Function-Oriented Design And Photocatalyst Performance Of MoS₂ Cocatalyst

Due to emerged energy crisis and global environmental awareness,photocatalytic technologies that use semiconductor photocatalysts to convert solar energy into chemical fuels have attracted widespread attention.This paper focuses on the study of highly efficient and stable photocatalytic hydrogen evolution materials.Based on the construction of a new functional-guided cocatalyst material and the regulation to structure and phase state of transition metal disulfides cocatalyst,and then complete systematic optimization for the light-absorbing semi-conducting catalyst to pursue further improvement.Moreover,the charge separation and electron transport mechanism was in-depth investigated.The primary study conclusions are summarized briefly as follows:(1)A multi-functionally modified MoS2 nanosheets(DRM)with defect-rich,O-incorporated and 1T phase was prepared by bottom-up one-step hydrothermal approach,which realized the multi-angle oriented design for the structure and phase state of material.Study shows that this multi-functional coordinated regulation not only can significantly increase the edge reactive sites of MoS2,but also can effectively improve its inherent intrinsic conductivity.For comparison,a defect-free,O-incorporated and 1T phase MoS2 nanosheets(DFM)with high crystallinity was synthesized simultaneously.Research indicates that the defect-rich structure can causes many fractures on the surface of the nanosheets,thereby fully exposing the active edge sites.Photoelectrochemical measurements and ESR characterization prove that the defect engineering has a significant enhancement effect on the active site density of the material.(2)The optimized cocatalyst will be loaded on the surface of CdS by a simple physical mixing method.The heterostructure hybrid catalysts(DRM-C and DFM-C)were formed through surface electrostatic interaction.A comparative study on DRM-C and DFM-C demonstrates that the photocatalytic HER activity of the former is superior to that of latter,predominantly due to the higher density of active sites originated from the abundant defects in DRM.Besides,DRM-C is proven to show more merits of charge transfer and separation in comparison with DFM-C.Under an optimized DRM/CdS ratio of 20 wt%,DRM-C achieves a remarkable enhanced visible light(?>420 nm)photocatalytic H2 production rate of 132.4 mmol h-1-g-1,far higher than that of pure CdS(20.0 mmol h-1 g-1),20 wt%DFM-C(102.1 mmol h-1 g-1)and conventional Pt/CdS(89.0 mmol h-1 g-1).Basides,the quantum efficiency of 20 wt%DRM-C up to 47%(?=420 nm),and it exhibits good photocatalytic stability.To the best of our knowledge,this heterostructure photocatalyst shows the advanced visible-light-driven photocatalytic HER performance among reported MoS2/CdS composites.(3)The PL,PEC,Mott-Schottky curve and other characterization methods prove that the DRM-C composites conform to H2 "band matching theory".Compared with DFM,the conduction band(CB)potential of DRM has a positive shift of 0.1 V.The photo-excited electrons from CdS would more be easier to be injected into the lower-level position DRM,which facilitates rapid transfer and efficient separation of charge carriers and thereby effectively improves the photocatalytic HER performance.