Dynamic Self‐Switching Electronic State of Pt Sites for Boosting Bifunctional Hydrogen Electrocatalysis and Low‐Temperature Energy Conversion

Abstract Developing efficient hydrogen evolution reaction (HER)/hydrogen oxidation reaction (HOR) bifunctional electrocatalysts is crucial for next‐generation hydrogen energy technologies. However, the fixed electronic structures of conventional catalysts fundamentally constrain their bifunctional performance. In this study, a Pt/WO ₃ ‐based catalyst with dynamic self‐switching electronic state was designed for boosting bifunctional HER/HOR electrocatalysis. During HER, the applied negative potential drives proton (H ⁺ ) insertion into WO ₃ , inducing a phase transition from semiconducting WO ₃ to metallic‐like H _x WO ₃ . Electron transfer from H _x WO ₃ to Pt shifts Pt sites from an electron‐deficient (Pt/WO ₃ , model 1) to an electron‐rich state (Pt/HxWO ₃ , model 2), reducing the HER energy barrier from 0.4391 to 0.327 eV. Conversely, during HOR, the positive potential extracts H ⁺ from H _x WO ₃ , restoring the WO ₃ phase and the electron‐deficient Pt state, thereby lowering the HOR energy barrier from 0.5761 (Pt/H _x WO ₃ ) to 0.3253 eV (Pt/WO ₃ ). The self‐switching electronic state (model 2/model 1) endows the Pt/WO ₃ ‐based catalyst with outstanding activity, featuring a low HER overpotential of 56 mV at 100 mA cm ⁻² and a high HOR exchange current density of 5.8 mA cm ⁻² . As an anode in hydrogen proton batteries (HPBs), it delivers a discharge capacity of 169.9 mAh g ⁻¹ at 0.1 A g ⁻¹ and maintains 80 mAh g ⁻¹ even at −40°C.