The high-dispersed nano complex ZnO/Co 3 O 4 was first prepared by calcining the ZIF-8@ZIF-67 in Air. Then, the ternary mix-heterojunction ZnIn 2 S 4 /CdIn 2 S 4 /Co 3 O 4 (CdIn 2 S 4 /Z/C) was first in situ constructed by introducing nano complex ZnO/Co 3 O 4 into the CdIn 2 S 4 precursor solution via a solvent thermal reaction. Overall, the CdIn 2 S 4 /Z/C photocatalyst exhibits excellent performance in the photoconversion of CO 2 and H 2 O, which increased by 18.1%∼34.1% for CO, 36.8%∼73.9% for H 2 , and 21.1%∼40.6% for syngas (CO+H 2 ), respectively, compared with CdIn 2 S 4 . The CdIn 2 S 4 /Z/C-40 shows the highest H 2 -evolution rate of 1661.8 μmolg −1 h −1 , which is 87.5% higher than that of CdIn 2 S 4 (886.3 μmolg −1 h −1 ). The CdIn 2 S 4 /Z/C exhibits higher surface S-vacancy concentration, larger specific surface area, stronger light absorption, and photocurrent density than that of CdIn 2 S 4 . The band structure reveals that the ZnIn 2 S 4 /CdIn 2 S 4 /Co 3 O 4 forms a tandem internal electric field at the double heterojunction interface, which is beneficial to improve the migration of photocarrier. This work provides a feasible strategy for constructing synergistic mix-heterojunction photocatalyst for photoconversion of CO 2 and H 2 O.
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.
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