Rapid synthesis of nanostructured Cu-TiO2-SiO2 composites for CO2 photoreduction by evaporation driven self-assembly

Nanostructured copper doped titania-silica (Cu-TiO2-SiO2) photocatalyst composite particles were directly formed in a rapid manner by evaporation driven self-assembly of nanocolloids in a furnace aerosol reactor (FuAR). Aqueous suspensions of nanosized TiO2 and SiO2 colloids and copper nitrate solution were used as precursors. The size, composition, and porosity of the composite particles were tailored by manipulating the precursor concentration, stoichiometric ratio, and synthesis temperature, respectively. The as-prepared composite particles were characterized by means of SEM, TEM, XRD, UV-VIS, and nitrogen physisorption measurements, to determine particle diameter, morphology, crystallinity, absorption band, surface area, and pore size. CO2 photoreduction was conducted inside a quartz reactor under illumination of UV light followed by GC analysis. The results revealed that the composite particles were submicrometre-sized mesoporous spheres with average pore sizes of 20 to 30 nm, having optimal molar percentages of TiO2 and Cu to the whole particle of 2% and 0.01%, respectively, achieving a relatively high CO2 conversion efficiency, i.e. a CO yield of approximately 20 mu mol/g TiO2/h.