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Title: CO oxidation over ceria supported Au 22 nanoclusters: Shape effect of the support

Abstract

Gold (Au) nanoclusters have recently emerged as ideal models for understanding Au catalysis, because the nanosized Au particles have precise atomic numbers and uniform size. Here, in this work, we studied for the first time the support shape effect on the catalysis of Au nanoclusters by using CO oxidation as a model reaction. Au 22(L 8) 6 (L = 1,8-bis(diphenylphosphino) octane) nanoclusters were supported on CeO 2 rods or cubes, then pretreated at different temperatures (up to 673 K), allowing the gradual removal of the organic phosphine ligands. CO oxidation test over these differently pretreated samples shows that CeO 2 rods are much better supports than cubes for Au 22 nanoclusters in enhancing the reaction rate. In situ IR spectroscopy coupled with CO adsorption indicates that the shape of CeO 2 support can impact the nature and quantity of exposed Au sites, as well as the efficiency of organic ligand removal. Although CeO 2 rods are helpful in exposing a greater percentage of total Au sites upon ligands removal, the percentage of active Au sites (denoted by Au δ+, 0 < δ < 1) is lower than that on CeO 2 cubes. The in situ extended X-ray absorption spectroscopy (EXAFS)more » and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) results show that the Au nanoclusters bound more strongly to the CeO 2 rods than to the cubes where the Au nanoclusters show more sintering. Considering the typical redox mechanism for CO oxidation over supported Au nanoclusters and nanoparticles, it is concluded that the reactivity of the lattice oxygen of CeO 2 is the determining factor for CO oxidation over Au 22/CeO 2. Lastly, CeO 2 rods offer more reactive lattice oxygen and abundant oxygen vacancies than the cubes and thus make the rods a superior support for Au nanoclusters in catalyzing low temperature CO oxidation.« less

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [2];  [3];  [3]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Science Division and Center for Nanophase Materials Sciences
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division
  3. Brown Univ., Providence, RI (United States). Department of Chemistry
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division
OSTI Identifier:
1468071
Grant/Contract Number:  
AC05-00OR22725; AC02-76SF00515; SC0012335
Resource Type:
Accepted Manuscript
Journal Name:
Chinese Chemical Letters
Additional Journal Information:
Journal Volume: 29; Journal Issue: 6; Journal ID: ISSN 1001-8417
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 36 MATERIALS SCIENCE; Gold nanoclusters; Ceria; Ligands; Support shape; CO oxidation

Citation Formats

Wu, Zili, Mullins, David R., Allard, Lawrence Frederick, Zhang, Qianfan, and Wang, Laisheng. CO oxidation over ceria supported Au22 nanoclusters: Shape effect of the support. United States: N. p., 2018. Web. doi:10.1016/j.cclet.2018.01.038.
Wu, Zili, Mullins, David R., Allard, Lawrence Frederick, Zhang, Qianfan, & Wang, Laisheng. CO oxidation over ceria supported Au22 nanoclusters: Shape effect of the support. United States. doi:10.1016/j.cclet.2018.01.038.
Wu, Zili, Mullins, David R., Allard, Lawrence Frederick, Zhang, Qianfan, and Wang, Laisheng. Wed . "CO oxidation over ceria supported Au22 nanoclusters: Shape effect of the support". United States. doi:10.1016/j.cclet.2018.01.038. https://www.osti.gov/servlets/purl/1468071.
@article{osti_1468071,
title = {CO oxidation over ceria supported Au22 nanoclusters: Shape effect of the support},
author = {Wu, Zili and Mullins, David R. and Allard, Lawrence Frederick and Zhang, Qianfan and Wang, Laisheng},
abstractNote = {Gold (Au) nanoclusters have recently emerged as ideal models for understanding Au catalysis, because the nanosized Au particles have precise atomic numbers and uniform size. Here, in this work, we studied for the first time the support shape effect on the catalysis of Au nanoclusters by using CO oxidation as a model reaction. Au22(L8)6 (L = 1,8-bis(diphenylphosphino) octane) nanoclusters were supported on CeO2 rods or cubes, then pretreated at different temperatures (up to 673 K), allowing the gradual removal of the organic phosphine ligands. CO oxidation test over these differently pretreated samples shows that CeO2 rods are much better supports than cubes for Au22 nanoclusters in enhancing the reaction rate. In situ IR spectroscopy coupled with CO adsorption indicates that the shape of CeO2 support can impact the nature and quantity of exposed Au sites, as well as the efficiency of organic ligand removal. Although CeO2 rods are helpful in exposing a greater percentage of total Au sites upon ligands removal, the percentage of active Au sites (denoted by Auδ+, 0 < δ < 1) is lower than that on CeO2 cubes. The in situ extended X-ray absorption spectroscopy (EXAFS) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) results show that the Au nanoclusters bound more strongly to the CeO2 rods than to the cubes where the Au nanoclusters show more sintering. Considering the typical redox mechanism for CO oxidation over supported Au nanoclusters and nanoparticles, it is concluded that the reactivity of the lattice oxygen of CeO2 is the determining factor for CO oxidation over Au22/CeO2. Lastly, CeO2 rods offer more reactive lattice oxygen and abundant oxygen vacancies than the cubes and thus make the rods a superior support for Au nanoclusters in catalyzing low temperature CO oxidation.},
doi = {10.1016/j.cclet.2018.01.038},
journal = {Chinese Chemical Letters},
number = 6,
volume = 29,
place = {United States},
year = {2018},
month = {1}
}

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