Boosting the durability of RuO2 via confinement effect for proton exchange membrane water electrolyzer

Ruthenium dioxide has attracted extensive attention as a promising catalyst for oxygen evolution reaction in acid. However, the over-oxidation of RuO 2 into soluble H 2 RuO 5 species results in a poor durability, which hinders the practical application of RuO 2 in proton exchange membrane water electrolysis. Here, we report a confinement strategy by enriching a high local concentration of in-situ formed H 2 RuO 5 species, which can effectively suppress the RuO 2 degradation by shifting the redox equilibrium away from the RuO 2 over-oxidation, greatly boosting its durability during acidic oxygen evolution. Therefore, the confined RuO 2 catalyst can continuously operate at 10 mA cm –2 for over 400 h with negligible attenuation, and has a 14.8 times higher stability number than the unconfined RuO 2 catalyst. An electrolyzer cell using the confined RuO 2 catalyst as anode displays a notable durability of 300 h at 500 mA cm –2 and at 60 °C. This work demonstrates a promising design strategy for durable oxygen evolution reaction catalysts in acid via confinement engineering. Ruthenium dioxide exhibits good activity for the oxygen evolution reaction in acidic conditions but fails to maintain stable performance over long periods. Here, the authors report a confinement strategy that suppresses ruthenium dioxide degradation, enhancing its long-term durability.