Strengthened Ru–O Bonds for Robust Oxygen Evolution in Acid Media

The development of cost-effective and acid-stable oxygen evolution reaction (OER) electrocatalysts is essential for the implementation of a proton exchange membrane-based water electrolyzer. Herein, we develop a catalyst composite featuring RuO2 nanoplates on a manganese–cobalt-spinel oxide (MnCo2O4.5) substrate for an acidic OER. The optimized RuO2/MnCo2O4.5 catalyst composite exhibits a low overpotential of 210 mV at 10 mA cm–2 and remarkable stability with a degradation rate as low as 30 μV h–1. Density functional calculations reveal that Co/Mn doping in the RuO2 nanoplates significantly enhances their OER activity and stability against Ru dissolution. Additionally, the pH-dependent and kinetic isotope experiments underscore that RuO2/MnCoO4.5 exhibits enhanced OER activity in an acidic electrolyte compared to that in an alkaline electrolyte, highlighting its potential for use in PEM electrolyzers. When integrated into a PEM electrolyzer, RuO2/MnCo2O4.5 achieves an encouragingly low cell voltage of 1.83 V at 1 A cm–2 and operates stably for over 130 h with negligible degradation. Overall, this study provides in-depth insights into OER mechanisms, particularly in mitigating Ru dissolution under acidic conditions, a critical factor for the development of robust and cost-effective OER catalysts.