Piezoelectric Field Driven Proton‐Coupled Electron Transfer Reaction and p‐Band Center Shift for H ₂ O ₂ Synthesis in Pure Water and Air

Abstract Piezocatalytic H 2 O 2 synthesis emerges as a promising and sustainable strategy by harnessing abundant mechanical energy alongside naturally available air and water. However, sluggish electron transport and uphill energy barriers with the formation of crucial intermediates severely hinder its efficiency. Herein, a Bi 4 O 5 Br 2 /NaNbO 3 S‐scheme heterojunction is designed to realize piezoelectric field‐driven proton‐coupled electron transfer (PCET) reaction for H 2 O 2 synthesis in pure water and air. The intrinsic piezoelectric field and interfacial electric field not only significantly lower the energy barrier for O 2 reduction to *OOH in oxygen reduction reaction (ORR) and water oxidation to hydroxyl species and protons in water oxidation reaction (WOR), but also facilitate the electron transfer to adsorbates, thereby promoting a fast PCET reaction. Additionally, the dual electric fields enhance the intermediates adsorption on Bi sites via modulating the Bi p‐band center, endowing the heterojunction with high activity and selectivity of 2e − ORR reaction. Benefiting from the synergistic effect of dual electric field, the optimized Bi 4 O 5 Br 2 /NaNbO 3 achieves an exceptional H 2 O 2 yield of 1192.9 µmol g −1 h −1 in pure water under ambient air, reaching an advanced level among inorganic piezocatalysts. This study offers deeper insights into piezocatalytic H 2 O 2 synthesis and the comprehension of the piezocatalytic mechanism in heterojunction systems.