Abstract
• H 2 O promotes the CO oxidation on Pr-CeO 2 nanorods supported Pd catalyst. • High dispersed Pd and oxygen vacancy served as the active sites for CO and O 2 activation in the presence of H 2 O. • CO oxidation mainly follows the H 2 O-mediated L-H mechanism and formate pathway in the presence of H 2 O. • Pd/Pr-CeO 2 -NRs catalyst exhibits outstanding SO 2 resistance in the presence of 100 ppm SO 2 . Catalytic oxidation is an effective method to remove CO in exhaust gas, yet it is challenging to enhance the H 2 O tolerance of catalysts at low temperature due to the strong competitive adsorption between H 2 O and reactants (CO and O 2 ). Here, we report that the precise control of the metal-support interaction by regulating the support crystal plane of Pd/Pr-CeO 2 catalysts leads to highly efficient CO oxidation catalysts under wet conditions. It has been found that the addition of H 2 O inhibits the CO oxidation activity of Pr-CeO 2 nano-cube and octahedron supported highly dispersed Pd catalysts, but enhances the CO oxidation activity over Pr-CeO 2 nanorod supported highly dispersed Pd catalysts. After introduction of H 2 O in feed gas, the T 99 (temperature to achieve 99% conversion of CO) decreases from 157 °C to 115 °C for Pd/Pr-CeO 2 -NRs (Nanorods) catalyst at a gas hourly space velocity of 70, 000 h -1 and remains stable for more than 2400 min in the presence of H 2 O. Systematic characterization reveals that the (110) crystal plane of CeO 2 nanorod enhance the interaction between Pd species and Pr-CeO 2 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-CeO 2 -NRs mainly follows the H 2 O-mediated Langmuir-Hinshelwood mechanism in the presence of H 2 O. H 2 O 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 H 2 O.
Published Version
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