Stable and Selective CO2 Hydrogenation over the Supported Rh Catalyst Modified with Titanium Oxide Overlayers

Catalytic hydrogenation of carbon dioxide (CO2) into carbon monoxide (CO) is a key process during the CO2 conversion into high-value chemicals but lacks stable and selective catalysts due to catalyst deactivation from surface restructuring under the reaction conditions. We showed that the supported Rh catalyst modified with titanium oxide overlayers (Rh@TiOx/TiO2) offered nearly full selectivity for conversion of CO2 to CO in a wide reaction temperature window, gas space velocities, and H2/CO2 ratios. The high CO selectivity was maintained even after treating the Rh@TiOx/TiO2 catalyst in oxidative, reductive, and humid atmospheres, giving good stability for 500 h at 500 °C. Kinetic studies and characterizations of the catalysts reveal that the high selectivity and stability result from the hindered CO-Rh interactions and stable Rh-TiOx interfaces. Similarly, supported Pd and Pt catalysts (Pd@TiOx/TiO2 and Pt@TiOx/TiO2) were also successfully prepared, which showed high CO selectivity and good stability in selective CO2 hydrogenation, providing a generalized route for the preparation of highly stable and selective hydrogenation catalysts.