Ce-Pr Mixed Oxide Catalysts with a Fibrous Morphology for Low-temperature PM Oxidation

Ceria (CeO2) is an effective precious-metal-free catalyst that combusts PM (particulate matter), due to its ability to switch between Ce4+ and Ce3+. In this work, to improve the activity of a ceria-based catalyst, cerium-praseodymium mixed oxide catalysts with various Ce-Pr ratios were synthesized with nanofiber morphologies, characterized, and compared with ceria catalysts. Two factors were considered: morphology and Ce-Pr ratio, which result in synergistic effects. In the ceria catalyst, we confirmed that a fibrous morphology is more advantageous for PM oxidation compared to nanocubes and nanorods with cubes, even though these samples have larger surface areas. In addition, the incorporation of Pr into the ceria nanofiber catalyst enhanced its intrinsic properties by promoting the reducibility and formation of oxygen vacancies. The analysis showed improved oxygen storage and supply capacity, especially for oxygen that is chemically adsorbed on the catalytic surface. PM oxidation tests demonstrated the Ce0.5Pr0.5O2-NF catalyst showed the best activity in air, which was consistent with the characterization results. Thus, the Ce0.5Pr0.5O2-NF sample was shown to be an effective and promising catalyst for PM oxidation.