Experimental and Theoretical Research on Photocatalytic Nitrogen Reduction Using MoS2 Nanosheets with Polysulfide Vacancies

MoS₂ nanosheets with different concentrations of S vacancies (V_S-MoS₂) were synthesized and used for photocatalytic nitrogen reduction reactions (pNRR), and the mechanism of S vacancies enhancing the activity of MoS₂ was explored through DFT calculation. The material characterization confirmed the successful construction of S vacancies at different concentrations on the spherical cluster structure of MoS₂. The experimental results show that the introduction of S vacancies significantly improves the activity of pNRR, and it increases significantly with the increase of vacancy number, consistent with the trend of photoelectric performance. V_S-MoS₂-3 exhibits the highest pNRR efficiency, which is 3.5 times higher than that of pristine MoS₂, and after being reused three times, the activity only decreased by about 11%. DFT calculation results indicate that the exposed Mo atoms generated by S vacancies alter the charge layout on the MoS₂ surface while providing abundant Mo active sites. Meanwhile, the band gap structure will narrow with the increase of S vacancies, which is beneficial for the transfer of surface charges. In addition, the increase of S vacancies, on the one hand, strengthens the adsorption of MoS₂ on N₂, weakens the adsorption of H, improves the selectivity of nitrogen, and is conducive to the progress of NRR. On the other hand, more electrons can be transferred from MoS₂ to the adsorbed N₂ molecules, enhancing the hybridization between them and better activating N₂.