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/WO₃-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 WO₃, inducing a phase transition from semiconducting WO₃ to metallic-like H_xWO₃. Electron transfer from H_xWO₃ to Pt shifts Pt sites from an electron-deficient (Pt/WO₃, model 1) to an electron-rich state (Pt/HxWO₃, model 2), reducing the HER energy barrier from 0.4391 to 0.327 eV. Conversely, during HOR, the positive potential extracts H⁺ from H_xWO₃, restoring the WO₃ phase and the electron-deficient Pt state, thereby lowering the HOR energy barrier from 0.5761 (Pt/H_xWO₃) to 0.3253 eV (Pt/WO₃). The self-switching electronic state (model 2/model 1) endows the Pt/WO₃-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.