Molecular Mechanism of Low-Temperature Passive NO x Adsorption (PNA) on Palladium-Loaded FER Zeolite

Palladium exhibits a complex chemistry in the PNA process, especially in the presence of gas mixtures containing CO and NO x . In this work the mechanism of NO x adsorption in gas mixtures with CO, O2, and H2O on a Pd/FER zeolite is investigated. The redox state of palladium and its clustering durin...

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Published inJournal of physical chemistry. C Vol. 127; no. 15; pp. 7119 - 7130
Main Authors Geerts-Claes, Hannelore, Smet, Sam, Hengst, Christoph, Schuetze, Frank-Walter, Verheyen, Elke, Minjauw, Matthias, Detavernier, Christophe, Pulinthanathu Sree, Sreeprasanth, Martens, Johan
Format Journal Article
LanguageEnglish
Published American Chemical Society 20.04.2023
Subjects
C: Chemical and Catalytic Reactivity at Interfaces
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Summary:Palladium exhibits a complex chemistry in the PNA process, especially in the presence of gas mixtures containing CO and NO x . In this work the mechanism of NO x adsorption in gas mixtures with CO, O2, and H2O on a Pd/FER zeolite is investigated. The redox state of palladium and its clustering during high-temperature pretreatment and NO x adsorption was investigated. Insight into the chemisorption mechanism was gained by detailed monitoring of the evolution of the NO x and CO x concentrations. Oxidized palladium is required for achieving NO x adsorption. Clustered zerovalent palladium reduced with H2 did not adsorb NO x in the presence of O2. Evidence is provided for a reaction mechanism departing from oxygen-bridged PdII–O–PdII moieties of PdO nanoclusters. The NO adsorption site on palladium is obtained by reduction of one of the two PdII atoms to the zerovalent state which occurs more readily with CO as compared to NO explaining the beneficial role of CO.
ISSN:1932-7447
1932-7455
DOI:10.1021/acs.jpcc.2c08643