Composition-dependent oxygen transfer and NOx-assisted soot oxidation over Ce-Pr mixed oxides for durable diesel particulate filter regeneration

Diesel particulate filters (DPFs) are widely used to control particulate emissions from diesel engines, while their regeneration remains challenging because soot oxidation is kinetically limited at typical exhaust temperatures. Developing catalysts that can efficiently utilize O 2 and NO x -derived oxidants while retaining their functionality during repeated high-temperature regeneration is therefore important for durable particulate control. Herein, a series of Ce-Pr mixed oxides with tunable compositions was prepared by CTAB-assisted coprecipitation and systematically evaluated for soot oxidation under O 2 and NO/O 2 atmospheres, together with thermal-aging tests at 800 °C. Pr incorporation progressively modified the Ce-Pr lattice environment, increased defect-associated oxygen species and Ce 3+ fraction, and enhanced low-temperature oxygen reducibility. However, soot oxidation activity did not increase monotonically with these redox descriptors. Ce 75 Pr 25 and Ce 85 Pr 15 exhibited the most favorable O 2 oxidation performance, with T 90 values of 389 and 385 °C, respectively, whereas the more Pr-rich compositions showed higher oxygen reducibility but lower soot oxidation activity. These results indicate that effective soot oxidation depends not only on oxygen activation but also on oxygen transport and accessibility at the soot–catalyst interface. Under NO/O 2 , Pr-rich compositions promoted NO oxidation to NO 2 and showed a stronger NO-assisted enhancement of soot oxidation, while in situ DRIFTS revealed the coexistence of nitrite- and nitrate-type surface species. Thermal aging further demonstrated the enhanced durability of the Ce-Pr mixed oxides: after aging at 800 °C, the T 50 increase was limited to 12–19 °C, compared with 194 °C for CeO 2 , accompanied by better retention of surface area, reducible oxygen and NO oxidation functionality. These findings demonstrate that composition-dependent regulation of oxygen transport, NOx chemistry and structural stability can provide a useful materials strategy for improving the durability of catalytic soot oxidation during DPF regeneration.