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Title: Nanoporous Au: an unsupported pure gold catalyst?

Abstract

The unique properties of gold especially in low temperature CO oxidation have been ascribed to a combination of various effects. In particular, particle sizes below a few nm and specific particle-support interactions have been shown to play important roles. On the contrary, recent reports revealed that monolithic nanoporous gold (npAu) prepared by leaching a less noble metal, such as Ag, out of the corresponding alloy can also exhibit remarkably high catalytic activity for CO oxidation, even though no support is present. Therefore, it was claimed to be a pure and unsupported gold catalyst. We investigated npAu with respect to its morphology, surface composition and catalytic properties. In particular, we studied the reaction kinetics for low temperature CO oxidation in detail taking mass transport limitation due to the porous structure of the material into account. Our results reveal that Ag, even if removed almost completely from the bulk, segregates to the surface resulting in surface concentrations of up to 10 at%. Our data suggest that this Ag plays a significant role in activation of molecular oxygen. Therefore, npAu should be considered as a bimetallic catalyst rather than a pure Au catalyst.

Authors:
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Publication Date:
Research Org.:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
956853
Report Number(s):
LLNL-JRNL-407229
Journal ID: ISSN 1932-7447; TRN: US201007%%87
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Journal Article
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 113; Journal Issue: 14; Journal ID: ISSN 1932-7447
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ALLOYS; CATALYSTS; GOLD; LEACHING; MORPHOLOGY; OXIDATION; OXYGEN; PARTICLE SIZE; REACTION KINETICS; TRANSPORT

Citation Formats

Wittstock, A, Neumann, B, Schaefer, A, Dumbuya, K, Kuebel, C, Biener, M, Zielasek, V, Steinrueck, H, Gottfried, M, Biener, J, Hamza, A, and B?umer, M. Nanoporous Au: an unsupported pure gold catalyst?. United States: N. p., 2008. Web.
Wittstock, A, Neumann, B, Schaefer, A, Dumbuya, K, Kuebel, C, Biener, M, Zielasek, V, Steinrueck, H, Gottfried, M, Biener, J, Hamza, A, & B?umer, M. Nanoporous Au: an unsupported pure gold catalyst?. United States.
Wittstock, A, Neumann, B, Schaefer, A, Dumbuya, K, Kuebel, C, Biener, M, Zielasek, V, Steinrueck, H, Gottfried, M, Biener, J, Hamza, A, and B?umer, M. 2008. "Nanoporous Au: an unsupported pure gold catalyst?". United States. https://www.osti.gov/servlets/purl/956853.
@article{osti_956853,
title = {Nanoporous Au: an unsupported pure gold catalyst?},
author = {Wittstock, A and Neumann, B and Schaefer, A and Dumbuya, K and Kuebel, C and Biener, M and Zielasek, V and Steinrueck, H and Gottfried, M and Biener, J and Hamza, A and B?umer, M},
abstractNote = {The unique properties of gold especially in low temperature CO oxidation have been ascribed to a combination of various effects. In particular, particle sizes below a few nm and specific particle-support interactions have been shown to play important roles. On the contrary, recent reports revealed that monolithic nanoporous gold (npAu) prepared by leaching a less noble metal, such as Ag, out of the corresponding alloy can also exhibit remarkably high catalytic activity for CO oxidation, even though no support is present. Therefore, it was claimed to be a pure and unsupported gold catalyst. We investigated npAu with respect to its morphology, surface composition and catalytic properties. In particular, we studied the reaction kinetics for low temperature CO oxidation in detail taking mass transport limitation due to the porous structure of the material into account. Our results reveal that Ag, even if removed almost completely from the bulk, segregates to the surface resulting in surface concentrations of up to 10 at%. Our data suggest that this Ag plays a significant role in activation of molecular oxygen. Therefore, npAu should be considered as a bimetallic catalyst rather than a pure Au catalyst.},
doi = {},
url = {https://www.osti.gov/biblio/956853}, journal = {Journal of Physical Chemistry. C},
issn = {1932-7447},
number = 14,
volume = 113,
place = {United States},
year = {Thu Sep 04 00:00:00 EDT 2008},
month = {Thu Sep 04 00:00:00 EDT 2008}
}