Unraveling Synergistic Effect of Defects and Piezoelectric Field in Breakthrough Piezo‐Photocatalytic N₂ Reduction

Abstract Piezo‐photocatalysis is a frontier technology for converting mechanical and solar energies into crucial chemical substances and has emerged as a promising and sustainable strategy for N₂ fixation. Here, for the first time, defects and piezoelectric field are synergized to achieve unprecedented piezo‐photocatalytic nitrogen reduction reaction (NRR) activity and their collaborative catalytic mechanism is unraveled over BaTiO₃ with tunable oxygen vacancies (OVs). The introduced OVs change the local dipole state to strengthen the piezoelectric polarization of BaTiO₃, resulting in a more efficient separation of photogenerated carrier. Ti³⁺ sites adjacent to OVs promote N₂ chemisorption and activation through d–π back‐donation with the help of the unpaired d‐orbital electron. Furthermore, a piezoelectric polarization field could modulate the electronic structure of Ti³⁺ to facilitate the activation and dissociation of N₂, thereby substantially reducing the reaction barrier of the rate‐limiting step. Benefitting from the synergistic reinforcement mechanism and optimized surface dynamics processes, an exceptional piezo‐photocatalytic NH₃ evolution rate of 106.7 µmol g⁻¹ h⁻¹ is delivered by BaTiO₃ with moderate OVs, far surpassing that of previously reported piezocatalysts/piezo‐photocatalysts. New perspectives are provided here for the rational design of an efficient piezo‐photocatalytic system for the NRR.