Work

Palladium-assisted NOx storage and release on CexZr1-xO2 for passive NOx adsorber in diesel exhaust aftertreatment

Year: 2024

Type: article

Abstract: Understanding Pd effects on NOx storage and release is crucial for designing passive NOx adsorber (PNA) to control NOx emissions during diesel cold-starts. Herein, we report two oxidation states of Pd species on CexZr1-xO2 regulated by metal-support interaction. Pdδ+ (0 < δ < 2) in Pd/Ce0.25Zr0.75O2 exhibits a high affinity for O2 adsorption, which promotes the oxidation of adsorbed NO to nitrates at 100 °C. These nitrates are thermally unstable due to electron transfer from the Pd atom to the N-O bond, facilitating the decomposition of nitrates to NO2 above 200 °C. In contrast, Pd2+ in Pd/Ce0.75Zr0.25O2 prefer to NO adsorption. A large amount of adsorbed NO and nitrites accumulate on Pd2+ and Ce4+ results in high levels of NO release below 200 °C. For the potential application in PNA, Pd/Ce0.25Zr0.75O2 is recommended due to its proper NOx release temperature as well as better water and SO2 resistance. Pd-exchanged zeolites are widely studied as passive NOx adsorber materials for emission control for combustion engines. Here, Yue Peng and colleagues reveal that a relatively strong metal-support interaction between Pd and Ce0.25Zr0.75O2 leads to two oxidation states of Pd optimizing NOx storage efficiency and NOx release temperature.

Source: Communications Engineering

DOI: 10.1038/s44172-024-00311-3