Oxygen‐Vacancy‐Regulated Piezoelectric Field‐Assisted Photocatalytic Nitrogen Fixation Over La 2 Ti 2 O 7 Nanosheets

Photocatalytic nitrogen fixation is commonly limited by sluggish N 2 activation and rapid recombination of photogenerated charge carriers. Here, layered piezoelectric La 2 Ti 2 O 7 (LTO) nanosheets were used as a model oxide, and Ti 3+ ‐associated oxygen vacancies were introduced by Ar/H 2 reduction. Oxygen vacancies created electron‐rich Ti sites, promoted N 2 adsorption and charge transfer, and enhanced the local electromechanical response. Under simultaneous light irradiation and ultrasonication, optimized LTO‐600 delivered an NH 3 production rate of 148.4 μmol g −1 h −1 in pure water without sacrificial agents. 15 N 2 isotope labeling confirmed that NH 3 originated from N 2 reduction. Site‐resolved calculations show that the vacancy‐neighboring Ti site is the principal electron donor, whereas neighboring La weakly polarizes and stabilizes the distal N atom. The combined defect‐mediated N 2 activation and piezoelectric‐field‐assisted charge separation account for the enhanced activity.