The Preparation,Structure Regulation And Photocatalytic Properties Of Bismuth Vanadate-based Photoanode

The rapid development of human society has led to excessive consumption on fossil fuels,exacerbated the global energy crisis and triggered a series of environmental problems.Therefore,it is very important to develop renewable energy that can replace fossil fuels.As an environment-friendly technology,semiconductor photocatalysis uses solar energy to drive the decomposition of water to obtain clean energy,which has attracted extensive attention in the field of environment and energy.Bismuth vanadate(BiVO4)is favored in the field of photocatalysis due to its suitable band gap,nontoxicity and photostability.Therefore,this research has probed into the photoelectrochemical performance of BiVO4based semiconductors adhering to the principle of sustainable development.(1)All-solid-state Z-scheme heterojunction was a ternary composite of Mo,W ion-doped BiVO4(Mo,W:BVO),hollow carbon nanospheres(HCSs)and BiOCl,prepared by simple solid-solution-drying-and-calcination(SSDC)method.The composite has accelerated carrier migration with the high redox capacity of photocatalyst.HCSs are used as electron transfer medium between BiVO4 and BiOCl owing to their excellent conductivity,which promotes the transfer of carriers.Compared with pure BiVO4,the prepared Mo,W:BVO/BiOCl@C photoanode shows excellent photoelectrochemical(PEC)performance due to its unique Z-scheme charge transfer system.Under simulated sunlight,the photocurrent density has been increased by about 5.4 times.(2)Mo,W:BVO/Ag/Bi multicomponent photocatalyst was synthesized by internal doping method.Bi-Ag alloy with multi-level layered structure was prepared by solvothermal method.After it was added to BiVO4 precursor solution,Mo,W:BVO/Ag/Bi composite photoanode was synthesized in situ by drop casting.Bi-Ag alloy is closely combined with BiVO4 to form electron transmission channels,which is conducive to the transfer of charge carriers,so as to improve the photocatalytic ability and stability of BiVO4.In addition,the introduction of Bi-Ag alloy has greatly widened the light response range of BiVO4,so as to improve the utilization of solar light by BiVO4 based semiconductors.The photoelectric conversion efficiency of Mo,W:BVO/Ag/Bi photoanode is 41%,while that of BiVO4 photoanode is only 2%.(3)ZnO/CdS composites were prepared by hydrothermal and chemical bath deposition(CBD)process.Mo,W:BVO/ZnO/CdS photocatalysts were obtained after evaporation solvent annealing in Mo,W:BVO precursor solution,and their photocatalytic properties have been tested.The layered structure of ZnO flower-like microspheres greatly increases the anchoring points of CdS nanoparticles,which is conducive to the formation of a large number of type-Ⅱ heterojunctions.At the same time,the close combination of BiVO4 and ZnO ensures the construction of type-Ⅱ heterojunction.The dual type-Ⅱ heterostructure realizes the spatial separation of electron holes and reduces the carrier recombination rate,which plays a key role in expanding the light absorption range and enhancing the photocatalytic performance.In the simulated sunlight test,the photocurrent density of Mo,W:BVO/ZnO/CdS photoelectric electrode reaches 2.9 mA/cm2,which is about three times higher than that of Mo,W:BVO photoelectric electrode.