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+ nm2 (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.
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