Preparation And Photocatalytic Properties Of Modified WO₃ Semiconductor Photocatalyst

Semiconductor photocatalyst has potential applications in the field of environment and energy.WO3 has been widely concerned owning to its characteristics,such as superior stability,strong oxidizing power of valence band holes,abundance,low cost and nontoxicity.Nevertheless,pure WO3 exhibits poor photocatalytic activity due to its poor utilization of solar spectrum and the rapid recombination of photogenerated electron-hole pairs caused by its low conduction band(CB)level.These drawbacks of WO3 limit its large-scale industrial utilization.In this paper,the WO3 photocatalyst was modified by Ag doping and Ag loading,respectively,and the influence of the calcining temperature of precursor on the performance of Ag doped WO3 photocatalyst was investigated in order to improve its photocatalytic performance.The main researches are listed as follows:(1)The Ag doped WO3 in this paper was synthesized by a one-step solid state synthesis method by using phosphotungstic acid and silver nitrate as the precursors,while pure WO3 was obtained by the decomposition of phosphotungstic acid.XRD,SEM,TEM,UV-vis DRS,Raman,ESR and XPS were employed to investigate the crystal phases,microstructure,morphology and optical absorption properties of the as-prepared photacatalysts.The results show that Ag was successfully doped into the WO3 lattice and induced the transformation of WO3 from the tetragonal phase to the orthogonal phase.The surface oxygen vacancies were produced while the bulk oxygen vacancies were reduced greatly in the progress of tetragonal WO3 transforming to orthorhombic WO3 induced by Ag doping.The photocatalytic degradation of Rhodamine B solution showed that Ag doping significantly enhanced the photocatalytic activity of WO3.Combined with the analysis of the influencing factors of photocatalysis and electrochemical testing,we have found that the surface oxygen vacancies are the centers of the separation of photogenerated electrons and holes,which are in favor of the photocatalytic reaction,while the bulk oxygen vacancies play the role as the recombination centers of the photoelectron and hole,which reduce the photocatalytic activity.(2)The influence of calcining temperature on the performance of Ag doped W03 photocatalyst was investigated by changing the calcination temperature of the precursor.XRD,SEM,UV-vis DRS,ESR and XPS were employed to investigate the crystal structure,chemical composition,micromorphology and optical absorption properties of as-prepared photacatalysts.The results showed that the crystallinity of the photocatalysts was improved,the grain size increased,and the optical absorption edge obtained a slight red-shift with the increasing of calcination temperature.The photocatalytic degradation of Rhodamine B showed that the photocatalytic performance of photocatalysts synthesized at 600℃ exhibited the best photocatalytic activity.(3)Ag/WO3 composite photocatalyst with high visible-light response was prepared by depositing Ag nanoparticles onto the surface of WO3 via a photoreduction process.XRD,SEM,TEM and UV-vis DRS were employed to investigate the crystal structure,chemical composition,micromorphology and optical absorption properties of the as-prepared photacatalysts.The results showed that Ag nanoparticles were successfully loaded on the WO3 surface,and the band gap of the Ag/WO3 composite photocatalyst was greatly reduced,the optical absorption edge obtained an obvious red shift and the absorbance increased.The photocatalytic degradation of Rhodamine B showed that the photocatalytic performance of phptocatalysts of Ag/WO3 composite photocatalyst is significantly enhanced compared with pure WO3.