Studies On Preparation And Properties Of 0D/2D Chalcogenide Nanocomposite Photocatalytic Materials

Metal chalcogenides are well known photocatalysts for photocatalytic hydrogen evolution,owing to their suitable band-gap structure and low cost.However,the poor photocatalytic activity and photostability limit their application.Transition metal dichalcogenides?TMDs?are two-dimensional?2D?materials with narrow band-gap structure,which can be used as cocatalysts to improve the photoelectron-hole pairs separation and transfer rate of photocatalysts.Besides,due to the large specific surface area of 2D TMDs,it can be used as the support of many photocatalysts to improve their photostability.In this paper,in order to improve the photoinduced electron-hole pairs separation and transfer rate,as well as the photostability of metal chalcogenides,a series of OD metal chalcogenide/2D TMDs nanocomposite photocatalysts have been designed and prepared,which can solve the poor photocatalytic activity and photostablity issues of metal chalcogenides.The main contents are as follow:?1?OD/2D CdS/WS2 nanocomposites with high photocatalytic activity and photostability were prepared,and the mechanism of photocorrosion-recrystallization to improve its photocatalytic performance was studied.In primary CdS/WS2 nanocomposites.CdS nanoparticles grew uniformly on the surface of WS2 nanosheets.The photocatalytic activity of CdS/WS2 nanocomposites increased with irradiation time increasing.After100 h irradiation,the photocatalytic activity reached the maximum value and showed excellent photostability.After 200 h irradiation,the size of CdS nanopauticles in the composite reduced,and the interaction intensity between CdS and WS2 nanosheet was enhanced.Combining with the ICP-AES characterization,the photocorrosion-recrystallization mechanism during the photocatalytic reaction was proposed.The results show that photocorrosion-recrystallization effect can be used to improve photocatalytic activity and photostability of OD/2D metal chalcogenide/TMDs nanocomposites.?2?OD/2D CdSe/WS2 nanocomposites with high photocatalytic activity and photostability were prepared and the mechanism of band-gap matching to improve its photocatalytic preformace was studied.Based on quantum size effect and band engineering theory,the band-gap between CdSe quantum dots?QDs?and WS2 nanosheeets were matched by controlling the size of CdSe QDs.CdSe QDs with different sizes grew uniformly on the surface of WS2 nanosheets by regulating reaction condiations.The band-gap structure of 7?8 nm CdSe QDs matched the band-gap structure of WS2 nanosheet exactly,realizing the effective separation and transfer rate of photogenerated electron-hole pairs.The photocatalytic properties characterizations proved that the band-gap matched CdSe/WS2 nanocomposite exhibited excellent photocatalytic activity and photostability.The results show that band-gap matched 0D/2D nanocomposites can effectively improve the photocatalytic activity and photostability.?3?0D/2D CoP/CdS/WS2 p-n-n tandem heterostructure nanocomposites were prepared,and the mechanism of photocatalytic hydrogen evolution without using sacrificial agent was studied.The p-n-n tandem heterostructure in CoP/CdS/WS2 nanocomposite benefited for the separation and transfer of photogenerated electron-hole pairs and prolonging the lifetimes of photogenerated carrier.The photocatalytic hydrogen evolution without using sacrifice agent,as well as the bifunctional photocatalytic reaction of degrading organic pollutants and producing hydrogen at the same time were achieved with excellent photostability.The results show that the design and preparation of nanocomposites with p-n-n tandem heterostructure provide a new way for the development of photocatalytic water spliitng without using sacrificial agent.?4?0D/2D ZnS/WS2 nanocomposites with high photocatalytic activity and photostability were studied,and the mechanism of photocatalytic hydrogen evolution by wide band-gap ZnS/narrow band-sap WS2 nanocomposite under full-light irradiation was proposed.By regulating the experimental conditions,ZnS nanoparticles grew uniformly on the surface of WS2 nanosheet.The photocurrent characterization of the nanocomposites demonstrated its high photogenerated electron-hole pairs separation rate.The photocatalytic characterizations of the nanocomposites demonstrated its high photocatalytic activity and photostability under full-light irradiation.The design and preparation of ZnS/WS₂ nanocomposites provide a new approach for the application of wide band-gap semiconductors in the field of photocatalysis.