Preparation Of Mesoporous Titanium Dioxide And Tungsten Trioxide Thin Films

Mesoporous materials with high specific surface area,uniform and adjustable pore size have been widely studied and used in the fields of adsorption,separation,catalysis,nano-reactors,bio-medicine,etc.Meanwhile,mesoporous film materials are very promising in applications,such as adsorption,catalysis and functional devices.Thus,this work focuses on the preparation of mesoporous titania(TiO2)and tungsten oxide(WO3)films using the casting method and dip-coating method,respectively.Experimental parameters and their influence on mesostructures were studied in detail.For mesoporous titania film,this work adopted an evaporation induced self-assembly(HW-EISA)process,using TiOSO4 as precursor of titanium,which is then transformed into peroxotitanic acid(PTA)sol,P123 as organic template,and PEG and phenolic resin as organic additives.By optimizing the synthetic conditions,including the amounts of the surfactant,drying time and temperature,etc.,micronmeter-thick TiO2 films can prepared.The results show:(1)The addition of P123 is essential for the formation of well-defined mesostructures,while the organic additives,PEG and phenolic resin,together with the P123,play key roles in the preparation crack-free mesoporous TiO2 films.To remove the residue of hydrogen peroxide in the sol is the key to obtaining the film free of cracks.The stirring of the mixed templating sol before coating is also found to be of great importance in achieving sol suitable for filming with good quality.The drying temperature was also found to significantly influence the mesostructures of the resultant mesoporous TiO2 film.(2)The optimized sol composition and conditions is achieved on the sample of P6G4F0.08-S-48h.Under such conditions by drying at 20?,mesoporous TiO2 film with high thickness up to 3 microns,large pore size of 11.5 nm and high specific surface area up to 138 m2g-1.can be obtained.When dried at 100 0C,mesoporous Ti02 films with large pore size of 15 nm and high specific surface area up to 158m2g-1 can be deposited.The power conversion efficiency of dye-sensitized solar cell based on mesoporous TiO2 film of P6G4F0.08-S-48h-100? is 2.77%.For mesoporous tungsten trioxide film,this work used tungstic acid as precursor for preparation of mesostructured tungsten oxide films via a simple surfactant templated sol-gel process by dip-coating method.The influence of the amounts of surfactant P123,drying temperatures and sintering temperatures on the mesoporous structures were studied.The results show:(1)above three parameters all have great influence on the mesoporous structure of tungsten trioxide.(2)Using sol with compositions of 5 PWA:2 P123:15 H2O,drying temperature set at 70 ?,the sintering process of 350 ? for 1h and 450? for 1h,the obtained tungsten trioxide film show the mesoporous structure with highest specific surface area reaching 68 m2g-1 and large pore size of 13.1 nm.(3)After two dip-coatings,crack-free WO3 film with thickness up to 500 nm can be obtained.