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1
Rahman, Sheikh Tareq, Kyong Yop Rhee, and Soo-Jin Park. "Nanostructured multifunctional electrocatalysts for efficient energy conversion systems: Recent perspectives." Nanotechnology Reviews 10, no. 1 (January 1, 2021): 137–57. http://dx.doi.org/10.1515/ntrev-2021-0008.
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Abstract Electrocatalysts play a significant performance in renewable energy conversion, supporting several sustainable methods for future technologies. Because of the successful fabrication of distinctive oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) electrocatalysts, bifunctional ORR/OER and HER/OER electrocatalysts have become a hot area of contemporary research. ORR, OER, and HER have gained considerable attention because of their strong performance in different energy conversion and storage devices, including water-splitting devices, fuel cells, and metal–air rechargeable batteries. Therefore, the development of effective nanostructured multifunctional electrocatalysts for ORR, OER, and HER is necessary; and there is a demand for their industrialization for sustainable energy technology. In this review, details of current improvements in multifunctional catalysts for ORR/OER as well as HER/OER are presented, focusing on insight into the theoretical considerations of these reactions through investigation and estimation of different multifunctional catalysts. By analyzing the universal principles for various electrochemical reactions, we report a systematic scheme to clarify the recent trends in catalyzing these reactions over various types of nanostructure catalysts. The relevant reaction pathways and the related activity details for these reactions in the current literature are also included. Overall, the current demands and future outlines for improving the prospects of multifunctional electrocatalysts are discussed.
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Yan, Zhenwei, Shuaihui Guo, Zhaojun Tan, Lijun Wang, Gang Li, Mingqi Tang, Zaiqiang Feng, Xianjie Yuan, Yingjia Wang, and Bin Cao. "Research Advances of Non-Noble Metal Catalysts for Oxygen Evolution Reaction in Acid." Materials 17, no. 7 (April 3, 2024): 1637. http://dx.doi.org/10.3390/ma17071637.
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Water splitting is an important way to obtain hydrogen applied in clean energy, which mainly consists of two half-reactions: hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). However, the kinetics of the OER of water splitting, which occurs at the anode, is slow and inefficient, especially in acid. Currently, the main OER catalysts are still based on noble metals, such as Ir and Ru, which are the main active components. Hence, the exploration of new OER catalysts with low cost, high activity, and stability has become a key issue in the research of electrolytic water hydrogen production technology. In this paper, the reaction mechanism of OER in acid was discussed and summarized, and the main methods to improve the activity and stability of non-noble metal OER catalysts were summarized and categorized. Finally, the future prospects of OER catalysts in acid were made to provide a little reference idea for the development of advanced OER catalysts in acid in the future.
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Morales, Dulce M., Mariya A. Kazakova, Maximilian Purcel, Justus Masa, and Wolfgang Schuhmann. "The sum is more than its parts: stability of MnFe oxide nanoparticles supported on oxygen-functionalized multi-walled carbon nanotubes at alternating oxygen reduction reaction and oxygen evolution reaction conditions." Journal of Solid State Electrochemistry 24, no. 11-12 (June 1, 2020): 2901–6. http://dx.doi.org/10.1007/s10008-020-04667-2.
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Abstract Successful design of reversible oxygen electrocatalysts does not only require to consider their activity towards the oxygen reduction (ORR) and the oxygen evolution reactions (OER), but also their electrochemical stability at alternating ORR and OER operating conditions, which is important for potential applications in reversible electrolyzers/fuel cells or metal/air batteries. We show that the combination of catalyst materials containing stable ORR active sites with those containing stable OER active sites may result in a stable ORR/OER catalyst if each of the active components can satisfy the current demand of their respective reaction. We compare the ORR/OER performances of oxides of Mn (stable ORR active sites), Fe (stable OER active sites), and bimetallic Mn0.5Fe0.5 (reversible ORR/OER catalyst) supported on oxidized multi-walled carbon nanotubes. Despite the instability of Mn and Fe oxide for the OER and the ORR, respectively, Mn0.5Fe0.5 exhibits high stability for both reactions.
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Hong, Yu-Rim, Sungwook Mhin, Jiseok Kwon, Won-Sik Han, Taeseup Song, and HyukSu Han. "Synthesis of transition metal sulfide and reduced graphene oxide hybrids as efficient electrocatalysts for oxygen evolution reactions." Royal Society Open Science 5, no. 9 (September 2018): 180927. http://dx.doi.org/10.1098/rsos.180927.
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The development of electrochemical devices for renewable energy depends to a large extent on fundamental improvements in catalysts for oxygen evolution reactions (OERs). OER activity of transition metal sulfides (TMSs) can be improved by compositing with highly conductive supports possessing a high surface-to-volume ratio, such as reduced graphene oxide (rGO). Herein we report on the relationship between synthetic conditions and the OER catalytic properties of TMSs and rGO (TMS–rGO) hybrids. Starting materials, reaction temperature and reaction time were controlled to synergistically boost the OER catalytic activity of TMS–rGO hybrids. Our results showed that (i) compared with sulfides, hydroxides are favourable as starting materials to produce the desired TMS–rGO hybrid nanostructure and (ii) high reaction temperatures and longer reaction times can increase physico-chemical interaction between TMSs and rGO supports, resulting in highly efficient OER catalytic activity.
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Kim, Yohan, Seongmin Kim, Minyoung Shim, Yusik Oh, Kug-Seung Lee, Yousung Jung, and Hye Ryung Byon. "Alteration of Oxygen Evolution Mechanisms in Layered LiCoO2 Structures By Intercalation of Alkali Metal Ions." ECS Meeting Abstracts MA2022-01, no. 34 (July 7, 2022): 1356. http://dx.doi.org/10.1149/ma2022-01341356mtgabs.
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The word ‘Sustainability’, including carbon neutrality, has dominated the direction of social development over the past decade. In particular, energy conversion reactions through electrochemical methods are one of the efficient methods of obtaining small carbon footprint fuels. The oxygen evolution reaction (OER) is a key step in determining the overall reaction efficiency of fuel-related electrochemical reactions such as CO2 reduction reaction and H2 evolution reaction. However, electron transfer is sluggish for OER due to 4 electrons per one O2 molecule. This promotes multiple studies on the metal oxide electrocatalyst structure. The Alkali-transition metal oxides with the layered structure are one of the attractive OER electrocatalyst series. For example, lithium cobalt oxide (LiCoO2, LCO) presented OER activity through Li+ extraction (delithiation) from the lattice structure. In this work, we investigated the insertion effect of large alkaline cations (A+: Na+, K+, and Cs+) at the delithiated LCO for OER activity and stability. The intercalations of hydrated Na+ and K+ induced significant phase transformation of the delithiated LCO structure. In addition, the relative ratio between Co and alkali metal species determined the average Co oxidation state of LCO. We found that OER activity was improved in the order of Li+ < Na+ < K+, which was associated with the increased Co valence state and the Co-O bond covalency. Consistently, density functional theory (DFT) simulation also predicted the formation of efficient OER active sites by the K+ insertion. In comparison, Cs+ insertion exhibited the highest OER activity and demonstrated different OER processes. Due to the larger Cs+ size, the cation insertion was predominantly achieved at the delithiated LCO surface, resulting in imposing tensile strain to the surface edge. This catalyst showed the significant pH dependency on the OER property, suggesting the lattice-oxygen-based pathway for LCO. However, the bulk structure was preserved with little phase transformation, demonstrating better OER stability than others. In the presentation, I will discuss the catalytic activity responsible for the cation sizes and two different mechanisms in detail. Figure 1
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Wan, Xin, Yingjie Song, Hua Zhou, and Mingfei Shao. "Layered Double Hydroxides for Oxygen Evolution Reaction towards Efficient Hydrogen Generation." Energy Material Advances 2022 (September 7, 2022): 1–17. http://dx.doi.org/10.34133/2022/9842610.
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Electrochemical water splitting is one of the effective ways to obtain highly pure hydrogen. However, as one of the two half reactions, oxygen evolution reaction (OER) has a high overpotential, resulting in the low-energy utilization efficiency. Therefore, numerous electrocatalysts have been developed to reduce the energy barrier of OER. Among them, layered double hydroxides (LDHs) are excellent OER electrocatalysts with flexible composition and structure, which have been widely investigated in the past decade. Recent studies have been focusing on the identification of active sites for LDHs during OER process, trying to reveal clear reaction mechanism for designing more efficient LDHs electrocatalysts. Hence, this review tries to discuss the advances in identifying active site of LDHs based OER electrocatalysts for efficient hydrogen generation. We first introduce the effect of structure, composition, and defects to the OER performance of LDHs. Furthermore, main attention is paid on the active sites and mechanisms during OER, especially the coordination structures and catalytic mechanisms of active sites. At the end of this review, we put forward the existing problems and shortcomings in this fields, and propose the corresponding solutions, aiming to further promote the development of outstanding OER electrocatalysts towards efficient hydrogen production.
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Fukushima, Tomohiro, Masaki Itatani, and Kei Murakoshi. "(Invited) Evaluation of Oxygen Evolution Reaction Electrodes through Machine-Learning Analysis and in-Situ Electrochemical Spectroscopy." ECS Meeting Abstracts MA2024-02, no. 59 (November 22, 2024): 4023. https://doi.org/10.1149/ma2024-02594023mtgabs.
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To enhance the catalysis of the oxygen evolution reaction (OER) at water electrolysis electrodes, it is imperative to eliminate the energy-consuming processes involved in multiple electron and proton transfer reactions. We propose employing a combination of machine-learning analysis of electrochemical activity and in-situ electrochemical Raman observation for the OER electrodes. The OER behavior can be categorized based on the contributions of Ni-OH and Ni-OOH, which serve as key OER intermediates. This information is utilized to elucidate the OER behavior through energetic and intermediate analyses. The presented study provides the direction for designing active OER catalysis in the future.
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Chae, Sangwoo, Akihito Shio, Tomoya Kishida, Kosuke Furutono, Yumi Kojima, Gasidit Panomsuwan, and Takahiro Ishizaki. "Synthesis of High-Entropy Perovskite Hydroxides as Bifunctional Electrocatalysts for Oxygen Evolution Reaction and Oxygen Reduction Reaction." Materials 17, no. 12 (June 17, 2024): 2963. http://dx.doi.org/10.3390/ma17122963.
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Oxygen reduction reaction (ORR) and oxygen evolutionc reaction (OER) are important chemical reactions for a rechargeable lithium–oxygen battery (LOB). Recently, high-entropy alloys and oxides have attracted much attention because they showed good electrocatalytic performance for oxygen evolution reaction (OER) and/or oxygen reduction reaction (ORR). In this study, we aimed to synthesize and characterize CoSn(OH)6 and two types of high-entropy perovskite hydroxides, that is, (Co0.2Cu0.2Fe0.2Mn0.2Mg0.2)Sn(OH)6 (CCFMMSOH) and (Co0.2Cu0.2Fe0.2Mn0.2Ni0.2)Sn(OH)6 (CCFMNSOH). TEM observation and XRD measurements revealed that the high-entropy hydroxides CCFMMSOH and CCFMNSOH had cubic crystals with sides of approximately 150–200 nm and crystal structures similar to those of perovskite-type CSOH. LSV measurement results showed that the high-entropy hydroxides CCFMMSOH and CCFMNSOH showed bifunctional catalytic functions for the ORR and OER. CCFMNSOH showed better catalytic performance than CCFMMSOH.
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Lin, Shiru, Haoxiang Xu, Yekun Wang, Xiao Cheng Zeng, and Zhongfang Chen. "Directly predicting limiting potentials from easily obtainable physical properties of graphene-supported single-atom electrocatalysts by machine learning." Journal of Materials Chemistry A 8, no. 11 (2020): 5663–70. http://dx.doi.org/10.1039/c9ta13404b.
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The oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) are three critical reactions for energy-related applications, such as water electrolyzers and metal–air batteries.
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Wu, Hengbo, Jie Wang, Wei Jin, and Zexing Wu. "Recent development of two-dimensional metal–organic framework derived electrocatalysts for hydrogen and oxygen electrocatalysis." Nanoscale 12, no. 36 (2020): 18497–522. http://dx.doi.org/10.1039/d0nr04458j.
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Developing efficient and low-cost electrocatalysts with unique nanostructures is of great significance for improved electrocatalytic reactions, including the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR).
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Öztürk, Secil, Yu-Xuan Xiao, Dennis Dietrich, Beatriz Giesen, Juri Barthel, Jie Ying, Xiao-Yu Yang, and Christoph Janiak. "Nickel nanoparticles supported on a covalent triazine framework as electrocatalyst for oxygen evolution reaction and oxygen reduction reactions." Beilstein Journal of Nanotechnology 11 (May 11, 2020): 770–81. http://dx.doi.org/10.3762/bjnano.11.62.
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Covalent triazine frameworks (CTFs) are little investigated, albeit they are promising candidates for electrocatalysis, especially for the oxygen evolution reaction (OER). In this work, nickel nanoparticles (from Ni(COD)2) were supported on CTF-1 materials, which were synthesized from 1,4-dicyanobenzene at 400 °C and 600 °C by the ionothermal method. CTF-1-600 and Ni/CTF-1-600 show high catalytic activity towards OER and a clear activity for the electrochemical oxygen reduction reaction (ORR). Ni/CTF-1-600 requires 374 mV overpotential in OER to reach 10 mA/cm2, which outperforms the benchmark RuO2 catalyst, which requires 403 mV under the same conditions. Ni/CTF-1-600 displays an OER catalytic activity comparable with many nickel-based electrocatalysts and is a potential candidate for OER. The same Ni/CTF-1-600 material shows a half-wave potential of 0.775 V for ORR, which is slightly lower than that of commercial Pt/C (0.890 V). Additionally, after accelerated durability tests of 2000 cycles, the material showed only a slight decrease in activity towards both OER and ORR, demonstrating its superior stability.
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Jeon, Jaeeun, Kyoung Ryeol Park, Kang Min Kim, Daehyeon Ko, HyukSu Han, Nuri Oh, Sunghwan Yeo, Chisung Ahn, and Sungwook Mhin. "CoFeS2@CoS2 Nanocubes Entangled with CNT for Efficient Bifunctional Performance for Oxygen Evolution and Oxygen Reduction Reactions." Nanomaterials 12, no. 6 (March 16, 2022): 983. http://dx.doi.org/10.3390/nano12060983.
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Exploring bifunctional electrocatalysts to lower the activation energy barriers for sluggish electrochemical reactions for both the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are of great importance in achieving lower energy consumption and higher conversion efficiency for future energy conversion and storage system. Despite the excellent performance of precious metal-based electrocatalysts for OER and ORR, their high cost and scarcity hamper their large-scale industrial application. As alternatives to precious metal-based electrocatalysts, the development of earth-abundant and efficient catalysts with excellent electrocatalytic performance in both the OER and the ORR is urgently required. Herein, we report a core–shell CoFeS2@CoS2 heterostructure entangled with carbon nanotubes as an efficient bifunctional electrocatalyst for both the OER and the ORR. The CoFeS2@CoS2 nanocubes entangled with carbon nanotubes show superior electrochemical performance for both the OER and the ORR: a potential of 1.5 V (vs. RHE) at a current density of 10 mA cm−2 for the OER in alkaline medium and an onset potential of 0.976 V for the ORR. This work suggests a processing methodology for the development of the core–shell heterostructures with enhanced bifunctional performance for both the OER and the ORR.
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Yao, Bin, Youzhou He, Song Wang, Hongfei Sun, and Xingyan Liu. "Recent Advances in Porphyrin-Based Systems for Electrochemical Oxygen Evolution Reaction." International Journal of Molecular Sciences 23, no. 11 (May 27, 2022): 6036. http://dx.doi.org/10.3390/ijms23116036.
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Oxygen evolution reaction (OER) plays a pivotal role in the development of renewable energy methods, such as water-splitting devices and the use of Zn–air batteries. First-row transition metal complexes are promising catalyst candidates due to their excellent electrocatalytic performance, rich abundance, and cheap price. Metalloporphyrins are a class of representative high-efficiency complex catalysts owing to their structural and functional characteristics. However, OER based on porphyrin systems previously have been paid little attention in comparison to the well-described oxygen reduction reaction (ORR), hydrogen evolution reaction, and CO2 reduction reaction. Recently, porphyrin-based systems, including both small molecules and porous polymers for electrochemical OER, are emerging. Accordingly, this review summarizes the recent advances of porphyrin-based systems for electrochemical OER. Firstly, the electrochemical OER for water oxidation is discussed, which shows various methodologies to achieve catalysis from homogeneous to heterogeneous processes. Subsequently, the porphyrin-based catalytic systems for bifunctional oxygen electrocatalysis including both OER and ORR are demonstrated. Finally, the future development of porphyrin-based catalytic systems for electrochemical OER is briefly prospected.
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Xu, Junhua, Daobin Liu, Carmen Lee, Pierre Feydi, Marlene Chapuis, Jing Yu, Emmanuel Billy, Qingyu Yan, and Jean-Christophe P. Gabriel. "Efficient Electrocatalyst Nanoparticles from Upcycled Class II Capacitors." Nanomaterials 12, no. 15 (August 5, 2022): 2697. http://dx.doi.org/10.3390/nano12152697.
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To move away from fossil fuels, the electrochemical reaction plays a critical role in renewable energy sources and devices. The anodic oxygen evolution reaction (OER) is always coupled with these reactions in devices but suffers from large energy barriers. Thus, it is important for developing efficient OER catalysts with low overpotential. On the other hand, there are large amounts of metals in electronic waste (E-waste), especially various transition metals that are promising alternatives for catalyzing OER. Hence, this work, which focuses on upcycling Class II BaTiO3 Multilayer Ceramic Capacitors, of which two trillion were produced in 2011 alone. We achieved this by first using a green solvent extraction method that combined the ionic liquid Aliquat® 336 and hydrochloride acid to recover a mixed solution of Ni, Fe and Cu cations, and then using such a solution to synthesize high potential catalysts NiFe hydroxide and NiCu hydroxide for OER. NiFe-hydroxide has been demonstrated to have faster OER kinetics than the NiCu-hydroxide and commercial c-RuO2. In addition, it showed promising results after the chronopotentiometry tests that outperform c-RuO2.
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Kim, Jeheon, Tomohiro Fukushima, Ruifeng Zhou, and Kei Murakoshi. "Revealing High Oxygen Evolution Catalytic Activity of Fluorine-Doped Carbon in Alkaline Media." Materials 12, no. 2 (January 10, 2019): 211. http://dx.doi.org/10.3390/ma12020211.
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Oxygen evolution reactions (OER) are important reactions for energy conversion. Metal-free carbon-based catalysts potentially contribute to the catalytic materials for OER. However, it has been difficult to understand the intrinsic catalytic activity of carbon materials, due to catalyst decomposition over the course of long-term reactions. Here, we report high oxygen evolution reaction catalytic activity of F-doped carbon in alkaline media. Intrinsic OER activity was evaluated from a combination of measurements using a rotating disk electrode and O2 sensor. The F-doped carbon catalyst is a highly active catalyst, comparable to state-of-the-art precious-metal-based catalysts such as RuO2.
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Sui, Chenxi, Kai Chen, Liming Zhao, Li Zhou, and Qu-Quan Wang. "MoS2-modified porous gas diffusion layer with air–solid–liquid interface for efficient electrocatalytic water splitting." Nanoscale 10, no. 32 (2018): 15324–31. http://dx.doi.org/10.1039/c8nr04082f.
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The formation and adsorption of bubbles on electrodes weaken the efficiency of gas evolution reactions such as the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) by hindering proton transfer and consuming nucleation energy.
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Ikezawa, Atsunori, Kotaro Seki, and Hajime Arai. "Rational Placement of Catalysts for Oxygen Reduction and Evolution Reactions Based on the Reaction Sites in Porous Gas Diffusion Electrodes." ECS Meeting Abstracts MA2022-02, no. 4 (October 9, 2022): 522. http://dx.doi.org/10.1149/ma2022-024522mtgabs.
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Metal-air secondary batteries using alkaline electrolyte solutions are promising candidates for next-generation large-scale energy storage systems because of their potential high capacity, low cost, and high safety standard. However, large overpotential of bifunctional air electrodes hindered their wide applications. Recently, increasing research on electrocatalysts for oxygen reduction reaction (ORR) and oxygen reduction reaction (OER) has been conducted to reduce the overpotential, and many active catalysts have been developed. On the other hand, formation of reaction sites is also important since the reaction sites for ORR and OER are basically different1. In this work, we investigated the reaction sites in porous gas diffusion electrodes (GDE) and constructed a GDE with a double-layered catalyst layer based on the difference in the reaction sites for ORR and OER2. La0.6Ca0.4CoO3 (LCCO, bifunctional catalyst), La0.4Sr0.6MnO3 (LSMO, ORR catalyst) and Ca2FeCoO5 (CFCO, OER catalyst) were synthesized by the polymerized complex method. Porous gas diffusion electrodes are constructed by the hot-press method. Catalyst layers were composed of the prepared catalyst (50 wt%), graphitized carbon black (35 wt%), and poly(tetrafluoroethylene) (15 wt%). Gas diffusion layers (GDL) were commercial carbon papers (TGP-H-030H, Chemix). IR-corrected polarization curves were measured by the constant current and AC impedance measurements. Oxygen diffusion resistances for ORR and OER were estimated from the difference in the steady-state potential between pure oxygen and air atmosphere (⊿E = |E O2 – Eair|). Larger increase in ⊿E indicates larger oxygen diffusion resistances in the oxygen reaction processes3. Figure 1 (a, b) shows ⊿E-I curves of LCCO-GDE for ORR and OER in 4.0 and 8.0 dm–3 KOHaq. The oxygen permeability(D O2×C O2) in 4.0 dm–3 KOHaq is 16 times as large as that in 8.0 dm–3 KOHaq while the ion conductivities of these electrolyte solutions are at the same extent. The increase in ⊿E for ORR was larger in 8.0 dm–3 KOHaq, indicating dissolved oxygen involved in the ORR process. In contrast, the ⊿E for OER was nearly negligible in these electrolyte solutions, suggesting that oxygen was mainly transported as bubbles. We also measured ⊿E-I curves of the LCCO-GDE in 8.0 dm–3 KOHaq having different catalyst layer thicknesses. The increases in ⊿E were almost independent of the catalyst layer thicknesses for ORR and OER, suggesting that the reaction sites were concentrated in the catalyst layer. Finally, we compared polarization curves of the GDEs with single-layered catalyst layer (LSMO+CFCO|DGL-GDE) and double-layered catalyst layers (LSMO|CFCO|GDL-GDE and CFCO|LSMO|GDL-GDE) to identify the reaction sites for ORR and OER (Fig. 1 (c, d)). The smallest overpotential of CFCO|LSMO|GDL-GDE for both ORR and OER showed that the reaction sites for ORR and OER were concentrated at the electrolyte-side and gas-side, respectively. In addition, CFCO|LSMO|GDL-GDE showed higher durability than LSMO+CFCO|DGL-GDE. From these results, it can be concluded that the placement of the ORR and OER catalysts on the electrolyte-side and gas-side of the CL can improve both activity and durability of the bifunctional air electrode. References [1] A. Ikezawa, K. Miyazaki, T. Fukutsuka, T. Abe, Electrochem. Commun., 84, 53-56 (2017). [2] A. Ikezawa, K. Seki and H. Arai, Electrochim. Acta, 394, 139128 (2021). [3] A. Kaisheva, I. Iliev, S. Gamburzev, J. Power Sources, 13, 181-195 (1984). Figure 1
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Milikić, Jadranka, Aldona Balčiūnaitė, Zita Sukackienė, Dušan Mladenović, Diogo M. F. Santos, Loreta Tamašauskaitė-Tamašiūnaitė, and Biljana Šljukić. "Bimetallic Co-Based (CoM, M = Mo, Fe, Mn) Coatings for High-Efficiency Water Splitting." Materials 14, no. 1 (December 28, 2020): 92. http://dx.doi.org/10.3390/ma14010092.
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Bimetallic cobalt (Co)-based coatings were prepared by a facile, fast, and low-cost electroless deposition on a copper substrate (CoFe, CoMn, CoMo) and characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray diffraction analysis. Prepared coatings were thoroughly examined for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline solution (1 M potassium hydroxide, KOH) and their activity compared to that of Co and Ni coatings. All five coatings showed activity for both reactions, where CoMo and Co showed the highest activity for HER and OER, respectively. Namely, the highest HER current density was recorded at CoMo coating with low overpotential (61 mV) to reach a current density of 10 mA·cm−2. The highest OER current density was recorded at Co coating with a low Tafel slope of 60 mV·dec−1. Furthermore, these coatings proved to be stable under HER and OER polarization conditions.
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Chen, Xiaodong, Jianqiao Liu, Tiefeng Yuan, Zhiyuan Zhang, Chunyu Song, Shuai Yang, Xin Gao, Nannan Wang, and Lifeng Cui. "Recent advances in earth-abundant first-row transition metal (Fe, Co and Ni)-based electrocatalysts for the oxygen evolution reaction." Energy Materials 2, no. 4 (2022): 28. http://dx.doi.org/10.20517/energymater.2022.30.
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The oxygen evolution reaction (OER) is of fundamental importance as a half reaction and rate-controlling step that plays a predominant function in improving the energy storage and conversion efficiency during the electrochemical water-splitting process. In this review, after briefly introducing the fundamental mechanism of the OER, we systematically summarize the recent research progress for nonprecious-metal-based OER electrocatalysts of representative first-row transition metal (Fe, Co and Ni)-based composite materials. We analyze the effects of the physicochemical properties, including morphologies, structures and compositions, on the integrated performance of these OER electrocatalysts, with the aim of determining the structure-function correlation of the electrocatalysts in the electrochemical reaction process. Furthermore, the prospective development directions of OER electrocatalysts are also illustrated and emphasized. Finally, this mini-review highlights how systematic introductions will accelerate the exploitation of high-efficiency OER electrocatalysts.
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Elbaz, Lior, and Wenjamin Moschkowitsch. "Electrocatalyzing Oxygen Evolution Reaction with Nifeooh Aerogels." ECS Meeting Abstracts MA2022-02, no. 44 (October 9, 2022): 1680. http://dx.doi.org/10.1149/ma2022-02441680mtgabs.
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Increasing the production capacity of electrical energy to fulfill the continuously rising global demand, while simultaneously trying to avoid greenhouse gas emissions in the process, and being environmentally sound, is one of the largest challenges of this era.One way to achieve it is to rely on hydrogen for energy storage. Nowadays, most of the hydrogen produced is mainly from fossil fuels, and the emission of detrimental gasses is only shifted. To get to a true green hydrogen, it is necessary to produce it in emissions-free processes. One method to achieve this is to use renewable energies in combination with electrochemical water electrolyzers, in which two distinct chemical reactions take place: the cathodic hydrogen evolution reaction (HER) and the anodic oxygen evolution reaction (OER). Both reaction require catalysts to execute at high rates, and while the HER is considered to be relatively facile and takes place at low overpotentials, the OER requires relatively high overpotentials and high loadings of precious metal catalysts. It is considered the bottleneck reaction. The OER is a four electrons oxidation reaction per generated O2 molecule, and proceeds in four distinct reaction steps. This leads to a very sluggish reaction kinetics and high overpotentials to reach viable current densities. In recent years, more and more non-precious metal OER catalyst have been developed. Most notably is the family of mixed nickel-iron oxyhydroxides (NiFeOOH), which are relatively cheap, selective and efficient catalysts in alkaline media, and their performance has been increased by optimizing the Ni:Fe ratio, adding a third metal that either further increase the performance of the catalyst or/and its stability and other methods. One challenge that still remains is to increase the NiFeOOH surface area, and by that the electrochemically active site density (EASD). In this regard, one class of materials that has been attracting the attention of materials’ scientists in recent years are aerogels. Aerogels can be made from many different materials, such as silicates, carbons, metal organic materials, bio-inspired molecules, metals, and metal oxides. They consist of distinct units which form a porous 3D covalent framework (COF). Because of their diversity, aerogels have many different applications, e.g. as insulators, sensors, or catalysts. In this presentation we will report the synthesis of NixFeyOz aerogels, with a modified easy synthetic method via an epoxide route. These aerogels show much higher utilization of the material and overall increase in mass activity when catalyzing the OER when compared to other NiFeOOH derived materials. They were tested for their OER electrocatalytic activity and to the best of our knowledge these are the first aerogel materials that propagate OER themselves, rather than being used merely as support material for OER catalysts. The catalytic activity depends largely on the Ni:Fe ratio and not the surface area, which can lead to mass transport limitations when too high, showing an optimum for the ratio and the surface area.
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Dymerska, Anna, Wojciech Kukułka, Marcin Biegun, and Ewa Mijowska. "Spinel of Nickel-Cobalt Oxide with Rod-Like Architecture as Electrocatalyst for Oxygen Evolution Reaction." Materials 13, no. 18 (September 4, 2020): 3918. http://dx.doi.org/10.3390/ma13183918.
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The renewable energy technologies require electrocatalysts for reactions, such as the oxygen and/or hydrogen evolution reaction (OER/HER). They are complex electrochemical reactions that take place through the direct transfer of electrons. However, mostly they have high over-potentials and slow kinetics, that is why they require electrocatalysts to lower the over-potential of the reactions and enhance the reaction rate. The commercially used catalysts (e.g., ruthenium nanoparticles—Ru, iridium nanoparticles—Ir, and their oxides: RuO2, IrO2, platinum—Pt) contain metals that have poor stability, and are not economically worthwhile for widespread application. Here, we propose the spinel structure of nickel-cobalt oxide (NiCo2O4) fabricated to serve as electrocatalyst for OER. These structures were obtained by a facile two-step method: (1) One-pot solvothermal reaction and subsequently (2) pyrolysis or carbonization, respectively. This material exhibits novel rod-like morphology formed by tiny spheres. The presence of transition metal particles such as Co and Ni due to their conductivity and electron configurations provides a great number of active sites, which brings superior electrochemical performance in oxygen evolution and good stability in long-term tests. Therefore, it is believed that we propose interesting low-cost material that can act as a super stable catalyst in OER.
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García Caballero, Ariadna D., and Jesus Adrián Diaz-Real. "Alternative Technique to RDE to Evaluate Photoelectrocatalysts for ORR." ECS Meeting Abstracts MA2024-01, no. 44 (August 9, 2024): 2438. http://dx.doi.org/10.1149/ma2024-01442438mtgabs.
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The scarcity of fuels due to the growing energy demand has encouraged research into topics such as energy conversion with materials that can take advantage of solar energy. Such situations have promote the emergence of various new materials to assist reactions of special interest such as oxygen reactions. (Oxygen Reduction Reaction, ORR and Oxygen Evolution Reaction, OER). Thus, numerous materials are emerging with the photoelectrocatalytic activity towards OER and ORR reactions. To evaluate the photo-assisted OER requires technical conditions that a rotating disk electrode (RDE) does not satisfy. In this work we present an alternative technique to RDE by adapting a flow in a microfluidic platform to satisfy the limit current while it can be irradiated and thus evaluate the photoelectocatalysis of a semiconductor that has the characteristic of a photoelectrocatalyst. To make the comparison, a glassy carbon electrode (GCE) was used using the Pt/C system in a three-electrode cell designed with a microfluidic channel where we found that the mass flow is comparable to rpm.
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Asad, Muhammad, Afzal Shah, Faiza Jan Iftikhar, Rafia Nimal, Jan Nisar, and Muhammad Abid Zia. "Development of a Binder-Free Tetra-Metallic Oxide Electrocatalyst for Efficient Oxygen Evolution Reaction." Sustainable Chemistry 3, no. 3 (June 21, 2022): 286–99. http://dx.doi.org/10.3390/suschem3030018.
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Water splitting has emerged as a sustainable, renewable and zero-carbon-based energy source. Water undergoes hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) during electrolysis. However, among these half-cell reactions, OER is more energy demanding. Hence, the development of efficient catalysts for speeding up OER is a key for boosting up the commercial viability of electrolyzers. Typical binders like Nafion and PVDF are not preferred for designing commercial electrocatalysts as they can compromise conductivity. Thus, we have designed a novel and cost-effective binder-free tetra-metallic (Co-Cu-Zn-Fe) oxide catalyst that efficiently catalyzes OER. This catalyst was grown over the surface of Fluorine doped tin oxide (FTO) transducer by a facile potentiodynamic method. The structure and morphology of the modified electrode were characterized by X-ray diffraction (XRD), scanning electron microscopy, and energy dispersive X-ray spectroscopy. XRD analysis confirmed the deposition of CoFe2O4 and CuCo2O4 along with alloy formation of Co-Fe and Co-Cu. Similarly, EDX and SEM results show the presence of metals at the surface of FTO in accordance with the results of XRD. Linear scan voltammetry was employed for testing the performance of the catalyst towards accelerating OER in strongly alkaline medium of pH-13. The catalyst demonstrated stunning OER catalytic performance, with an overpotential of just 216 mV at 10 mA cm−2 current density. Moreover, the chronopotentiometric response revealed that the designed catalyst was stable at a potential of 1.80 V for 16 h. Thus, the designed catalyst is the first example of a highly stable, efficient, and inexpensive catalyst that catalyzes OER at the lowest overpotential.
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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.
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Puthiyapura, Vinod Kumar, Christopher Mark Zalitis, and James Stevens. "Gas Diffusion Electrode for Oxygen Evolution Reaction Catalyst Testing." ECS Meeting Abstracts MA2023-02, no. 37 (December 22, 2023): 1726. http://dx.doi.org/10.1149/ma2023-02371726mtgabs.
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The oxygen evolution reaction (OER) is one of the major contributors of efficiency loss in water electrolysis and consequently, development of OER catalysts to improve the electrolyser efficiency is a major reasearch theme in the field. Though the current commercial PEMWE may operate at anode potential <1.60 V, futue PEMWE may operate at potential higher than this as the drive to operate PEMWE at high current density is inceasing. Inorder to achieve this, an active and stable catalyst is required that can operate at this regime. Also, the potential experienced by the anode during the startup/shutdown of an electrolyser are different to the steady state value. Conventional OER testing involves catalysts coated on a conductive substrate submerged in an electrolyte solution, in a three electrode cell. However, such techniques are generally limited to low current densities due to oxygen bubble formation and site blocking at high current density limiting the system to study the OER kinetics below realistic operating current density. Although Rotating Disk Electrode(RDE) is widely employed to mitigate this, the RDE system is still not effective enough to remove the bubbles1. A floating electrode system developed by Kucernak et al2 shows that combining direct access with a lower catalyst loading improves the O2 gas mass transport and a higher current density could be achieved for the ORR. This technique also used for OER by Arenz et al.3, for easier bubble removal. Combining these two above mentioned systems, we have developed a new GDE cell system which allows screening of OER catalyst at industrially relevant current densities. This cell allows to study the OER kinetics at very realistic voltage/current regime and the information obtained helps to develop more active/stable catalyst. The OER catalyst diagnostics test from our GDE cell was comparable to the standard three electrode cell with an additional advantage of extended potential window upto 1.80 V vs.RHE. Preliminary results obtained from our study shows a promising opportunity to study the OER at high current densities. Reference FathiTovini, A.Hartig-Weiß, H.A.Gasteigerand, H.A.El Sayed, Journal of The ElectrochemicalSociety, 2021, 168, 014512. M.Zalitis,D.KramerandA.R.Kucernak,Phys.Chem.Chem.Phys.,2013,15,4329-4340 Schröder,V.A.Mints,A.Bornet,E.Berner,M.FathiTovini,J.Quinson,etal., JACS Au 2021,1(3),247-25
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Shafath, Sadiyah, Khulood Logade, Anand Kumar, and Ibrahim Abu Reesh. "(Digital Presentation) Multifunctional Lanthanum Perovskite Electrocatalysts (LaMnxCo1-xO3 (0≤x≤1)) for Alkaline Medium Methanol Oxidation and Oxygen Catalysis." ECS Meeting Abstracts MA2022-02, no. 43 (October 9, 2022): 1629. http://dx.doi.org/10.1149/ma2022-02431629mtgabs.
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Lanthanum-based synthetic perovskites (LaMnxCo1-xO3 (0≤x≤1)) were synthesized using a solution combustion synthesis technique with variable ratios of Co and Mn to investigates the surface and electrocatalytic property (activity and stability of catalysts) for methanol oxidation reaction (MOR), oxygen reduction reaction (ORR), oxygen evolution reaction (OER) under alkaline medium (KOH). The structural and morphological characterizations of the synthesized catalyst were performed by XRD, FTIR, SEM, TEM and XPS techniques. The structural and chemical properties systematically changed by varying the Mn to Co ratio in the perovskite structure. To observe the completion of combustion and temperature characteristics during the synthesis process, which are known to impact structural qualities, the time temperature profile during the combustion process was monitored. SEM/EDX and XPS analysis confirmed the formation of targeted ratio of Mn and Co on the catalyst. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) results revealed that all perovskite samples with different Co:Mn ratios were active for ORR, OER and MOR. The LaMnxCo1-xO3 perovskite with x=0.4 showed the highest current density compared to other samples towards all the investigated electrocatalytic reactions (MOR, ORR and OER) under alkaline reaction conditions.
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Zhang, Pengfei, Hongmei Qiu, Huicong Li, Jiangang He, Yingying Xu, and Rongming Wang. "Nonmetallic Active Sites on Nickel Phosphide in Oxygen Evolution Reaction." Nanomaterials 12, no. 7 (March 29, 2022): 1130. http://dx.doi.org/10.3390/nano12071130.
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Efficient and durable catalysts are crucial for the oxygen evolution reaction (OER). The discovery of the high OER catalytic activity in Ni12P5 has attracted a great deal of attention recently. Herein, the microscopic mechanism of OER on the surface of Ni12P5 is studied using density functional theory calculations (DFT) and ab initio molecular dynamics simulation (AIMD). Our results demonstrate that the H2O molecule is preferentially adsorbed on the P atom instead of on the Ni atom, indicating that the nonmetallic P atom is the active site of the OER reaction. AIMD simulations show that the dissociation of H from the H2O molecule takes place in steps; the hydrogen bond changes from Oa-H⋯Ob to Oa⋯H-Ob, then the hydrogen bond breaks and an H+ is dissociated. In the OER reaction on nickel phosphides, the rate-determining step is the formation of the OOH group and the overpotential of Ni12P5 is the lowest, thus showing enhanced catalytic activity over other nickel phosphides. Moreover, we found that the charge of Ni and P sites has a linear relationship with the adsorption energy of OH and O, which can be utilized to optimize the OER catalyst.
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Geppert, Janis, Philipp Röse, and Ulrike Krewer. "The Microkinetic Performance Barriers of Ruthenium and Iridium Oxides during the Electrocatalytic Oxygen Evolution Reaction." ECS Meeting Abstracts MA2022-01, no. 34 (July 7, 2022): 1370. http://dx.doi.org/10.1149/ma2022-01341370mtgabs.
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Electrocatalytic water splitting is currently one of the most promising reactions to produce green hydrogen in a de-fossilized energy system.[1] The performance of PEM electrolyzers is substantially determined by the sluggish reaction kinetics of the oxygen evolution reaction (OER). Even highly active catalysts such as nanoparticulated transition metal oxides IrO2, RuO2 and their mixtures IrxRu1-xO2 exhibit overpotentials up to several hundreds of millivolts.[2] Dynamic microkinetic modeling is a powerful tool to analyze the single reactions and their interplay during OER at the electrode surface.[3] Quantitative insight into process-limiting steps on different active sites on the material surface can be used to suggest ways to improve dynamic OER operation. In this work, we present the analysis of an experimentally validated microkinetic model. It allows to study the electrocatalytic reaction mechanism including the coverage of emerging surface species (e.g. *OH, *O, *OOH and *OO) for a wide potential range including OER. We show that there is a correlation between performance and the Ir:Ru ratio, that can be explained by two different potential determining deprotonation steps. In particular, the highest equilibrium potentials of 1.44 V and 1.58 V are quantified for the production of the adsorbate species *OOH on rutile RuO2 and *OO on IrO2, respectively. During OER at a potential of >1.5 V, adsorbed oxygen *O covers >40 % of the active sites, suggesting that subsequent water adsorption is the major process limitation. The surface of the oxide mixtures IrxRu1-xO2, is found to consist of actives sites of both Ir and Ru on which the OER mechanism is processed independently and at different overpotentials. Compared to the pure oxides, the mixtures reveal reduced reaction energies of the potential determining deprotonation processes. One can conclude that incorporating Ru into IrO2 provides higher overall performance while stability is remained. Dynamic microkinetic modelling is therefore a viable method to study catalytic surface processes as well as their limitations and to make suggestions for improving the performance of electrocatalytic systems. [1] K. Kalz et al., ChemCatChem, 2017, 9, 17. [2] D. Escalera-López et al., ACS Catalysis, 2021, 11, 15, 9300. [3] J. Geppert et al., Electrochimica Acta, 2021, 380, 137902.
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Elbaz, Lior. "(Keynote) Development of Advanced High Surface Area Metal Oxide Aerogels for Oxygen Evolution Reaction Electrocatalysis." ECS Meeting Abstracts MA2023-02, no. 58 (December 22, 2023): 2793. http://dx.doi.org/10.1149/ma2023-02582793mtgabs.
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The growing demand to shift energy production to sustainable sources poses some serious challenges. One of the biggest are the intermittent energy (wind and sun). To mitigate this issue, there is a critical need for large energy storage technologies, to store excess energy during the peak hours and carry it over for the rest of the day, weeks, and seasons. The best way to do so is through the Hydrogen Economy. At the heart of this scheme is green hydrogen production using water electrolysis. There are two distinct chemical reactions that take place in water electrolyzers: the cathodic hydrogen evolution reaction (HER), and the anodic oxygen evolution reaction (OER). Both reaction require catalysts to execute at high rates, and while the HER is considered to be relatively facile and takes place at low overpotentials, the OER requires relatively high overpotentials and high loadings of precious metal catalysts. It is considered the bottleneck reaction. The OER is a four electrons oxidation reaction per generated O2 molecule and proceeds in four distinct reaction steps. This leads to a very sluggish reaction kinetics and high overpotentials to reach viable current densities. In recent years, more and more non-precious metal OER catalyst have been developed. Most notably is the family of mixed nickel-iron oxyhydroxides (NiFeOOH), which are relatively cheap, selective and efficient catalysts in alkaline media, and their performance has been increased by optimizing the Ni:Fe ratio. One challenge that still remains is to increase the NiFeOOH surface area, and by that the electrochemically active site density (EASD). In this regard, one class of materials that has been attracting the attention of materials’ scientists in recent years are aerogels. Aerogels can be made from many different materials, such as silicates, carbons, metal organic materials, bio-inspired molecules, metals, and metal oxides. They consist of distinct units which form a porous 3D covalent framework (COF). Because of their diversity, aerogels have many different applications, e.g. as insulators, sensors, or catalysts. In this talk we will report the synthesis of NixFeyMzOOH aerogels, with a modified easy synthetic method via an epoxide route. These aerogels show much higher utilization of the material and overall increase in mass activity when catalyzing the OER when compared to other NiFeOOH derived materials. They were tested for their OER electrocatalytic activity and to the best of our knowledge these are the first aerogel materials that propagate OER themselves, rather than being used merely as support material for OER catalysts. The catalytic activity depends largely on the Ni:Fe ratio and not the surface area, which can lead to mass transport limitations when too high, showing an optimum for the ratio and the surface area.
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Gao, Chang, Haiyu Yao, Peijie Wang, Min Zhu, Xue-Rong Shi, and Shusheng Xu. "Carbon-Based Composites for Oxygen Evolution Reaction Electrocatalysts: Design, Fabrication, and Application." Materials 17, no. 10 (May 11, 2024): 2265. http://dx.doi.org/10.3390/ma17102265.
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The four-electron oxidation process of the oxygen evolution reaction (OER) highly influences the performance of many green energy storage and conversion devices due to its sluggish kinetics. The fabrication of cost-effective OER electrocatalysts via a facile and green method is, hence, highly desirable. This review summarizes and discusses the recent progress in creating carbon-based materials for alkaline OER. The contents mainly focus on the design, fabrication, and application of carbon-based materials for alkaline OER, including metal-free carbon materials, carbon-based supported composites, and carbon-based material core–shell hybrids. The work presents references and suggestions for the rational design of highly efficient carbon-based OER materials.
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Kim, Myeong-Geun, and Sung Jong Yoo. "Surface Reconstruction of Iridium Nanoparticles for Enhanced Oxygen Evolution Reaction in Alkaline Medium." ECS Meeting Abstracts MA2022-01, no. 34 (July 7, 2022): 1400. http://dx.doi.org/10.1149/ma2022-01341400mtgabs.
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An electrochemical water splitting is a promising technology that can generate green hydrogen using renewable energy sources. However, the sluggish oxygen evolution reaction (OER) in an anodic side hinders their large scale applications. Many efforts have been focused on developing efficient electrocatalysts; iridium-based catalysts have gained much attentions due to remarkable intrinsic activities and high stability. Technically, however, the properties are derived from amorphous iridium oxide (IrOx) rather than metallic Ir. During an electrochemical activation process, the Ir metal is easily converted into oxidized species with multiple oxidation states of iridium, which are highly active toward OER. Similarly, many catalysts undergo changes during OER process (e.g., oxidation of precatalysts), resulting in enhancement of activities for OER beyond corresponding original catalysts. Accordingly, the reconstruction process involving surface oxidation and leaching of metal cations should be investigated to develop efficient OER electrocatalysts. Herein, we prepared chalcogen atom modified Ir/IrOx core/shell nanoparticles for enhanced alkaline OER performances (electrolyte: 1M KOH). The S-modified Ir/IrOx exhibited remarkable OER performances with current density of 10 mA cm−2 at overpotentials as low as 180 mV. Incorporation of chalcogen atoms induce surface reconstruction of the Ir/IrOx nanoparticles during OER measurements. It was observed that electrocatalytic activities of Ir/IrOx were varied depending on the type and concentration of chalcogen atoms. There were no observable morphological and structural changes in Ir/IrOx electrocatalyst, whereas the atomic ratio of chalcogen atoms noticeably decreased after OER tests. The result suggests that incorporated chalcogen atoms play a role in modifying the surface of Ir nanoparticles, rather than participating OER as active sites. In addition, XPS measurements were conducted in order to detect changes in chemical states of the catalysts during electrochemical process. We thus believe that the chalcogen atom induced surface reconstruction can be the strategy to efficiently improve the various electrochemical reactions.
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Dogutan, Dilek K., D. Kwabena Bediako, Daniel J. Graham, Christopher M. Lemon, and Daniel G. Nocera. "Proton-coupled electron transfer chemistry of hangman macrocycles: Hydrogen and oxygen evolution reactions." Journal of Porphyrins and Phthalocyanines 19, no. 01-03 (January 2015): 1–8. http://dx.doi.org/10.1142/s1088424614501016.
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The splitting of water into its constituent elements is an important solar fuels conversion reaction for the storage of renewable energy. For each of the half reactions of the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), multiple protons and electrons must be coupled to avoid high-energy intermediates. To understand the mechanistic details of the PCET chemistry that underpins HER and OER, we have designed hangman porphyrin and corrole catalysts. In these hangman constructs, a pendant acid/base functionality within the secondary coordination sphere is "hung" above the macrocyclic redox platform on which substrate binds. The two critical thermodynamic properties of a PCET event, the redox potential and pKa may be tuned with the macrocycle and hanging group, respectively. This review outlines the synthesis of these catalysts, as well as the examination of the PCET kinetics of hydrogen and oxygen evolution by the hangman catalysts. The insights provided by these systems provide a guide for the design of future HER and OER catalysts that use a secondary coordination sphere to manage PCET.
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Choi, Yun-Hyuk. "Electrocatalytic Activities of High-Entropy Oxides for the Oxygen Evolution Reaction." ECS Meeting Abstracts MA2023-02, no. 54 (December 22, 2023): 2604. http://dx.doi.org/10.1149/ma2023-02542604mtgabs.
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Electrocatalytic water-splitting hydrogen generation consists of the cathodic hydrogen evolution reaction (HER) and the anodic oxygen evolution reaction (OER), where the four-electron-relevant OER is the rate-determining step. So far, there have been many efforts to substitute for the highly expensive noble-metal electrocatalysts (platinum, ruthenium or rhodium oxides, etc.). Transition-metal oxides based on Co, Ni, Mn, and V have been suggested as such alternatives, due to their low cost, high efficiency, and high stability. Recently, since the compositional diversity can provide a new breakthrough in that area, a high-entropy oxide (HEO) with five transition-metal cations has been suggested as a promising electrocatalyst toward the OER. In our studies, two kinds of HEOs were prepared and their OER activities were investigated. To begin with, for the (Mg0.2Fe0.2Co0.2Ni0.2Cu0.2)O, the effect of constituent cations on the OER activity was unveiled. Furthermore, a core cation driving the high OER activity was found. For it, the medium-entropy oxides (MEOs) with four cations are prepared by subtracting each cation (Mg, Fe, Co, Ni, or Cu) from the HEO, exhibiting homogeneous morphology, equiatomic composition, and single-phase rocksalt structure. As a result, it is found that the highest concentration of Co3+ in the MEO (w/o Cu) leads to the best OER activity, and thus Co3+ is the core ion driving the high OER activity. Furthermore, it is regarded that Cu2+ ions prevent the conversion of Co or Fe cations from 2+ to 3+ in the HEO and MEOs. Accordingly, maximizing the concentration of Co3+ within electrocatalysts is suggested as an effective design strategy for the high-efficiency electrocatalysts based on high or medium entropy materials. Secondly, the relationship between structure and OER activity was elucidated for the (Mg0.2Fe0.2Co0.2Zn0.2Cu0.2)O with a temperature-dependent rocksalt-to-spinel transition.
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Eskandrani, Areej A., Shimaa M. Ali, and Hibah M. Al-Otaibi. "Study of the Oxygen Evolution Reaction at Strontium Palladium Perovskite Electrocatalyst in Acidic Medium." International Journal of Molecular Sciences 21, no. 11 (May 27, 2020): 3785. http://dx.doi.org/10.3390/ijms21113785.
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The catalytic activity of Sr2PdO3, prepared through the sol-gel citrate-combustion method for the oxygen evolution reaction (OER) in a 0.1 M HClO4 solution, was investigated. The electrocatalytic activity of Sr2PdO3 toward OER was assessed via the anodic potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The glassy carbon modified Sr2PdO3 (GC/Sr2PdO3) electrode exhibited a higher electrocatalytic activity, by about 50 times, in comparison to the unmodified electrode. The order of the reaction was close to unity, which indicates that the adsorption of the hydroxyl groups is a fast step. The calculated activation energy was 21.6 kJ.mol−1, which can be considered a low value in evaluation with those of the reported OER electrocatalysts. The Sr2PdO3 perovskite portrayed a high catalyst stability without any probability of catalyst poisoning. These results encourage the use of Sr2PdO3 as a candidate electrocatalyst for water splitting reactions.
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Vitale-Sullivan, Molly E., Quinn Quinn Carvalho, and Kelsey A. Stoerzinger. "Facet-Dependent Selectivity of Rutile IrO2 for Oxygen and Chlorine Evolution Reactions." ECS Meeting Abstracts MA2023-01, no. 50 (August 28, 2023): 2577. http://dx.doi.org/10.1149/ma2023-01502577mtgabs.
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Water electrolysis is a promising route for sustainable production of hydrogen as an energy storage medium and valuable precursor for industrial chemical syntheses such as ammonia and methanol. Direct electrolysis of seawater circumvents costly desalination and purification steps to reduce the price of renewable hydrogen to achieve cost parity with carbon-intensive steam reforming. However, the significant concentration of chloride salts in seawater poses a challenge to selectivity of seawater electrolysis. In aqueous chloride electrolytes, the chlorine evolution reaction (CER) is kinetically favored over the oxygen evolution reaction (OER). Rutile-type iridium dioxide (IrO2) is a state-of-the-art electrocatalyst for water electrolysis but is also a benchmark chlorine evolution electrocatalyst in the industrial chlor-alkali process. Understanding OER/CER selectivity is needed to make seawater electrolysis a viable energy conversion technology in the future. In this work, we seek to understand the relationship between crystallographic facet and competitive reaction pathway between OER and CER on epitaxial, rutile IrO2 thin films. We investigate facet-dependent OER and CER activity on a series of single-crystalline IrO2 thin films using a rotating disk electrode geometry. The OER/CER selectivity, reaction rate order, and reaction intermediate electroadsorption affinities are explored to add fundamental insight into the reactivity of rutile IrO2 surface. To gain further insight into OER intermediate adsorption affinities, we paired electrochemical measurements with surface-sensitive ambient pressure x-ray photoelectron spectroscopy (AP-XPS). Moving forward, our facet-dependent study of OER/CER selectivity of rutile IrO2 can be used to design selective seawater electrocatalysts for cost-effective and sustainable hydrogen production.
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Cheng, J., P. Ganesan, Z. Wang, M. Zhang, G. Zhang, N. Maeda, J. Matsuda, M. Yamauchi, B. Chi, and N. Nakashima. "Bifunctional electrochemical properties of La0.8Sr0.2Co0.8M0.2O3−δ (M = Ni, Fe, Mn, and Cu): efficient elemental doping based on a structural and pH-dependent study." Materials Advances 3, no. 1 (2022): 272–81. http://dx.doi.org/10.1039/d1ma00632k.
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Perovskite oxides with a low cost and high catalytic activity are considered as suitable candidates for the oxygen evolution reaction (OER)/oxygen reduction reaction (ORR), but most of them favour only either the ORR or the OER.
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Yin, Shikang, Xiaoxue Zhao, Enhui Jiang, Yan Yan, Peng Zhou, and Pengwei Huo. "Boosting water decomposition by sulfur vacancies for efficient CO2 photoreduction." Energy & Environmental Science 15, no. 4 (2022): 1556–62. http://dx.doi.org/10.1039/d1ee03764a.
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As the rate-determining half reaction (OER) in the overall CO2 photoreduction, the four-electron-involving OER on S-vacancy sites was favored, therefore facilitating the hole-elimination/proton release and unleashing the CO2 reduction half reaction.
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Li, Yaxin, Xin Yu, Juan Gao, and Yurong Ma. "Hierarchical Ni2P/Zn-Ni-P Nanosheet Array for Efficient Energy-Saving Hydrogen Evolution and Hydrazine Oxidation." Journal of Materials Chemistry A, 2023. http://dx.doi.org/10.1039/d2ta08366c.
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Electrochemical overall water splitting (OWS) includes two half reactions of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Due to the limitation of the slow kinetic process of OER,...
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Wang, Zeyu, William A. Goddard, and Hai Xiao. "Potential-dependent transition of reaction mechanisms for oxygen evolution on layered double hydroxides." Nature Communications 14, no. 1 (July 15, 2023). http://dx.doi.org/10.1038/s41467-023-40011-8.
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AbstractOxygen evolution reaction (OER) is of crucial importance to sustainable energy and environmental engineering, and layered double hydroxides (LDHs) are among the most active catalysts for OER in alkaline conditions, but the reaction mechanism for OER on LDHs remains controversial. Distinctive types of reaction mechanisms have been proposed for the O-O coupling in OER, yet they compose a coupled reaction network with competing kinetics dependent on applied potentials. Herein, we combine grand-canonical methods and micro-kinetic modeling to unravel that the nature of dominant mechanism for OER on LDHs transitions among distinctive types as a function of applied potential, and this arises from the interplay among applied potential and competing kinetics in the coupled reaction network. The theory-predicted overpotentials, Tafel slopes, and findings are in agreement with the observations of experiments including isotope labelling. Thus, we establish a computational methodology to identify and elucidate the potential-dependent mechanisms for electrochemical reactions.
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Maduraiveeran, Govindhan. "Transition metal nanomaterial-based electrocatalysts for water and CO2 electrolysis: preparation, catalytic activity, and prospects." Frontiers in Energy Research 12 (October 24, 2024). http://dx.doi.org/10.3389/fenrg.2024.1433103.
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The production of hydrogen (H2) and multi-carbon fuels through water electrolysis (oxygen evolution reaction (OER)/hydrogen evolution reaction (HER)) and water–CO2 co-electrolysis (OER/CO2 reduction reaction (CO2RR)), respectively, is supposed to be the emergent energy carrier. These electrochemical processes are essential chemical conversion pathways that initiate the changes toward production of renewable energy. This review summarizes the systematic design of earth-abundant transition metal-based nanomaterials and their electrocatalytic activities toward electrochemical energy conversion reactions such as OER, HER, and CO2RR. The primary focus is on fabricating highly effective, low-cost, and advanced transition metal-based nanostructures for both the OER/HER and OER/CO2RR systems. Developing synthetic strategies for surface morphology-controlled nanostructured electrocatalysts, engineering the electrode surface, enhancing the electrocatalytic activity, understanding the relationship between intrinsic catalytic activity and preparation approaches or precursor choices, and exploring the reaction mechanism are focused on. Furthermore, the current challenges, figure-of-merit, and prospects of transition metal-based nanomaterials and their electrocatalytic activities toward water electrolysis and water–CO2 co-electrolysis are described. This study may open new opportunities to develop shape-controlled and high-performance electrocatalysts for electrochemical energy conversion and storage reactions.
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Chen, Xiaodong, Zhiyuan Zhang, Ya Chen, Runjing Xu, Chunyu Song, Tiefeng Yuan, Wenshuai Tang, Xin Gao, Nannan Wang, and Lifeng Cui. "Research advances in earth-abundant-element-based electrocatalysts for oxygen evolution reaction and oxygen reduction reaction." Energy Materials, 2023. http://dx.doi.org/10.20517/energymater.2023.12.
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The oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are crucial half-reactions of green electrochemical energy storage and conversion technologies, such as electrochemical water-splitting devices and regenerative fuel cells. Researchers always committed to synthesizing earth-abundant-element-based nanomaterials as high-efficiency electrocatalysts for realizing their industrial applications. In this review, we briefly elaborate on the underlying mechanisms of OER and ORR during the electrochemical process. Then, we systematically sum up the recent research progress in representative metal-free carbon (C)-based electrocatalysts; metal-nitrogen-C electrocatalysts; and nonprecious-metal OER/ORR electrocatalysts, including transition-metal oxides, phosphides, nitrides/oxynitrides, chalcogenides, and carbides. Among these, some representative bifunctional electrocatalysts for the OER/ORR are mentioned. In particular, we discuss the effects of physicochemical properties-morphology, phases, crystallinity, composition, defects, heteroatom doping, and strain engineering-on the comprehensive performance of the abovementioned electrocatalysts, with the aim of establishing the nanostructure-function relationships of the electrocatalysts. In addition, the development directions of OER and ORR electrocatalysts are determined and highlighted. The generic approach in this review expands the frontiers of and provides inspiration for developing high-efficiency OER/ORR electrocatalysts.
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., Krishankant, Aashi Chauhan, Zubair Ahmed, A. Srinivasan, Ashish Gaur, Rajdeep Kaur, and Vivek Bagchi. "Nano-interfaced tungsten oxide inwrought with layer double hydroxides for oxygen evolution reaction." Sustainable Energy & Fuels, 2022. http://dx.doi.org/10.1039/d2se00929c.
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Layered double-hydroxides (LDHs) have emerged as a benchmark catalyst for oxygen evolution reactions (OER). To accelerate the reaction kinetics for OER, it became important to design a hybrid interfacial material...
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Huang, Xianggang, Xin Wang, Mengling Zhang, Qilei Jiang, Zheng Qin, Yingxin Liu, Yan Hou, Xueqin Cao, and Hongwei Gu. "Manganese- and Selenium-codoping CeO2@Co3O4 Porous Core-shell Nanospheres for Enhanced Oxygen Evolution Reaction." Energy Advances, 2023. http://dx.doi.org/10.1039/d2ya00315e.
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As one of the semi-reactions of water splitting, electrocatalytic oxygen evolution reaction (OER) is a key process to generate sustainable energy. Co-based spinel oxides are deemed as promising OER electrocatalysts,...
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Abdollahi, Maliheh, Sara Al Sbei, Miriam A. Rosenbaum, and Falk Harnisch. "The oxygen dilemma: The challenge of the anode reaction for microbial electrosynthesis from CO2." Frontiers in Microbiology 13 (August 3, 2022). http://dx.doi.org/10.3389/fmicb.2022.947550.
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Microbial electrosynthesis (MES) from CO2 provides chemicals and fuels by driving the metabolism of microorganisms with electrons from cathodes in bioelectrochemical systems. These microorganisms are usually strictly anaerobic. At the same time, the anode reaction of bioelectrochemical systems is almost exclusively water splitting through the oxygen evolution reaction (OER). This creates a dilemma for MES development and engineering. Oxygen penetration to the cathode has to be excluded to avoid toxicity and efficiency losses while assuring low resistance. We show that this dilemma derives a strong need to identify novel reactor designs when using the OER as an anode reaction or to fully replace OER with alternative oxidation reactions.
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Huang, Shih‐Ching, Hsiang‐Chun Yu, Chun‐Kuo Peng, Yan‐Gu Lin, and Chia‐Yu Lin. "P‐Doped NiFe Alloy‐Based Oxygen Evolution Electrocatalyst for Efficient and Stable Seawater Splitting and Organic Electrosynthesis at Neutral pH." Small, December 24, 2024. https://doi.org/10.1002/smll.202408957.
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AbstractDevelopment of high‐performance and inexpensive electrocatalysts for oxygen evolution reaction (OER) at neutral pH is important for direct seawater splitting and organic electrosynthesis but remains challenging due to the sluggish OER kinetics and diverse side reactions inherent to the constituents of working electrolytes. Herein, we report on a P:NiFe electrode, containing P‐doped NiFe alloy, as an excellent electrocatalyst for hydrogen evolution reaction (HER) and OER pre‐catalyst for efficient OER in both seawater and organic electrolyte for adiponitrile (ADN) electrosynthesis at neutral pH. Fe and P species modulate the coordination environment of nickel sites, which enables the simultaneous formation of OER‐active nickel species and FePOx passivation layer, thus transforming HER‐active P:NiFe to OER‐active a‐P:NiFe. Besides, the redox‐dependent interconversion between HER‐active P:NiFe and OER‐active a‐P:NiFe is fast and reversible. Finally, efficient and stable overall seawater‐splitting and ADN electrosynthesis at an industrially relevant current density (100 mA cm−2) in pH‐neutral media are also demonstrated.
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Xiao, Zhifei, Haoliang Huang, Sixia Hu, Zhuanglin Weng, Yuping Huang, Bing Du, Xierong Zeng, Yuying Meng, and Chuanwei Huang. "Bifunctional Square‐Planar NiO4 Coordination of Topotactic LaNiO2.0 Films for Efficient Oxygen Evolution Reaction." Small Methods, November 27, 2023. http://dx.doi.org/10.1002/smtd.202300793.
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AbstractThe high‐efficient and low‐cost oxygen evolution reaction (OER) is decisive for applications of oxide catalysts in metal‐air batteries, electrolytic cells, and energy‐storage technologies. Delicate regulations of active surface and catalytic reaction pathway of oxide materials principally determine thermodynamic energy barrier and kinetic rate during catalytic reactions, and thus have crucial impacts on OER performance. Herein, a synergistic modulation of catalytically active surface and reaction pathway through facile topotactic transformations switching from perovskite (PV) LaNiO3.0 film to infinite‐layer (IL) LaNiO2.0 film is demonstrated, which absolutely contributes to improving OER performance. The square‐planar NiO4 coordination of IL‐LaNiO2.0 brings about more electrochemically active metal (Ni+) sites on the film surface. Meanwhile, the oxygen‐deficient driven PV‐ IL topotactic transformations lead to a reaction pathway converted from absorbate evolution mechanism to lattice‐oxygen‐mediated mechanism (LOM). The non‐concerted proton–electron transfer of LOM pathway, evidenced by the pH‐dependent OER kinetics, further boosts the OER activity of IL‐LaNiO2.0 films. These findings will advance the in‐depth understanding of catalytic mechanisms and open new possibilities for developing highly active perovskite‐derived oxide catalysts.
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Deng, Bohan, Guang-Qiang Yu, Wei Zhao, Yuanzheng Long, Cheng Yang, Peng Du, Xian He, et al. "A Self-Circulating Pathway for Oxygen Evolution Reaction." Energy & Environmental Science, 2023. http://dx.doi.org/10.1039/d3ee02360e.
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The oxygen evolution reaction (OER) suffers from its sluggish kinetics of traditional four-electron-transfer pathways (4e--OER). Herein, we propose a self-circulating electrochemical-thermal OER mechanism (SET-OER) as a new pathway for high-efficiency...
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Wu, Zhong. "Transition Metal Selenides for Oxygen Evolution Reaction." Energy Technology, April 3, 2024. http://dx.doi.org/10.1002/ente.202301574.
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Oxygen evolution reaction (OER) is essential to the water splitting and CO2 reduction reactions, while this reaction is kinetically sluggish and demands the efficient electrocatalyst. Transition metal selenides (TMSes) have gained greater attention as nonprecious metal‐based electrocatalysts due to their low cost, earth abundance, and high efficiency. Typically, TMSe can exhibit superior OER activity to their counterparts such as hydroxides/oxyhydroxides and sulfides. As such, their unique way to boost the catalytic activity is intriguing to researchers and many studies have been recently carried out. The last decades have witnessed the rapid development of TMSe‐based electrocatalysts in design and preparation for OER. However, there is still no exclusive review summarizing the recent development of this material for OER electrocatalysis. Herein, this article underscores the significant promise of TMSes in advancing the field of high‐performance OER electrocatalysts. The research progress is summarized and the importance of strategies to improve the performance of selenide electrodes including multimetal composite, hybrid composite with carbonaceous materials, morphological engineering, heterostructure engineering, and vacancies engineering is emphasized. Finally, the future challenges and opportunities concerning the improvement of TMSe electrocatalysts are outlined, which are essential for their further application in electrochemical energy conversion.
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Hu, Mengyu, Hanzhi Yu, Chong Chen, Yukun Zhang, Changjiang Hu, and Jun Ma. "Gamma-rays induced strong coupling between Ru nanoparticle and cobalt-based metal organic framework nanolayer for methanol oxidation and hydrogen evolution." New Journal of Chemistry, 2024. http://dx.doi.org/10.1039/d4nj04418e.
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The development of anodic reactions with accelerated kinetics to replace the oxygen evolution reaction (OER) reaction to promote the hydrogen evolution reaction (HER) with high value-added production is of crucial...
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Chen, Ligang, Wei Zhao, Juntao Zhang, Min Liu, Yin Jia, Ruzhi Wang, and Maorong Chai. "Recent Research on Iridium‐Based Electrocatalysts for Acidic Oxygen Evolution Reaction from the Origin of Reaction Mechanism." Small, June 28, 2024. http://dx.doi.org/10.1002/smll.202403845.
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AbstractAs the anode reaction of proton exchange membrane water electrolysis (PEMWE), the acidic oxygen evolution reaction (OER) is one of the main obstacles to the practical application of PEMWE due to its sluggish four‐electron transfer process. The development of high‐performance acidic OER electrocatalysts has become the key to improving the reaction kinetics. To date, although various excellent acidic OER electrocatalysts have been widely researched, Ir‐based nanomaterials are still state‐of‐the‐art electrocatalysts. Hence, a comprehensive and in‐depth understanding of the reaction mechanism of Ir‐based electrocatalysts is crucial for the precise optimization of catalytic performance. In this review, the origin and nature of the conventional adsorbate evolution mechanism (AEM) and the derived volcanic relationship on Ir‐based electrocatalysts for acidic OER processes are summarized and some optimization strategies for Ir‐based electrocatalysts based on the AEM are introduced. To further investigate the development strategy of high‐performance Ir‐based electrocatalysts, several unconventional OER mechanisms including dual‐site mechanism and lattice oxygen mediated mechanism, and their applications are introduced in detail. Thereafter, the active species on Ir‐based electrocatalysts at acidic OER are summarized and classified into surface Ir species and O species. Finally, the future development direction and prospect of Ir‐based electrocatalysts for acidic OER are put forward.