Performance Of Polyoxometalates-Modified Wide Band Gap Oxide Semiconductors And Photoelectrocatalytic Applications

Solar energy is clean and abundant,and its development and utilization relying mainly on semiconductor materials.Semiconductor materials can realize direct conversion of solar energy to electrical energy or chemical energy.Especially in terms of photoelectric catalysis,which can realize the photoelectric catalytic degradation of organic pollutants,water oxidation and solar cell,etc.However,the photoconductivity of them is very unsatisfactory;this is because their high number of surface defects and interior electron-hole recombination cause low carrier mobility.Polyoxometalates?POMs?,a type of molecular metal oxide,have shown superior physicochemical properties.In particular,POMs can not only act as a strong electron acceptor but can also maintain an intact structure after undergoing reversible multielectron redox reactions,so POMs are an efficient electron scavenger to capture and transport photogenerated electrons from the conduction band of a semiconductor and thus increase the photovoltaic response.In this paper,we prepared a series of POMs/semiconductors composite films and investigated their photovoltaic performances and photoconductive performances.Specific work is presented as follows:1.Different numbers of Ti-substituted POMs PW₁₁Ti and PW₁₀Ti₂ modified TiO₂ films were prepared.We investigated the interface modification on grain boundaries of commercially available approximately 25 nm TiO₂ nanoparticles?commercial name P25?by use of different POMs,including monosubstituted Keggin POMs PW₁₁Ti and disubstituted Keggin POMs PW₁₀Ti₂ to improve the photoelectric performance of TiO₂.Then their photoconductive properties were investigated by means of a self-made photoconductive device.Moreover,we compared the photoconductive properties of TiO₂/PW₁₁Ti and PW₁₀Ti₂/TiO₂ with those of PW₁₂/TiO₂.Furthermore,we investigated their gas sensing for acetone by means of the photoconductive changes in POMs/TiO₂ nanocomposites to explore their suitability as a gas sensor,because a photoconductive gas sensor is advantageous because of low power consumption and fast response to the surroundings.2.We prepared the Zn O nanorods by the second hydrothermal method and prepared POMs/ZnO by successive ionic layer adsorption and reaction?SILAR?method.We investigated their photoelectrocatalytic degradation of organic compounds such as rhodamine B and phenol under visible light.The results show that the secondary hydrothermally grown ZnO nanorods can provide more catalytic sites,and the introduction of POMs increases the degradation efficiency of ZnO on rhodamine B and phenol.3.The TiO₂ films modified with POMs were prepared.And we investigated the effects of Mo₆O₁₉,Mo₈O₂₆6 and W₁₀O₃₂ on the photoelectric properties of TiO₂.Besides,the adsorption performance of Mo₈O₂₆ for rhodamine B was studied.The results showed that the photo-electrochemical properties of TiO₂ with POMs were improved.And the adsorption efficiency of 5 mg of Mo₈O₂₆ to rhodamine B could be achieved 98.5%within 1 min.Desorption desorption tests showed that when the volume ratio of ethanol to water was 4:1,the desorption efficiency was about 90%.