Synergistic effect of Mo and Sn in a quaternary metal sulphide to activate N₂ adsorption for selective solar-driven ammonia production

Photocatalytic nitrogen fixation struggles with low efficiency, owing to the challenges involved in breaking the nonpolar N = N bond. Designing photocatalysts that convert N₂ to NH₃ under ambient conditions is key, as is improving adsorption sites and active centers for N₂ reduction to boost overall performance. Although CdS photocatalysts show promise, their efficiency is limited due to poor visible light absorption, slow carrier migration, and few active sites. This study presents a quaternary metal sulfide (Cd_1−2xMo_xSn_xS) synthesized via a hydrothermal method, resulting in exceptional durability and remarkable selectivity for N₂ reduction. The optimal % of Cd, Mo and Sn in Cd_1−2xMo_xSn_xS overcomes CdS's photo-corrosion issues, achieving NH₃ production rates up to 8 times higher (521.29 μmol g⁻¹ h⁻¹) than that of pure CdS (67.18 μmol g⁻¹ h⁻¹) under simulated solar light. Fourier transform infrared spectroscopy suggests that the fabricated robust photocatalyst follows a symmetric alternating pathway as the operation mechanism. DFT simulations illustrate the relationship between the d-band center and adsorption properties of Cd, Mo, and Sn, demonstrating that Mo and Sn synergistically enhance N₂ activation and NH₃ production. Experimental and theoretical results confirm that Mo and Sn synergistically boost photocatalytic N₂ reduction efficiency in Cd_0.60Mo_0.20Sn_0.20S.