A Study On The Preparation Of CdS-TiO₂ Compound Semiconductor Film And The Potocatalytic Performance

This paper aimed at enhancing the photoactivity of nano-TiO2, disclosing the nature of effects of doping on nano-TiOP2 and also conducting the research on practical use. According to the current problems such as low quantum efficiency. limited available sun energy spectrum range, and inefficient recovery, resulted from the practical using of photocatalysis, using the narrowband semiconductor CdS (Eg = 2.5ev) to compound with TiO2 seems to be an effective solution. since it will not only enlarge the region of the absorption with the proper narrow band of CdS but also improve the photodegradation efficiency on account of the band overlap of the two, which makes the photo induced electron and holes separate more easily.The TiO2, CdS and CdS-TiO2 films on the common glass substrate were prepared, respectively, using Ti(OC4H9)4, Cd(COOCH3)2 and SCN2H4 as raw materials by sol-gel method. The influences of manifold preparing parameters (such as the concentration of sol , the amount of the PEG . the number of coatings , the heat-treated temperature and time) on the structure and performance were studied. The structure, the morphology, the element and absorbency of the films were researched with the tests of XRD, SEM. EDXA and UV-Vis absorption. Meanwhile the photocatalytic performance of the films by using of rhodamine B as evaluation standards was studied.The results showed that in this experiment condition the optimal preparation condition for TiO2 films which have better photoactivity was found to be: TiO2 sol concentration 0.7mol/l, the amount of PEG 0.5g, coating cycles 3, heat-treated terms 480 C, Ih. However, the suitable parameters for CdS-TiO2 compound thin films were described as following: compounded quantity of CdS in TiO2 was 5%(the mol ration), coating number was 3, heating treatment was under N2 atmosphere, 480 C,1h.The influences of initiative concentration of rhodamine B, and the acidity of solution on the degradation rate of the TiO2 films were discussed in the part ofphotodegradation of dye rhodamine B. The results indicated that the dye had the best photodegradation efficiency when the concentration of rhodamine B was 10mg/l and the acidity of solution was 3. Kinetic analysis indicated that the photocatalytic degradation of dye rhodamine B was one order reaction.TiO2 films doping with CdS can improve not only the performance of the spectrum absorption but also the efficiency of the photocatalytic degradation. In this paper, with the TiO2 films, the range of the absorption was enlarged from 380nm to 550nm and the rate of photodegradation was improved from 60.5% to 78.5%.