could be identified followed by drug development for drug resistant strains providing wide ranges of novel targets in the development of new therapy. The new approaches and targets mentioned in the manuscript provide a basis for the development of new unique strategies for antimalarial therapy with limited off-target effects in the near future.
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Reber, David, Jonathan R. Thurston, Maximilian Becker, Gregory F. Pach, Marc E. Wagoner, Brian H. Robb, Scott E. Waters, and Michael Marshak. "Mediating Anion-Cation Interactions to Improve Aqueous Flow Battery Electrolytes." ECS Meeting Abstracts MA2022-02, no. 46 (October 9, 2022): 1709. http://dx.doi.org/10.1149/ma2022-02461709mtgabs.
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Development of energy dense aqueous redox flow batteries is held back by high cost, chemical instability of highly soluble active compounds, or solubility limits of more suitable active materials. Here, we study solubilizing effects of inexpensive polar additives on metal-organic chelates based on aminopolycarboxylate ligands, a particularly promising family of compounds for application in negative electrolytes in near neutral pH aqueous flow batteries with demonstrated discharge voltages as high as 2.1 V.[1] Upon addition of certain additives, cation-dependent solubilities of chromium 1,3-propylenediaminetetraacetate (CrPDTA) and chromium ethylenediaminetetraacetate (CrEDTA) salts are enhanced by 60% and 125%, respectively, resulting in maximum solubilities of e.g., 1.5 м for KCrPDTA and 2.2 м for NaCrEDTA. We elucidate the mechanism behind enhanced solubility of aminopolycarboxylate chelates and study the impact of the additive on the electrochemical performance of near neutral pH flow batteries, demonstrating 50% higher anolyte capacities, up to 40 Ah L−1, than previously reported for this class of materials. In capacity balanced full cells, using ferrocyanide catholytes, we observe excellent Coulombic efficiencies >99.6% and voltage efficiencies >78% at average discharge voltages of ca. 1.5 V when cycling at 100 mA cm−2. Peak discharge power densities of >400 mW cm−2 further highlight the potential of our facile and cost-effective approach. Finally, we discuss avenues for future work to further exploit the solubilizing effect described herein. References: [1] B.H. Robb, J.M. Farrell, M.P. Marshak, Chelated chromium electrolyte enabling high-voltage aqueous flow batteries, Joule 2019, 3, 2503–2512.
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Kwabi, David G. "Modeling and Experimental Analysis of pH Swing-Based Approaches to Electrochemical CO2 Capture." ECS Meeting Abstracts MA2022-02, no. 58 (October 9, 2022): 2186. http://dx.doi.org/10.1149/ma2022-02582186mtgabs.
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The use of renewable electricity to drive large-scale electrochemical CO2 removal and concentration from point sources, air, and seawater is receiving considerable interest as one strategy for mitigating climate change.1 The low concentration of CO2 in air however makes rapid and energy-efficient CO2 capture challenging. Understanding and optimizing the energetic cost of CO2 separation at practically reasonable throughputs is a prerequisite for engineering devices that can be widely deployed. I will review our past and current efforts at developing electrochemical pH-swing-based CO2 separation (EPCS) using a combination of modeling and experiments. In EPCS, CO2 is captured from a mixture of gases into an aqueous electrolyte in the form of (bi)carbonate ions when its pH is increased from acidic to strongly alkaline conditions, and then released as a pure gas when the pH is reversed. We have shown that CO2 separation is experimentally possible for less than 100 kJ/molCO2 using such a pH swing cycle that is driven by proton-coupled electron transfer (PCET).2 Thermodynamic modeling shows that the minimum work input for electrochemical CO2 separation is the sum of exergy losses incurred from differences in CO2 partial pressure between the CO2 source/exit streams and the electrolyte. This framework rationalizes minimum work inputs for pH-swing and redox-mediator-based CO2 separation cycles, and motivates the measurement or estimation of the aforementioned CO2 partial pressures in future experimental studies. More recently, we have begun to consider a new design for EPCS in which PCET-active species are conformally attached to the internal surface area of a highly porous electrode, and effect a reversible pH swing in an adjacent layer of aqueous electrolyte upon redox cycling. We have formulated a continuum reaction-transport model that simulates reactive CO2 capture into and release from the electrolyte layer, as well as transport of (bi)carbonate species, and protons, in response to an applied current or voltage. Possible pathways toward achieving an energetic cost of direct air capture of CO2 less than 100 kJ/molCO2 will be discussed, as well as our efforts toward experimental demonstration of this concept. References Renfrew, S. E.; Starr, D. E.; Strasser, P., Electrochemical Approaches toward CO2 Capture and Concentration. ACS Catalysis 2020, 10 (21), 13058-13074. Jin, S.; Wu, M.; Gordon, R. G.; Aziz, M. J.; Kwabi, D. G., pH swing cycle for CO2 capture electrochemically driven through proton-coupled electron transfer. Energy & Environmental Science 2020.
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Raza, Hassan, Junye Cheng, Guohua Chen, and Zheng Guangping. "Low-Temperature Calcination of Metal-Organic Frameworks(MOFs) to Derive the High Entropy Stabilized Oxide for High Performance Lithium-Sulfur Batteries." ECS Meeting Abstracts MA2022-01, no. 6 (July 7, 2022): 2432. http://dx.doi.org/10.1149/ma2022-0162432mtgabs.
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Lithium-sulfur (Li-S) battery owing to high energy density and theoretical capacity is anticipated as a high-performance rechargeable power source for flexible electronic devices and electric vehicles. However, the rapid capacity fade, low Coulombic efficiency, and significant self-discharge capacity loss due to the polysulfides shuttling are the major constraints of its real-world applications. To conquer these challenges, despite the physical encapsulation of polysulfides, chemical interactions between shuttle effect-suppressive sulfur host materials and soluble lithium polysulfides have recently been emphasized. Herein, a novel approach to synthesize the high entropic stabilized oxide (HEO) at low temperature is developed from the self-sacrificing template of metal-organic frameworks (MOFs) to chemically anchor the lithium polysulfides. As-synthesized HEO850 at 850 ºC (transition temperature) exhibited a single-phase rocksalt crystalline structure with homogenous dispersion of Ni, Mg, Cu, Co, and Zn and reversible entropic phase stabilization in the certain temperature range (750-850 ºC). When employed as a chemical anchor to lithium polysulfides (LIPSs) and compared the electrochemical performance of Li-S cells with medium configurational entropic oxide (MEOs) (HEOs-one metal cation), low entropy oxide (LEOs) (HEOs-three metal cations), and routine sulfur ketjen black (S/KB) cells, it revealed a competitive reversible capacity, excellent cycling stability and a low capacity decay rate by immobilizing the LIPSs and facilitating the redox reaction in the cathode. The cells with HEO850/KB/S cathode delivered a higher initial specific discharge capacity of 1244.1 mAh g-1 than those of MEO850/S/KB (979.625 mAh g-1), LEO850/S/KB (908 mAh g-1), and S/KB (966 mAh g-1). After 800 cycles of continuous charging and discharging at 0.5 C, the capacity of 784.1 mAh g-1 with outstanding Coulombic efficiency of 99.66 % is still retained demonstrating excellent cycling stability with a negligible capacity fade rate of 0.04% per cycle. This outstanding performance could be attributed to the synergistic contribution and exposure of numerous active sites of randomly dispersed elements in the HEO850. This study not only highlights the extraordinary electrochemical performance of Li-S battery with efficient immobilization of LIPSs but also provide a novel strategy for the synthesis of HEOs at lower calcination temperature for various energy conversion and storage applications. After getting confidence with these prilimary results, Ti-based HEOs owing to both high ionic and electric conductivities will be investigated at coin and pouch cell level as future research direction.
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Phela, Manoko, Phumlani Fortune Msomi, and Rhudzani Sigwadi. "Proton Exchange Membrane for Iron Air/Flow Battery Application." ECS Meeting Abstracts MA2022-02, no. 4 (October 9, 2022): 513. http://dx.doi.org/10.1149/ma2022-024513mtgabs.
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Iron air/redox flow battery is the next promising battery system that can bridge the drawbacks of a static battery, at least in medium to high storage systems, due to the distinguishing difference from its static counterpart. It comes with the main advantages: the high current discharge and a flowing electrolyte, which can significantly suppress the formation of dendrite and passivation without imposing permanent damage to the cell structure. Iron, the fourth most abundant metal on the earth's crust, comes at a lower cost and requires less corrosion protection. This technology has received less attention than others due to overpotential/overvoltage and high Hydrogen evolution reaction on the anode. Different promising approach has been explored to improve the cycling stability of iron air batteries; by adding different electrolyte additives to suppress passivation and hydrogen evolution during discharge, improving the air cathode design by including dual or bifunctional electrocatalyst, and recent modification of the anode has helped realize a better iron air battery by facilitating a high surface area iron electrode using nanosized iron particle, and these create more electrode available to electrolyte and further adding a suitable additive to the electrode and electrolyte and increase charge capacity. Nonetheless, the battery working components begin to degrade as they interact; these cannot be stopped as batteries are consumable objects, but they can be delayed by improving the membrane separator's physical-chemical properties like conductivity, swelling ratio, selectivity, and membrane stability. Membrane's critical role aid in the improvement of the battery performance by separating the air cathode and metal anode electrode compartments to prevent short-circuiting, facilitate proton transfer, act as an electron insulator, and prevent fuel crossover, therefore improving the battery cycle life. The presentation will cover the basic working principle of the iron-air/redox flow battery and its prospective future in grid application and a brief report on the role of composite proton exchange membrane and their influence on cycle stability. References Sakai, T., Inoishi, A., Ogushi, M., Ida, S., & Ishihara, T. (2016). Characteristics of fe-air battery using Y2O3-stabilized-ZrO2 electrolyte with Ni–Fe electrode and Ba0.6La0.4CoO3-δ electrode operated at intermediate temperature. Journal of Energy Storage, 7, 115-120. Abbasi, A., Hosseini, S., Somwangthanaroj, n., Cheacharoen, R., Olaru, S., & Kheawhom, S. (2020). Discharge profile of a zinc-air flow battery at various electrolyte flow rates and discharge currents. Scientific Data, 7(1), 196. Leung, P., Li, X., De León, C. P., Berlouis, L., Low, C. J., & Walsh, F. C. (2012). Progress in redox flow batteries, remaining challenges and their applications in energy storage. Rsc Advances, 2(27), 10125-10156. Karomah, A. (2021). Iron-air batteries: A breakthrough in green energy. . Retrieved 17 march, 2022, from https://www.azom.com/article.aspx?ArticleID=20872. McKerracher, R., Ponce de León, C., Wills, R. G. A., Shah, A., & Walsh, F. (2014). A review of the Iron–Air secondary
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Freitas, Felipe S., Philip A. Pika, Sabine Kasten, Bo B. Jørgensen, Jens Rassmann, Christophe Rabouille, Shaun Thomas, Henrik Sass, Richard D. Pancost, and Sandra Arndt. "New insights into large-scale trends of apparent organic matter reactivity in marine sediments and patterns of benthic carbon transformation." Biogeosciences 18, no. 15 (August 13, 2021): 4651–79. http://dx.doi.org/10.5194/bg-18-4651-2021.
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Abstract. Constraining the mechanisms controlling organic matter (OM) reactivity and, thus, degradation, preservation, and burial in marine sediments across spatial and temporal scales is key to understanding carbon cycling in the past, present, and future. However, we still lack a detailed quantitative understanding of what controls OM reactivity in marine sediments and, consequently, a general framework that would allow model parametrization in data-poor areas. To fill this gap, we quantify apparent OM reactivity (i.e. OM degradation rate constants) by extracting reactive continuum model (RCM) parameters (a and v, which define the shape and scale of OM reactivity profiles, respectively) from observed benthic organic carbon and sulfate dynamics across 14 contrasting depositional settings distributed over five distinct benthic provinces. We further complement the newly derived parameter set with a compilation of 37 previously published RCM a and v estimates to explore large-scale trends in OM reactivity. Our analysis shows that the large-scale variability in apparent OM reactivity is largely driven by differences in parameter a (10−3–107) with a high frequency of values in the range 100–104 years. In contrast, and in broad agreement with previous findings, inversely determined v values fall within a narrow range (0.1–0.2). Results also show that the variability in parameter a and, thus, in apparent OM reactivity is a function of the whole depositional environment, rather than traditionally proposed, single environmental controls (e.g. water depth, sedimentation rate, OM fluxes). Thus, we caution against the simplifying use of a single environmental control for predicting apparent OM reactivity beyond a specific local environmental context (i.e. well-defined geographic scale). Additionally, model results indicate that, while OM fluxes exert a dominant control on depth-integrated OM degradation rates across most depositional environments, apparent OM reactivity becomes a dominant control in depositional environments that receive exceptionally reactive OM. Furthermore, model results show that apparent OM reactivity exerts a key control on the relative significance of OM degradation pathways, the redox zonation of the sediment, and rates of anaerobic oxidation of methane. In summary, our large-scale assessment (i) further supports the notion of apparent OM reactivity as a dynamic ecosystem property, (ii) consolidates the distributions of RCM parameters, and (iii) provides quantitative constraints on how OM reactivity governs benthic biogeochemical cycling and exchange. Therefore, it provides important global constraints on the most plausible range of RCM parameters a and v and largely alleviates the difficulty of determining OM reactivity in RCM by constraining it to only one variable, i.e. the parameter a. It thus represents an important advance for model parameterization in data-poor areas.
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Kim, Kyung-Hwan, and Yun-Hyuk Choi. "Surface oxidation of cobalt carbonate and oxide nanowires by electrocatalytic oxygen evolution reaction in alkaline solution." Materials Research Express 9, no. 3 (March 1, 2022): 034001. http://dx.doi.org/10.1088/2053-1591/ac5f89.
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Abstract The electrocatalytic water electrolysis is the most eco-friendly technique for hydrogen generation, which is governed by the electrode reaction kinetics involving cathodic hydrogen evolution reaction (HER) and anodic oxygen evolution reaction (OER) in common alkaline electrolytes. Cobalt oxide (Co3O4) and related compounds are the most efficient OER catalysts, replacing the noble metals. In this work, the surface oxidations of the cobalt carbonate (Co(CO3)0.5OH·0.11H2O) and Co3O4 nanowires during the OER are carefully investigated by contrasting the polarization curves, Tafel plots, and x-ray photoelectron spectroscopy (XPS) spectra, before and after the 1000th cyclic voltammetry (CV) cycling in 1 M KOH alkaline solution. The overpotentials required to reach a current density (j) of 20 mA cm−2 (η 20) are estimated to be 313 mV for the 300 °C-calcined Co3O4, 350 mV for the 400 °C-calcined Co3O4, 365 mV for the 500 °C-calcined Co3O4, and 373 mV for the cobalt carbonate (Co(CO3)0.5OH·0.11H2O). The Tafel slope of cobalt carbonate (Co(CO3)0.5OH·0.11H2O) nanowires is the highest at 93 mV dec−1, while it is measured to be 57 mV dec−1 for the 300 °C-calcined Co3O4, 47 mV dec−1 for the 400 °C-calcined Co3O4, and 79 mV dec−1 for the 500 °C-calcined Co3O4. As a result, the oxidation from Co2+ to Co3+ within Co3O4 during the OER is detected, which improves the OER activity. On the other hand, the formation of cobalt hydoxide is found on the surface of the Co3O4 nanowires during the OER in alkaline solution, which decreases the OER activity. For the surface oxidation of the cobalt carbonate (Co(CO3)0.5OH·0.11H2O) nanowires, the increase in the amounts of Co3+ and oxygen vacancy and the formation of O-C-O and carbonates are found, which highly enhance the OER activity. These findings indicate that the surface redox kinetics during the electrocatalytic reactions should be considered important in order to enhance the electrocatalytic activity, and furthermore can provide insight into future challenges in designing advanced electrocatalysts.