Catalytic role and location of Cs promoter in Cs-Au/TiO2 catalysts for propanol synthesis from CO2, C2H4 and H2

A series of Cs-Au/TiO2 (anatase) catalysts with a Cs loading between 0 wt% and 13 wt% was synthesized by impregnation of Au/TiO2 and tested for CO2 conversion with C2H4 into propanol in presence of H-2. Cs loading was found to significantly influence the target selectivity, which passes over a maximum over the catalysts with 4 wt% and 7 wt% Cs. The results of catalysts characterization by various spectroscopic techniques (HAADF-STEM, XPS, and UV-vis) revealed that Cs species are located on both the support and the Au NP and favor stabilization of Au delta+ species. The presence of Cs was also established to increase the rate of CO insertion into C2H4; thus, improving the selectivity to propanol. The positive effect disappears for the catalysts with Cs loading above 7 wt%, which possess larger Au NP (around 17 nm) than the selective catalysts (1-7 wt% Cs) with Au NP between 4.5 nm and 7 nm. (C) 2015 Elsevier B.V. All rights reserved.