Preparation Of M_xWO₃（M=Pt/Ag/Cs） And Its Mixture With SiO₂ Aerogels And Their Photocatalytic Properties

In recent years,with the increasingly prominent problem of environmental pollution,finding effective,stable and non-toxic photocatalysts for photocatalytic degradation of organic pollutants has been attracting more and more attention.Tungsten trioxide,owing to its narrow band(2.4-2.8ev)and high oxidation potential(+3.1-3.2 vs.NHE)of the valence band,is able to absorb visible light to degrade organic matte.However,due to its lower conduction band boundary(+0.3-0.5 vs.NHE),it is likely to cause oxygen reduction,and the recombination probability of photogenerated electron hole pairs increase,thereby reducing the photocatalytic efficiency.Therefore,according to the "filling mechanism",better photocatalytic efficiency can be achieved by doping metal ions to increase the band gap energy,limiting the conduction band photoelectron excitation and extending the service life.Silica aerogel usually refers to a solid material consisting of light aggregates of nanoscale particles.The SiO2 aerogels have nanoporous structure with the diameter of nanoparticles 1-20nm and the pore size 2-50nm.The porosity of the nanoparticles can be up to 90%,and it has a three-dimensional cross-linked porous structure with significant adsorption effect.Especially for the adsorption of pollutants and oily substances,it has a satisfactory adsorption effect.In this paper,the photocatalytic performance of Cs,Pt,Ag,Yb,Tm and Ti-doped WO3 and silica composite aerogels were studied.The photocatalytic activity of Cs-doped WO3 and SiO2 composite aerogels was emphatically investigated.The effects of cellulose as a template on the photocatalytic performance of platinum-doped tungsten oxide was discussed.A new kind of solar cell with metal doped tungsten oxide as anode was assembled so as to explore its photoelectric performance.Moreover,the effect of rare earth ions doping on the photocatalysis was explored.The crystal structure,microstructure,porosity and specific surface area of the prepared samples were characterized by XRD,TEM,SEM,BET and UV-Vis spectra,and the adsorption/photocatalytic degradation for Rhodamine B was investigated by photochemical reaction apparatus.It was found that the as-prepared Pt-doped WO3 using cellulose as template by hydrothermal method has better photocatalytic performance than that without using cellulose as template.The 3wt%Pt-doped WO3 exhibited best adsorption performance for Rhodamine B,and 4wt%Pt-doped WO3 had best photocatalytic performance.The efficiency of solar cells doped with WO3 as a photoanode is higher than that of Ag-doped WO3 solar cells.The addition of rare earth ions promoted the absorption of CsxWO3 in the whole spectrum with emitting yellow and green ligh.The addition of rare earth ions promoted the fromation of regular CsxWO3 nanorods and reduced the size of particles.Under the irradiation of ultraviolet light,sample CsxWO3:Yb,Tm with 5%Yb3+and 1.0%Tm3+had the best photocatalytic effect,and the degradation rate of Rhodamine B was 99%.When the molar amount of F ions was 0.5,the Rhodamine B degradation had reached 100%after 110 minutes.The pore volume and specific surface area of the CsxWO3-SiO2(CWS)composite aerogels are 1.11-1.86 cm3/g and 265-465 m2/g,respectively.The adsorption/photocataytic activity test results indicated that the composite aerogels exhibited higher adsorption/photocatalytic degradation of RhB.The adsorption process of the composite aerogels is mainly based on chemical adsorption and physical adsorption plays a role as assistance.In addition,the composite aerogels exhibited excellent adsorption/photocatalytic degradation rate and higher recycling performance with the adsorption/photocatalytic degradation rate for RhB achieving 90.55%after 40 min,and can still attain to 70%after four cycles.WOx-TiO2-SiO2 composite aerogels and TiO2-SiO2 composite aerogels synthesized by sol-gel method were mesoporous structures with specific surface area 243.7-423.1 m2/g and pore volume 0.914-3.315 cc3/g.The photocatalytic perfromance of WOx-TiO2-SiO2 composite aerogels is better than that of TiO2-SiO2 composite aerogels,and 15%-WOx-TiO2-SiO2 composite aerogels has the best photocatalytic performance.