Hierarchical Sheet-on-Sheet ZnTi-LDHs/g-C3N4 composites with enhanced photocatalytic activity prepared by mechanical mixing

Constructing 2D/2D heterostructures with face-to-face contact (e.g. sheet-on-sheet and layer-by-layer) has been considered as an effective way to enhance the photocatalytic activity of materials. However, the preparation of 2D/2D heterostructures is always a complicated process. In this work, the “sheet-on-sheet” hierarchical composites based on Zn,Ti-layered double hydroxides (ZnTi-LDHs) and carbon nitride (g-C3N4) were investigated. ZnTi-LDHs/g-C3N4 were fabricated by a simple mechanical mixing method. For comparison, ZnTi-LDHs/g-C3N4 composites were also prepared by the electrostatic self-assembly method and the hydrothermal method. The effects of preparation methods on the structure, morphology, interfacial contact, and photocatalytic properties of ZnTi-LDHs/g-C3N4 composites were investigated. Experimental results show that the ZnTi-LDHs/g-C3N4 composites prepared by the mechanical mixing method exhibited better photocatalytic activity than the other two methods for the decomposition of methyl orange. The hierarchical “sheet-on-sheet” contact between g-C3N4 and ZnTi-LDHs in the composites efficiently promoted the photo-induced charge separation and improved the photocatalytic property. This study proves that a 2D/2D heterojunction with sheet-on-sheet contact can be prepared by a simple mechanical mixing method, which provides a feasible way for further design and synthesis of photocatalysts.