Interfacial Oxygen Spillover Between Ru Single-Atom and Ni Cluster in Efficient Water Electrolysis

The sluggish oxygen evolution reaction (OER) remains a major kinetic bottleneck limiting the efficiency of alkaline water electrolysis, largely owing to the intrinsic scaling relationship among oxygen-containing intermediates on conventional single active sites. Here, a Ru single-atom/Ni cluster interfacial catalyst supported on nitrogen-doped carbon nanotubes (RuSA-NiClu/NCNT) is constructed through an ultrafast pulsed-discharge strategy. Operando spectroscopic investigations combined with density functional theory calculations reveal a unique division-of-labor mechanism at the atomic-cluster interface, where Ru single atoms facilitate hydroxyl activation, while neighboring Ni clusters promote O─O coupling and oxygen evolution. The interfacial electronic interaction induces charge redistribution and generates a built-in electric field, enabling directional oxygen spillover between adjacent active sites. This interfacial oxygen transfer pathway spatially decouples elementary OER steps, optimizes oxygen intermediate adsorption, and optimizes the adsorption energetics of oxygenated intermediates. Benefiting from the tailored interfacial electronic structure, RuSA-NiClu/NCNT achieves an overpotential of only 224 mV at 10 mA cm^-2 with a Ru loading of 2.3 wt%. Moreover, the catalyst enables stable operation of an anion exchange membrane water electrolyzer (AEMWE) for over 500 h at 1 A cm^-2. This work establishes single-atom/cluster interfaces as a promising platform for regulating catalytic division of labor toward efficient and durable water electrolysis.