Bidirectional Hydrogen Spillover Enables High Activity Catalysts for Rechargeable Hydrogen Batteries.

Rechargeable hydrogen batteries exhibit superior electrochemical activity for hydrogen evolution and oxidation reactions (HER/HOR) in acidic media compared to alkaline counterparts, making them promising for large-scale energy storage. However, the development of efficient electrocatalysts for both HER and HOR in acidic media remains challenging, as conventional platinum-based catalysts face intrinsic limitations in simultaneously achieving high activity and long-term stability under harsh operating conditions. Herein, we introduce a bidirectional hydrogen spillover strategy to enable synergistic bifunctional HER/HOR catalysts for hydrogen batteries. We demonstrate a Ru-WO catalyst grown on Cu foam (Ru-WO@CF), where the interaction between Ru and WO enables dynamic shuttling of adsorbed hydrogen species under alternating potentials. The Ru-WO@CF electrode demonstrates exceptional HER/HOR bifunctionality in acidic media (0.5 M HSO), achieving an ultralow HER overpotential of 17 mV at 10 mA cm and an HOR current density of 21.5 mA cm at 50 mV - both significantly outperforming commercial Pt/C benchmarks. The hydrogen battery fabricated with Ru-WO@CF demonstrates exceptional performance across a wide range of temperatures. This work aims to explore the feasibility of bidirectional hydrogen spillover in enhancing the bifunctional catalytic activities toward HER/HOR, providing new insights for high-performance hydrogen batteries.