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 (Cu0, CuI, CuII) 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 Cu2+ nm−2 (≈2.2 wt% of Cu), as indicated by XRD analysis. The activation energy (Ea) for Degussa-P25 and 3%CuO/TiO2 is ca. +26 and +12 kJ/mol, respectively. These Ea values suggest that the desorption event is a rate limiting step, and the lower Ea of 3%CuO/TiO2 may suggest a catalytic role of copper species that enhance the methanol production.