Crystal plane induced metal-support interaction in Pd/Pr-CeO2 catalyst boosts H2O-assisted CO oxidation

Catalytic oxidation is an effective method to remove CO in exhaust gas, yet it is challenging to enhance the H2O tolerance of catalysts at low temperature due to the strong competitive adsorption between H2O and reactants (CO and O2). Here, we report that the precise control of the metal-support interaction by regulating the support crystal plane of Pd/Pr-CeO2 catalysts leads to highly efficient CO oxidation catalysts under wet conditions. The addition of H2O inhibits the CO oxidation activity of Pr-CeO2 nano-cube and octahedron supported highly dispersed Pd catalysts, but enhances the CO oxidation activity over Pr-CeO2 nanorod supported highly dispersed Pd catalysts. After introduction of H2O in feed gas, the T99 (Temperature to achieve 99 % conversion of CO) decreases from 157 °C to 115 °C for Pd/Pr-CeO2-NRs (Nanorods) catalyst at a gas hourly space velocity of 70, 000 h−1 and remains stable for more than 2000 min in the presence of H2O. Systematic characterization reveals that the (1 1 0) crystal plane of Pr-CeO2 nanorod enhance the interaction between Pd species and support, resulting in the formation of abundant high dispersed Pd-oxygen vacancy (Ov) active sites. The kinetics study and in-situ DRIFTS characterization confirmed that CO oxidation Pd/Pr-CeO2-NRs mainly follows the H2O-mediated Langmuir-Hinshelwood mechanism in the presence of H2O. H2O promote the formation of active OH groups and accelerate CO oxidation through formate pathway at low temperature. In contrast, the CO oxidation follow traditional MvK mechanism in the absence of H2O.