Qianyi Zhang

Photocatalytic conversion of CO2 and H2O to fuels by nanostructured Ce–TiO2/SBA-15 composites

Cerium-doped titanium oxide (Ce–TiO2) nanoparticles were prepared by a simple sol–gel method. Ce-doping decreased the crystal size of TiO2, increased the catalyst surface area, and inhibited the growth of rutile TiO2 crystals. Ce–TiO2 nanoparticles were also dispersed on SBA-15, mesoporous silica with one-dimensional pores, forming a Ce–TiO2/SBA-15 nanocomposite. The nanocomposite materials were well characterized and tested as photocatalysts to convert CO2 and H2O to value-added fuels, mainly CO and CH4, under UV-vis illumination. Compared with pristine TiO2, TiO2 doped by 1 or 3% Ce improved the production of CO by four times. The reason may be due to the facilitated charge transfer induced by the doped Ce ions, the higher surface area of the catalyst, as well as the stabilization of anatase phase. However, too high a Ce concentration reduced the catalytic activity, likely due to the formation of recombination centers. Compared with unsupported Ce–TiO2, Ce–TiO2 supported on SBA-15 remarkably enhanced the CO2 reduction rate. Ce–TiO2/SBA-15 with a Ti : Si ratio of 1 : 4 demonstrated 8-fold enhancement in CO production and 115-fold enhancement in CH4 production. By contrast, amorphous silica as the substrate was much inferior to SBA-15. The findings in this work reveal a promising nanostructured catalyst material for solar fuel production using CO2 and H2O as the feedstock.

Enhanced disinfection of Escherichia coli and bacteriophage MS2 in water using a copper and silver loaded titanium dioxide nanowire membrane

AbstractTitanium dioxide (TiO2) is a widely used photocatalyst that has been demonstrated for microorganism disinfection in drinking water. In this study, a new material with a novel structure, silver and copper loaded TiO2 nanowire membrane (Cu-Ag-TiO2) was prepared and evaluated for its efficiency to inactivate E. coli and bacteriophage MS2. Enhanced photo-activated bactericidal and virucidal activities were obtained by the Cu-Ag-TiO2 membrane than by the TiO2, Ag-TiO2 and Cu-TiO2 membranes under both dark and UV light illumination. The better performance was attributed to the synergies of enhanced membrane photoactivity by loading silver and copper on the membrane and the synergistic effect between the free silver and copper ions in water. At the end of a 30 min test of deadend filtration under 254 nm UV irradiation, the Cu-Ag-TiO2 membrane was able to obtain an E. coli removal of 7.68 log and bacteriophage MS2 removal of 4.02 log, which have met the US EPA standard. The free metal ions coming off the membrane have concentrations of less than 10 ppb in the water effluent, far below the US EPA maximum contaminant level for silver and copper ions in drinking water. Therefore, the photo-activated disinfection by the Cu-Ag-TiO2 membrane is a viable technique for meeting drinking water treatment standards of microbiological water purifiers.