Multi-Effect Synergy Confined Osmium for Robust Hydrogen Evolution

Developing non-platinum (Pt) electrocatalysts that couple high activity with long-term stability is essential for hydrogen production via water electrolysis. Osmium (Os), with high cost-advantage and distinctive electronic structures, is a highly promising catalyst for the hydrogen evolution reaction (HER). However, its overly strong hydrogen adsorption and limited stability have hindered practical applications. Herein, by virtue of grain-boundary and oxygen-vacancy engineering, we construct a cerium dioxide support featuring a “grain boundary-oxygen vacancy dual-defect” network (GBOV-CeO x ). The dual-defect network stabilizes ultrafine Os nanoclusters (Os-GBOV-CeO x ) by strengthening the electronic metal–support interaction (EMSI), enhancing the durability of the catalyst. In addition, the oxygen-vacancy-induced charge redistribution tunes the Os d-band center, mitigating excessive adsorption of hydrogen intermediates and accelerating HER kinetics. Meanwhile, the permeable grain-boundary network provides rapid charge-transport pathways and reduces interfacial resistance. As a result, Os-GBOV-CeO x delivers an ultralow alkaline HER overpotential of only 11.2 mV at 10 mA cm −2 and an ultrahigh mass activity over 56 times larger than that of commercial Pt, with high stability for more than 1000 h. When deployed as the cathode in an anion-exchange membrane water electrolyzer (AEMWE), it even reaches 1 A cm −2 at 1.71 V and operates stably for over 240 h. This work highlights the critical role of a multi-effect synergy design in activating and stabilizing metal sites for advanced energy conversion.