Noble-metal-free catalysts for the oxygen evolution reaction in acids

Oxygen evolution catalysts are critical components of proton exchange membrane water electrolysers (PEMWEs), playing a decisive role in determining both the performance and cost of these devices. Non-noble metal-based oxygen evolution catalysts have recently drawn significant attention as potential alternatives to expensive noble metal catalysts. This review systematically summarizes the mechanism of non-noble metal catalysts for the oxygen evolution reaction in acids with respect to their activity and stability, incorporating theoretical calculations and the Pourbaix diagram. Advanced in situ techniques are highlighted as powerful tools for probing intermediate evolution and valence changes and further elucidating the catalytic mechanism. Furthermore, key strategies for enhancing catalytic activity and durability, such as elemental doping, the support effect, surface protection and novel phase design, are discussed. Finally, this review provides insights into the remaining challenges and emerging opportunities for advancing practical oxygen evolution catalysts in PEMWEs.