Unveiling the Mechanism of Aerobic Photocatalytic Nitrogen Fixation over Dynamic Structural Renovation on Bi₂MO₆ (M = Mo, W)

Abstract

The aerobic photocatalytic nitrogen reduction reaction (pNRR) is the photocatalytic synthesis of ammonia with air (N 2 /O 2 ) instead of a high-purity nitrogen source, which can avoid the use of high-cost air separation equipment, thus reducing the production cost of synthetic ammonia. Nevertheless, the mechanism of the effect of oxygen (O 2 ) on the structure and catalytic performance of photocatalysts in the aerobic pNRR is still unclear. Herein, a trace Bi 0 loaded Bi 2 MO 6 (M = Mo, W) was ingeniously synthesized by a solvothermal strategy, which demonstrated a superior aerobic pNRR performance. The mechanism of the aerobic pNRR was elucidated by quasi in situ X-ray photoelectron spectroscopy, in situ electron spin resonance and density functional theory calculation. The presence of O 2 inhibited the formation of excess Bi 0 by competing for photogenerated electrons and generating ·O 2 –, which dynamically renovated the structure of the catalyst. The polarization dipole field induced by an appropriate amount of Bi 0 boosted the photocarrier spatial separation/transfer of the aerobic pNRR.