Effect of Copper Species in a Photocatalytic Synthesis of Methanol from Carbon Dioxide over Copper-doped Titania Catalysts

Abstract

2 Abstract: Synthesis of methanol from CO by a photocatalytic reduction process over copper-doped TiO has 2 2 been investigated. It has been reported in the literature that copper species could enhance methanol production in a photocatalytic reduction of CO . However, which species of copper (e.g. Cu , Cu , or Cu ) and how do the 2 0 I II copper species play a role still unclear. In this paper we will report and discuss our finding that each copper species play a different role. By using modified-impregnation method in preparing copper/TiO it was revealed 2 that CuO is the copper species, which resulting much better enhancement in methanol production than the others. The activation energy (E ) for TiO Degussa-P25 and 3%CuO/TiO is ca. 26 and 12 kJ/mol, respectively. a 2 2 The lower E of 3%CuO/TiO may suggest a catalytic role of copper species that increase the methanol a 2 production. Furthermore, an in situ FTIR study revealed appearance of formate and methoxy intermediates on the CuO/TiO surface, while none if the undoped TiO catalyst was employed. This may indicate a catalytic 2 2 nature of copper species as an active site to give methanol. Enhancement of product yield was also observed indicates that the copper species act as an electron trapper and prohibit electron-hole recombination.