Construction of g‑C₃N₄/Zn_0.11Sn_0.12Cd_0.88S_1.12 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 Zn_0.11Sn_0.12Cd_0.88S_1.12 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 N₂ molecules but also promote interfacial charge transfer from ZnSnCdS to N₂ 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