Triggering charge redistribution–induced oxygen spillover mechanism in VO x -supported IrSn alloy toward industrial water electrolysis

Developing advanced iridium (Ir)–based oxygen evolution reaction (OER) catalysts is critical for proton exchange membrane water electrolyzers (PEMWEs). Unfortunately, conventional adsorbate evolution mechanism (AEM) and lattice oxygen mechanism (LOM) pathways suffer from an activity-stability trade-off, posing substantial challenges for catalyst design. Here, we report a charge-redistribution-induced oxygen (O) spillover strategy by designing amorphous VO x -supported iridium-tin (IrSn) alloy OER catalysts, which can effectively transfer the poisoning oxygenated intermediates and maintain Ir valence stability (+2.5) during the dynamic OER to enhance activity and stability. In particular, the IrSn-VO x –based PEMWE anode can deliver a current density of 3.0 amperes per square centimeter @ 1.798 volts (0.4 milligrams of platinum and Ir per square centimeter), surpassing the US Department of Energy (DOE) 2026 targets. A 25–square centimeter PEMWE operates stably for 5000 hours at industrial currents (≥25 amperes) with an exceptionally low degradation rate of 5.6 microvolts per hour, representing one of the best OER catalysts reported for practical PEMWEs. Theoretical calculations predict that the charge redistribution within IrSn-VO x could reduce the kinetic energy barrier for *O spillover (from Ir to VO x ) by 69% relative to O-O coupling, thus triggering the O spillover against the Ir overoxidation/dissolution. Consequently, IrSn–VO x follows a support-involved LOM pathway with a reduced rate-determining-step barrier (0.37 electron volts) relative to IrSn following AEM (0.66 electron volts). In addition, Sn doping in IrSn-VO x can further promote the regeneration of VO x lattice O and improve stability.