Construction of g-C3N4/Zn0.11Sn0.12Cd0.88S1.12 Hybrid Heterojunction Catalyst with Outstanding Nitrogen Photofixation Performance Induced by Sulfur Vacancies

Nitrogen fixation is the second most important chemical process in nature next to photosynthesis. Herein, we report a novel g-C3N4/ZnSnCdS heterojunction photocatalyst prepared using the hydrothermal method that has an outstanding nitrogen photofixation ability under visible light. The as-prepared ZnSnCdS is the ternary metal sulfide Zn0.11Sn0.12Cd0.88S1.12 with many sulfur vacancies, not a mixture of ZnS, SnS2, and CdS. Strong electronic coupling, as evidenced by the ultraviolet-visible, X-ray photoelectron spectroscopy, photoluminescence, and electrochemical impedance spectra results, exists between two components in the g-C3N4/ZnSnCdS heterojunction photocatalysts, leading to more effective separation of photogenerated electron-hole pairs and faster interfacial charge transfer. The sulfur vacancies on ternary metal sulfide not only serve as active sites to adsorb and activate N-2 molecules but also promote interfacial charge transfer from ZnSnCdS to N-2 molecules, thus significantly improving the nitrogen photofixation ability. With the ZnSnCdS mass percentage of 80%, the as-prepared heterojunction photocatalyst exhibits the highest NH4+ generation rate under visible light, which is 33.2-fold and 1.6-fold greater than those of individual g-C3N4 and ZnSnCdS.