CO2 hydrogenation across the pressure gap over Ag/ZnO:Al2O3 catalysts

Abstract

Abstract The hydrogenation of carbon dioxide to value-added chemicals is a major challenge. Metal-oxide interfaces and surface structures play fundamental roles and govern the selectivity of this reaction; thus, catalysts must be investigated under relevant reaction conditions to identify structure-activity relationships and engineer more efficient materials. This work aims to elucidate mechanisms of carbon dioxide hydrogenation to methanol and side products by using operando characterization techniques within a pressure range of 1 mbar up to 15 bar. Bifunctional Ag/ZnO and Ag/ZnO:Al 2 O 3 catalysts are studied using multiple spectroscopic techniques combined with online product analysis. During catalyst activation in hydrogen, several restructuring processes of the catalyst occur at different pressures. Under carbon dioxide hydrogenation reaction conditions carbonate, formate and CH x surface intermediates show strong pressure-dependent abundances. Combining thermodynamics with in situ and operando investigations of pressure-dependent structures and intermediates allows assessing carbon dioxide hydrogenation through the pressure gap.