FeS₂ Cocatalyst-based S-scheme Heterostructure With Enhanced Photocatalytic Hydrogen Evolution Performance

Photocatalytic water decomposition for hydrogen（H₂）production is the best technology to transform sustainable solar energy into clean and pollution-free hydrogen energy.It is suitable for the current situation of global energy crisis and environmental pollution,and is expected to replace the traditional industrial hydrogen production technology.The preparation of high efficiency,low cost and stable semiconductor photocatalyst is a hot topic at present.Ferrous disulfide（FeS₂）is a narrow bandgap（1.77 eV）metal sulfide semiconductor material,with a conduction band potential to meet the photocatalytic hydrogen evolution half-reaction（HER）,is a potential co-catalyst for H₂production.By coupling suitable semiconductor catalysts to construct FeS₂@X complex,the purpose of simultaneous driving oxidation half-reaction and reduction half-reaction can be realized.The formation of composite catalyst can not only improve the utilization rate of light energy,but also inhibit the photocorrosion of sulfide,so as to improve the efficiency of photocatalytic H₂production.In this paper,the photocatalytic HER mechanism and the improvement of the H₂production performance of the composite catalysts were studied by constructing different FeS₂@X heterogeneous structures.（1）The unique hollow double shell structure of S-doped ZnSnO₃（S-ZnSnO₃）was prepared by coprecipitation,solvothermal and calcination methods.Then,the FeS₂@S-ZnSnO₃heterogeneous structure was successfully constructed by loading FeS₂on the surface of S-ZnSnO₃sample through secondary hydrothermal method.The HER activity of the composite catalyst was significantly increased compared with that of the original ZnSnO₃and FeS₂.The improvement of H₂production performance can be attributed to the synergistic actions of S doping and cocatalyst FeS₂coupling.（2）The ZnIn₂S₄microspheres and FeS₂nanoparticles were prepared by hydrothermal method,and then the FeS₂@ZnIn₂S₄heterojunction was constructed by electrostatic self-assembly.The formation of heterostructures not only promotes the efficiency of carrier separation through interfacial electron transfer,but also broadens the range of light absorption,thus improving the performance of photocatalytic H₂production.（3）Cd _XMn_1-XS solid solution was prepared by hydrothermal method,and the FeS₂was then loaded as H₂production cocatalyst on the surface by electrostatic self-assembly,forming the FeS₂@Cd_0.3Mn_0.7S heterogeneous structure.The optimal Cd doped solid solution was obtained by adjusting the Cd/Mn ratio,and the band structure of Cd _XMn_1-XS was optimized.The load of FeS₂cocatalyst promotes the separation and transfer of photogenerated carriers and achieves higher light energy utilization.