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 g_MeOH h⁻¹ g_cat⁻¹ at 300 °C and 5 MPa.