| Photocatalytic hydrogen evolution is a key research direction for future hydrogen energy development.The development of efficient and stable photocatalyst plays a crucial role in improving the photocatalytic hydrogen evolution performance.ZnIn2S4 has drawn keen interest because of its approprite band gap(2.2-2.6 eV),stable chemical property as well as tunable electronic structure.However,the lower photogenerated carrier separation and migration efficiency,sluggish surface reaction kinetics and photocorrosion severely restrict the catalytic activity of intrinsic ZnIn2S4.In this paper,we focus on the structure-activity relationship between structural modulation and photocatalytic activity of ZnIn2S4.We propose to optimize the electronic structure,charge flow and surface reaction kinetics of the material by elemental doping and heterojunction building techniques to achieve significant improvement in the photocayalytic performance of ZnIn2S4-based materials.The research includes the following three parts:(1)The Ni,In co-doped ZnIn2S4 catalyst was synthesized by a microwave-assisted solvothermal method with a rapid heating conditions,which achieved the charge flow modulation and H adsorption/desorption optimization.Due to the bond order(B)relationship(B[InS]6<B[InS]4<B[ZnS]4),the tetrahedron[ZnS]4 layer was more easily formed during hydrothermal synthesis,thus the substitution of In for Zn atoms was difficult to realize.The microwave synthesis induced a rapid heating rate,the ultrafast crystallization of ZnIn2S4 resulted in partial In and Ni atoms substituted Zn atom during the formation of[ZnS]4 layer.The DFT results showed In doping reduced the electronic potential wells along Z axis and promoted the electron transfer of In-ZnIn2S4.Furthermore,the Ni doping induced an increased H adsorption behavior on S sites of In-ZIS,which modulated the H absorption ability and balanced the H adsorption/desorption.(2)The hollow Fe-doped ZnIn2S4 nanosphere catalyst was synthesized by a low-temperature solvothermal method,using ZnFe2O4 as a sacrificial template and Fe source.Owing to the bond order(B)relationship(B[Fe-S]4>B[Zn-S]4),FeSx precipitates were easily generated when a lot of Fe ions were present during the solvothermal synthesis.In this study,a controlled preparation of Fe-ZnIn2S4 catalyst was achieved by etching ZnFe2O4 with slow release of Fe ions in the presence of H2S,which was generated from the decomposition of thioacetamide under acidic conditions.The experimental and DFT results showed that Fe doping elevated the valence band position,shortened the band gap,thus improving the light absorption.Further,the Fe doping reduces the electrostatic potential energy of the surrounding S site and endows it excellent hydrogen evolution kinetics.(3)A hierarchical NiTiO3@ZnIn2S4 direct Z-scheme heterojunction catalyst was synthesized by a solvothermal method,which exhibited the rapid the carrier separation and transport as well as the favourable stability.The intimate contact interface between NiTiO3 and ZnIn2S4 promoted the efficient separation and transport of photogenerated electrons-hole.Meanwhile,the Z type charge transport mechanism between NiTiO3 and ZnIn2S4 achieved the effective separation of photogenerated electrons-hole in space and endowed photogenerated electrons and holes with strong redox capabilities.Furthemore,the Z type heterojunction effectively avoided the photocorrosion of ZnIn2S4,and improved the activity and stability of the catalyst. |
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