Boosting CO2 hydrogenation to methanol by adding trace amount of Au into Cu/ZnO catalysts

Abstract

Boosted CO2 hydrogenation to methanol was achieved by introducing appropriate amount of Au into conventional Cu-based catalysts. The AuxCu/ZnO bimetallic catalysts with various Au/Cu molar ratio (x = 0.001, 0.005, 0.02 and 0.05) were prepared by the co-precipitation method, among which the Au0.005Cu/ZnO catalyst exhibited the highest methanol production rate. The formation of Au-Cu alloy was identified on the AuxCu/ZnO bimetallic catalysts. Experimental characterizations and density functional theory (DFT) calculations suggested metal-oxide interfaces with oxygen vacancies as intrinsic active sties for both un-promoted and Au-promoted Cu/ZnO catalysts. The promotion effect of Au in bimetallic catalysts was correlated with the increase of active sites, facilitation of CO2 activation and modification of intermediate adsorption. The present work for the first time develops a promising Au0.005Cu/ZnO bimetallic catalyst with trace amount of Au (only 0.4 wt%) and provides insight into the reaction mechanism over Au-promoted Cu/ZnO catalysts for methanol synthesis via CO2 hydrogenation.