Regulating Electronic Properties of Bi2MoO6 via Atomic-Scale Sn Engineering to Construct Multiple Active Sites for Solar Nitrogen Fixation Under Ambient Conditions.

Photocatalytic ammonia (NH3) production provides a green alternative to the energy-intensive Haber-Bosch process; however, low efficiency and limited understanding of N2 activation hinder progress. Experimental results, supported by density functional theory (DFT), demonstrate that Sn-doped Bi2MoO6 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 NH3 production rate of 2.07 mmol g-1, which is 10.9 times greater than that of pristine Bi2MoO6 under simulated solar irradiation (Xenon lamp). The presence of high amount of oxygen vacancies in the 10% Sn-BMO promotes N2 adsorption and activation, facilitating N≡N bond dissociation through proton coupling. The N2 fixation pathway was elucidated by tracking reaction dynamics through infrared spectroscopy. A solar-to-NH3 efficiency of ∼1.04% in pure water positions this breakthrough as a viable pathway toward decentralized NH3 production with improved accessibility and sustainability. Moreover, under natural sunlight in the designed prototype system, 10% Sn-BMO exhibits an NH3 production rate of ∼450 µmol g-1. These findings validate efficient laboratory and outdoor solar-driven NH3 production through rational catalyst design for sustainable ammonia synthesis.