Synergistic effects of g-C3N4 three-dimensional inverse opals and Ag modification toward high-efficiency photocatalytic H2 evolution

Photocatalytic hydrogen evolution is considered as a sustainable and economical scheme to meet the energy demand and solve the environmental pollution. Herein, we developed a sandwich sintering strategy to improve the production yield and uniformity of g-C3N4 inverse opal (CN IO) nanostructure via SiO2 colloidal crystal template. Based on the highly ordered CN IO nanostructure, novel photocatalysts of silver-modified CN IO (Ag–CN IO) nanocomposites were presented. The formation mechanism, morphology, microstructure, element content and distribution, optical and electrochemical properties were investigated. The photocatalytic performances were evaluated by H2 evolution under visible light irradiating. Also, the effects of Ag content and morphology of the nanostructures on the photocatalytic performances were studied. The results show that the as-developed Ag–CN IO exhibits the best H2 evolution performance among all the tested samples. The enhanced photocatalytic performance of the Ag–CN IO is mainly attributed to the Ag nanoparticles and IO structure, which can synergistically improve the light absorption and charge transfer as well as the surface kinetics. The photocatalytic mechanism of the Ag–CN IO was also proposed.