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 RuO₂ into soluble H₂RuO₅ species results in a poor durability, which hinders the practical application of RuO₂ in proton exchange membrane water electrolysis. Here, we report a confinement strategy by enriching a high local concentration of in-situ formed H₂RuO₅ species, which can effectively suppress the RuO₂ degradation by shifting the redox equilibrium away from the RuO₂ over-oxidation, greatly boosting its durability during acidic oxygen evolution. Therefore, the confined RuO₂ 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 RuO₂ catalyst. An electrolyzer cell using the confined RuO₂ 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.