Boosted Scavenger-Free Overall Nitrogen Photofixation with Molybdenum Incorporated Bismuth-Rich Oxychlorides

The design of highly efficient photocatalysts to photoreduce nitrogen (N₂) to ammonia (NH₃) under mild conditions is extremely challenging. In this work, various molar ratio of molybdenum (Mo) is incorporated into Bi₁₂O₁₇Cl₂ via a hydrothermal process. The resulting Mo-doped Bi₁₂O₁₇Cl₂ exhibits remarkable solar-driven activity for N₂ photo fixation without any scavengers or sacrificial agents. The optimal sample with 5% Mo dopants displays an NH₃ yield of 39.83 µmol g^-1 h^-1, a 1.6-fold improvement over undoped pristine Bi₁₂O₁₇Cl₂. The impressive performance is attributed to the synergistic effects of oxygen vacancies (OVs) and Mo-loading, enhancing light absorption and extending photo-response through band gap reduction. Additional contributions arise from the enriched active sites, facilitating N₂ adsorption and electron transport to the reactants. Density functional theory calculations reveal that Mo integration induces significant charge redistribution around the active sites, thereby reducing the energy barrier associated with N₂ activation and protonation. In-depth investigation into the reaction pathway unravels the step-by-step reaction process which further elucidates the beneficial role of Mo loading in the overall N₂ photoconversion process. As a whole, this work promotes a simple and effective engineering approach based on heteroatom doping as an efficacious strategy to design highly active photocatalysts toward N₂ photo fixation.