Preparation And Characterisation Of Photocatalytic TiO₂ Films

The preparation of high efficient TiO₂ photocatalyst is an important topic in the field of TiO₂ photocatalysis,and the immobilization of TiO₂ can contribute to the industrial application of TiO₂ photocatalyst.Pyrolysis and electrophoresis are two important methods for immobilization of TiO₂ photocatalysts because of their easiness and low cost.In this thesis,we immobilize TiO₂ photocatayst on glass substrate by these two methods,investigate the photocatalytic properties of TiO₂ films as prepared,and characterize the films by XRD,AFM,SEM and ATRPreparation of TiO₂ films by pyrolysis was first investigated.Butyl titanate was dispersed in ethanol solvent,with ACAC as chelatant to prevent the butyl titanate from hydrolyzing,and then the chelated butyl titanate was vaporized and decomposed,and TiO₂ films were deposited on glass substrate.The results showed the best thermal treatment temperature is 500℃.For different amount of ACAC, different pyrolysis temperatures were required to achieve best photocatalytic properties.The photocatalytic properties were not related to times of pyrolysis coating of TiO₂.SEM showed the films comprised of titania particles with diameter of several hundred nano-meters.ATR showed there are Ti-O-Ti bonds in the films and the films absorb water and hydrogen.AFM showed TiO₂ particle size increases as the temperature increases or ACAC amount increases.Spin-coating and pyrolysis were also studied to prepare TiO₂ films.Butyl titanate,ACAC,and PEG were dissolved in ethanol solvent,the mixture was spin-coated on glass substrate for several times,and coatings were pyrolyzed to prepare TiO₂ films.The experiment results showed that 5 times coating can achieve good photocatalytic properties.DTA showed that chelated butyl titanate was decomposed from 300℃to form amorphous TiO₂,and the amorphous TiO₂ was transformed into anatase TiO₂ at 500℃.The best solution recipe for the photocatalytical properties was 4ml butyl titanate,50g PEG,and 3ml ACAC.The incorporation of Cu and Sn improved the photocatalytic properties of TiO₂ films,and TiO₂ films doped with Cu or Sn showed better crystallinity of TiO₂ particles. Microemulsion systems of water/SDBS/isoamyl alcohol/cyclohexane and water/OP-10/isoamyl alcohol/cyclohexane were utilized to prepare nano TiO₂ powders.It was shown that TiO₂ particle size after annealing was slightly related to size of water drop.The influence of dispersants on the dispersion of TiO₂ powder in butanol was investigated.Butanol is a good solvent for the dispersion of TiO₂ powder.When the weight percent of triethanolamine,Tween-80,SDBS,and OP-10 were 1.4%,0.8%,0.8%,0.6%respectively,the TiO₂ suspension has the maximum absorbance,with smallest particle size and high Zeta potential,indicating the system has better dispersion stability.Titania coatings were prepared by electrophoresis of powders in butanol,and their photocatalytic properties were measured.The deposit was in a linear relationship with applied potential and time to a certain coating thickness,and after that the linear relationship does not exist any more whether adding PEG or not.The binder PEG will significantly reduce the deposit of TiO₂,but the photocatalytic properties are greatly improved.The degradation rate of methyl orange will increase as the increase of TiO₂ deposit.But when the coating reaches to a certain thickness, the degradation rate will decline.For the composite TiO₂ sol which is composed of TiO₂ particles and TiO₂ sol, the Zeta potential was smaller than that of corresponding TiO₂ sol.As the amount of PEG increases,the deposit of TiO₂ will increase also.As the concentration of TiO₂ particle or the TiO₂ sol increases,the deposit will increase.The TiO₂ powder was prepared by firing the TiO₂ sol at different temperatures.The result showed that when the temperature increases,the titania crystalline will improve.Anatase TiO₂ peaks appear at 200℃,and futile TiO₂ peaks appear at 550℃.The experiment of photocatalytic properties showed that the photocatalytical property for sol is better than that for composite TiO₂ sol.