Study On Preparation And Photocatalytic Performance Of Graphene-based Cobalt-doped TiO₂

In the prevention and control of volatile organic compounds（VOCs）pollution,the use of photocatalytic technology is recognized as one of the most promising technologies due to its advantages,such as easy operation,high degradation efficiency,few by-products.CO₂ and H₂O are the final products under normal temperature and pressure.Thus the preparation of a photocatalytic catalyst with high photocatalytic activity,simple and easy to be obtained and the ability of high degradation efficiency has become the focus of this research.This study is to solve the problems above,and three parts of experiments were carried out:the cobalt ions were doped in TiO₂ through heat treatment,and Co-TiO₂fibers were got through electrostatic spinning process.After freeze drying,Co-TiO₂/RGO photocatalyst was obtained.The photocatalytic performance of it could be evaluated.Then,a series of characterization of the above materials was carried out,such as SEM,XRD,EDX,UV-VIS,BET,PL,XPS,etc.It was found that the microstructure of Co-TiO₂/RGO composite was good and presented micro-nano-level fibrous structure.No other impurities were found in the composite photocatalyst,and the mass of Co:Ti did not change before and after the photocatalyst was loaded on graphene.The photocatalytic materials prepared included the two crystal shapes of rutile and anatase,and the stability of anatase TiO₂ was enhanced after Co doping.Co doped TiO₂ could increase the absorption range of visible light.The 1%Co-TiO₂fibers with calcination temperature of 600℃for 4 h had a better crystal.The specific surface area of photocatalytic materials was increased after loading RGO.Co doping declined the two characteristic peaks of photoluminescence,which indicated that Co made the photocatalyst show better photoluminescence performance.Characterization of XPS further indicated that Co doping into TiO₂ lattice and supporting graphene also changed the internal structure of TiO_2.It resulted in more defects and oxygen vacancies in photocatalyst,which could capture more electrons and inhibit electron-hole pair recombination so as to improve the performance of photocatalyst.The photocatalytic performance was mainly studied from the preparation conditions,such as Co doping amount,calcination temperature,photocatalyst load,gas residence time,relative humidity,etc.The experimental results of degradation of tolune by the photocatalyst showed that when the amount of Co doping was 1%,the temperature of calcination was 600℃,the time of photocatalytic reaction was 100min,the relative humidity was 100%,and the capacity of Co-TiO₂ loading was 1 g,the degradation rate of toluene by Co-TiO₂/RGO photocatalyst was the most ideal,up to 99.1%.Finally,the mechanism of toluene degradated by this novel photocatalyst was investigated:After TiO₂modified by Co and Co-TiO₂ fibers were loaded to RGO,the defects of TiO₂only responsed to UV light was improved.At the same time,specific surface area of the photocatalyst increased.After activated by light,lots of·OH and·O₂^-were generated and reacted with toluene.Finally,H₂O and CO₂ were produced.In summary,compared with the photocatalysts on the market,the new photocatalytic composite material Co-TiO₂/RGO prepared in this study has the advantages of high photocatalytic degradation efficiency,stable physicochemical properties,easy fixation and uneasy to fall off.It can be widely used in the chemical industry.It is expected to solve a large number of VOCs produced by chemical and pharmaceutical industries which cause serious environmental pollution.