REGULARITIES OF HYDROGEN EVOLUTION FROM ALKALINE SOLUTION AT CATHODES SINTERED FROM NICKEL, TUNGSTEN AND TUNGSTEN SILICIDE POWDERS

• Datum: 2024
• Hauptverfasser: Pirskyy, Yuriy, Manilevich, Fedor, Kutsyi, Andrii, Bogdanova, Alina
• Format: Artikel
• Sprache: English
• Veröffentlicht: V.I.Vernadsky Institute of General and Inorganic Chemistry 2024
• Online Zugang: https://ucj.org.ua/index.php/journal/article/view/655
• Назва журналу: Ukrainian Chemistry Journal

Among the known methods of hydrogen generation, electrochemical water splitting is an attractive technology that does not pollute the environment with carbon oxides and allows obtaining a high-purity product.However, it requires significant energy resources and is therefore not cost-effective enough.One of the obvious ways to eliminate this drawback is the creation and use of catalytically active cathodes on which hydrogen is evolved with a low voltage at a high exchange current.In addition, cathodes that do not contain precious metals and have high chemical resistance in an electrolyte solution have potential for practical application. In this work, composite cathodes sintered from mixtures of two (Ni + WSi2) and three (Ni + W + WSi2) powders were manufactured, studied, and used to evolve hydrogen from a 30% KOH solution.It was found that new phases (NiWSi, W5Si3, SiC, NiW) were formed during powder sintering at 1200 C, and the resulting electrode materials had a highly developed and microstructured surface. The overpotential of hydrogen evolution from 30 % KOH solution at 26 °C on the cathode based on three powders was lower than on the cathode based on two powders, and it significantly decreased with increasing temperature to 70 °C.In addition, the electrode based on Ni + W + WSi2 had a higher exchange current and lower activation energy of hydrogen evolution than the electrode based on Ni + WSi2.Therefore, the cathode based on three powders was more active in the hydrogen evolution reaction than the cathode based on two powders.At the same time, the rate of hydrogen evolution on both cathodes was controlled by kinetic limitations, as evidenced by high activation energy values ​​(59.7 kJ/mol on Ni + WSi2 based cathode and 56.8 kJ/mol on Ni + W + WSi2 based cathode).The angular coefficients of the linear sections of the Tafel dependences of hydrogen evolution on both cathodes had close values ​​(b =  at α ≈ 0.5), from which a conclusion was made about the same stage mechanism of the electrode process on such cathodes with a limiting electrochemical stage of formation of adsorbed hydrogen atoms. Considering the low cost, high chemical resistance and sufficiently high activity of Ni + W + WSi2 based cathode in the reaction of hydrogen evolution from an alkaline solution at elevated temperatures, it can be considered promising for practical application.