Articoli di riviste: "Alkaline reaction environment"

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Nikolaychuk, P. A. "Determination of Partial Reaction Orders of the Reduction of Potassium Permanganate by Ethanol in Various Environments". Herald of the Bauman Moscow State Technical University. Series Natural Sciences, n. 3 (108) (giugno 2023): 118–30. http://dx.doi.org/10.18698/1812-3368-2023-3-118-130.

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A spectrophotometric kinetic study of the reaction of the potassium permanganate reduction by excess ethanol in acidic, neutral and alkaline environments was performed. The reaction mixtures were prepared from the solutions of potassium permanganate of different concentrations (0.0004, 0.001 and 0.002 М) and either the solutions of sulphuric acid (1, 3 and 10 %), water, or the solutions of sodium hydroxide (0.01, 0.04 and 0.1 М). The kinetic curves were recorded with the spectrophotometer at the wavelengths of 525 nm (in acidic environment), 400 nm (in neutral environment) and 605 nm (in alkaline environment). The initial reaction rates were determined from the slopes of the initial linear parts of the kinetic curves. Using the differential van’t Hoff method, the partial reaction orders were determined. It was shown that in the acidic environment the partial reaction order with respect to permanganate is close to 1.5, and that with respect to hydrogen ions is close to 0.6. In the neutral and alkaline environments the reaction obeys the first partial order with respect to permanganate, and the partial order of the reaction in alkaline environments with respect to hydroxyl-ions is close to 0.8. It was also shown that the effective rate constants of the reaction in acidic and alkaline environments are significantly higher than that in neutral environment

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Reddy, K. Chiranjeevi, e Kolluru V. L. Subramaniam. "Quantitative phase analysis of slag hydrating in an alkaline environment". Journal of Applied Crystallography 53, n. 2 (13 marzo 2020): 424–34. http://dx.doi.org/10.1107/s1600576720001399.

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An X-ray diffraction (XRD)-based evaluation of the crystalline and amorphous phases in slag hydrating in an alkaline environment is presented. A method is developed for the quantification of the amorphous phases present in hydrating slag in a sodium hydroxide solution. In hydrating slag, the amorphous reaction product is identified as calcium aluminosilicate hydrate. A water-soluble sodium-based amorphous reaction product is also produced. The XRD-based quantification method relies on the direct decomposition of the XRD intensity pattern of the total amorphous phase present in partially hydrated slag into the intensity patterns of the amorphous unreacted slag, the hydrate and the sodium-based product. The unreacted slag content in partially hydrated slag is also determined from the decomposition of the intensity signature of the total amorphous phase. An independent verification of the amorphous unreacted slag content in hydrating slag is obtained from measurements of blends of unhydrated and partially hydrated slag. The XRD-based phase-quantification procedure developed here provides a basis for evaluating the extent of reaction in hydrating slag.

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Tutolo, Benjamin M., Robert Perrin, Rachel Lauer, Shane Bossaer, Nicholas J. Tosca, Alec Hutchings, Serhat Sevgen et al. "Groundwater-Driven Evolution of Prebiotic Alkaline Lake Environments". Life 14, n. 12 (7 dicembre 2024): 1624. https://doi.org/10.3390/life14121624.

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Alkaline lakes are thought to have facilitated prebiotic synthesis reactions on the early Earth because their modern analogs accumulate vital chemical feedstocks such as phosphate through the evaporation of dilute groundwaters. Yet, the conditions required for some building block synthesis reactions are distinct from others, and these conditions are generally incompatible with those permissible for nascent cellular function. However, because current scenarios for prebiotic synthesis have not taken account of the physical processes that drive the chemical evolution of alkaline lakes, the potential for the co-occurrence of both prebiotic synthesis and the origins and early evolution of life in prebiotic alkaline lake environments remains poorly constrained. Here, we investigate the dynamics of active, prebiotically relevant alkaline lakes using near-surface geophysics, aqueous geochemistry, and hydrogeologic modeling. Due to their small size, representative range of chemistry, and contrasting evaporation behavior, the investigated, neighboring Last Chance and Goodenough Lakes in British Columbia, Canada offer a uniquely tractable environment for investigating the dynamics of alkaline lake behavior. The results show that the required, extreme phosphate enrichments in alkaline lake waters demand geomorphologically-driven vulnerability to evaporation, while the resultant contrast between evaporated brines and inflowing groundwaters yields Rayleigh–Taylor instabilities and vigorous surface–subsurface cycling and mixing of lake and groundwaters. These results provide a quantitative basis to reconcile conflicting prebiotic requirements of UV light, salinity, metal concentration, and pH in alkaline lake environments. The complex physical and chemical processing inherent to prebiotic alkaline lake environments thus may have not only facilitated prebiotic reaction networks, but also provided habitable environments for the earliest evolution of life.

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Wei, Shaohua, Hongpeng Zhang, Haiyan Zhu, Lianyuan Wang, Jing Liang e Zhenxing Cheng. "Study on detoxification property of alkaline-modified MoO42--H2O2 decontaminants against PhSMe under subzero environment". E3S Web of Conferences 267 (2021): 02061. http://dx.doi.org/10.1051/e3sconf/202126702061.

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The decontaminant activated by MoO42- (MoO42--H2O2) suitable for subzero environment shows strong oxidizing ability and weak nucleophilicity due to its acid. In this paper, in order to improve nucleophilicity and retain oxidation of MoO42--H2O2 as far as possible, NH3 and NaOH were used as alkaline modifiers, and PhSMe was used as a simulant of HD to study the oxidation rate and products of sulfides by alkaline-modified MoO42--H2O2 below zero. Results showed that the reaction rate constants decreased with the increase of pH in both NH3 and NaOH modified MoO42--H2O2 at -20°C, and the relative ratio of sulfone to sulfoxide increased especially at pH>9. The reaction activation energy Ea of PhSMe oxidation in the alkaline-modified MoO42--H2O2 decontaminants was lower than that in the MoO42--H2O2 decontaminant, which indicated that the sensitivity of the oxidation reaction rate to temperature in MoO42--H2O2 was reduced after modification.

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Koyama, M., Y. Amano, S. Liu e T. Ishimoto. "Reaction Mechanism of Ethanol Oxidation over Gold Catalyst under Alkaline Environment". ECS Transactions 50, n. 2 (15 marzo 2013): 1907–12. http://dx.doi.org/10.1149/05002.1907ecst.

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Zhao, Wan, Hongshuai Cao, Liting Ruan, Shaoying He, Zhiai Xu e Wen Zhang. "High-performance self-supporting AgCoPO₄/CFP for hydrogen evolution reaction under alkaline conditions". RSC Advances 12, n. 25 (2022): 15751–58. http://dx.doi.org/10.1039/d2ra02621j.

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Krnel, Kristoffer, Goran Dražič e Tomaž Kosmač. "Degradation of AlN Powder in Aqueous Environments". Journal of Materials Research 19, n. 4 (aprile 2004): 1157–63. http://dx.doi.org/10.1557/jmr.2004.0150.

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The reactivity of AlN powder in an aqueous environment was studied by measuring the pH and the temperature during the hydrolysis of the powder at room and elevated temperatures. The influences of the powder concentration and the starting pH of the slurry were also investigated. The results of the measurements at room temperature show that there is an incubation time before the start of the AlN hydrolysis reactions. Once this incubation time is over, the pH and the temperature of the slurry start to increase, indicating the onset of the reactions. A higher starting temperature not only speeds up the reaction of the AlN powder with water, but it also shortens the incubation time. In addition, the starting temperature influences the morphology of the reaction product: at temperatures below 60 °C, the final product of the hydrolysis is crystalline Al(OH)3, whereas at higher temperatures (above 60 °C), crystalline AlOOH is formed. At very low pH values (pH = 1), the reaction of AlN powder with water is prevented (i.e., the incubation time is very long), whereas in an alkaline environment, the incubation time is approximately the same as in distilled water, but the reaction is accelerated.

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Mendonça Inocêncio, Carlos Victor Mendonça, Claudia Morais e Boniface Kokoh. "Transition Metal Sulfide-Based Electrocatalysts for Hydrogen Evolution Reaction in Alkaline Environment". ECS Meeting Abstracts MA2021-01, n. 47 (30 maggio 2021): 1922. http://dx.doi.org/10.1149/ma2021-01471922mtgabs.

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Fu, Luhong, Shupeng Wang, Junlin Cai, Hongpu Huang, Fulin Yang e Shuifen Xie. "Recent advances in platinum-group-metal based electrocatalysts for alkaline hydrogen oxidation reaction". Chemical Synthesis 3, n. 4 (2023): 53. http://dx.doi.org/10.20517/cs.2023.53.

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The reaction kinetics of hydrogen oxidation reactions (HOR) unfavorably decreases by 2~3 orders of magnitude under alkaline conditions, even on the most active platinum-group-metal (PGM) electrocatalysts. This sticky problem severely restricts the efficiency and commercialization of anion-exchange membrane fuel cells (AEMFCs). So far, no other material has HOR electrocatalytic performance comparable to PGM-based electrocatalysts. Forced by the scarce reserves and high prices of PGMs, it is significant to elaborately design and synthesize PGM-based electrocatalysts with ultimately atomic utilization and substantially improved alkaline HOR performance. In this review, we summarize recent advances in the structure engineering approaches to synthesis of advanced PGM-based nanocatalysts toward enhanced alkaline HOR performance. The generally acknowledged catalytic mechanisms with corresponding activity descriptors are reviewed ﬁrstly to deeply understand the discrepancies in the HOR kinetics of alkaline and acidic reactions. Then, several representative strategies are emphasized and discussed at length by changing the chemical and coordination environment and size/morphology of nanocatalysts. Meanwhile, the inﬂuence factors for the performance of AEMFC devices constructed by PGM-based anode catalysts are brieﬂy highlighted. In conclusion, strategies for boosting the electrocatalytic performance and challenges on the roles of catalytic mechanism insights and practical AEMFC applications are finally outlined. We hope this review will guide the design and catalytic mechanism research of novel PGM-based alkaline HOR catalysts, thereby promoting their further development and application in AEMFC technologies.

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An, Lingyun, Chenggong Chang, Fengyun Yan e Jianhong Peng. "Study on the Deterioration Mechanism of Magnesium Oxychloride Cement under an Alkaline Environment". Materials 16, n. 17 (30 agosto 2023): 5924. http://dx.doi.org/10.3390/ma16175924.

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The deterioration process and deterioration mechanism of magnesium oxychloride cement (MOC) in an alkaline environment were studied using a scanning electron microscope (SEM), an X-ray diffractometer (XRD), a Fourier transform infrared spectrometer (FT-IR) and a micro-electro-hydraulic servo pressure testing machine to investigate the effects of soaking time in 10 wt.% NaOH solution on the macro- and micro-morphology, phase composition and compressive strength of MOC samples. The results show that the deterioration of MOC samples under an alkaline environment is mainly caused by the alkaline environment providing more OH− ions, which can react with 5Mg(OH)2·MgCl2·8H2O (P 5) in the sample. The resulting reaction gives rise to a faster decomposition of 5Mg(OH)2·MgCl2·8H2O (P 5) and a substantial reduction in the strength of the sample, and finally leads to a gradual deterioration of MOC samples. Meanwhile, immersion time exhibits a significant effect on MOC samples. The extension of immersion time coincides with more OH− ions entering the sample, and the greater presence of OH ions increases the likelihood that more P 5 will produce a hydrolysis reaction, further resulting in the increased deterioration of the sample. After soaking for 6 h in alkaline media, the main phase composition of the surface layer of an MOC sample changes to MgO and Mg(OH)2, and its microscopic morphology is also dominated by round sheets, giving rise to a sharp decrease in its compressive strength (52.2%). When the immersion time is prolonged to 72 h, OH− ions have already immersed into the inner core of the sample, causing the disappearance of P 5 from the whole sample. At the same time, both the surface and inner core of the sample exhibit a disc-shaped morphology, and chalking phenomena also appear on the surface of the sample. This reduces the compressive strength of the sample to 13.5 MPa, only 20% of its compressive strength in water. The compressive strength of the sample after 120 h of immersion is as low as 8.6 MPa, which is lower than that of the sample dipped in water for 21 days (9.5 MPa). As a result, the MOC samples studied in alkaline environments exhibit a faster deterioration rate, mainly because of a faster hydrolysis reaction by P 5, caused by more OH− ions.

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Tian, Gui-Peng, Qian-Yuan Wu, Ang Li, Wen-Long Wang e Hong-Ying Hu. "Enhanced decomposition of 1,4-dioxane in water by ozonation under alkaline condition". Water Science and Technology 70, n. 12 (30 ottobre 2014): 1934–40. http://dx.doi.org/10.2166/wst.2014.414.

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1,4-Dioxane is a probable human carcinogenic and refractory substance that is widely detected in aquatic environments. Traditional wastewater treatment processes, including activated sludge, cannot remove 1,4-dioxane. Removing 1,4-dioxane with a reaction kinetic constant of 0.32 L/(mol·s) by using ozone, a strong oxidant, is difficult. However, under alkaline environment, ozone generates a hydroxyl radical (•OH) that exhibits strong oxidative potential. Thus, the ozonation of 1,4-dioxane in water under different pH conditions was investigated in this study. In neutral solution, with an inlet ozone feed rate of 0.19 mmol/(L·min), the removal efficiency of 1,4-dioxane was 7.6% at 0.5 h, whereas that in alkaline solution was higher (16.3–94.5%) within a pH range of 9–12. However, the removal efficiency of dissolved organic carbon was considerably lower than that of 1,4-dioxane. This result indicates that several persistent intermediates were generated during 1,4-dioxane ozonation. The pseudo first-order reaction further depicted the reaction of 1,4-dioxane. The obvious kinetic constants (kobs) at pH 9, 10, 11 and 12 were 0.94, 2.41, 24.88 and 2610 L/(mol·s), respectively. Scavenger experiments on radical species indicated that •OH played a key role in removing 1,4-dioxane during ozonation under alkaline condition.

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Давтян, В. А., e Г. О. Торосян. "DETECTION AND DETOXICATION OF MALATHION IN THE ENVIRONMENT". Химическая безопасность / Chemical Safety Science 2, n. 1 (30 giugno 2018): 220–26. http://dx.doi.org/10.25514/chs.2018.1.12896.

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Приведены результаты исследований по обнаружению и детоксикации фосфорорганического пестицида - малатиона (МЛТ), представляющего опасность в связи с его интенсивным использованием в сельском хозяйстве и последующим быстрым распространением в окружающей среде. Для обнаружения МЛТ применен гибридный метод высокоэффективной жидкостной хроматографии в сочетании с тандемной масс-спектрометрией. Детоксикацию МЛТ предложено проводить с помощью щелочного гидролиза. Показано, что в ходе щелочного гидролиза происходит детоксикация МЛТ по типу реакции Гофмановского расщепления ониевых соединений, что позволяет избежать образования крайне токсичного соединения малаоксона. Abstract - The results of studying detection and removal of organophosphorus pesticide chemical - malathion are presented taking into consideration its potential hazard due to an intensive use in agriculture followed by rapid spread in the environment. Detection of malathion can be carried out by a highly effective HPLC-MS/MS hybrid method, while detoxification can be performed by means of alkaline hydrolysis. It is shown that the alkaline hydrolysis results in the malathion detoxification through the Hoffmann splitting reaction of onium compounds, thus avoiding the formation of an extremely toxic malaoxon compound.

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Hou, Ying Ying, Ming Shuo Geng, Xiang Feng Zeng e Zu Wei Wang. "A New Montmorillonite/Humic Acid Complex Prepared in Alkaline Condition to Remove Cadmium from Waste Water". Applied Mechanics and Materials 522-524 (febbraio 2014): 547–51. http://dx.doi.org/10.4028/www.scientific.net/amm.522-524.547.

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A new montmorillonite/humic acid complex preparation method in alkaline environment was studied by experiment, and the complex effect on remediation of heavy metal pollution was verified. The best technologic condition of the montmorillonite/humic acid complex preparation in alkaline environment was that the mass ratio between montmorillonite and humic acid was 100:3, the reaction solution was 0.01 mol/L sodium nitrate solution, the pH value of the reaction solution was 8.5, and the reaction time was 24 hours. The complex has better remediation effect on cadmium waste water. The cadmium adsorption capacity of the complex was 18.96 mg/g, and the pH value ranges of cadmium waste water suited for the complex was from 5 to 9. When the ratio of Cd initiative concentration/the complex quantity was lower than 300:1 and the pH value of the waste water was higher than 8, almost all of the Cd in waste water can be removed.

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Singh, Tejpal. "Kinetic study of L-lysine and L-arginine by hexacyanoferrate (III) ion in presence of Os (VIII)". Research Journal of Chemistry and Environment 27, n. 2 (15 gennaio 2023): 62–72. http://dx.doi.org/10.25303/2702rjce062072.

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Amino acids and their metal complexes have vital role in functioning the metabolism of all living system. Amino acids can undergo many types of reactions in acidic as well as in alkaline medium. The reactions of L-lysine and L-arginine amino acids have been selected in alkaline medium for the present study. The kinetics of oxidation of L-lysine and L-arginine by alkaline Os (VIII), which was continuously regenerated by hexacyanoferrate (III) ion, was studied in the 0.01- 0.10 M and 298 K – 318 K temperature range. The rate of reaction was found to be zero with respect to [Fe(CN6)]3- and one with respect to Os (VIII).

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Li, Zhao, Wenhan Niu, Zhenzhong Yang, Abdelkader Kara, Qi Wang, Maoyu Wang, Meng Gu, Zhenxing Feng, Yingge Du e Yang Yang. "Boosting alkaline hydrogen evolution: the dominating role of interior modification in surface electrocatalysis". Energy & Environmental Science 13, n. 9 (2020): 3110–18. http://dx.doi.org/10.1039/d0ee01750g.

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The alkaline hydrogen evolution reaction (A-HER) holds great promise for clean hydrogen fuel generation but its practical utilization is severely hindered by the sluggish kinetics for water dissociation in alkaline solutions.

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Girimonte, Aldo, Andrea Stefani, Clara Mucci, Roberto Giovanardi, Andrea Marchetti, Massimo Innocenti e Claudio Fontanesi. "Electrochemical Performance of Metal-Free Carbon-Based Catalysts from Different Hydrothermal Carbonization Treatments for Oxygen Reduction Reaction". Nanomaterials 14, n. 2 (12 gennaio 2024): 173. http://dx.doi.org/10.3390/nano14020173.

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This research investigates the difference between products obtained through two hydrothermal carbonization treatments. Our aim is to synthesize metal-free, carbon-based catalysts for the oxygen reduction reaction (ORR) to serve as efficient and cost-effective alternatives to platinum-based catalysts. Catalysts synthesized using the traditional hydrothermal approach exhibit a higher electrocatalytic activity for ORR in alkaline media, despite their more energy-intensive production process. The superior performance is attributed to differences in the particle morphology and the chemical composition of the particle surfaces. The presence of functional groups on the surfaces of catalysts obtained via a traditional approach significantly enhances ORR activity by facilitating deprotonation reactions in an alkaline environment. Our research aims to provide a reference for future investigations, shifting the focus to the fine-tuning of surface chemical compositions and morphologies of metal-free catalysts to enhance ORR activity.

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Wang, Tingting, Miao Wang, Hao Yang, Mingquan Xu, Chuandong Zuo, Kun Feng, Miao Xie et al. "Weakening hydrogen adsorption on nickel via interstitial nitrogen doping promotes bifunctional hydrogen electrocatalysis in alkaline solution". Energy & Environmental Science 12, n. 12 (2019): 3522–29. http://dx.doi.org/10.1039/c9ee01743g.

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Liu, Tong, Wei Zhang, Tao Chen, Dong Liu, Linlin Cao, Tao Ding, Xiaokang Liu et al. "Regulating the Coordination Environment of Ruthenium Cluster Catalysts for the Alkaline Hydrogen Evolution Reaction". Journal of Physical Chemistry Letters 12, n. 33 (17 agosto 2021): 8016–23. http://dx.doi.org/10.1021/acs.jpclett.1c01936.

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Rani, B. Jansi, G. Ravi, R. Yuvakkumar, S. I. Hong, Dhayalan Velauthapillai, M. Thambidurai, Cuong Dang e B. Saravanakumar. "Neutral and alkaline chemical environment dependent synthesis of Mn3O4 for oxygen evolution reaction (OER)". Materials Chemistry and Physics 247 (giugno 2020): 122864. http://dx.doi.org/10.1016/j.matchemphys.2020.122864.

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Liu, Zhehao, Hefeng Yuan, Zihao Wan, Zizai Ma, Xiaoyang Deng e Xiaoguang Wang. "Nanostructured Co3O4@NiFe-LDH heterojunction catalysts for improving oxygen evolution reaction in alkaline environment". Journal of Alloys and Compounds 983 (maggio 2024): 173837. http://dx.doi.org/10.1016/j.jallcom.2024.173837.

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Buchauer, Fabian Luca, Søren Bredmose Simonsen e Christodoulos Chatzichristodoulou. "Screening of Perovskites as Oxygen Evolution Reaction Catalysts in Alkaline Environment Tested Under Industrially Relevant Conditions". ECS Meeting Abstracts MA2023-01, n. 36 (28 agosto 2023): 2088. http://dx.doi.org/10.1149/ma2023-01362088mtgabs.

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In recent years the research in catalyst development for the Oxygen Evolution Reaction (OER) in alkaline media has focused on finding the catalytically most active materials. Furthermore, catalysts are usually tested in an RDE setup at room temperature in 0.1 or 1 M concentrated KOH solution, which is far from industrial application conditions, where commonly temperatures between 70-100 ⁰C and highly concentrated electrolyte (6-10 M KOH) are used [1]. This is problematic as the material response is very different at higher temperatures and concentration of electrolyte. The expected thermally activated OER performance is often accompanied by severe degradation, observed already after short-term operation at industrially relevant conditions [2]. Eventually this results in severe loss in performance. For example, Pascuzzi et al. reported fast electrode degradation at industrial operating conditions (75 ⁰C; 10 M KOH and 100 mA/cm2) due to the breakdown of the platelet-like morphology of NiFeOxHy layered double hydroxide (LDH) [3]. While the long-term durability of NiFeOxHy LDH remains questionable, with conflicting findings suggesting a rather complex interplay between structure-composition-operating conditions and activity-stability, perovskites offer an interesting alternative as they can accommodate a broad range of elements on both the A- and B-site, allowing for tuning the material properties. Perovskite catalysts have in some cases shown good activity and stability, one good example is PrBa0.5Sr0.5FexCo2-xO5+ 𝛿, which showed an overpotential of 290 mV at 10 mA/cm2 and stable operation for 2000 h in 1 M KOH [4]. However, in most cases critical raw materials (CRM) are involved in high performance perovskite catalysts. Furthermore, the stability of the host perovskite remains a challenge under industrial OER conditions even for rather stable perovskite compositions. For instance, Adolphsen et al. observed the formation of secondary phases in La, Ni and Fe based perovskites at 100 ⁰C when immersed in 31 wt.% KOH electrolyte [5]. In this study the performance and stability of different perovskite materials, including some of the most prominent OER perovskite catalyst materials from the literature, are explored at room temperature and at industrial operating conditions. Our tests of the most prominent catalyst materials show low stability and strong signs of decomposition at industrial operating conditions. [1] Zeng, K., & Zhang, D. (2010). Recent progress in alkaline water electrolysis for hydrogen production and applications. Progress in Energy and Combustion Science, 36(3), 307–326. https://doi.org/10.1016/j.pecs.2009.11.002 [2] Lohmann-Richters, F. P., Renz, S., Lehnert, W., Müller, M., & Carmo, M. (2021). Review—Challenges and Opportunities for Increased Current Density in Alkaline Electrolysis by Increasing the Operating Temperature. Journal of The Electrochemical Society, 168(11), 114501. https://doi.org/10.1149/1945-7111/ac34cc [3] Etzi Coller Pascuzzi, M., Man, A. J. W., Goryachev, A., Hofmann, J. P., & Hensen, E. J. M. (2020). Investigation of the stability of NiFe-(oxy)hydroxide anodes in alkaline water electrolysis under industrially relevant conditions. Catalysis Science and Technology, 10(16), 5593–5601. https://doi.org/10.1039/d0cy01179g [4] Jo, H., Yang, Y., Seong, A., Jeong, D., Kim, J., Joo, S. H., Kim, Y. J., Zhang, L., Liu, Z., Wang, J. Q., Kwak, S. K., & Kim, G. (2022). Promotion of the oxygen evolution reaction: Via the reconstructed active phase of perovskite oxide. Journal of Materials Chemistry A, 10(5), 2271–2279. https://doi.org/10.1039/d1ta08445c [5] Adolphsen, J. Q., Sudireddy, B. R., Gil, V., & Chatzichristodoulou, C. (2018). Oxygen Evolution Activity and Chemical Stability of Ni and Fe Based Perovskites in Alkaline Media. Journal of The Electrochemical Society, 165(10), F827–F835. https://doi.org/10.1149/2.0911810jes

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Kočí, V., M. Keppert e R. Černý. "Reaction kinetics of basaltic elements in cementitious matrices: theoretical considerations". Journal of Physics: Conference Series 2628, n. 1 (1 ottobre 2023): 012011. http://dx.doi.org/10.1088/1742-6596/2628/1/012011.

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Abstract Basalt fibers, the frequently mentioned alternative to those made of steel, possess very good mechanical properties and temperature resistance. The alkaline environment of cement matrix makes it vulnerable due to partial fiber decomposition by the effects of OH- ions. This paper aims at computational modelling of such reactions in order to approximate the course of degradation or to predict it lately. The isothermal reaction models are discussed to reveal their strong/weak points by means of fundamental reaction mechanisms analysis. The shape factor and diffusion-based deceleration of the reactions are mentioned as the most significant ones in that respect. The model accuracy is quantified based on fitting the modelling outputs to reference experimental data. The effect of discussion was found to be the most significant factor as the model fitting reached the lowest RMSE (0.0047). Further application of a diffusion model is therefore recommended. The geometrical models need to have reaction rate reduction explicitly incorporated in the reaction constant, otherwise inapplicable data is produced (RMSE = 0.0193).

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Ozdemir, Ismail, Bahattin Bulbul, Thomas Grund e Thomas Lampke. "Wear and Corrosion Behavior of Cold-Sprayed Cu-10Sn Coatings". Crystals 13, n. 3 (18 marzo 2023): 523. http://dx.doi.org/10.3390/cryst13030523.

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Gas-atomized Cu-10Sn powders as a potential substitute for sintered bronze layers are usually employed in plain-bearing shells produced by cold spray (CS) processes on steel substrates (AISI 1010). In this study, the effective thickness, i.e., approx. 450 µm, of the bronze overlay required for the bearing shell was successfully and cost-effectively deposited in a short time. A ball-on-disc test setup was used to explore the tribological behavior of cold-sprayed bronze coatings under dry sliding conditions, and the electrochemical corrosion behaviors of sprayed coatings at room temperature were also evaluated by using the potentiodynamic scanning (PDS) technique in acidic (0.01 M Na2SO4) and alkaline (3.5% NaCl) environments. The characterization of the sprayed bronze coatings revealed no formation of oxidation or new phases during cold spraying and that the coatings were well-adhered to the substrates, implying good bonding. The wear results demonstrated that, as the load and sliding distance increased, the friction coefficients and wear rates of the sprayed coatings decreased. The PDS results showed that the corrosion resistance of the Cu-10Sn coating layer in an acidic environment is higher than that in an alkaline environment. In addition, the coated layer presented no passivation or pitting onset due to the heavy corrosion reaction in an alkaline solution.

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Chen, Lei, Yijia Yin, Linjia Jian, Xianglong Han, Xuefeng Zhao e Donghui Wang. "Enhanced Bactericidal Effect of Calcinated Mg–Fe Layered Double Hydroxide Films Driven by the Fenton Reaction". International Journal of Molecular Sciences 24, n. 1 (23 dicembre 2022): 272. http://dx.doi.org/10.3390/ijms24010272.

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Osteogenic and antibacterial abilities are the permanent pursuit of titanium (Ti)-based orthopedic implants. However, it is difficult to strike the right balance between these two properties. It has been proved that an appropriate alkaline microenvironment formed by Ti modified by magnesium–aluminum layered double hydroxides (Mg–Al LDHs) could achieve the selective killing of bacteria and promote osteogenesis. However, the existence of Al induces biosafety concerns. In this study, iron (Fe), an essential trace element in the human body, was used to substitute Al, and a calcinated Mg–Fe LDH film was constructed on Ti. The results showed that a proper local alkaline environment created by the constructed film could enhance the antibacterial and osteogenic properties of the material. In addition, the introduction of Fe promoted the Fenton reaction and could produce reactive oxygen species in the infection environment, which might further strengthen the in vivo bactericidal effect.

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Viola, Veronica, Prince Allah, Priyadharshini Perumal e Michelina Catauro. "Alkali Activation of Metakaolin and Wollastonite: Reducing Sodium Hydroxide Use and Enhancing Gel Formation through Carbonation". Materials 17, n. 19 (8 ottobre 2024): 4910. http://dx.doi.org/10.3390/ma17194910.

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Alkali activated materials (AAMs) offer significant advantages over traditional materials like Portland cement, but require the use of strong alkaline solutions, which can have negative environmental impacts. This study investigates the synthesis of AAMs using metakaolin and wollastonite, aiming to reduce environmental impact by eliminating sodium silicate and using only sodium hydroxide as an activator. The hypothesis is that wollastonite can provide the necessary silicon for the reaction, with calcium from wollastonite potentially balancing the negative charges usually countered by sodium in the alkaline solution. This study compares raw and carbonated wollastonite (AAM-W and AAM-CW) systems, with raw materials carefully characterized and binding networks analyzed using TGA, FT-IR, and XRD. The results show that while wollastonite can reduce the amount of sodium hydroxide needed, this reduction cannot exceed 50%, as higher substitution levels lead to an insufficiently alkaline environment for the reactions. The carbonation of wollastonite enhances the availability of silicon and calcium, promoting the formation of both N-A-S-H and C-A-S-H gels.

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Melar, Jaroslav, Vratislav Bednarik, Roman Slavik e Miroslav Pastorek. "Effect of hydrothermal treatment on the structure of an aluminosilicate polymer". Open Chemistry 11, n. 5 (1 maggio 2013): 782–89. http://dx.doi.org/10.2478/s11532-013-0204-9.

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AbstractThe effect of hydrothermal treatment on the structure of an aluminosilicate polymer prepared by a polycondensation reaction between silicate and hydroxoaluminate in alkaline aqueous solution was studied. The structural changes were investigated using X-ray diffraction analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy imaging and thermogravimetric analysis. The results indicated that the amorphous aluminosilicate polymer transformed into a crystalline product during the hydrothermal treatment at 145°C. The crystalline phase was identified as a mineral of the zeolite group, most likely phillipsite. This transformation required an alkaline environment during the hydrothermal treatment.

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27

Luo, Liuxuan, Cehuang Fu, Shuiyun Shen, Fengjuan Zhu e Junliang Zhang. "Probing structure-designed Cu–Pd nanospheres and their Pt-monolayer-shell derivatives as high-performance electrocatalysts for alkaline and acidic oxygen reduction reactions". Journal of Materials Chemistry A 8, n. 42 (2020): 22389–400. http://dx.doi.org/10.1039/d0ta05905f.

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Composition-graded Cu–Pd nanospheres are annealed for highly efficient alkaline oxygen reduction reaction, and further coated with Pt monolayer shells for high-performance acidic oxygen reduction reaction.

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Xiao, Peng, Mahasin Alam Sk, Larissa Thia, Xiaoming Ge, Rern Jern Lim, Jing-Yuan Wang, Kok Hwa Lim e Xin Wang. "Molybdenum phosphide as an efficient electrocatalyst for the hydrogen evolution reaction". Energy Environ. Sci. 7, n. 8 (2014): 2624–29. http://dx.doi.org/10.1039/c4ee00957f.

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29

Chen, Zhijie, Xiaoguang Duan, Wei Wei, Shaobin Wang e Bing-Jie Ni. "Recent advances in transition metal-based electrocatalysts for alkaline hydrogen evolution". Journal of Materials Chemistry A 7, n. 25 (2019): 14971–5005. http://dx.doi.org/10.1039/c9ta03220g.

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Choi, Yong-Wook. "Exploring on Stainless Steel Based Electrodes for Oxygen Evolution Reaction Under Alkaline Electrolyte". ECS Meeting Abstracts MA2024-02, n. 56 (22 novembre 2024): 3754. https://doi.org/10.1149/ma2024-02563754mtgabs.

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The clean energy, namely hydrogen, has been spotted lighted as a promising means for tackling down the problem of climate change. Alkaline Water Electrolysis (AWE) is identified as the representative method for obtaining hydrogen through sustainable way, because it needs only water and electricity (supplied from renewable energy sources such as solar light and wind). Especially, cheaper electrode materials like transition metal (Nickel) could be employed for both cathode and anode, whereas the other method (PEM-WE) should use only more expensive Pt-group materials. Herein, we explored the possibility of stainless steel (SS) for anode under alkaline environment. SS based electrodes showed steady performance over the versatile range of current densities (from 10 mA/cm2 to 100 mA/cm2). These novel results would provide subsequent research with how to design for alternative electrode materials. Figure 1

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31

Tuan Anh, Le, Nguyen Thuy Ninh, Le Quoc Phong Huu, Le Sinh Hoang e Nguyen Khoa Tan. "Influence of fly ash and blast furnace slag on characteristics of geopolymer non-autoclaved aerated concrete". Transport and Communications Science Journal 72, n. 1 (25 gennaio 2021): 25–32. http://dx.doi.org/10.47869/tcsj.72.1.4.

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Geopolymer materials are known as sustainable and environmental material. The main constituents of geopolymer material are alumina and silicon, which can be activated in an alkaline environment. In this paper, the reaction of alumino-silicate materials in the alkaline agent is investigated on geopolymer non-autoclaved aerated concrete (GNAAC). The main constituents of GNAAC are fly ash (FA), blast furnace slag (BSF), lime, gypsum, aluminium powder, and alkaline solution. In the mix proportions, FA and BSF are used to replace crushed sand and cement. The results indicate that the GNAAC can be produced similarly as traditional autoclaved aerated concrete. Besides, the flow diameter of the mixture using blast furnace slag is lower than that of fly ash. The temperature and expansion ability decrease with an increase in FA/BFS – Lime and alkaline content. Furthermore, the compressive strength of GNAAC can be determined by synthesizing geopolymer without steam and pressure curing conditions.

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Guo, Hao, Hyeon-Jung Kim e Sang-Young Kim. "Research on Hydrogen Production by Water Electrolysis Using a Rotating Magnetic Field". Energies 16, n. 1 (21 dicembre 2022): 86. http://dx.doi.org/10.3390/en16010086.

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In this paper, the effect of rotating magnetic fields on hydrogen generation from water electrolysis is analyzed, aiming to provide a research reference for hydrogen production and improving hydrogen production efficiency. The electrolytic environment is formed by alkaline solutions and special electrolytic cells. The two electrolytic cells are connected to each other in the form of several pipes. The ring magnets are used to surround the pipes and rotate the magnets so that the pipes move relative to the magnets within the ring magnetic field area. Experimentally, the electrolysis reaction of an alkaline solution was studied by using a rotating magnetic field, and the effect of magnetic field rotation speed on the electrolysis reaction was analyzed using detected voltage data. The experimental phenomenon showed that the faster the rotation speed of the rotating magnetic field, the faster the production speed of hydrogen gas.

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Adabi Firouzjaie, Horie, Abolfazl Shakouri, Christopher Williams, John R. Regalbuto, Alexey Serov, William Earl Mustain, Andrea Zitolo, Tristan Asset, Frederic Jaouen e Horie Adabi Firouzjaie. "Multi-Atom PGM Based Catalyst for Highly Efficient Oxygen Reduction Reaction(ORR) and Hydrogen Oxidation Reaction (HOR) in Alkaline Environment". ECS Meeting Abstracts MA2022-02, n. 39 (9 ottobre 2022): 1439. http://dx.doi.org/10.1149/ma2022-02391439mtgabs.

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Anion exchange membrane fuel cells (AEMFCs) have recently seen significant growth in interest as their achievable current density, peak power density, and longevity have been improved dramatically. Though these advances in performance have been important for demonstrating the feasibility of the technology, nearly all AEMFCs reported in the literature have required a relatively high loading of platinum group metal (PGM)-based catalysts at both the anode and cathode electrodes [1]. However, to take command of the low-temperature fuel cell market, AEMFCs cannot simply reach the same performance as incumbent proton exchange membrane fuel cells (PEMFCs), which have had decades of development and investment. AEMFCs must realize their most widely quoted advantage over PEMFCs and be produced at a much lower cost than PEMFCs. The most likely pathway to acceptably low cost will involve reducing the PGM loading in both electrodes. At the cathode, reasonable PGM-free catalysts exist, as will be shown in this work. At the anode; however, there are no practical contenders that exist to replace PGM-based catalysts. Hence, the most practical approach is to create transitional catalysts with ultra-low PGM content until future PGM-free catalysts can be realized. To reduce the platinum group metal (PGM) loading in anion exchange membrane fuel cell (AEMFC) electrodes, it is important to transition to catalysts with very low PGM content, and eventually to create catalysts that are completely PGM-free. One approach that can be used in both cases is to create atomically dispersed metals on a carbon support. In this work, four catalysts were prepared using a new, simple, scalable Controlled Surface Tension (CST) method: Pt/C, Pt/NC, PtRu/C, and PtRu/NC. CST is unique as it allows for a high density of very small multi-atom clusters, facilitated by altering the surface tension in the synthesis medium. The catalysts were physically characterized using a wide array of techniques, including high-resolution Cs aberration-corrected scanning transmission electron microscopy (STEM), extended X-ray absorption fine structure (EXAFS), and X-ray Absorption Near-Edge Structure (XANES). The catalysts were also tested for their oxygen reduction reaction and hydrogen oxidation reaction activity both ex-situ on a rotating ring-disk electrode and in-situ while integrated into the anode (PtRu) and cathode (Pt) of operating AEMFCs. With this new generation of low-PGM materials, it was possible to reduce the PGM loading by a factor of 14 while achieving comparable performance to commercial catalysts with a peak power density approaching 2 W/cm2. AEMFCs were also assembled with ultralow PGM loading (0.05 mgPGM/cm2), where PtRu/NC anodes were paired with Fe–N–C cathodes [2], which allowed for the demonstration of cells with a specific power of 25 W/mgPGM (40 W/mgPt).

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Jalilov, Almaz S. "Activated Vacuum Residue for Efficient Oxygen Reduction Reaction in Alkaline Media". ECS Meeting Abstracts MA2023-02, n. 54 (22 dicembre 2023): 2631. http://dx.doi.org/10.1149/ma2023-02542631mtgabs.

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As a potential replacement for Pt-based materials, the heteroatom-doped and metal-free porous carbons have always been a crucial challenge in modern electrocatalysis. On the other hand, petroleum waste, particularly, vacuum residue presents as a carbon-rich precursor for the development of porous carbons for electrocatalysis. Herein, the new catalysts were prepared from vacuum residue gained from the local petroleum industry. The porous carbons (PCs) as the catalysts were prepared via a simple single route activation at 800 °C and 2 hours in the presence of phosphoric acid. PC possesses a high surface area at ~2200 m2/g with mixed micro- and meso porosities as well as high graphitization content. Spectroscopic analyses reveal up to ~6 % of phosphorous doping content. PCs were tested against oxygen reduction reaction (ORR) as an important challenge in electrochemistry. The structural features and the differences in the activating agents for the development of the PCs were compared to decipher the importance of the doped heteroatoms’ environment in ORR. The ORR efficiency of the electrocatalysts was compared against the commercial 5% Pt/C under alkaline conditions to show the potential of the vacuum residue-derived PCs as the sustainable utilization of petroleum waste.

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Yuan, Nan Nan, e Jun Hong. "The Research on RhodamineB Degradation in MW/H₂O₂ System under Alkaline Environment". Applied Mechanics and Materials 105-107 (settembre 2011): 1505–8. http://dx.doi.org/10.4028/www.scientific.net/amm.105-107.1505.

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In this work, the degradation of Rhodamine B by hydrogen peroxide under microwave irradiation is studied and the optimum conditions are designed by single factor experiment. The UV-VIS spectral changes of RhB solution is detected under the optimum conditions. The results indicate that microwave induction can efficiently improve the oxidative degradation of RhB by hydrogen peroxide in alkaline solution, espcially the dye has the best photodegradation efficiency more than 99% when the concentration of RhB was 300mg/l and the pH of solution was 12 after irradiated for 10min, It is better than RhB under visible irradiation in alkaline environment with hydrogen peroxide. The solution initial pH has no effect on the temporal absorption spectral of RhB. The process of reaction conforms to the first-order kinetic equation.

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Zhang, Bao, Lishang Zhang, Qiuyang Tan, Jinsong Wang, Jia Liu, Houzhao Wan, Ling Miao e Jianjun Jiang. "Simultaneous interfacial chemistry and inner Helmholtz plane regulation for superior alkaline hydrogen evolution". Energy & Environmental Science 13, n. 9 (2020): 3007–13. http://dx.doi.org/10.1039/d0ee02020f.

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Developing highly efficient and durable alkaline hydrogen evolution reaction (HER) electrocatalysts composed of earth-abundant materials is crucial for large-scale electrochemical hydrogen production.

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Liu, Yu, Panpan Li, Zegao Wang e Liangjuan Gao. "Shape–Preserved CoFeNi–MOF/NF Exhibiting Superior Performance for Overall Water Splitting across Alkaline and Neutral Conditions". Materials 17, n. 10 (7 maggio 2024): 2195. http://dx.doi.org/10.3390/ma17102195.

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This study reported a multi–functional Co0.45Fe0.45Ni0.9–MOF/NF catalyst for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and overall water splitting, which was synthesized via a novel shape–preserving two–step hydrothermal method. The resulting bowknot flake structure on NF enhanced the exposure of active sites, fostering a superior electrocatalytic surface, and the synergistic effect between Co, Fe, and Ni enhanced the catalytic activity of the active site. In an alkaline environment, the catalyst exhibited impressive overpotentials of 244 mV and 287 mV at current densities of 50 mA cm−2 and 100 mA cm−2, respectively. Transitioning to a neutral environment, an overpotential of 505 mV at a current density of 10 mA cm−2 was achieved with the same catalyst, showing a superior property compared to similar catalysts. Furthermore, it was demonstrated that Co0.45Fe0.45Ni0.9–MOF/NF shows versatility as a bifunctional catalyst, excelling in both OER and HER, as well as overall water splitting. The innovative shape–preserving synthesis method presented in this study offers a facile method to develop an efficient electrocatalyst for OER under both alkaline and neutral conditions, which makes it a promising catalyst for hydrogen production by water splitting.

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38

Bo, Xin, Rosalie K. Hocking, Si Zhou, Yibing Li, Xianjue Chen, Jincheng Zhuang, Yi Du e Chuan Zhao. "Capturing the active sites of multimetallic (oxy)hydroxides for the oxygen evolution reaction". Energy & Environmental Science 13, n. 11 (2020): 4225–37. http://dx.doi.org/10.1039/d0ee01609h.

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Mancera, C., F. Ferrando, J. Salvadó e N. E. El Mansouri. "Kraft lignin behavior during reaction in an alkaline medium". Biomass and Bioenergy 35, n. 5 (maggio 2011): 2072–79. http://dx.doi.org/10.1016/j.biombioe.2011.02.001.

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40

Song, Xiaoyun, Qimei Yang, Kaisheng Zou, Zhenyang Xie, Jian Wang e Wei Ding. "Intrinsic Activity: A Critical Challenge of Alkaline Hydrogen Oxidation Reaction". Advanced Functional Materials, 16 novembre 2024. http://dx.doi.org/10.1002/adfm.202414570.

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AbstractAnion exchange membrane fuel cells (AEMFCs) are advantageous for reducing or even eliminating the dependency on platinum resources, as the alkaline environment allows the use of non‐precious metal catalysts for oxygen reduction reaction at the cathode. However, the intrinsic activity of hydrogen oxidation reaction (HOR) catalysts in alkaline environments is 2 to 4 orders of magnitude lower than in acidic environments, which becomes the major challenge for AEMFCs. This review examines the current developments in the intrinsic activity of alkaline HOR catalysts and systematically summarizes the hydrogen activation mechanism with a focus on potential influencing factors and enhancement strategies. Furthermore, it offers insights into the prospects for developing more efficient alkaline HOR catalysts.

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41

Xie, Xiaohong, Lei Du, Litao Yan, Sehkyu Park, Yang Qiu, Joshua Sokolowski, Wei Wang e Yuyan Shao. "Oxygen Evolution Reaction in Alkaline Environment: Material Challenges and Solutions". Advanced Functional Materials, 13 marzo 2022, 2110036. http://dx.doi.org/10.1002/adfm.202110036.

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42

Xu, Qiang, Leqing Tao, Tengfei Nie, Liang Liang, Yonglu She e Mengsha Wang. "Mechanism of pH Effect on Mass Transfer During Bubble Evolution on Photoelectrode Surfaces". Journal of The Electrochemical Society, 8 gennaio 2024. http://dx.doi.org/10.1149/1945-7111/ad1c18.

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Abstract This study conducted in-depth research on the limitation problem of the mass transfer of gas molecules on the surface of the photoelectrode to the efficiency of photoelectrochemical (PEC) water splitting. Experimental results reveal significant differences in the dynamic characteristics of bubbles and mass transfer mechanisms during bubble growth under different pH conditions. As the pH deviates from 7.0 (vs. rotating hydrogen electrode, RHE), the reaction rate increases, the bubble nucleation voltage decreases, and the terminal rising velocity increases significantly. During the rapid growth phase of bubbles, the mass transfer coefficient reaches its peak, accounting for only 1% of the entire evolution cycle. In a neutral environment (pH 7.0), the transient mass transfer coefficient reaches a maximum at approximately 1 s of bubble growth, while in an alkaline environment (pH 12.0), it reaches a maximum at around 0.1 s. In strongly alkaline environments (pH 13.0), the PEC reaction rate and mass transfer rate increase, resulting in the highest gas production efficiency. The mass transfer coefficients were improved by about 72.4% and 42.8% (vs. Ag/AgCl) and by about 22.2% and 33.3% (vs. RHE) in the strong alkaline environment relative to the strong acid environment (pH = 1.0) and the neutral environment, respectively.

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Hou, Liqiang, Zijian Li, Haeseong Jang, Min Gyu Kim, Jaephil Cho, shangguo Liu e Xien Liu. "Grain Boundary Tailors the Local Chemical Environment on Iridium Surface for Alkaline Electrocatalytic Hydrogen Evolution". Angewandte Chemie, 27 dicembre 2023. http://dx.doi.org/10.1002/ange.202315633.

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Even though grain boundaries (GBs) have been previously employed to increase the number of active catalytic sites or tune the binding energies of reaction intermediates for promoting electrocatalytic reactions, the effect of GBs on the tailoring of the local chemical environment on the catalyst surface has not been clarified thus far. In this study, a GBs‐enriched iridium (GB‐Ir) was synthesized and examined for the alkaline hydrogen evolution reaction (HER). Operando Raman spectroscopy and density functional theory (DFT) calculations revealed that a local acid‐like environment with H3O+ intermediates was created in the GBs region owing to the electron‐enriched surface Ir atoms at the GBs. The H3O+ intermediates lowered the energy barrier for water dissociation and provided enough hydrogen proton to promote the generation of hydrogen spillover from the sites at the GBs to the sites away from the GBs, thus synergistically enhancing the hydrogen evolution activity. Notably, the GB‐Ir catalyst exhibited a high alkaline HER activity (10 mV @ 10 mA cm‐2, 20 mV dec‐1). We believe that our findings will promote further research on GBs and the surface science of electrochemical reactions.

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Hou, Liqiang, Zijian Li, Haeseong Jang, Min Gyu Kim, Jaephil Cho, shangguo Liu e Xien Liu. "Grain Boundary Tailors the Local Chemical Environment on Iridium Surface for Alkaline Electrocatalytic Hydrogen Evolution". Angewandte Chemie International Edition, 27 dicembre 2023. http://dx.doi.org/10.1002/anie.202315633.

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Abstract (sommario):

Even though grain boundaries (GBs) have been previously employed to increase the number of active catalytic sites or tune the binding energies of reaction intermediates for promoting electrocatalytic reactions, the effect of GBs on the tailoring of the local chemical environment on the catalyst surface has not been clarified thus far. In this study, a GBs‐enriched iridium (GB‐Ir) was synthesized and examined for the alkaline hydrogen evolution reaction (HER). Operando Raman spectroscopy and density functional theory (DFT) calculations revealed that a local acid‐like environment with H3O+ intermediates was created in the GBs region owing to the electron‐enriched surface Ir atoms at the GBs. The H3O+ intermediates lowered the energy barrier for water dissociation and provided enough hydrogen proton to promote the generation of hydrogen spillover from the sites at the GBs to the sites away from the GBs, thus synergistically enhancing the hydrogen evolution activity. Notably, the GB‐Ir catalyst exhibited a high alkaline HER activity (10 mV @ 10 mA cm‐2, 20 mV dec‐1). We believe that our findings will promote further research on GBs and the surface science of electrochemical reactions.

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"Reaction Mechanism of Ethanol Oxidation over Gold Catalyst under Alkaline Environment". ECS Meeting Abstracts, 2012. http://dx.doi.org/10.1149/ma2012-02/13/1322.

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Mallia, Christopher, e Fikile R. Brushett. "Phenomenological observations of quinone-mediated zinc oxidation in an alkaline environment". Chemical Communications, 2024. http://dx.doi.org/10.1039/d4cc02746a.

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Redox-mediated electrochemistry is an area of growing interest, particularly in the context of energy storage. The development of such systems requires knowledge of underlying reaction mechanisms, which bear similarities to...

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47

Tan, Hao, Bing Tang, Ying Lu, Qianqian Ji, Liyang Lv, Hengli Duan, Na Li et al. "Engineering a local acid-like environment in alkaline medium for efficient hydrogen evolution reaction". Nature Communications 13, n. 1 (19 aprile 2022). http://dx.doi.org/10.1038/s41467-022-29710-w.

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AbstractTuning the local reaction environment is an important and challenging issue for determining electrochemical performances. Herein, we propose a strategy of intentionally engineering the local reaction environment to yield highly active catalysts. Taking Ptδ− nanoparticles supported on oxygen vacancy enriched MgO nanosheets as a prototypical example, we have successfully created a local acid-like environment in the alkaline medium and achieve excellent hydrogen evolution reaction performances. The local acid-like environment is evidenced by operando Raman, synchrotron radiation infrared and X-ray absorption spectroscopy that observes a key H3O+ intermediate emergence on the surface of MgO and accumulation around Ptδ− sites during electrocatalysis. Further analysis confirms that the critical factors of the forming the local acid-like environment include: the oxygen vacancy enriched MgO facilitates H2O dissociation to generate H3O+ species; the F centers of MgO transfers its unpaired electrons to Pt, leading to the formation of electron-enriched Ptδ− species; positively charged H3O+ migrates to negatively charged Ptδ− and accumulates around Ptδ− nanoparticles due to the electrostatic attraction, thus creating a local acidic environment in the alkaline medium.

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Berretti, Enrico, Luigi Osmieri, Vincenzo Baglio, Hamish A. Miller, Jonathan Filippi, Francesco Vizza, Monica Santamaria, Stefania Specchia, Carlo Santoro e Alessandro Lavacchi. "Direct Alcohol Fuel Cells: A Comparative Review of Acidic and Alkaline Systems". Electrochemical Energy Reviews 6, n. 1 (24 agosto 2023). http://dx.doi.org/10.1007/s41918-023-00189-3.

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AbstractIn the last 20 years, direct alcohol fuel cells (DAFCs) have been the subject of tremendous research efforts for the potential application as on-demand power sources. Two leading technologies respectively based on proton exchange membranes (PEMs) and anion exchange membranes (AEMs) have emerged: the first one operating in an acidic environment and conducting protons; the second one operating in alkaline electrolytes and conducting hydroxyl ions. In this review, we present an analysis of the state-of-the-art acidic and alkaline DAFCs fed with methanol and ethanol with the purpose to support a comparative analysis of acidic and alkaline systems, which is missing in the current literature. A special focus is placed on the effect of the reaction stoichiometry in acidic and alkaline systems. Particularly, we point out that, in alkaline systems, OH− participates stoichiometrically to reactions, and that alcohol oxidation products are anions. This aspect must be considered when designing the fuel and when making an energy evaluation from a whole system perspective. Graphical Abstract

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Sun, Zijun, Rui Li, Qing Xi, Fangxia Xie, Xuan Jian, Xiaoming Gao, Houfen Li et al. "Single atom supported on MXenes for the alkaline hydrogen evolution reaction: species, coordination environment, and action mechanism". Physical Chemistry Chemical Physics, 2023. http://dx.doi.org/10.1039/d3cp00779k.

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Yoo, Su-Hyun, Leonardo Shoji Aota, Sangyong Shin, Ayman A. El-Zoka, Phil Woong Kang, Yonghyuk Lee, Hyunjoo Lee, Se-Ho Kim e Baptiste Gault. "Dopant Evolution in Electrocatalysts after Hydrogen Oxidation Reaction in an Alkaline Environment". ACS Energy Letters, 14 luglio 2023, 3381–86. http://dx.doi.org/10.1021/acsenergylett.3c00842.

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