Recent advances of ruthenium-based materials for acidic oxygen evolution reaction: from catalyst design to proton exchange membrane water electrolysers

Harvesting renewable energy to split water offers an ideal approach to the production of clean hydrogen energy. Among various water electrolysis devices, the proton exchange membrane water electrolyser (PEMWE) with a high current density, quick response operation, and compact design has attracted much attention. The anodic oxygen evolution reaction (OER) in an acidic electrolyte seriously relies on iridium-based catalysts, but their use is limited owing to their scarcity and high cost. Ruthenium (Ru)-based catalysts have been considered as the most promising candidates to replace Ir in acidic OER, due to their low cost and high activity. Nevertheless, there is still much room to enhance the OER activity and durability of Ru-based catalysts for the practical application in PEMWEs. Herein, we first give a brief introduction of the main configuration and operating factors of PEMWEs. Then we discuss three OER mechanisms and reasons for the degradation of Ru-based catalysts in acid. Afterwards, the performance improvement strategies of Ru-based acidic OER catalysts are emphatically summarized. We further spotlight some typical examples of PEMWEs using Ru-based OER catalysts as anodes. Finally, further challenges and directions in the development of high-performance Ru-based OER catalysts in PEMWEs are offered and speculated.