Photocatalytic reduction of CO2 was carried out on villiform spherical catalysts of Pd-TiO2 in isopropanol solution.The catalysts were synthesized by hydrothermal method,their structures,morphologies and optical absorption properties were characterized by X-ray diffraction（XRD）,energy dispersive X-ray spectroscopy（EDS）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,highresolution transmission electron microscopy（HRTEM）and UV-vis absorption spectroscopy（UV-vis）.The photocatalytic activities with different loading amounts and morphologies were evaluated for determining the dominant effect and optimizing the catalyst preparation.Based on a villiform spherical TiO2 with the largest specific surface area in our experiments,we prepared a set of catalysts with various loading amounts of palladium and tested them by bubbling CO2 through the slurry of catalyst and isopropanol.The highest formation rate of isopropyl formate was 276.6μmol/g？cat/h.Eventually we proposed the reaction mechanism.
ZnFe2O4-BiOC1 composites were prepared by both hydrothermal and direct precipitation processes and the structures and properties of the samples were characterized by various instrumental techniques. The samples were then used as catalysts for the photocatalytic reduction of CQ in cyclohexanol under ultraviolet irradiation to give cyclohexanone （CH） and cyclohexyl formate （CF）. The photocatalytic CO2 reduction activities over the hydrothermally prepared ZnFeaO4-BiOCl composites were higher than those over the directly-precipitated composites. This is because compared to the direct-precipitation sample, the ZnFe2O4 nanoparticles in the hydrothermal sample were smaller and more uniformly distributed on the surface of BiOCl and so more heterojunctions were formed. Higher CF and CH yields were obtained for the pure BiOCl and BiOCl composite samples with more exposed （001） facets than for the samples with more exposed （010） facets. This is due to the higher density of oxygen atoms in the exposed （001） facets, which creates more oxygen vacancies, and thereby improves the separation efficiency of the electron-hole pairs. More importantly, irradiation of the （001） facets with ultraviolet light produces photo-generated electrons which is helpful for the reduction of CO2 to -CO2^-. The mechanism for the photocatalytic reduction of CO2 in cyclohexanol over ZnFe204-BiOCl composites with exposed （001） facets involves electron transfer and carbon radical formation.
