Regulating Electronic Properties of Bi ₂ MoO ₆ via Atomic‐Scale Sn Engineering to Construct Multiple Active Sites for Solar Nitrogen Fixation Under Ambient Conditions

ABSTRACT Photocatalytic ammonia (NH 3 ) production provides a green alternative to the energy‐intensive Haber–Bosch process; however, low efficiency and limited understanding of N 2 activation hinder progress. Experimental results, supported by density functional theory (DFT), demonstrate that Sn‐doped Bi 2 MoO 6 significantly enhances photocatalytic nitrogen reduction reaction (PNRR) by tuning electronic structure and enriched active sites. This work reports at the optimal Sn incorporation, 10% Sn‐BMO with a preferentially exposed (131) facet accompanied by a substantial concentration of oxygen vacancies delivers an NH 3 production rate of 2.07 mmol g −1 , which is 10.9 times greater than that of pristine Bi 2 MoO 6 under simulated solar irradiation (Xenon lamp). The presence of high amount of oxygen vacancies in the 10% Sn‐BMO promotes N 2 adsorption and activation, facilitating N≡N bond dissociation through proton coupling. The N 2 fixation pathway was elucidated by tracking reaction dynamics through infrared spectroscopy. A solar‐to‐NH 3 efficiency of ∼1.04% in pure water positions this breakthrough as a viable pathway toward decentralized NH 3 production with improved accessibility and sustainability. Moreover, under natural sunlight in the designed prototype system, 10% Sn‐BMO exhibits an NH 3 production rate of ∼450 µmol g −1 . These findings validate efficient laboratory and outdoor solar‐driven NH 3 production through rational catalyst design for sustainable ammonia synthesis.