Design of ultrathin CoAl-LDHs/ZnIn₂S₄ with strong interfacial bonding and rich oxygen vacancies for highly efficient hydrogen evolution activity

Designing a semiconductor-based heterostructure photocatalyst is very important way to enhance the hydrogen production activity. Here, a novel 2D/2D CoAl-LDHs/ZnIn₂S₄ S-scheme heterostructure with an ultrathin structure was synthesized by electrostatic attraction between CoAl-LDHs and ZnIn₂S₄ nanosheets. The presence of oxygen vacancies in the monolayer CoAl-LDHs nanosheet promotes the formation of Co-S_X bonds, which serve as charge transfer channels at the interface of the CoAl-LDHs/ZnIn₂S₄ heterostructure. The ultrathin CoAl-LDHs/ZnIn₂S₄ exhibits broadened light absorption in the near-infrared range due to the occurrence of Co-S_X chemical bonds. The CoAl-LDHs/ZnIn₂S₄ with a mass ratio of 1:2 demonstrated the highest photocatalytic hydrogen evolution activity (1563.64 μmol g⁻¹ h⁻¹) under the simulated sunlight, which is 4.6 and 9.7 times than that of the ZnIn₂S₄ and CoAl-LDHs/ZnIn₂S₄(bulk), respectively. The enhanced photocatalytic activity of ultrathin 2D/2D CoAl-LDHs/ZnIn₂S₄ should attributed to the shorter carriers path that benefit from the ultrathin structure and the quicker photogenerated charge transfer and the S-scheme migration pathway accelerated by the charge channel of Co-S_X bonds. These new ideas should be inspiring for the design and construction of heterostructures for higher photocatalytic hydrogen evolution activity.