Investigating the role of oxygen vacancies and basic site density in tuning methanol selectivity over Cu/CeO2 catalyst during CO2 hydrogenation

Abstract

Efficient conversion of CO2 captured from industrial flue gases into platform chemicals like methanol is a promising solution for mitigating its emission and to meet the sustainability goals. In this study, CeO2, ZrO2 and ZnO supported Cu catalysts were synthesized and the effect of oxygen vacancies and basic sites on the catalytic activity has been intensively investigated. The physicochemical properties of the catalysts were determined by XRD, BET, H2-TPR, HR-TEM and CO2-TPD techniques. The Cu/ZnO catalyst shows highest CO2 conversion (14.6% at 280 °C). Whereas Cu/CeO2 exhibits more than 90% methanol selectivity at 220 °C and 30 bar. The superior methanol selectivity over Cu/CeO2 catalyst can be attributed to stability of key reaction intermediates (COOH spices) on the active sites. This may be due to excess surface oxygen vacancies which facilitates stability of Cu in variable oxidation states and higher basic site density of Cu/CeO2 catalyst.