Self-assembly method assisted synthesis of g-C3N4/ZnO heterostructure nanocomposites with enhanced photocatalytic performance

Abstract

Designing heterostructure photocatalysts by simple and efficient methods has attracted increasing attention nowadays, since the heterojunction between two different semiconductors would promote the separation of photogenerated electron-hole pairs, and improve the photocatalytic activity. In this study, the efficient g-C3N4/ZnO nanocomposite photocatalysts with outstanding separation ability of photogenerated carriers were synthesized via a facile approach of electrostatic self-assembly combined with low-temperature precipitating method. The treatment of concentrated sulphuric acid endows g-C3N4 with more negative polarity and more active sites, which serves the deposition of ZnO nanoparticles. Besides, the in-situ growth way produces a tight and perfect heterojunction for speedy electron transfer between g-C3N4 and ZnO. The g-C3N4/ZnO composite samples exhibited much ehanced photocatalytic performance than single catalysts, and the degradation efficiency of the optimal product for decomposition of methylene blue (MB) reached to 60% within 120 min, of which the total reaction rate constant was about 3.9 times higher than that of pure ZnO. The trapping experiments showed that the •OH radical was the major reactive oxygen species for degradation of MB, and it dropped approximate 50% of the degradation efficiency after the addition of the scavengers of ·OH. The Z-scheme mechanism is employed to explain the electron transfer pathway, which is a main reason for the enhancement of photocatalytic activity. This work provides a facile synthetic method and new sight for constructing heterojunctions for photocatalytic decompositing organic pollutants.