Interface-induced tensile strain stabilizes ruthenium oxide for high-performance acidic water oxidation

Developing ruthenium-based catalysts that combine high activity with long-term stability in acid is important for reducing reliance on iridium in proton-exchange membrane water electrolyzer. Here we show that coupling carbon dots with ruthenium oxide creates a strongly connected interface that anchors ruthenium sites and improves charge transport. The optimized two-dimensional ruthenium oxide-carbon catalyst, with the low Ru loading (25.8 μgRu cm−2), achieves a low overpotential of 140 mV at 10 mA cm−2 and operates stably for > 1900 hours. In a proton-exchange membrane device, it delivers 3 A cm−2 at 1.833 V, and remains stable for more than 800 hours at 1.43 V. In-situ characterizations, transient photoinduced voltage and theoretical calculations reveal that interfacial coupling and tensile strain suppress overoxidation and reduce the Gibbs free-energy barrier of the oxygen evolution reaction. This work establishes carbon dots-enabled interfacial strain engineering as a promising approach for low-ruthenium, efficient, and durable water electrolyzers across a wide power range. Ruthenium oxide can lower the demand for scarce iridium in acidic water electrolysis, but its long-term stability is limited. Here, the authors report a two-dimensional carbon-ruthenium oxide composite that stabilizes active sites and enables durable water-splitting performance.