The Study Of Preparationand Photocatalytic Performance Of Compound Nanomaterials TiO₂/SnO₂（Ⅱ）

TiO₂is recognized as the one of the most potential catalysts in thephotocatalytic field, but it receives great restriction in actual applicationbecause of its light absorption in narrow range and low photocatalyticquantum efficiency. One way to improve the efficiency of thephotocatalytic quantum is mixing TiO₂with semiconductor such as SnO₂whose conduction and valence band match with TiO₂’s. In this paper, thecrystal and morphology of TiO₂/SnO₂composite catalyst which wasprepared under different conditions （preparation methods, the ratio ofWTiO₂/WSnO₂, heat treatment） were characterized by XRD、SEM、TEM, andit’s catalytic activity was judged by the ability of degradating toluene.Through analysising the reactant and product’s distribution in the processof the toluene degradation, we deduced the degradation reactionmechanism. The results indicated that: （1） Homogeneous nucleation did not exsit in the process of preparingTiO₂/SnO₂composite catalysts with the sol-gel method—adding to TiO₂sol SnO₂powder with particle size of about5um which was calcined at400℃. Whether on the surface of SnO₂particles of5um or in smallparticles precipitated out in the peptization, the particles were the crystalmixture of TiO₂and SnO₂with the size about5to10nm.（2） As for TiO₂/SnO₂composite catalysts prepared with hydrotheralmethod, the results were the same as that in the sol-gel method when theratio of WTiO₂/WSnO₂was less than0.024; yet when the ratio was more than0.12, both heterogeneous nucleation similar to what in the sol-gel methodand homogeneous nucleation occurred, and TiO₂particle blocks formed.（3） From the perspective of the degradation rate of toluene and thereaction selectivity of CO₂, the results indicated that composite catalyst（R0.012） which was prepared by sol-gel method and calcined at300℃had the best catalytic activity. The degradation rate and reaction selectivityof the above mentioned composite catalyst were50.0%and68.9%, with40.8and19.4percentage respectively higer than the two iterms of DegussaP-25, which were35.5%and57.7%respectively.（4） According to the analysis of the reactant and product’s distributionin the process of the toluene degradation, the possible mechanism ofdegradating toluene on TiO₂/SnO₂composite was as follows showed:...