Mechanistic Investigations on Thermal Hydrogenation of CO2 to Methanol by Nanostructured CeO2(100): The Crystal-Plane Effect on Catalytic Reactivity

As a key structural parameter, a crystal plane has a distinguished impact on the catalytic performance. Different exposed crystal planes exhibit different reactivities. CeO 2 nanostructured powders are usually exposed to three low-index surfaces, which are (111), (110), and (100) surfaces. Because of the unique structure and low stability of the (100) surface, the investigation of the catalytic reaction mechanism on this surface is rarely involved. Here, density functional theory calculations suggest that the CeO 2 (100) surface exhibits the strongest reactivity for H 2 oxidation, attributed to the coordination unsaturation of surface oxygen atoms. For the hydrogenation of CO 2 to methanol on the defective CeO 2 (100) surface, CO 2 is prone to adsorb at the oxygen vacancy in a nearly linear configuration and the formate pathway was verified as the dominant one. The bi-H 2 COO* can easily convert to bi-H 2 CO* with the vacancy site filled, in which bi-H 2 CO* serves as the key intermediate in the methanol synthesis. This study aims at providing a better understanding of the catalytic reactivity of the CeO 2 (100) surface and theoretical insights into the experimental design of thermal CO 2 -to-methanol conversion.