Synthesis And Characterization Of TiO₂/CdS Composite Nanostructures

TiO₂, because of its characteristics such as high activity, chemical inertness,nontoxicity and low cost, is widely used in the fields of renewable energy andenvironmental protections. However, only the light with the wavelength equal to orsmaller than387nm can be absorbed for TiO₂, this limits the efficient utilization ofsolar energy. Coupling TiO₂with a smaller band gap semiconductor CdS is a commonand effective approach to accommodate the visible-light photon energy. The CdScoupled TiO₂composite materials have important applications in photocatalysis andsolar cell. In this paper, the synthesis and characterization of CdS couplled TiO₂composite materials were studied.1、We report a simple method to fabricate novel CdS@TiO₂or TiO₂@CdSdouble-shelled hollow spheres （DHS）, using SiO₂spheres as templates, and study thephotocatalytic performance of the DHS. Firstly, anatase TiO₂hollow spheres weresynthesized by a sol-gel method using SiO₂nanospheres as templates. The effects ofthe subsequent calcination at different temperatures on the morphology, crystallinityand photocatalytic property of the TiO₂hollow spheres were systematically studied.Secondly, zinc blende CdS hollow spheres were synthesized by an ultrasound-drivenmethod. The effect of the quantity of ammonia on the formation of CdS shell wasinvestigated. Findly, the novel CdS@TiO₂or TiO₂@CdS DHS was fabricated. Theexperimental results shows that the absorption edge of the TiO₂hollow spheres isobviously red-shifted to the visible region after TiO₂coupling with CdS. Thephotodegradation of Rhodamine B under visible-light shows that the TiO₂@CdS DHSexhibits the best photocatalytic activity among the two DHS samples, pure TiO₂and CdS hollow spheres.2、Synthesis and characterization of CdS_xSe_1-xquantum dots （QDs） sensitized TiO₂solar cell. Near monodisperse colloidal CdS_xSe_1-xQDs were synthesized by anon-injection method. The UV-vis spectra of CdS_xSe_1-xQDs gradually blue-shifted byincreasing the S/Se ratios, indicating that the bandgap energy of CdS_xSe_1-xQDsgradually increased from CdSe, CdS_0.25Se_0.75, CdS_0.5Se_0.5, CdS_0.75Se_0.25to CdS. Theproperties of CdS_xSe_1-xQDs sensitized TiO₂solar cells were investigated. It wasfound that the incident photon-to-current efficiency （IPCE） of the CdS_xSe_1-xQDssensitized TiO₂solar cell increased while the short-circuit current of the solar celldecreased with the gradual increasing of the amount of S in CdS_xSe_1-xQDs.