Recent advances and modulation tactics in Ru- and Ir-based electrocatalysts for PEMWE anodes at large current densities

Proton exchange membrane water electrolyzer (PEMWE) technology is regarded as one of the most promising methods for green hydrogen generation. The oxygen evolution reaction (OER) at the anode is the primary bottleneck preventing the industrial-scale application of PEMWEs due to its sluggish kinetics, and it presently relies upon electrocatalysts that use scarce, costly Ru and Ir. In addition, most of the Ru- and Ir-based electrocatalysts developed to date need high noble metal loading and present good activity only at low current density for a short period. In this review, we systematically elaborate upon various effective strategies for modulating Ru- and Ir-based catalysts to achieve large current density, high stability, and high atom economy, including single-atom designs, heteroatom doping, defect/vacancy creation, alloying, and heterojunction engineering. The structure–performance relationships of OER catalysts synthesized using different strategies are elucidated, along with the importance of substrate materials. We conclude by discussing the remaining challenges and future prospects for OER electrocatalysts in acid.