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

The aerobic photocatalytic nitrogen reduction reaction (pNRR) is the photocatalytic synthesis of ammonia with air (N2/O2) 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 (O2) on the structure and catalytic performance of photocatalysts in the aerobic pNRR is still unclear. Herein, a trace Bi0 loaded Bi2MO6 (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 O2 inhibited the formation of excess Bi0 by competing for photogenerated electrons and generating ·O2–, which dynamically renovated the structure of the catalyst. The polarization dipole field induced by an appropriate amount of Bi0 boosted the photocarrier spatial separation/transfer of the aerobic pNRR.