Coupled theoretical and experimental analysis of surface coverage effects in Pt-catalyzed NO and O 2 reaction to NO 2 on Pt(1 1 1)
Batch reactor results and analysis are reported for the reaction of NO with O 2 to form NO 2 over a Pt(1 1 1) single crystal at atmospheric pressure. The apparent activation energy and NO, O 2, and NO 2 reaction orders are found to be 80 kJ mol −1, 1.3, 1, and −2 and are comparable to previous studi...
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Published in | Catalysis today Vol. 136; no. 1; pp. 84 - 92 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
Elsevier B.V
2008
|
Subjects | |
Online Access | Get full text |
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Summary: | Batch reactor results and analysis are reported for the reaction of NO with O
2 to form NO
2 over a Pt(1
1
1) single crystal at atmospheric pressure. The apparent activation energy and NO, O
2, and NO
2 reaction orders are found to be 80
kJ
mol
−1, 1.3, 1, and −2 and are comparable to previous studies on supported Pt catalysts which take inhibition by the product NO
2 into account. The absolute rates on a per Pt atom basis are the highest yet reported 0.34
±
0.02
s
−1, at 300
°C, 73
ppm NO, 27
ppm NO
2 and 5% O
2. Auger electron spectroscopy and X-ray photoelectron spectroscopy are used to show that the surface chemisorbed oxygen coverage under reaction conditions is 0.76
±
0.06
ML, consistent with a coverage controlled by NO
2 dissociation. DFT calculations are used to compare the stability of possible surface intermediates on a clean Pt(1
1
1) surface with those on a
p(√3
×
√3)-2O (2/3
ML) ordering surface. In contrast to the clean surface, O
2 adsorption and dissociation are endothermic at 2/3
ML oxygen, but a peroxynitrite intermediate OONO* is slightly stable and may provide an alternative, associative pathway to NO
2 formation that is consistent with the observed first order reaction kinetics in O
2. |
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ISSN: | 0920-5861 1873-4308 |
DOI: | 10.1016/j.cattod.2007.12.139 |