Photocatalytic reduction of CO2 on copper-doped Titania catalysts prepared by improved-impregnation method

Photocatalytic reduction Of CO2 by copper-doped titania catalysts has been investigated. The photocatalysts with various copper species (Cu-0, Cu-I, Cu-II) were prepared by an improved-impregnation method, where copper nitrate is doped into TiO2 Degussa-P25. It is likely that copper present on the catalyst surface and the grain size of copper-titania catalysts is uniform, with crystallite size approximately 23 nm. The dispersion capacity of CuO in the vacant sites of TiO2 is about 4.16 Cu (2+) nm(-2) (approximate to 2.2 wt% of Cu), as indicated by XRD analysis. The activation energy (E-a) for Degussa-P25 and 3%CuO/TiO2 is ca. +26 and +12 kJ/mol, respectively. These E. values suggest that the desorption event is a rate limiting step, and the lower E. of 3%CuO/TiO2 may suggest a catalytic role of copper species that enhance the methanol production. (c) 2005 Elsevier B.V. All rights reserved.