Carbon-Encapsulated Ru–Co₃O₄ Nanosheets as Electrocatalysts for Acidic Water Oxidation

Developing stable and highly active electrocatalysts for the oxygen evolution reaction (OER) in acidic media holds significant importance for proton-exchange membrane water electrolysis. Here, we report a carbon-protected, low Ru-doped cobalt oxide nanosheet array electrode (C–Ru–Co 3 O 4 ) for acid OER. The doping of Ru adjusts the electronic structure, optimizing the adsorption of reaction intermediates. Additionally, amorphous carbon, derived from polydopamine, effectively inhibits the overoxidation of Ru–Co 3 O 4 . Furthermore, the sheetlike structure and strong interplay between the catalyst and support promote mass and charge transfer while extending the long-term durability. Compared to Co 3 O 4 and commercial RuO 2 catalysts, C–Ru–Co 3 O 4 catalyst exhibits enhanced OER performance and stability. The optimized catalyst shows an overpotential of 252 mV at 10 mA cm –2 and can operate continuously in acidic media for more than 30 h, while the activity of commercial RuO 2 sharply decreases within 1 h. Notably, C–Ru–Co 3 O 4 also exhibits good hydrogen evolution reaction (HER) activity, with an overpotential of 125 mV at 10 mA cm –2 . Furthermore, the acid water splitting electrolyzer, based on bifunctional C–Ru–Co 3 O 4, can be effectively driven by a solar panel, revealing its potential for converting solar energy into clean chemical energy.