Active and durable RMnRuO pyrochlores with low Ru content for acidic oxygen evolution.

The production of green hydrogen in water electrolyzers is limited by the oxygen evolution reaction (OER). State-of-the-art electrocatalysts are based on Ir. Ru electrocatalysts are a suitable alternative provided their performance is improved. Here we show that low-Ru-content pyrochlores (RMnRuO, R = Y, Tb and Dy) display high activity and durability for the OER in acidic media. YMnRuO is the most stable catalyst, displaying 1.5 V at 10 mA cm for 40 h, or 5000 cycles up to 1.7 V. Computational and experimental results show that the high performance is owed to Ru sites embedded in RuMnO surface layers. A water electrolyser with YMnRuO (with only 0.2 mg cm) reaches 1 A cm at 1.75 V, remaining stable at 200 mA cm for more than 24 h. These results encourage further investigation on Ru catalysts in which a partial replacement of Ru by inexpensive cations can enhance the OER performance.