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

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.