Morphology Effect of CeO2 Support in the Preparation, Metal–Support Interaction, and Catalytic Performance of Pt/CeO2 Catalysts

Abstract

AbstractPt/CeO2 catalysts with various Pt loadings were prepared by a conventional incipient wetness impregnation method that employed CeO2 cubes (c‐CeO2), rods (r‐CeO2), and octahedra (o‐CeO2) as the support and Pt(NH3)4(NO3)2 as the metal precursor. Their structures and catalytic activities in CO oxidation in excess O2 and the preferential oxidation of CO in a H2‐rich gas (CO‐PROX) were studied, and strong morphology effects were observed. The impregnated Pt precursor interacts more strongly with CeO2 rods and cubes than with CeO2 octahedra, and the reduction/decomposition of the Pt precursor impregnated on CeO2 octahedra is easier than that on CeO2 rods and cubes. With the same Pt loading, the Pt/o‐CeO2 catalyst contains the largest fraction of metallic Pt, whereas the Pt/c‐CeO2 catalyst contains the largest fraction of Pt2+ species. The reducibility of pure CeO2 and CeO2 in the Pt/CeO2 catalysts follows the order r‐CeO2>c‐CeO2>o‐CeO2, and the reducibility of CeO2 depends on the Pt loading for the Pt/c‐CeO2 catalysts but not much for the Pt/r‐CeO2 and Pt/o‐CeO2 catalysts. The catalytic performance of Pt/CeO2 catalysts in both CO oxidation and the CO‐PROX reaction follows the order Pt/r‐CeO2>Pt/c‐CeO2> Pt/o‐CeO2. The Pt0‐CeO2 ensemble is more active than the Pt2+‐CeO2 ensemble in the catalysis of CO oxidation in excess O2. H2‐assisted CO oxidation catalyzed by the Pt/CeO2 catalysts was observed in the CO‐PROX reaction, and the Pt2+ species and CeO2 with a large concentration of oxygen vacancies constitute the active structure of the Pt/CeO2 catalyst for the CO‐PROX reaction. The effect of the morphology of the CeO2 support in the preparation, metal–support interaction, and catalytic performance of Pt/CeO2 catalysts can be correlated the exposed crystal planes and surface composition/structure of the CeO2 support with different morphologies. These results not only demonstrate that the structure and catalytic performance of oxide‐supported catalysts can be tuned by controlling the morphology of the oxide support but also deepens the fundamental understanding of CO oxidation reactions catalyzed by Pt/CeO2 catalysts.