Non-precious transition metal-based OER catalysts for PEM water electrolysis: a mini review

As a cornerstone technology for decarbonizing energy systems, PEM water electrolysis demands highly efficient and durable catalysts to drive the OER, which remains a critical bottleneck in achieving scalable green hydrogen production. Conventional OER catalysts, predominantly based on scarce and expensive precious metal oxides (e.g., IrO₂ and RuO₂), make significant economic and scalability challenges for widespread adoption. In response, researchers have intensified efforts to develop non-precious metal OER catalysts derived from earth-abundant transition metals (e.g., Fe, Co, Ni) and their compounds. These alternatives aim to balance catalytic activity, stability under PEM water electrolysis conditions, and cost-effectiveness, thereby accelerating the transition toward scalable and economically viable hydrogen economies. This review critically examines recent advancements, persistent challenges, and future prospects of non-precious transition metals OER catalysts in redefining the landscape of PEM water electrolysis stacks.