Understanding Catalyst Design of High-Entropic Non-Noble Metal Alloys for the Oxygen Evolution Reaction in Acidic Media

Non-noble metal-based anodes are crucial for the replacement of noble metal-based anodes in proton-exchange membrane electrolyzers. However, the catalyst design is challenging for use in acidic electrolytes since the catalytically active elements accelerate anode degradation, while the corrosion-resistant elements reduce the catalytic activity. To solve this trade-off, this study systematically investigates the composition ratios of catalytically active elements (Cr, Mn, Fe, Co, and Ni) and passivation elements (Ti, Zr, Nb, and Mo) and defines the optimal elemental composition to mimic the acid stability exhibited by nonary alloys. The results indicate that the compositional ratio affects the corrosion mechanism. Although a stable system can be achieved using fewer elements (Ti, Co, Ni, Zr, and Nb), the anode performance is reduced compared to that of the nonary alloy. This study provides useful insights into the design of acid-stable non-noble metal-based anodes to replace noble metal-based anodes.