CO2 hydrogenation to methanol over Pd/In2O3: effects of Pd and oxygen vacancy

CO2 hydrogenation to methanol has attracted increasing attention. Previous theoretical study suggested that Pd/In2O3 has a high activity for CO2 hydrogenation to methanol with the Pd-In2O3 interfacial sites being the active ones. However, the strong interaction between Pd and In2O3 during the catalyst preparation leads to the formation of Pd-In bimetallic species and, consequently, reduces methanol yield. In this work, the Pd/In2O3 catalyst was prepared by firstly mixing In2O3 powder with Pd/peptide composite, which was followed by thermal treatment to remove the peptide. The resulting Pd/In2O3 catalyst is In2O3 supported highly-dispersed Pd-nanoparticles exposing predominately the (111) facets with particle sizes of 3.6 nm. Such Pd nanoparticles have a better ability to dissociatively adsorb hydrogen, thereby supplying hydrogen for the hydrogenation steps and facilitating oxygen vacancy creation. The interfacial sites are also active for enhanced CO2 adsorption and hydrogenation. All these factors contribute to a superior performance of the Pd/In2O3 catalyst for CO2 hydrogenation to methanol with a CO2 conversion >20% and methanol selectivity >70%, corresponding to a STY up to 0.89 gMeOH h−1 gcat−1 at 300 °C and 5 MPa.