Preparation Of Bismuth Vanadate-Based Heterojunctions And Investigation Of The Control And Mechanism Of Catalytic Activity

Bismuth vanadate（BiVO₄）is a type of vanadate compound that possesses suitable band structure,broad light absorption range,and stable chemical properties,among other advantages.These features make BiVO₄ highly promising for applications in photocatalytic pollutant degradation and photoelectrochemical（PEC）water splitting.However,the photocatalytic efficiency of pure BiVO₄ is relatively low.Therefore,this study aims to enhance the performance of BiVO₄ through modification techniques such as doping,semiconductor coupling,and catalyst modification.A p-n heterojunction Co-BiVO₄/Bi₂O₃ composite was formed by combining electrospinning and calcination methods to incorporate Co-doped BiVO₄ nanofibers with Bi₂O₃.The Co doping enhanced the visible light absorption and utilization capability of BiVO₄,while the p-n heterojunction formed by the combination of Co-BiVO₄ and Bi₂O₃effectively reduced the recombination of photogenerated electrons and holes,thereby improving the photocatalytic performance of the Co-BiVO₄/Bi₂O₃ catalyst.Compared to pure BiVO₄ and Bi₂O₃,3Co-BiVO₄/Bi₂O₃ exhibited the best photocatalytic performance,achieving a degradation efficiency of 97.3%for Rh B within 90 min and 97.7%for MBT within 40 min.Furthermore,the intermediate degradation products of MBT were analyzed using HPLC-MS.Finally,an analysis of the photocatalytic degradation mechanism was conducted.This work provides a simple and effective approach for designing photocatalysts for the degradation of organic pollutants.A novel heterostructured BiVO₄-Ni/Ag VO₃ nanofiber was prepared through electrospinning and hydrothermal methods.The improved photocatalytic performance of BiVO₄ can be attributed to the synergistic strategy of Ni doping and Ag VO₃ coupling.Compared to BiVO₄,BiVO₄-Ni/Ag VO₃ exhibited increased specific surface area and visible light absorption.Additionally,the formation of impurity energy levels and heterojunction effectively enhanced the separation efficiency of photogenerated charge carriers.Therefore,the optimized BiVO₄-Ni-1/Ag VO₃-25 photocatalyst achieved a photocatalytic reduction efficiency of 99.7%for Cr⁶⁺within 80 min and a degradation efficiency of 98.6%for Rh B within 30 min.Furthermore,the Z-scheme charge transfer mechanism of BiVO₄-Ni/Ag VO₃ was explained through free radical capture experiments and band alignment.The successful fabrication of Z-scheme heterojunction BiVO₄-based photocatalysts holds significant potential for applications in the photocatalytic degradation of pollutants and reduction of metal ions.A high-performance BiVO₄ photoanode for photoelectrochemical（PEC）water splitting was prepared by adjusting the deposition time and calcination temperature using an electrochemical deposition method combined with calcination.Subsequently,a co-catalyst,Co Ni OOH,was deposited on the surface of the BiVO₄ photoanode through a simple impregnation method.At 1.23 V vs.RHE,the BiVO₄/Co Ni OOH photoanode exhibited a higher photocurrent density（1.2 m A/cm²）,which was approximately 2.1 times that of the BiVO₄ photoanode（0.55 m A/cm² at 1.23 V vs.RHE）.Furthermore,the modification with the Co Ni OOH co-catalyst effectively improved the photoelectrochemical conversion efficiency,water oxidation kinetics,bias photon-to-current efficiency,charge separation and transfer rate,and reduced the onset potential of the BiVO₄ photoanode.Additionally,the Co Ni OOH-modified BiVO₄ photoanode demonstrated stable photocurrent density even after 8000 s of stability testing,indicating that the co-catalyst modification effectively reduced the photo-corrosion of the BiVO₄ photoanode.