Simple Synthesis And Study Of Bismuth-based Heterojunction And Its Visible Light Catalytic Performance

Bismuth-based semiconductors are considered to be candidate catalysts for visible light response due to their rich crystal structure and suitable band gap energy.However,the rapid photo-generated electron-hole recombination results in the lower photocatalytic activity of Bi-based semiconductors.Constructing heterostructures is a simple and effective strategy to separate photogenerated carriers.Based on this,this article first introduced the photocatalytic mechanism and application of heterogeneous semiconductors;then,from the perspective of synthesis,the simple preparation of bismuth-based composite materials and the treatment of high concentrations of Rh B and Cr（VI）by visible-light catalysis were carried out.And the catalytic mechanism of related materials were thought about.The main research contents are as follows:First,the p-n-typeα-Bi₂O₃/Sr Ti O₃heterojunction was prepared by ultrasonic dispersion-annealing treatment and applied to the photocatalytic degradation of Rh B(0.1 g L^-1).The characterization results showed that the two components may be combined by Ti-O-Bi bond.Tests and catalysis experiments indicated that the existence of a large number of metal oxygen bridge bonds and the narrowing of the band gap（reduced by～0.44 e V）promote the composite material to have a fast charge transfer rate,a low carrier recombination rate,and small interface mass transfer resistance.The photocurrent response of up to 6.1 times and the photocatalytic degradation rate of 1.35 times confirmed that the application performance of theα-Bi₂O₃/Sr Ti O₃heterojunction is better than that of a single component.Subsequently,the n-p type Zn O/Bi OI heterojunction was synthesized by wet chemical method and applied to the photocatalytic reduction of Cr（VI）.Compared with a single Bi OI component,the adsorption capacity and reduction rate of the composite material for chromium are increased by about 9.8 times and 5.2 times,respectively.Smaller mesoporous pore size（19.87 vs.6.61 nm）,larger specific surface area(7.07 vs.38.8 m²g^-1),and the introduction of positively charged Zn O on the surface have triggered an improvement in the photoelectric response of heterogeneous materials(0.336 m A cm^-2).The photocatalytic reduction rate of0.00208 min^-1showed that the Zn O/Bi OI heterojunction has the ability to treat high-concentration chromium-containing wastewater(0.2 g L^-1).Finally,α-Bi₂O₃/Au andβ-Bi₂O₃/Bi₂O₂CO₃/Au heterojunctions were prepared by thermal oxidation of a single bismuth precursor and sodium citrate reduction.Compared with a single component,the loading of Au initiated a red shift of the light absorption edge of the catalyst,and improved the effective separation rate of carriers.Compared withα-Bi₂O₃/Au,the multi-level structure and tightly coupled heterogeneous interface promotedβ-Bi₂O₃/Bi₂O₂CO₃/Au to exhibit higher adsorption and photocatalytic activity.The photocatalytic degradation rate of 0.0030 min^-1showed that the latter is capable of treating high-concentration organic dye wastewater(0.2 g L^-1).