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Title: Population and hierarchy of active species in gold iron oxide catalysts for carbon monoxide oxidation

Abstract

The identity of active species in supported gold catalysts for low temperature carbon monoxide oxidation remains an unsettled debate. With large amounts of experimental evidence supporting theories of either gold nanoparticles or sub-nm gold species being active, it was recently proposed that a size-dependent activity hierarchy should exist. Here we study the diverging catalytic behaviors after heat treatment of Au/FeO x materials prepared via co-precipitation and deposition precipitation methods. After ruling out any support effects, the gold particle size distributions in different catalysts are quantitatively studied using aberration corrected scanning transmission electron microscopy (STEM). A counting protocol is developed to reveal the true particle size distribution from HAADF-STEM images, which reliably includes all the gold species present. As a result, correlation of the populations of the various gold species present with catalysis results demonstrate that a size-dependent activity hierarchy must exist in the Au/FeO x catalyst.

Authors:
 [1];  [2];  [2];  [2];  [3];  [4];  [4];  [2];  [5]
  1. Lehigh Univ., Bethlehem, PA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Cardiff Univ., Cardiff (United Kingdom)
  2. Cardiff Univ., Cardiff (United Kingdom)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Tokyo Metropolitan Univ., Tokyo (Japan)
  5. Lehigh Univ., Bethlehem, PA (United States)
Publication Date:
Research Org.:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS)
Sponsoring Org.:
USDOE
OSTI Identifier:
1329164
Grant/Contract Number:
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 7; Journal ID: ISSN 2041-1723
Publisher:
Nature Publishing Group
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; catalyst synthesis; heterogeneous catalysis

Citation Formats

He, Qian, Freakley, Simon J., Edwards, Jennifer K., Carley, Albert F., Borisevich, Albina Y., Mineo, Yuki, Haruta, Masatake, Hutchings, Graham J., and Kiely, Christopher J.. Population and hierarchy of active species in gold iron oxide catalysts for carbon monoxide oxidation. United States: N. p., 2016. Web. doi:10.1038/ncomms12905.
He, Qian, Freakley, Simon J., Edwards, Jennifer K., Carley, Albert F., Borisevich, Albina Y., Mineo, Yuki, Haruta, Masatake, Hutchings, Graham J., & Kiely, Christopher J.. Population and hierarchy of active species in gold iron oxide catalysts for carbon monoxide oxidation. United States. doi:10.1038/ncomms12905.
He, Qian, Freakley, Simon J., Edwards, Jennifer K., Carley, Albert F., Borisevich, Albina Y., Mineo, Yuki, Haruta, Masatake, Hutchings, Graham J., and Kiely, Christopher J.. 2016. "Population and hierarchy of active species in gold iron oxide catalysts for carbon monoxide oxidation". United States. doi:10.1038/ncomms12905. https://www.osti.gov/servlets/purl/1329164.
@article{osti_1329164,
title = {Population and hierarchy of active species in gold iron oxide catalysts for carbon monoxide oxidation},
author = {He, Qian and Freakley, Simon J. and Edwards, Jennifer K. and Carley, Albert F. and Borisevich, Albina Y. and Mineo, Yuki and Haruta, Masatake and Hutchings, Graham J. and Kiely, Christopher J.},
abstractNote = {The identity of active species in supported gold catalysts for low temperature carbon monoxide oxidation remains an unsettled debate. With large amounts of experimental evidence supporting theories of either gold nanoparticles or sub-nm gold species being active, it was recently proposed that a size-dependent activity hierarchy should exist. Here we study the diverging catalytic behaviors after heat treatment of Au/FeOx materials prepared via co-precipitation and deposition precipitation methods. After ruling out any support effects, the gold particle size distributions in different catalysts are quantitatively studied using aberration corrected scanning transmission electron microscopy (STEM). A counting protocol is developed to reveal the true particle size distribution from HAADF-STEM images, which reliably includes all the gold species present. As a result, correlation of the populations of the various gold species present with catalysis results demonstrate that a size-dependent activity hierarchy must exist in the Au/FeOx catalyst.},
doi = {10.1038/ncomms12905},
journal = {Nature Communications},
number = ,
volume = 7,
place = {United States},
year = 2016,
month = 9
}

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  • Amorphous metal alloys with the compositions (at. %) Au{sub 5}FeZr{sub 14} and Au{sub 5}AgZr{sub 14} have been used as precursors for the preparation of gold-zirconia-iron oxide and gold-silver-zirconia catalysts for low-temperature CO oxidation. The catalysts were prepared by in situ activation (oxidation) of the glassy metal alloys under CO oxidation conditions at 280{degrees}C. The structural and chemical changes occurring during the transformation of the precursor alloys to the active stable catalysts were followed by thermal analysis, X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. When exposed to CO reaction conditions, the glassy metal alloys exhibited initially very little activitymore » due to the very low surface area of the alloys (<0.02 m{sup 2}/g). The activity developed with time on stream reaching a steady state after complete oxidation of the alloys. The stable active catalyst derived from Au{sub 5}FeZr{sub 14} was made up of gold particles supported on zirconia in which the iron oxide was dispersed. The catalyst prepared from Au{sub 5}AgZr{sub 14} contained gold-silver particles supported on zirconia. The zirconia formed by oxidation of the zirconium constituent was present in both catalysts as a mixture of poorly crystalline monoclinic and tetragonal phases. Both catalysts were microporous with BET surface areas of 30 mg{sup 2}/g (Au{sub 5}FeZr{sub 14}) and 45 m{sup 2}/g (Au{sub 5}AgZr{sub 14}). Kinetic tests performed in a continuous tubular microreactor in the temperature range from -20 to 50{degrees}C showed that both catalysts are highly active for CO oxidation at low temperature. CO oxidation rates increased considerably if the CO:O{sub 2} ratio in the reactant feed was changed from stoichiometry (2:1) to conditions of excess oxygen (1:2). 33 refs., 13 figs., 1 tab.« less
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