Study On Surface/interface Modulation And The Photocatalytic Properties Of Bismuthbased Photocatalyst

Bismuth bromide?BiOBr?and bismuth vanadate?BiVO₄?have been widely studied by researchers because of their suitable band gaps.However,BiOBr and BiVO₄ have some problems,such as low transport efficiency and easy recombination of photogenerated carriers.In this paper,the photocatalysis performance of bismuth-based photocatalyst has been improved effectively by controlling the surface and interface of semiconductor BiOBr and BiVO₄.The main research contents and results are as follows:1. The BiOBr?010?and BiOBr?001?were prepared by hydrothermal method,and BiOBr?001?/BiOBr?010??BB?composites were prepared by chemical conversion method based on BiOBr?exposed?010?facet?.The samples were characterized by XRD,SEM,TEM and PL.The analysis results show that the BB homojunction are formed by the attachment of nanosheet of BiOBr?001?on the BiOBr?010?nanosheet.By electrochemical impedance and Mott-Schottky analyses,it is found that BB homojunction show lower resistance,higher carrier lifetime and higher carrier concentration.Compared with BiOBr?001?and BiOBr?010?,BB homojunction show stronger photocatalytic activity under simulated sunlight irradiation.The cycling experiments of photodegradating Rh B show that the BB homojunction samples have strong stability.By photocatalytic reduction of Ag⁺on the surface of BiOBr?001?/BiOBr?010?,it is found that Ag⁺is selectively deposited on BiOBr?001?and Mn element is selectively deposited on BiOBr?010?by photocatalytic oxidation of Mn²⁺,which indicates that the reasonable surface/interface design of BiOBr could change the transfer direction of photogenerated electrons and holes and effectively promote the transport and separation of photogenerated carriers.2. msBiVO₄ samples with different?010?and?110?facet exposure ratio were prepared by hydrothermal method.The crystal structure,morphology and photophysical properties of BiVO₄ were characterized by XRD,SEM,TEM,XPS,PL and UV-vis.The SEM and TEM results show that the?110?facet exposure ratio of BiVO₄ increases with the increase of p H value of BiVO₄ precursor solution.When the p H value of precursor is 7,the plated-like msBiVO₄ exhibites higher transfer efficiency and more negative conduction potential.The photocatalytic performance results of oxygen production by water decomposition under simulated sunlight irradiation show that the plate-like msBiVO₄ has excellent O₂ evolution ability,which is about 4 times of the bipyramid msBiVO₄.There is a positive correlation relationship between the photocatalytic activity?O₂ evolution ability?of msBiVO₄ and the exposure ratio of?010?crystal surface.The results of photocatalytic degradation of thymol blue show that the plate-like msBiVO₄ exhibits excellent photocatalytic performance compared with the?110?-dominated msBiVO₄.After simulated sunlight irradiation 5 h,the photocatalytic degradation efficiency of plate-like msBiVO₄ on the thymol blue was 77.2%.The built-in electric field is generated between?110?and?010?crystal surface of msBiVO₄,resulting in a difference in electric potential energy level,which further enhances the transfer and separation efficiency of photogenerated electron hole pairs.