ZIF-67 derived hierarchical hollow Co3S4@Mo2S3 dodecahedron with an S-scheme surface heterostructure for efficient photocatalytic hydrogen evolution

Abstract

An S-scheme surface heterojunction between Co₃S₄ and Mo₂S₃ was constructed successfully via a stepwise hydrothermal method. A rhombic dodecahedral cobalt-based metal–organic zeolite imidazole framework (ZIF-67) is used as the cobalt source and template to participate in the reaction process. ZIF-67 with a dodecahedral structure is first reshaped into cobalt sulfide with a hollow polyhedral structure via a one-step sulfidation reaction. And then, Mo and S species were introduced on the surface of Co₃S₄ to fabricate Co₃S₄@Mo₂S₃ with a hierarchical core–shell structure and S-scheme heterojunction. In comparison, the H₂ evolution activity of Co₃S₄@Mo₂S₃ is about 7 and 3 times higher than those of pure Mo₂S₃ and Co₃S₄. Density functional theory (DFT) calculations were used to construct the molecular model of Co₃S₄ and Mo₂S₃, and the sample's energy band structure was also analyzed. Based on the analysis of a series of characterization results, a H₂ evolution mechanism of Co₃S₄@Mo₂S₃ with a S-scheme surface heterojunction was proposed. The formation of the S-scheme surface heterojunction between Co₃S₄ and Mo₂S₃ results in a more developed channel to transfer photogenerated electrons and allows the system to retain a more effective redox potential. Besides, the Mo₂S₃ nanosheet's criss-cross growth on the Co₃S₄ surface is beneficial to the improvement of the cycle stability of the Co₃S₄@Mo₂S₃ composite. This work uses a ZIF-67 polyhedron as the template to provide a new strategy for preparing a hierarchical S-scheme surface heterojunction photocatalyst based on MOFs.