Managing Proton-Involved Kinetics via Cooperative Acceptance and Diffusion of Protons for Stable Acidic Water Oxidation under Fluctuating Power

Practical application of RuO2 for the acidic oxygen evolution reaction (OER) is hindered by its sluggish kinetics and serious degradation. Here, we manage proton-involved kinetics via cooperative acceptance and diffusion of protons by constructing CrOx islands on the RuO2 surface. This architecture renders two distinct yet spatially coupled functions: interfacial Cr–OH groups at the perimeters act as proton acceptors to promote the deprotonation of OER intermediates, while the hydroxyl-rich CrOx islands dynamically restructure interfacial water networks with potentials to facilitate proton diffusion away from catalyst-electrolyte interfaces. This enhances the OER kinetics but, more critically, reduces the local acidification to secure operational stability under fluctuating power. Water electrolyzers with this CrOx/RuO2 need a low voltage of 1.61 V at 1 A cm–2 and operate for over 1600 h under square-wave loading conditions (cycling between 0.1 and 1 A cm–2, each for 12 h), exceeding that using RuO2 (stability <12 h).