Abstract: Productive and economical electrocatalysts for the oxygen evolution reaction (OER) are vital for reducing green hydrogen production costs and advancing the adoption of proton exchange membrane water electrolysis (PEMWE). However, the OER at the PEMWE anode involves complex proton-coupled electron transfer processes, leading to slow kinetics that limits electrolysis efficiency. Moreover, most OER catalysts are highly prone to corrosion in acidic solutions, challenging the long-term stable operation of PEMWE. Currently, OER catalysts rely heavily on iridium-based materials, which are expensive and scarce, hindering large-scale commercialization. Ruthenium, a less expensive platinum group metal, shows promising acidic OER activity but requires improved stability. Therefore, novel ruthenium-based OER catalysts are urgently needed. To achieve these goals, a thorough understanding of the acidic OER mechanisms, clear methods for material design, and the establishment of dependable performance evaluation metrics are necessary. In this review, we systematically summarize the extensively accepted mechanisms for acidic OER activity expression, which include the adsorption-desorption mechanism, multi-active centre mechanism, and lattice oxygen oxidation mechanism, to guide the microstructural design of catalysts. Additionally, we introduce commonly used indicators for evaluating catalytic activity, aiming to provide a basis for catalyst screening. We subsequently discuss and review several types of recently reported Ru-based OER catalysts, namely, Ru metals, Ru alloys, and Ru-based oxide catalysts, with a focus on how their performance can be regulated and the potential structure-performance relationships. Finally, we summarize some important issues that need attention in future research in this field to promote further study of Ru-based acidic oxidation catalysts.

Key words: Oxygen evolution reaction, Proton exchange membrane water electrolysis, Low-ruthenium, Catalytic mechanism of activity and stability