Morphology Control,Photocatalysis And Electrochemical Properties Of Vanadate Semiconductor

At present,there have been many reports on the research of metal vanadate materials.Among them,Ferric vanadate（FeVO₄）and Bismuth vanadate（BiVO₄）,due to their narrow band gap and special electronic structure,have shown excellent performance in the fields of photocatalysis and electrode materials for lithium-ion batteries.In order to explore the regular morphology and stable synthesis of nano-sized grains of FeVO₄ and BiVO₄,and to study their photocatalytic and electrochemical properties.In this paper,FeVO₄,BiVO₄crystals and BiVO₄/FeVO₄ heterojunctions were synthesized by hydrothermal method,using XRD,SEM,EDS,UV-vis,FT-IR and other characterization methods analyzed the synthesized samples and tested the performance of different samples.FeVO₄ crystals with different F^-（and precursor diluted 10 times and different hydrothermal time when F^-content is 1:1）,Cl^-,Ethylenediamine（en）and Ethylenediaminetetraacetic acid（EDTA）were synthesized by hydrothermal method with deionized water as solvent.It can prepare pure FeVO₄ and Fe₂O₃/FeVO₄ heterojunctions with different morphologies.Among them,Fe₂O₃/cube-shaped FeVO₄ heterojunction had the highest photocatalytic performance,and the degradation efficiency of methylene blue solution（MB）can reach 96%in 200minutes;The specific capacity of the uncalcined sample was the highest,which was328.17F/g.LSS system hydrothermal method can be used to prepare granular Fe₂O₃/truncated octahedral FeVO₄ heterojunction when n(Fe³⁺):n（F^-）=1:1.Compared with the photocatalytic efficiency of the same sample under the water system,it can increase by18%,but the specific capacity was not much different.Furthermore,the influence of p H on the phase composition and morphology of FeVO₄ was explored.According to the experimental results and related literature,the optimal p H value for FeVO₄ was 4.BiVO₄ and BiVO₄/FeVO₄ heterojunction were synthesized by hydrothermal method with deionized water as solvent.BiVO₄ crystals with uniform three-dimensional cross-shaped structure can be obtained at 160℃,and the photocatalytic efficiency can reach 80%under200min;As the F^-content increases,the morphology changed from a uniform three-dimensional cross-shaped structure to a cross-shaped and three-dimensional hexagonal coexisting structure formed by the self-assembly of nanoparticles and then to a nano-particle shape;When the F^-content was 1:3,as the hydrothermal time increases,the morphology changed from a two-dimensional sheet-like cross-like structure to a three-dimensional cross-like and nano-particle coexisting state and then into a granular shape,and under 0.1h the degradation rate of synthetic samples can reach 96%in 120 minutes.In order to improve the photocatalytic efficiency of pure-phase BiVO₄ and FeVO₄,a BiVO₄/FeVO₄ heterojunction was synthesized.When n（BiVO₄）:n（FeVO₄）=1:1,the degradation rate of the sample was the highest,which can reach 98%under 100min.The electrochemical test showd that the specific capacity of the sample was 120.37 F/g when the current density was 1A/g,compared with pure single-phase BiVO₄ and FeVO₄,the photocatalytic efficiency and specific capacity are improved.