Spatially Decoupling and Kinetically Matching the Oxygen Evolution Reaction via Hydroxyl Spillover at NiO/RuO2 Heterointerfaces

Abstract Anodic oxygen evolution reaction (OER) in anion-exchange membrane water electrolysis (AEMWE) relies on sequential hydroxyl capture and intermediate conversion, yet the sluggish kinetics remain a critical challenge. Herein, we report the rational design of NiO/RuO2 heterostructures (NRO) via a template-sacrificial strategy. The integrated heterointerfaces within NRO enable spatial decoupling of OER steps through hydroxyl spillover. Specifically, the NiO domain serves as a hydroxyl reservoir to capture OH–, while the adjacent RuO2 domain facilitates subsequent O–O bond formation. Moreover, spontaneous interfacial electron transfer generates a built-in electric field that drives directional hydroxyl migration across the heterointerface. Enabled by kinetically matched tandem catalysis with continuous hydroxyl supply and rapid intermediate conversion, the optimized NRO catalyst requires overpotentials of only 196 and 251 mV to deliver current densities of 10 and 100 mA cm–2, respectively, and maintains stable operation for over 300 h. The assembled AEMWE achieves 1.0 A cm–2 at a low cell voltage of 1.86 V and operates stably for over 150 h. This interfacial engineering strategy integrates spatial reaction decoupling and electronic modulation, providing a promising approach for developing durable AEMWE anode catalysts.