The Effect of Different Membrane Types on the Activity and Stability of Nickel-Based Catalysts for Water Splitting
Authors: Hotko Miha , Marsel Aleš , Bele Marjan , Hodnik Nejc 
Published: December 2024

Due to the increasing annual rise in carbon dioxide levels from burning fossil fuels for energy, which is accelerating climate change, countries are moving away from fossil fuels and turning to hydrogen as a sustainable, renewable alternative. Hydrogen offers more than twice as much energy per mass compared to other fuels and can be produced renewably through water electrolysis using wind or solar energy. Electrolysis requires electrocatalysts that control the half-reactions of water splitting at a low enough overpotential, i.e. the difference between the theoretical potential and the actual potential at which these reactions take place.

Platinum group metals (PGMs) are the favored electrocatalysts due to their efficiency, but they are expensive and only available in small quantities in the earth's crust. Efforts are therefore being made to replace them with more abundant and less expensive transition metals such as nickel. Nickel is an excellent OER catalyst under alkaline conditions and has recently also shown promise as a HER catalyst. Such catalysts are used in zero-gap electrolyzers, where the separators between the anode and cathode are membranes, however, recently it has been shown that these separators can be improved to limit gas crossover and metal cross-contamination. 1

In this work we present how different types of exchange membranes affect activity and stability of nickel-based electrocatalysts. It is well known that different metals that form alloys with nickel affect its electrochemistry, such as the effect of iron on nickel that increases the activity of the OER. The experiments were conducted in a gas diffusion electrode (GDE) with which we achieve higher current densities than standard laboratory scale methods mainly the rotating disc electrode. Another benefit of GDE is that it can utilize a membrane, so it closely resembles membrane electrode assemblies (MEAs), which are the benchmark used for testing catalyst for industrial application. With these results we wish to stress the importance of using the right separator with respect to the activity and stability of nickel-based electrocatalysts.2,3

(1) Cohen, L. A.; Weimer, M. S.; Yim, K.; Jin, J.; Fraga Alvarez, D. V.; Dameron, A. A.; Capuano, C. B.; Ouimet, R. J.; Fortiner, S.; Esposito, D. V. How Low Can You Go? Nanoscale Membranes for Efficient Water Electrolysis. ACS Energy Lett.
2024, 1624–1632. https://doi.org/10.1021/acsenergylett.4c00170.

(2) Hales, N.; Schmidt, T. J.; Fabbri, E. Reversible and Irreversible Transformations of Ni-Based Electrocatalysts during the Oxygen Evolution Reaction. Curr. Opin. Electrochem.
2023, 38, 101231. https://doi.org/10.1016/j.coelec.2023.101231.

(3) Ehelebe, K.; Schmitt, N.; Sievers, G.; Jensen, A. W.; Hrnjić, A.; Collantes Jiménez, P.; Kaiser, P.; Geuß, M.; Ku, Y.-P.; Jovanovič, P.; Mayrhofer, K. J. J.; Etzold, B.; Hodnik, N.; Escudero-Escribano, M.; Arenz, M.; Cherevko, S. Benchmarking Fuel Cell Electrocatalysts Using Gas Diffusion Electrodes: Inter-Lab Comparison and Best Practices. ACS Energy Lett.
2022, 7 (2), 816–826. https://doi.org/10.1021/acsenergylett.1c02659.