Preparation Of BiVO₄-based Composites And Their Photocatalytic Properties Study

With the rapid development of the global economy,humanity have possess better living conditions,but also accompanied by serious environmental remediation.As a prerequisite for humanbeing living,the purified water has been suffered from serious pollution.Exploiting the excellent performance photocatalysts to decompose the organic pollutions in the wastewater is one of an important development trend in future due to its ultize the solar energy which is abundant and low cost.In this paper,we fabricated BiVO₄ fibers via electrospinning.In order to improve the photocatalytic performance,we taken three methods by the transition metal Mo ions doping,the construction heterojunctions with g-C₃N₄ via heat treatment and finally growth nanosheets on BiVO₄ surface to construct three-dimensionally branched?3DB?nanoarray structure via hydrothermal procedure.Work mainly includes the following aspects:?1?The pure BiVO₄ fibers were succesfully prepared via electrospun.The effects of heating rates on the morphologies and properties were analyzed in details.It is indicated that the sample with a heating rate of 1oC/min keep the best fibers morphology and possess the best photocatalytic property.Based on the above study,Mo@BiVO₄ composite photocatalysts were fabricated via electrospinning by the means of adding different concentration of molybdenum to the above mentioned precusor.The scanning electron microscopy?SEM?images of samples showed that the doping concentration of Mo has an important effect on the fibers morphologies.The photocatalytic evaluation for methylene blue?MB?indicated that the better photocatalytic activity of Mo@BiVO₄ are ascribed to lower doping concentration.Although the two higher content of Mo samples possessed stronger absorbtion property,the photocatalytic performance is similar with pure BiVO₄.This is due to the decrease of lattice defects when the concentration is high,simultaneously,the formation of MoO₃ particles near the BiVO₄ edges is easy to form the carrier recombination centers.So the most appropriate concentration is 1%Mo@Bi VO4.?2?The g-C₃N₄/BiVO₄ composites were obtained by the means of heat treatment mixing BiVO₄ fibers and urea.The morphology of g-C₃N₄/BiVO₄ turned to big particles and its surface area was apparently lower than BiVO₄,however,the photocatalytic performance of g-C₃N₄/BiVO₄ composites was as about 8 times as high than pure BiVO₄.The improved photocatalytic activity of composites is ascribed to the broaden response range of solar spectra and the formation of heterojunctions which promote the separation of photogenerated electron-holes.This method is very simple and low cost,which is different from traditional complex methods.?3?The black powders with the morphology of irregularly arranged nanosheets grown on the BiVO₄ fibers surface were obtained via hydrothermal method,that is the typical 3DB structure.The X-ray diffraction?XRD?and X-ray photoelectron spectroscopy?XPS?results demonstrated that in this 3DB structure there main existing BiVO₄,MoS₂,Bi₂S₃.This heterojunctions structure possessed excellent absorption property when compared with BiVO₄.