Preparation of g-C3N4/ZnMoCdS hybrid heterojunction catalyst with outstanding nitrogen photofixation performance under visible light via hydrothermal post-treatment

Abstract

Nitrogen fixation is the second most important chemical process in nature, next to photosynthesis. Herein, we report a novel g-C₃N₄/ZnMoCdS heterojunction photocatalyst with outstanding nitrogen photofixation ability under visible light prepared by hydrothermal post-treatment. The as-prepared ZnMoCdS is the ternary metal sulfide Zn_0.12Mo_0.12Cd_0.9S_1.14 with many sulfur vacancies, not a mixture of ZnS, MoS₂ and CdS. Strong electronic coupling, as evidenced by the UV-Vis, XPS and EIS results, exists between two components in g-C₃N₄/ZnMoCdS heterojunction photocatalysts, leading to more effective separation of photogenerated electron–hole pairs and faster interfacial charge transfer. The sulfur vacancies on ternary metal sulfides not only serve as active sites to adsorb and activate N₂ molecules but also promote interfacial charge transfer from the catalyst to N₂ molecules, thus significantly improving their nitrogen photofixation ability. With an optimal ZnMoCdS mass percentage of 80%, the as-prepared heterojunction photocatalyst exhibits the highest NH₄⁺ generation rate under visible light, which is 13.5-fold and 1.75-fold greater than those of individual g-C₃N₄ and ZnMoCdS, respectively.