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

MoS2 nanosheets with different concentrations of S vacancies (VS-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. VS-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.