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Title: Single Pd Atoms on θ-Al 2O 3 (010) Surface do not Catalyze NO Oxidation

Abstract

New convenient wet chemistry synthetic routes have made it possible to explore catalytic activities of a variety of single supported atoms. The majority of single supported atoms have been synthesized on active supports which participate in oxidation reactions. The single supported atoms on inert substrates (e.g. alumina) are limited to Pt adatoms and Pd cations, and are generally active toward CO oxidation. In this manuscript, we show that single Pd atoms on -alumina show high CO oxidation activity; however, they exhibit no detectable NO oxidation under our experimental conditions. This led us to employ first principles modeling to explore multiple Langmuir-Hinshelwood-type pathways to explain high CO oxidation activity but lack of NO oxidation activity. For completeness, we have also examined Eley-Riedel pathways. We find that a pathway that involves carbonate or nitrate as an intermediate can explain the experimental results of CO and NO oxidation on single alumina supported Pd cations.

Authors:
ORCiD logo [1];  [1]; ORCiD logo [2];  [1];  [3]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science & Technology Division
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Energy & Transportation Science Division
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V)
OSTI Identifier:
1349596
Grant/Contract Number:
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Scientific Reports
Additional Journal Information:
Journal Volume: 7; Journal Issue: 1; Journal ID: ISSN 2045-2322
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE

Citation Formats

Narula, Chaitanya K., Allard, Lawrence F., Moses-DeBusk, Melanie, Stocks, G. Malcom, and Wu, Zili. Single Pd Atoms on θ-Al2O3 (010) Surface do not Catalyze NO Oxidation. United States: N. p., 2017. Web. doi:10.1038/s41598-017-00577-y.
Narula, Chaitanya K., Allard, Lawrence F., Moses-DeBusk, Melanie, Stocks, G. Malcom, & Wu, Zili. Single Pd Atoms on θ-Al2O3 (010) Surface do not Catalyze NO Oxidation. United States. doi:10.1038/s41598-017-00577-y.
Narula, Chaitanya K., Allard, Lawrence F., Moses-DeBusk, Melanie, Stocks, G. Malcom, and Wu, Zili. Mon . "Single Pd Atoms on θ-Al2O3 (010) Surface do not Catalyze NO Oxidation". United States. doi:10.1038/s41598-017-00577-y. https://www.osti.gov/servlets/purl/1349596.
@article{osti_1349596,
title = {Single Pd Atoms on θ-Al2O3 (010) Surface do not Catalyze NO Oxidation},
author = {Narula, Chaitanya K. and Allard, Lawrence F. and Moses-DeBusk, Melanie and Stocks, G. Malcom and Wu, Zili},
abstractNote = {New convenient wet chemistry synthetic routes have made it possible to explore catalytic activities of a variety of single supported atoms. The majority of single supported atoms have been synthesized on active supports which participate in oxidation reactions. The single supported atoms on inert substrates (e.g. alumina) are limited to Pt adatoms and Pd cations, and are generally active toward CO oxidation. In this manuscript, we show that single Pd atoms on -alumina show high CO oxidation activity; however, they exhibit no detectable NO oxidation under our experimental conditions. This led us to employ first principles modeling to explore multiple Langmuir-Hinshelwood-type pathways to explain high CO oxidation activity but lack of NO oxidation activity. For completeness, we have also examined Eley-Riedel pathways. We find that a pathway that involves carbonate or nitrate as an intermediate can explain the experimental results of CO and NO oxidation on single alumina supported Pd cations.},
doi = {10.1038/s41598-017-00577-y},
journal = {Scientific Reports},
number = 1,
volume = 7,
place = {United States},
year = {Mon Apr 03 00:00:00 EDT 2017},
month = {Mon Apr 03 00:00:00 EDT 2017}
}

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Cited by: 2works
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  • This paper studies the mechanism of low temperature CO oxidation over catalysts of 0.003%-0.1 wt.% palladium supported on gamma-Al/sub 2/O/sub 3/, and over a solid solution of copper in gamma-Al/sub 2/O/sub 3/ (0.5-3.0 wt.% CuO). In order to obtain information about the reactive forms of oxygen in CO oxidation over these catalysts, the authors used tagged oxygen (ca 80 atom %) and secondary ion mass spectrometry. To confirm the effect of oxygen isotope exchange on the tracer content of the CO/sub 2/, CO oxidation was carried out with CO/sub 2/ freeze-out in the cycle. CO oxidation over supported palladium, undermore » conditions of reduction or of catalysis, can go via reaction with OH oxygen atoms, but the temperature ranges of these conditions differ by more than 250 degrees. It is noted that over Pd.Cu/Al/sub 2/O/sub 3/ catalysts the mechanism represented is only partly realized. Along with OH oxygen, an adsorbed form of oxygen evidently also contributes to CO formation over these catalysts.« less
  • By systematically changing growth parameters, the growth of β-(Al{sub x}Ga{sub 1−x}){sub 2}O{sub 3}/Ga{sub 2}O{sub 3} (010) heterostructures by plasma-assisted molecular beam epitaxy was optimized. Through variation of the Al flux under O-rich conditions at 600 °C, β-(Al{sub x}Ga{sub 1−x}){sub 2}O{sub 3} (010) layers spanning ∼10% to ∼18% Al{sub 2}O{sub 3} were grown directly on β-Ga{sub 2}O{sub 3} (010) substrates. Nominal β-(Al{sub x}Ga{sub 1−x}){sub 2}O{sub 3} (010) compositions were determined through Al:Ga flux ratios. With x = ∼0.18, the β-(Al{sub x}Ga{sub 1−x}){sub 2}O{sub 3} (020) layer peak in a high-resolution x-ray diffraction (HRXRD) ω-2θ scan was barely discernible, and Pendellösung fringes were not visible.more » This indicated that the phase stability limit of Al{sub 2}O{sub 3} in β-Ga{sub 2}O{sub 3} (010) at 600 °C was less than ∼18%. The substrate temperature was then varied for a series of β-(Al{sub ∼0.15}Ga{sub ∼0.85}){sub 2}O{sub 3} (010) layers, and the smoothest layer was grown at 650 °C. The phase stability limit of Al{sub 2}O{sub 3} in β-Ga{sub 2}O{sub 3} (010) appeared to increase with growth temperature, as the β-(Al{sub x}Ga{sub 1−x}){sub 2}O{sub 3} (020) layer peak with x = ∼0.18 was easily distinguishable by HRXRD in a sample grown at 650 °C. Cross-sectional transmission electron microscopy (TEM) indicated that β-(Al{sub ∼0.15}Ga{sub ∼0.85}){sub 2}O{sub 3} (010) layers (14.4% Al{sub 2}O{sub 3} by energy dispersive x-ray spectroscopy) grown at 650 °C were homogeneous. β-(Al{sub ∼0.20}Ga{sub ∼0.80}){sub 2}O{sub 3} (010) layers, however, displayed a phase transition. TEM images of a β-(Al{sub ∼0.15}Ga{sub ∼0.85}){sub 2}O{sub 3}/Ga{sub 2}O{sub 3} (010) superlattice grown at 650 °C showed abrupt layer interfaces and high alloy homogeneity.« less
  • Temperature-programmed desorption (TPD) and oxidation (TPO) were used to study the decomposition and oxidation of methanol, ethanol, acetaldehyde, formic acid, and acetic acid on Al{sub 2}O{sub 3}, Pd/Al{sub 2}O{sub 3}, and PdO/Al{sub 2}O{sub 3} catalysts. The oxidation and decomposition rates were much higher on Pd/Al{sub 2}O{sub 3} than on Al{sub 2}O{sub 3}, even though the volatile organic compounds (VOCs) were adsorbed on the Al{sub 2}O{sub 3} support in both cases. The VOCs surface-diffused to Pd and mostly dehydrogenated during TPD whereas they oxidized to CO{sub 2} and H{sub 2}O in the presence of oxygen. Partial oxidation products also apparently formedmore » on the surface during TPO and they oxidized completely above 550 K. Above 600 K, VOCs oxidation was consistent with the Mars-van Krevelen mechanism, involving the oxidation and reduction of Pd and PdO, but PdO was less active than Pd metal for VOC decomposition. Oxidation began at the same temperatures on PdO/Al{sub 2}O{sub 3} whether or not O{sub 2} was present, indicating that extraction of lattice oxygen from PdO was the limiting factor initially. After lattice oxygen was removed, metallic Pd decomposed VOCs and also adsorbed O{sub 2}, which was incorporated into the Pd lattice above 600 K. The reduction of PdO during TPD resulted in an autocatalytic oxidation since metallic Pd was more active than PdO. A portion of the VOCs reacted in parallel on Al{sub 2}O{sub 3} since these sites are active for dehydration and dehydrogenation at moderate to high temperatures. 38 refs., 20 figs.« less
  • A kinetics study of the CO + NO reaction over Pd has been carried out using single-crystal, model planar-supported, and conventional high-surface-area Pd/Al{sub 2}O{sub 3} catalysts. A pronounced structure sensitivity is evident that results in a rate enhancement over the Pd(111) single crystal relative to the more open (100) and (110) faces, and for larger supported particles relative to smaller ones. Temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) data indicate that the Pd(100) face is more active for NO dissociation and atomic N stabilization than the close-packed (111) plane. Similarly, TPD results show that smaller particles in the modelmore » supported catalysts are more active for atomic N formation and stabilization. The inverse correlation between reaction activity and N, formation and stabilization suggests that an inactive atomic N species plays a role in determining the reaction rate. 33 refs., 11 figs., 1 tab.« less