Preparation Of ZnCdS Semiconductor Enhanced By Cocatalysts And Study On Its Photocatalytic Hydrogen Evolution Performance

With the rapid depletion of fossil fuels and more and more serious pollution,clean energy is becoming more and more important.Photocatalytic technology to convert solar energy into clean hydrogen energy is considered to be an effective solution,especially for the development and design of visible light-responsive photocatalyst semiconductors.ZnCdS,as a CdS-based semiconductor material,has a narrow band gap and suitable band edge potential.Therefore,it is considered as one of the most valuable visible light photocatalytic catalysts for hydrogen production.However,the photogenerated electrons and holes of ZnCdS are still easy to recombine,which limits the further improvement of its photocatalytic performance.Co-catalyst engineering is considered to be one of the most effective strategies to improve photocatalytic performance and restrain photocorrosion by promoting charge transfer.Through the supported co-catalyst,the design and construction of semiconductor heterojunction can effectively promote the transfer of photogenerated carriers and improve photocatalytic performance.In this paper,mesoporous multicomponent ZnCdS-based metal sulfide semiconductor composites were explored from four aspects:the design of synthesis methods,the microscopic characterization of nanostructures,the application of photocatalytic hydrogen production,and the mechanism of photocatalytic performance improvement.The main research results are as follows:1.In this work,MoS2/ZnCdS multiple metal sulfide mesoporous nanospheres were generated by in-situ self-assembly via a one-step mild hydrothermal method.A photocatalyst with a double-heterojunction synergistic structure and a large specific surface area was constructed to form a high-speed charge transfer channel as a mechanism to promote photocatalytic hydrogen production.The best quaternary catalyst MoS2/ZnCdS-5 has a hydrogen evolution yield of 23.32 mmol·h^-1·g^-1,which is 53 times and 11 times that of the corresponding binary（Cd S）and ternary（ZnCdS）compounds,respectively,and still has high stability within 20 h.Furthermore,the MoS2/ZnCdS-5 gets an apparent quantum efficiency（AQE）of 6.9%at 420 nm.Through further analysis,such as photoluminescence（PL）and photoelectrochemical,etc.,the enhanced photocatalytic performance of MoS2/ZnCdS-5 can be attributed to the synergistic effect of the heterojunction between Zn S and Cd S and the heterojunction between ZnCdS and MoS₂.In addition,the Pt-like structure of molybdenum sulfide cocatalyst can lead to efficient photoinduced charge separation and transfer.Meanwhile,the mesoporous structure endows the material with abundant reactive sites and increases the catalytic reaction efficiency.The unique in situ construction method of this work also provides a reference for the design and synthesis of heterojunction metal sulfide catalysts for green energy conversion.2.In this work,popcorn-like MoS2/ZnCdS@Co3O4 nanospheres with a mesoporous structure supported on double co-catalysts were prepared by a facile in-situ one-pot solvothermal method combined with photodeposition.Under visible light,the hydrogen evolution rate of Mo/ZCS@Co-0.5 with optimal cocatalysts loading can be as high as 18.73 mmol·h^-1·g^-1,which is 50 times higher than that of unmodified ZCS,and it still has high stability after 20 hours cycle test.In addition,the apparent quantum yield（AQY）at 420 nm is as high as 10.11%.Through further analysis and characterization by spectroscopy,photoelectrochemistry,etc.,the enhanced photocatalytic performance of Mo/ZCS@Co-0.5 can be attributed to the synergistic regulation of charge by the heterojunction between the dual co-catalysts and the main catalyst.Pt-like MoS₂ can effectively induce the separation and transfer of photogenerated electrons.P-type semiconductor Co₃O₄ accumulates photogenerated holes through the p-n junction.In addition,the special mesoporous structure endows the materials with abundant reactive sites.The unique construction method of this work provides a reference for the design and synthesis of double co-catalyst synergistic photocatalysts for green energy conversion.In summary,this paper proposes some effective solutions to the challenges of low hydrogen production efficiency faced by ZnCdS-based photocatalytic nano-semiconductor materials in hydrogen production applications.Mainly around the co-catalyst engineering strategy,the co-catalysts are loaded by the one-pot hydrothermal method,in-situ solvothermal method,or photodeposition method,and the materials are endowed with abundant active sites by designing the mesoporous structure.At the same time,the heterojunction structure is designed to regulate the migration path of photogenerated carriers.Then,in terms of performance and application,we mainly explore photocatalytic hydrogen production under visible light.While the catalytic performance and stability of the catalyst are significantly improved,the mechanism of the photocatalysis is explored,and the structure-activity relationship between the photocatalyst and the performance is explained.