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

Abstract

Photocatalytic nitrogen fixation struggles with low efficiency, owing to the challenges involved in breaking the nonpolar N[triple bond, length as m-dash]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 (Cd1−2xMoxSnxS) synthesized via a hydrothermal method, resulting in exceptional durability and remarkable selectivity for N2 reduction. The optimal % of Cd, Mo and Sn in Cd1−2xMoxSnxS 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 Cd0.60Mo0.20Sn0.20S.