Sc-Doped Sulfur Vacancy MoS2 Photocatalytic Nitrogen Reduction to Ammonia: Experimental and Theoretical Investigation

This paper combines defect engineering and metal doping to prepare transition metal Sc-doped molybdenum sulfide-containing sulfur vacancies (Sc@V S –MoS 2 ), which is used for photocatalytic nitrogen reduction to synthesize ammonia (pNRR). The activity of Sc@V S –MoS 2 for pNRR is as high as 124.26 μmol g –1 h –1, which is 6.16, 2.23, and 2.69 times for MoS 2, V S -MoS 2, and Sc@MoS 2, respectively. This indicates that the combination of S vacancies and Sc doping can significantly improve the photocatalytic performance of MoS 2 materials. Theoretical calculations show that the energy barrier U L of the potential determining step (PDS) is only −0.393 V, much lower than V S –MoS 2, making Sc@V S –MoS 2 exhibit excellent nitrogen reduction activity for ammonia synthesis. Computational results demonstrate that Sc@V S –MoS 2 exhibits outstanding N 2 adsorption and activation properties, with 0.533 e charge transfer to N 2 that significantly reduces the free energy barrier for the first hydrogenation step. Moreover, its hydrogen adsorption free energy is substantially lower than that of V S -MoS 2, effectively suppressing the competing hydrogen evolution reaction and enhancing N 2 reduction selectivity. In situ infrared spectroscopy showed the formation of −N 2 H y species on the catalyst surface, indicating that the enzyme pathway is the most likely reaction pathway, consistent with the calculated results.