Preparation And Photoelectric Properties Of BiVO₄-Bi₂O₃ Heterojunction Electrode

With the first industrial revolution in the middle of the eighteenth century,all countries in the world vigorously developed their own industries.During the development of industry,printing and dyeing techniques are accompanied by each other.This may cause the discharge of printing and dyeing wastewater and cause damage to the water environment.Therefore,it is particularly important to develop a technology to solve this problem.In recent years,bismuth-based photocatalysts have been favored by scholars from various countries.Bismuth vanadate?BiVO₄?as a narrow band gap photocatalyst,has a wider light response range,can be excited by visible light and efficiently remove organic pollutants.In this study,for the first time,BiVO₄-Bi₂O₃ photocatalyst was induced by rare earth element Yb under liquid phase conditions.And it was loaded on the surface of the FTO conductive glass by a blade coating method to obtain a BiVO₄-Bi₂O₃ photoeletrocatalytic electrode.The photocatalytic activity of methylene blue?MB?was evaluated by photocatalytic degradation of methylene blue?MB?under the condition of1.0V applied bias voltage while irradiated by artificial sunlight.In order to investigate the reasons for its enhanced photoeletrocatalytic activity,we performed XRD,FESEM,TEM,XPS,UV-vis DRS,PL,EIS,and photocurrent tests on the prepared samples,and examined their microstructure,morphology,and photoelectricity.The performance was characterized and the following conclusions were obtained:Using Yb?NO₃?₃·5H₂O as the Yb source,add it to the BiVO₄ precursor solution at a molar ratio of 0at%,2at%,3at%,4at%,5at%.Corresponding materials are prepared by one-step hydrothermal method.When Yb³⁺is added at 2at%or less.The product is pure monoclinic phase BiVO₄.No secondary phase formation.When Yb³⁺is added at 3at%or more.The crystal phase of BiVO₄ not only undergoes a transition from a monoclinic phase to a tetragonal phase,but also Bi₂O₃ appeared.In terms of microscopic morphology,the addition of Yb³⁺caused the morphology of BiVO₄ to change from flaky to square prism.In photoeletrocatalytic degradation experiments the addition of Yb³⁺can improve the photoeletrocatalytic activity of the material.This is because Bi₂O₃ induced by Yb³⁺is in close contact with BiVO₄ to form a heterojunction.Greatly reduces the recombination efficiency of photo-generated electrons and holes,and increases the lifetime of photo-generated carriers.Among them,the sample with 4at%Yb³⁺showed the best photoeletrocatalytic performance,and the degradation rate of the 10 mg/L methylene blue aqueous solution was 83.2%within 2 hours.In addition,we also performed stability tests on the prepared electrodes.After four repeated degradations,its photocatalytic activity can still be maintained above 95%.This shows that the electrode we prepared has good stability and high photoeletrocatalytic activity.In order to further improve the photoeletrocatalytic activity of the heterojunction electrode.We selected three surfactants as sodium dodecylbenzenesulfonate?SDBS?,tetradecyltrimethylammonium bromide?TTAB?,and cetyltrimethylammonium bromide?CTAB?as morphologies to control agent controls its morphology.After the preliminary process exploration.We added 0.87g SDBS,0.84g TTAB,and 1.82g CTAB to the precursor solution of heterojunction photocatalyst,respectively.Heterojunction photocatalysts modified with different surfactants were obtained by a one-step hydrothermal method.In the FESEM image,we can see that the heterojunction photocatalyst modified by SDBS has a needle-like distribution,the heterojunction photocatalyst modified by TTAB has a spherical distribution,and the photocatalysis of CTAB modified heterojunction has no regular flake and block distribution.In the photocatalytic degradation test of simulated pollutants at specific concentrations,the SDBS modified heterojunction photocatalyst showed the best photocatalytic activity,and methylene blue could be completely removed within 2 hours.Compared with the other two types of surfactant-modified heterojunction photocatalysts,the photoeletrocatalytic activity of the heterojunction photocatalysts has decreased to different extents compared with the unmodified heterojunction photocatalysts.Therefore,we conclude that anionic surfactants can promote their photocatalytic activity,while cationic surfactants have an inhibitory effect on their photocatalytic activity.