Research On Construction And Photoelectrochemical Properties Of WO₃-based Heterojunction Composite Structures

Since one of the severe problems the world facing today is the energy crisis and environment issue,hydrogen generated by photoelectrochemical water splitting has received widespread attention.A significant amount of effort has been dedicated to develop semiconductor photocatalysts responsed to visible light,broaden the light response range of semiconductors,promote the transfer and separation efficiency of photogenerated charge and improve the efficiency of solar energy conversion.In situ WO₃ of different morphologies have been synthesized via hydrothermal method and the morphological effect on the photoelectrocatalytic activity of the obtained samples has been researched.One-dimensional WO₃ nanorods have been modified by metal sulfide of narrow bandgap and applied in photoelectrochemical water splitting.The influence and mechanism of excellent PEC performance has been researched in detail.In this work,In situ WO₃ nanorods,WO₃ nanoplates and WO₃ microcrystals have been synthesized via hydrothermal method by changing the p H value in the precursor solution.One-dimensional WO₃ nanorods can facilitate charge transport by providing a direct pathway for the photogenerated electrons.On this basis,the heterojunction composite structure has been constructed by coupling WO₃ nanorods with metal sulfide of narrow bandgap which aims to further broaden the range of photo responsiveness and improve the separation efficiency of photogenerated electron-holes.WO₃/CdS NRs?WO₃/Sb₂S₃ NRs heterojunction composite structures have been fabricated via successive ionic layer adsorption and reaction?SILAR?technique and water bath method coupled with hydrothermal method in order to improve the photoelectrocatalytic efficiency.The morphology,structures and photoelectrochemical performance of the as-prepared samples have been studied,the morphological effect on the photoelectrocatalytic activity of the obtained samples has been discussed and the influence of coupling with narrow band gap semiconductor to photoelectrochemical performance of composite photoelectrode have been researched.WO₃ of different morphologies synthesized via hydrothermal method by changing the p H value in the precursor solution possess varied crystal strctures.The photocurrent of the monoclinic WO₃ NRs and WO₃ MPs is 0.39 m A/cm2?0.36 m A/cm2 at 0.80 V?vs.RHE?,respectively,while hexagonal WO₃ MCs achieved a photocurrent of 0.45 m A/cm2.Based on the excellent charge transport efficiency of one-dimensional WO₃ nanorods,the heterojunction composite structure has been constructed coupled with metal sulfide of narrow bandgap.The as-obtained WO₃/CdS NRs?WO₃/Sb₂S₃ NRs heterojunction composite photoelctrodes achieved enhanced photocurrent of 0.85 m A/cm2 and 1.20 m A/cm2 at 0.80 V?vs.RHE?;is about 118% and 208% greater than the values of bare pristine WO₃?0.39 m A/cm2?.The results demonstrated that the heterojunction exhibited more efficient photoelectrocatalytic performance.This excellent performance is achieved owing to broaden light absorbance spectrum and enhanced light absorbance sensitized by narrow bad gap Cd S;the direct pathway to facilitate charge transport supplied by one-dimensional?1D?WO₃ nanorod;reduced charge recombination rate thanks to the appropriate gradient energy gap structure of WO₃/metal sulfide.