Chemisorption and reaction of NO and N{sub 2}O on oxidized and reduced ceria surfaces studied by soft X-ray photoemission spectroscopy and desorption spectroscopy

Journal Article · Fri Sep 10 04:00:00 EDT 1999 · Journal of Catalysis

DOI:https://doi.org/10.1006/jcat.1999.2577· OSTI ID:687741

Overbury, S H; Mullins, D R; Huntley, D R; Kundakovic, L ^[1]

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1. Oak Ridge National Lab., TN (United States)

The authors have examined the chemisorption and reaction of NO and N{sub 2}O on ceria surfaces by soft X-ray photoelectron spectroscopy (SXPS), X-ray absorption spectroscopy, and isothermal and temperature programmed desorption (TPD) spectroscopy. Samples include highly oriented CeO{sub 2}(100) and CeO{sup 2}(111) thin films with surfaces of variable oxidation states. CeO{sub 2}(111) thin films were grown in situ allowing control over the initial oxidation state of the ceria surface, quantitatively determinedly by valence band, Ce 4d, and Ce 3d photoemission. Following NO exposure, various N-containing surface species were observed by N 1s photoemission, and the distribution of these species depended upon surface oxidation state, exposure, and adsorption temperature. These species included N{sub 2}O, nitrite, NO{sup {minus}}, and three states believed to be associated with atomic or anionic forms of N. Nitrite and N{sub 2}O are seen on a fully oxidized surface while NO{sup {minus}}, N{sub 2}O, and dissociation products are observed on a reduced surface. The primary reaction of NO with reduced ceria is reoxidation of the ceria by the NO, both by NO{sup {minus}} formation and by NO dissociation, leading to immediate and thermally induced N{sub 2} desorption. Adsorption of NO at 150 K is predominantly molecular while exposure to NO at 400 K leads to a thermally activated nitride which desorbs at temperatures above 500 K. Dissociative adsorption of NO leads to the displacement of N{sup 3{minus}} at high exposures.

• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC05-96OR22464; AC02-76CH00016
• OSTI ID: 687741
• Journal Information: Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 2 Vol. 186; ISSN JCTLA5; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

33 ADVANCED PROPULSION SYSTEMS
54 ENVIRONMENTAL SCIENCES
AIR POLLUTION CONTROL
CERIUM OXIDES
CHEMISORPTION
NITRIC OXIDE
NITROUS OXIDE
REDUCTION
SORPTIVE PROPERTIES