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 RuO 2 nanoplates on a manganese–cobalt-spinel oxide (MnCo 2 O 4.5 ) substrate for an acidic OER. The optimized RuO 2 /MnCo 2 O 4.5 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 RuO 2 nanoplates significantly enhances their OER activity and stability against Ru dissolution. Additionally, the pH-dependent and kinetic isotope experiments underscore that RuO 2 /MnCoO 4.5 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, RuO 2 /MnCo 2 O 4.5 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.