Nickel alloy electrodes for the evolution reaction of hydrogen and oxygen in a water-alkaline electrolyser

Hydrogen as an energy carrier is a promising solution to the problems associated with the current fuel-based energy system [1]. It provides a sustainable fuel for a wide range of applications, from transport to small electronic devices or stationary applications. Among various methods, water electrolysis is one way, if not the only way, to produce green H2. This is possible if the electrical input is provided by a renewable energy (RE) source. Alkaline electrolysis has recently gained considerable attention as a viable method for producing green hydrogen from renewable sources, as its technology is cheaper than that based on acid solutions, since it requires precious metals as electrocatalysts [8-9]. Researchers currently focus on improving electrolyzers, such as increasing their dynamics and efficiency. This work investigates the fabrication and characterization of nanostructured Ni alloy and Ni foam electrodes with the aim of reducing the overpotential losses associated with driving the anode oxygen evolution reaction (OER) and the cathode hydrogen evolution reaction (HER) in alkaline environments. Ni alloy nanowires with very high surface area and high electrocatalytic activity were prepared by template electrosynthesis [4-7]. It has been found that alkaline electrolysers with Ni nanowire electrodes coated with different electrocatalysts have good performance and are stable even at room temperature [8-11]. For comparison, Ni foam (NF) and Ni foil (NS), differently functionalised with the same electrocatalysts, were tested. The electrodes were characterized by SEM and EDS. Quasi-steady-state polarization (QSSP), galvanostatic step (GS) and galvanostatic tests were then performed on each electrode. The electrodes were tested individually and compared. The best performing electrodes in terms of OER and HER were identified. Each test was carried out in an alkaline electrolyte (aqueous potassium hydroxide solution, 30% by weight). The electrodes were then tested in an alkaline electrolyser for a period of 6 hours at a constant current density in order to evaluate their performance. The cell consists of two vessels separated by a polystyrene membrane to ensure electrical continuity and prevent gas mixing (one for the anode and one for the cathode). Following individual tests of the nanostructured Ni alloy electrodes and Ni foam with nickel alloy as anode and cathode, the performance of the foam and nanostructured electrodes used as electrolysers was evaluated. Quasi steady-state polarizations were performed by scanning the cell potential at a rate of 0.1667 mVs-1 from 1.48 V, which is the thermodynamic cell potential, E°, to 4.5 V. The tests were stopped when a current density of 0.5 Acm-2 was reached. The results are very encouraging, as the high ratio of real surface area to geometric surface area was immediately beneficial. This work was partially financed by the project "SiciliAn MicronanOTecH Research And Innovation CEnter "SAMOTHRACE" (MUR, PNRR-M4C2, ECS_00000022), spoke 3 - Università degli Studi di Palermo "S2-COMMs - Micro and Nanotechnologies for Smart & Sustainable Communities". References [1] Amores, E.; Rodríguez, J.; Carreras, C. Influence of operation parameters in the modeling of alkaline water electrolyzers for hydrogen production. Int. J. Hydrogen Energy 2014, 39, 13063–13078. [2] D. M. F. Santos, C. A. C. Sequeira, J. L. Figueiredo, “Hydrogen Production by Alkaline Water Electrolysis”, Química Nova, vol. 36, 8, pp. 1176-1193, 2013. [3] K. Zeng, D. Zhang, “Recent Progress in Alkaline Water Electrolysis for Hydrogen Production and Applications”, Progress in Energy and Combustion Science, vol. 36, 3, pp. 307-326, 2010. [4] Sunseri, C.; Cocchiara, C.; Ganci, F.; Moncada, A.; Oliveri, R.L.; Patella, B.; Piazza, S. Rosalinda Inguanta Nanostructured electrochemical devices for sensing, energy conversion and storage. Chem. Eng. Trans. 2016,47, 43–48. [5] Oliveri, R.L.; Patella, B.; Di Pisa, F.; Mangione, A.; Aiello, G.; Inguanta, R. Fabrication of CZTSe/CIGS Nanowire Arrays by One-Step Electrodeposition for Solar-Cell Application. Materials 2021, 14, 2778 [6] Insinga, M.G.; Oliveri, R.L.; Sunseri, C.; Inguanta, R. Template electrodeposition and characterization of nanostructured Pb as a negative electrode for lead-acid battery. J. Power Sources 2019, 413, 107–116. [7] F. Ganci, S. Lombardo, C. Sunseri, R. Inguanta, “Nanostructured electrodes for hydrogen production in alkaline electrolyzer”, Renewable Energy, Elsevier, 2018 vol. 123, pp. 117-124. [8] Ganci, F.; Cusumano, V.; Livreri, P.; Aiello, G.; Sunseri, C.; Inguanta, R. Nanostructured Ni–Co alloy electrodes for both hydrogen and oxygen evolution reaction in alkaline electrolyzer. Int. J. Hydrogen Energy 2021, 46, 10082–10092. [9] Bocci E, Zuccari F, Dell’Era A. Renewable and hydrogen energy integrated house. Int J Hydrogen Energy 2011; 36:7963e8. [10] Yilmaz F, Balta MT, Selbas R. A review of solar based hydrogen production methods. Renew Sustain Energy Rev 2016; 56:171e8. [11] Rodriguez CA, Modestino MA, Psaltis D, Moser C. Design and cost considerations for practical solar-hydrogen generators. Energy Environ Sci 2014; 7:3828e35.