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

Abstract

A series of Cs–Au/TiO2 (anatase) catalysts with a Cs loading between 0wt% and 13wt% was synthesized by impregnation of Au/TiO2 and tested for CO2 conversion with C2H4 into propanol in presence of H2. Cs loading was found to significantly influence the target selectivity, which passes over a maximum over the catalysts with 4wt% and 7wt% 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 Auδ+ 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 7wt%, which possess larger Au NP (around 17nm) than the selective catalysts (1–7wt% Cs) with Au NP between 4.5nm and 7nm.