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Title: NO2 uptake under practically relevant conditions on BaO/Pt(111)

Abstract

The formation of nitrites and nitrates (Ba(NOx)2) under practically relevant conditions (PNO2 up to 1.0 Torr and T = 500 K) and their thermal decomposition on BaO (>20 monolayer equivalent (MLE))/Pt(1 1 1) were studied using temperature programmed desorption (TPD), infrared reflection absorption (IRA), and Xray photoelectron (XP) spectroscopies. The exposure of BaO to 1.0 × 10-8 Torr NO2 at 500 K leads to the formation of a Ba(NOx)2 layer with small, disordered crystalline nitrate clusters. Under these conditions (PNO2 = 1.0 × 10-8 Torr and T = 500 K) only the top portion of the BaO layer converts to Ba(NOx)2 and the nitrites in this Ba(NOx)2 layer stay without converting completely to nitrates even after 100 min of NO2 exposure. In the thermal decomposition of Ba(NOx)2, first nitrites decompose, releasing NO and then the decomposition of nitrates occurs via two pathways releasing NO2 and NO + O2. At 500 K and PNO2 ≥ 1.0 × 10-7 Torr, first NO2 reacts with BaO to form small disordered crystalline Ba(NO3)2 particles and then these particles agglomerate to form large, well-ordered (bulk-like) crystalline nitrates as the NO2 exposure increases. The thermal decomposition of these well-ordered, bulk-like crystalline nitrate aggregates occurs in twomore » steps releasing NO2 and NO + O2 in each step in two different temperature regions. NO2 pressure ≥1.0 × 10-5 Torr is required for the complete oxidation of initially formed nitrites to nitrates and the full nitration of the BaO layer at 500 K sample temperature. We gratefully acknowledge the US Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences for the support of this work. The research described in this paper was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle Memorial Institute under contract number DE-AC05-76RL01830.« less

Authors:
;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1047386
Report Number(s):
PNNL-SA-85709
Journal ID: ISSN 0920-5861; 830403000; TRN: US201216%%245
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Journal Name:
Catalysis Today
Additional Journal Information:
Journal Volume: 181; Journal Issue: 1; Journal ID: ISSN 0920-5861
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ABSORPTION; DECOMPOSITION; DESORPTION; ENERGY; LAYERS; NITRATES; NITRATION; NITRITES; OXIDATION; PARTICLES; PYROLYSIS; REFLECTION; UPTAKE; Model NSR catalysts NO2 uptake Disordered/ordered nitrate phase

Citation Formats

Mudiyanselage, Kumudu, and Szanyi, János. NO2 uptake under practically relevant conditions on BaO/Pt(111). United States: N. p., 2012. Web. doi:10.1016/j.cattod.2011.05.033.
Mudiyanselage, Kumudu, & Szanyi, János. NO2 uptake under practically relevant conditions on BaO/Pt(111). United States. doi:10.1016/j.cattod.2011.05.033.
Mudiyanselage, Kumudu, and Szanyi, János. Wed . "NO2 uptake under practically relevant conditions on BaO/Pt(111)". United States. doi:10.1016/j.cattod.2011.05.033.
@article{osti_1047386,
title = {NO2 uptake under practically relevant conditions on BaO/Pt(111)},
author = {Mudiyanselage, Kumudu and Szanyi, János},
abstractNote = {The formation of nitrites and nitrates (Ba(NOx)2) under practically relevant conditions (PNO2 up to 1.0 Torr and T = 500 K) and their thermal decomposition on BaO (>20 monolayer equivalent (MLE))/Pt(1 1 1) were studied using temperature programmed desorption (TPD), infrared reflection absorption (IRA), and Xray photoelectron (XP) spectroscopies. The exposure of BaO to 1.0 × 10-8 Torr NO2 at 500 K leads to the formation of a Ba(NOx)2 layer with small, disordered crystalline nitrate clusters. Under these conditions (PNO2 = 1.0 × 10-8 Torr and T = 500 K) only the top portion of the BaO layer converts to Ba(NOx)2 and the nitrites in this Ba(NOx)2 layer stay without converting completely to nitrates even after 100 min of NO2 exposure. In the thermal decomposition of Ba(NOx)2, first nitrites decompose, releasing NO and then the decomposition of nitrates occurs via two pathways releasing NO2 and NO + O2. At 500 K and PNO2 ≥ 1.0 × 10-7 Torr, first NO2 reacts with BaO to form small disordered crystalline Ba(NO3)2 particles and then these particles agglomerate to form large, well-ordered (bulk-like) crystalline nitrates as the NO2 exposure increases. The thermal decomposition of these well-ordered, bulk-like crystalline nitrate aggregates occurs in two steps releasing NO2 and NO + O2 in each step in two different temperature regions. NO2 pressure ≥1.0 × 10-5 Torr is required for the complete oxidation of initially formed nitrites to nitrates and the full nitration of the BaO layer at 500 K sample temperature. We gratefully acknowledge the US Department of Energy (DOE), Office of Basic Energy Sciences, Division of Chemical Sciences for the support of this work. The research described in this paper was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle Memorial Institute under contract number DE-AC05-76RL01830.},
doi = {10.1016/j.cattod.2011.05.033},
journal = {Catalysis Today},
issn = {0920-5861},
number = 1,
volume = 181,
place = {United States},
year = {2012},
month = {2}
}