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Title: Mechanistic Study of Nitric Oxide Reduction by Hydrogen on Pt(100) (I): A DFT Analysis of the Reaction Network

Abstract

Periodic, self-consistent density functional theory (DFT-GGA, PW91) calculations are used to study the reaction mechanism for nitric oxide (NO) reduction by hydrogen (H 2) on Pt(100). Energetics of various N–O activation paths, including both direct and hydrogen-assisted N–O bond-breaking paths, and the formation of three different N-containing products (N 2, N 2O, and NH3), are systematically studied. On the basis of our analysis, NO* dissociation has a lower barrier than NO* hydrogenation to HNO* or NOH*, and therefore, the direct NO dissociation path is predicted to dominate N–O activation on clean Pt(100). The reaction of atomic N* with N* and NO* is proposed as the mechanism for N 2 and N 2O formation, respectively. NH 3 formation from N* via three successive hydrogenation steps is also studied and is found to be kinetically more difficult than N 2 and N 2O formation from N*. Finally, NO adsorption phase diagrams on Pt(100) are constructed, and these phase diagrams suggest that, at low temperatures (e.g., 400 K), the Pt(100) surface may be covered by half a monolayer of NO. We propose that high NO coverage might affect the NO + H 2 reaction mechanism, and therefore, one should explicitly take the NOmore » coverage into consideration in first-principles studies to determine the reaction mechanism on catalyst surfaces under reaction conditions. In conclusion, a detailed analysis of high NO coverage effects on the reaction mechanism will be presented in a separate contribution.« less

Authors:
 [1]; ORCiD logo [1]
  1. Univ. of Wisconsin-Madison, Madison, WI (United States)
Publication Date:
Research Org.:
Univ. of Wisconsin-Madison, Madison, WI (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Contributing Org.:
EMSL at Pacific Northwest National Laboratory (PNNL); the Center for Nanoscale Materials at Argonne National Laboratory (ANL); and the National Energy Research Scientific Computing Center (NERSC)
OSTI Identifier:
1355944
Alternate Identifier(s):
OSTI ID: 1397268
Grant/Contract Number:
FG02-05ER15731
Resource Type:
Journal Article: Published Article
Journal Name:
Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry
Additional Journal Information:
Journal Volume: 122; Journal Issue: 2; Journal ID: ISSN 1520-6106
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE

Citation Formats

Bai, Yunhai, and Mavrikakis, Manos. Mechanistic Study of Nitric Oxide Reduction by Hydrogen on Pt(100) (I): A DFT Analysis of the Reaction Network. United States: N. p., 2017. Web. doi:10.1021/acs.jpcb.7b01115.
Bai, Yunhai, & Mavrikakis, Manos. Mechanistic Study of Nitric Oxide Reduction by Hydrogen on Pt(100) (I): A DFT Analysis of the Reaction Network. United States. doi:10.1021/acs.jpcb.7b01115.
Bai, Yunhai, and Mavrikakis, Manos. Mon . "Mechanistic Study of Nitric Oxide Reduction by Hydrogen on Pt(100) (I): A DFT Analysis of the Reaction Network". United States. doi:10.1021/acs.jpcb.7b01115.
@article{osti_1355944,
title = {Mechanistic Study of Nitric Oxide Reduction by Hydrogen on Pt(100) (I): A DFT Analysis of the Reaction Network},
author = {Bai, Yunhai and Mavrikakis, Manos},
abstractNote = {Periodic, self-consistent density functional theory (DFT-GGA, PW91) calculations are used to study the reaction mechanism for nitric oxide (NO) reduction by hydrogen (H2) on Pt(100). Energetics of various N–O activation paths, including both direct and hydrogen-assisted N–O bond-breaking paths, and the formation of three different N-containing products (N2, N2O, and NH3), are systematically studied. On the basis of our analysis, NO* dissociation has a lower barrier than NO* hydrogenation to HNO* or NOH*, and therefore, the direct NO dissociation path is predicted to dominate N–O activation on clean Pt(100). The reaction of atomic N* with N* and NO* is proposed as the mechanism for N2 and N2O formation, respectively. NH3 formation from N* via three successive hydrogenation steps is also studied and is found to be kinetically more difficult than N2 and N2O formation from N*. Finally, NO adsorption phase diagrams on Pt(100) are constructed, and these phase diagrams suggest that, at low temperatures (e.g., 400 K), the Pt(100) surface may be covered by half a monolayer of NO. We propose that high NO coverage might affect the NO + H2 reaction mechanism, and therefore, one should explicitly take the NO coverage into consideration in first-principles studies to determine the reaction mechanism on catalyst surfaces under reaction conditions. In conclusion, a detailed analysis of high NO coverage effects on the reaction mechanism will be presented in a separate contribution.},
doi = {10.1021/acs.jpcb.7b01115},
journal = {Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry},
number = 2,
volume = 122,
place = {United States},
year = {Mon May 08 00:00:00 EDT 2017},
month = {Mon May 08 00:00:00 EDT 2017}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1021/acs.jpcb.7b01115

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  • Periodic, self-consistent density functional theory (DFT-GGA, PW91) calculations are used to study the reaction mechanism for nitric oxide (NO) reduction by hydrogen (H 2) on Pt(100). Energetics of various N–O activation paths, including both direct and hydrogen-assisted N–O bond-breaking paths, and the formation of three different N-containing products (N 2, N 2O, and NH3), are systematically studied. On the basis of our analysis, NO* dissociation has a lower barrier than NO* hydrogenation to HNO* or NOH*, and therefore, the direct NO dissociation path is predicted to dominate N–O activation on clean Pt(100). The reaction of atomic N* with N* andmore » NO* is proposed as the mechanism for N 2 and N 2O formation, respectively. NH 3 formation from N* via three successive hydrogenation steps is also studied and is found to be kinetically more difficult than N 2 and N 2O formation from N*. Finally, NO adsorption phase diagrams on Pt(100) are constructed, and these phase diagrams suggest that, at low temperatures (e.g., 400 K), the Pt(100) surface may be covered by half a monolayer of NO. We propose that high NO coverage might affect the NO + H 2 reaction mechanism, and therefore, one should explicitly take the NO coverage into consideration in first-principles studies to determine the reaction mechanism on catalyst surfaces under reaction conditions. In conclusion, a detailed analysis of high NO coverage effects on the reaction mechanism will be presented in a separate contribution.« less
  • Reaction pathways are explored for low temperature (e.g., 400 K) reduction of nitric oxide by hydrogen on Pt(111). First-principles electronic structure calculations based on periodic, self-consistent density functional theory(DFT-GGA, PW91) are employed to obtain thermodynamic and kinetic parameters for proposed reaction schemes on Pt(111). The surface of Pt(111) during NO reduction by H₂ at low temperatures is predicted to operate at a high NO coverage, and this environment is explicitly taken into account in the DFT calculations. Maximum rate analyses are performed to assess the most likely reaction mechanisms leading to formation of N₂O, the major product observed experimentally atmore » low temperatures. The results of these analyses suggest that the reaction most likely proceeds via the addition of at least two H atoms to adsorbed NO, followed by cleavage of the N-O bond.« less
  • Cited by 14
  • The catalytic activity of nanocrystalline Group IIIB metal oxides for the reduction of nitric oxide with methane was shown to be comparable to that of Co-ZSM-5. The mechanism of selective catalytic reduction of nitric oxide with methane in excess oxygen was examined over nanocrystalline yttrium oxide. A series of heterogeneous and homogeneous reaction steps was proposed to account for the observed trends in catalytic properties. Methyl radicals generated at the catalyst surface desorb into the gas phase, where they react with nitric oxide to form nitrosomethane. Nitrosomethane then decomposes in a series of homogeneous and heterogeneous reactions to produce nitrogenmore » and nitrous oxide. Evidence for gas-phase reaction of methyl radicals with nitric oxide was found in the adsorption studies of nitric oxide on yttrium oxide, the presence of ethane and ethene in the reactor effluent, catalytic studies involving nitrosomethane and nitromethane, as well as the successful prediction of methane selectivities based on a homogeneous reaction mechanism for methyl radical consumption. The proposed pathway for nitrogen production was supported by the observation of hydrogen cyanide under certain operating conditions, as well as adsorbed NCO species detected by infrared spectroscopy.« less