(Invited) Strengthening Ru−O Bonds with Co and Mn Dopants for Robust Oxygen Evolution in Acid Media

The development of cost-effective and acid-stable oxygen evolution reaction (OER) electrocatalysts to replace iridium-based catalysts is essential for the implementation of proton exchange membrane (PEM)-based water electrolysis at gird scale. While ruthenium (Ru) oxide is highly efficient in acidic environments, severe Ru dissolution, caused by the formation of highly oxidized RuO4 species, hinders its adoption. Herein, we develop a catalyst composite consisting of RuO2 skin deposited on a manganese-cobalt-spinel oxide (MnCo2O4.5) substrate, which demonstrates high active and stability towards acidic OER. Specifically, the optimized Ru/MnCo2O4.5 catalyst exhibits a low overpotential of 210 mV at 10 mA cm− 2 and outstanding stability with negligible degradation rate under practical conditions. When integrated into a PEM electrolyser as the anode catalyst, Ru/MnCo2O4.5 achieves an encouragingly low cell voltage of 1.83 V to reach 1 A cm−2. Moreover, the PEM electrolyser demonstrates stable operation at 1 A cm−2 for over 130 h. Additionally, we conducted pH-dependent and kinetic isotope experiments to probe the rate-determining steps under varying reaction conditions. Our findings demonstrate that Ru/MnCoO4.5 exhibits similar, if not improved, OER activity in acidic electrolyte compared to that in alkaline electrolyte. Finally, density functional theory calculations revealed that the incorporation of Co and Mn foreign atoms enhances the OER activity of RuO2 and stabilizes the RuO2 against dissolution by hindering its overoxidation into soluble RuO4 species.