The Preparation And Performance Of The BiVO₄ Composite Materials

As a photocatalyst,semiconductor has been widely used in solving energy crisis and environmental degradation by solar energy.How to prepare visible light catalysts with high catalytic activity,low price and easy synthesis has become the focus of research.Bismuth vanadate（BiVO₄）has been widely used in photocatalysis due to its narrow band gap（2.4 eV）,high catalytic activity and low price.In order to further improve its photocatalytic activity,bismuth vanadate was synthesized with different non-noble metals.The specific research content is as follows:（1）A series of different loading ratios of NiAl-MMO/BiVO₄ materials were prepared by a hydrothermal method,using P123 as template agent.NiAl-MMO were derived from NiAl-CO₃ LDHs/BiVO₄.It is found that the absorption range of visible light can be expanded and the recombination rate of photogenerated electrons and holes can be significantly reduced when metal oxides are loaded.Under visible light irradiation,photocatalytic oxidation of thiophene in simulated oil was carried out.The experiment found that when the NiAl-MMO load was 0.2,the conversion rate of thiophene could reach 95.4%.This is due to the formation of p-n heterostructure between NiAl-MMO/BiVO₄ composites,which effectively promotes the transfer of electrons and inhibits the combination of electrons and holes,thus greatly improving the photocatalytic performance.（2）BiVO₄ was prepared by hydrothermal method using SDBS as template.With FeCl₃·6H₂O as the iron source,two kinds of crystal FeOOH/BiVO₄ with different compound proportions were prepared,namely,amorphous FeOOH/BiVO₄（A-FeOOH/BiVO₄）andβ-FeOOH/BiVO₄.Under the visible light,the performance of the composite catalyst was tested.The results showed that the oxygen production performance of the composite catalyst was higher than that of BiVO₄,in which A-FeOOH/BiVO₄（8 wt%）andβ-FeOOH/BiVO₄（5 wt%）had the best performance.The evolution rates of the photocatalytic oxygen were 1206.3μmol h^-1 g^-1 and 636.5μmol h^-1 g^-1,respectively,which were 7.4 times and 3.9 times of that of BiVO₄(162.3μmol h^-1 g^-1).Through XRD,XPS,SEM,TEM and other tests on the structure and morphology of the composite materials,it was found that the composite FeOOH did not change the structure of BiVO₄.From HRTEM,it was observed that the composite photocatalyst A-FeOOH/BiVO₄ was coated with a uniform amorphous layer.β-FeOOH/BiVO_4,on the other hand,is encased in crystalline layers of varying thickness.By UV-Vis,PL analysis,instantaneous current and impedance testing,the test results show that the composite photocatalyst,the range of light absorption absorption intensity bigger,stronger,light electrons and holes separation ability increase,which due to the amorphous structure has more narrow band gap width,the lack of an orderly atomic arrangement,have more defects.These characteristics can make their light absorption range wider,promote electron transfer and provide more active sites,thus enhancing the photocatalytic performance.