Graphdiyne based Zn_{0. 5}Cd_{0. 5}S and NiO dual S-scheme heterojunction boosting photocatalytic hydrogen evolution

As a novel carbon-based material with two-dimensional (2D) characteristics, graphdiyne (GDY) shows great potential in constructing active catalytic sites due to its distinctive atomic configuration and sp/sp² conjugated hybrid two-dimensional networks. In this study, the layered GDY was synthesized using the ball milling method, and Zn_0.5Cd_0.5S/Graphdiyne/NiO (ZnCdS/GDY/NiO) composite was synthesized by in-situ composite and physical mixing method. The prepared ZnCdS/GDY/NiO has good photostability outstanding performance in photocatalytic hydrogen production. When exposed to 5 W of white light, the ZnCdS/GDY/NiO photocatalyst demonstrates a hydrogen production rate of 24.44 mmol·g^-1·h^-1, which was 8.4 times greater than that of pure Zn_0.5Cd_0.5S under the same conditions. Various characterization tests and theoretical calculations show that the improved photocatalytic efficiency resulted from the formation of a dual S-scheme heterostructure in the ZnCdS/GDY/NiO composite catalyst, which promoted the recombination of relatively useless photogenerated electron holes. Furthermore, strong photogenerated holes and electrons in the more positive valence band (VB) and the more negative conduction band (CB) were retained, which significantly improved the photogenerated carrier separation ability of the composite catalyst, and thus enhances the hydrogen evolution activity.