The feasibility study of the indium oxide supported silver catalyst for selective hydrogenation of CO2 to methanol

Silver catalyst has been extensively investigated for photocatalytic and electrochemical CO 2 reduction. However, its high activity for selective hydrogenation of CO 2 to methanol has not been confirmed. Here, the feasibility of the indium oxide supported silver catalyst was investigated for CO 2 hydrogenation to methanol by the density functional theoretical (DFT) study and then by the experimental investigation. The DFT study shows there exists an intense Ag–In 2 O 3 interaction, which causes silver to be positively charged. The positively charged Ag species changes the electronic structure of the metal, facilitates the formation of the Ag–In 2 O 3 interfacial site for activation and dissociation of carbon dioxide. The promoted CO 2 dissociation leads to the enhanced methanol synthesis via the CO hydrogenation route as CO 2 ∗→CO∗→HCO∗→H 2 CO∗→H 3 CO∗→H 3 COH∗. The Ag/In 2 O 3 catalyst was then prepared using the deposition-precipitation method. The experimental study confirms the theoretical prediction. The methanol selectivity of CO 2 hydrogenation on Ag/In 2 O 3 reaches 100.0% at reaction temperature of 200 °C. It remains more than 70.0% between 200 and 275 °C. At 300 °C and 5 MPa, the methanol selectivity still keeps 58.2% with a CO 2 conversion of 13.6% and a space-time yield (STY) of methanol of 0.453 g methanol g cat −1 h −1 , which is the highest methanol STY ever reported for silver catalyst. The catalyst characterization confirms the intense Ag–In 2 O 3 interaction as well, which causes high Ag dispersion, increases and stabilizes the oxygen vacancies and creates the active Ag–In 2 O 3 interfacial site for the enhanced CO 2 hydrogenation to methanol.