Effects Of High Crystallinity And Cu Modification On Photocatalytic Performance Of TiO₂ Materials And Its Mechanism

In photocatalytic research,TiO₂ is a typical photocatalytic material.Compared with other photocatalytic materials,TiO₂ has the advantages of safety,non-toxicity,stable nature and low price.There are many factors that determine the photocatalytic performance of TiO₂.Among them,crystallinity is one of the most important factors,which can affect the surface chemistry and influence the photocatalytic activity of TiO₂.Due to the phase transition from anatase to rutile during annealing,it is difficult to synthesize anatase TiO₂ material with highly crystallinity.Developing a simple experimental method to obtain highly-crystalline anatase TiO₂ and studying its corresponding photocatalytic activity are meaningful.In addition,doping modification is a common way to change the photocatalytic activity of TiO₂.In principle,it mainly improves the photocatalytic activity of materials by adjusting the charge kinetics process.Although many research work has been done in this area,the understanding of its activity mechanism is not comprehensive enough,and it is necessary to adopt a new method to carry out more detailed research.Based on the above understanding,we study the effect of improving the crystallinity on the photocatalytic performance of TiO₂ material in this paper.The effect of Cu modification on the photocatalytic activity of TiO₂ was also studied in detail,and the process and mechanism of charge transfer kinetics were analyzed.Highly-crystalline TiO₂ material is prepared by a hydrothermal reaction in combination with a subsequent heat treatment.The TiOF₂ precursor is prepared by adding a suitable concentration of HF solution in the hydrothermal reaction,and then the anatase TiO₂ is prepared by high temperature annealing with the inhibition effect of F ion on the crystal transformation.Finally,high crystallinity anatase TiO₂ was obtained at high annealing temperature?700 and 800�C?,which show higher degradation performance of volatile formaldehyde pollutants is compared with the sample annealing at 500�C.The Au nanoparticle is supported on the surface of high crystallinity samples through a deposition-precipitation method.Due to the local plasmon resonance absorption effect of Au nanoparticles,the TiO₂ material shows obvious visible light catalytic activity for acetone degradation.In order to explore how the modified Cu affects the photocatalytic performance by adjusting charge kinetics,Cu-modified TiO₂ sample was prepared by hydrothermal method,in which an appropriate amount of HF was added to improve the exposure of{001}facets.The sample has a large specific surface area and a relatively average particle size,and it shows high photocatalytic activity at the same time.The effects of modified Cu on the photocatalytic process of TiO₂ and its mechanism were studied by measuring the photocatalytic activity of the sample and vacuum photoconductivityat different temperatures.The results show that the modification of Cu improves the activity of TiO₂ in the gas phase photocatalytic degradation of acetone.It was found that the modified Cu reduced the apparent activation energy of acetone degradation using TiO₂ photocatalyst,which proved that the photocatalytic reaction path of acetone was changed.The results of vacuum photoconductivity further demonstrate that modified Cu reduces the apparent activation energy in the process of electron interface transfer to O2 from TiO2.The results also proved the change of electron interface transfer path and acceleration of O₂ activation process.Photocatalysis is determined by electrons and holes together,the above results indicate that the reduction of apparent activation energy in electron interface transfer process is an important reason for improvement of the photocatalytic activity of TiO₂ material after modification of Cu.This research has a guiding significance for the understanding of physical and chemical mechanism when using modification method to improve the proverty of photocatalysts.