Optimized oxygen defect engineering enabling efficient alkaline hydrogen evolution on Ru/MoO2−x

The sluggish water dissociation kinetics and suboptimal hydrogen adsorption on Ru-based catalysts remain major challenges for efficient alkaline hydrogen evolution reaction (HER). Constructing spatially coupled yet functionally distinct active sites through metal-support interaction (MSI) offers a promising route to overcome these intrinsic kinetic limitations. Herein, a pathway-controlled defect engineering strategy is developed, in which carbon is introduced in situ during oxide reduction to generate oxygen-vacancy-rich MoO 2− x supports and thereby establish strong MSI with Ru. Structural and spectroscopic analyses reveal that oxygen vacancies in MoO 2− x preferentially adsorb and activate interfacial water, while defect-mediated MSI electronically modulates Ru to optimize *H binding. In situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) and density functional theory calculations collectively demonstrate that this interfacial synergy induces strong water-support interactions, effectively lowering the Volmer-step energy barrier under alkaline conditions. As a result, Ru/C-MoO 2− x -800 delivers outstanding alkaline HER performance, achieving an overpotential of 23 mV at 10 mA cm −2 with a Tafel slope of 35 mV dec −1 . The catalyst sustains stable operation for 1000 h at an application-relevant current density of 250 mA cm −2 in an anion exchange membrane water electrolyzer (AEMWE). This work establishes defect-regulated MSI as an effective design principle for decoupling water activation and hydrogen adsorption in alkaline HER. Tailored oxygen vacancy engineering strengthens Ru-MoO 2− x metal-support interactions and regulates interfacial water activation and hydrogen adsorption energetics, enabling efficient and durable alkaline hydrogen evolution. Download: Download high-res image (210KB) Download: Download full-size image