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Title: Water-Gas Shift Activity of Cu Surfaces and Cu Nanoparticles Supported on Metal Oxides

Abstract

Oxide supported Cu catalysts show significant activity for the water-gas shift reaction (WGS, CO + H{sub 2}O {yields} H{sub 2} + CO{sub 2}) but their performance is not fully understood and is highly dependent on the synthesis conditions or the nature of the oxide support. This article describes a series of new studies examining the water-gas shift activity of Cu/MgO(1 0 0) surfaces and compares it to the activities found for pure copper systems, Cu nanoparticles in contact with well-defined surfaces of TiO{sub 2}, ZnO, MoO{sub 2} and CeO{sub 2}, and Cu cations present in mixed-metal oxides. Catalytic tests performed over CuFe{sub 2}O{sub 4}, Ce{sub 1-x}Cu{sub x}O{sub 2} or CuMoO{sub 4} show significant WGS activity only when the Cu cations in the mixed-metal oxide are reduced to metallic copper. Thus, Cu nanoparticles were deposited on different oxide surfaces and their WGS activity was measured in a batch reactor (P{sub CO} = 20 Torr; P{sub H{sub 2}O} = 10 Torr; T = 575-650 K). The WGS activity of the Cu nanoparticles supported on MgO(1 0 0) was 2-3 times larger than that of Cu(1 0 0). Even better WGS catalysts were obtained when Cu was deposited on CeO{sub 2}(1 1 1)more » or TiO{sub 2}(1 1 0). An apparent activation energy of 13.8 kcal/mol was found for the WGS on Cu/MgO(1 0 0). This is smaller than the value of 15.2 kcal/mol observed on Cu(1 0 0), and substantially larger than the values of 7-9 kcal/mol seen for the apparent activation energies of the Cu/CeO2(1 1 1) and Cu/TiO2(1 1 0) catalysts. Post-reaction surface characterization pointed to the lack of O vacancies in the Cu/MgO(1 0 0) catalysts. This is in contrast to results found for Cu/CeO{sub 2}(1 1 1) and Cu/TiO{sub 2}(1 1 0), where the oxide support exhibits a significant concentration of O vacancies as a consequence of the WGS reaction. The oxygen vacancies present in Cu/CeO{sub 2}(1 1 1) and Cu/TiO{sub 2}(1 1 0) help in the dissociation of the water molecule and reduce the apparent activation energy for the WGS process. Such a phenomenon cannot occur on the Cu/MgO(0 0 1) catalysts, and the main steps of the WGS probably take place on the Cu nanoparticles.« less

Authors:
; ; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Lab. (BNL), Upton, NY (United States). National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
980677
Report Number(s):
BNL-93595-2010-JA
Journal ID: ISSN 0920-5861; CATTEA; TRN: US201015%%2062
DOE Contract Number:  
DE-AC02-98CH10886
Resource Type:
Journal Article
Journal Name:
Catalysis Today
Additional Journal Information:
Journal Volume: 143; Journal Issue: 1-2; Journal ID: ISSN 0920-5861
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ACTIVATION ENERGY; CATALYSTS; CATIONS; COPPER; DISSOCIATION; METALS; MOLECULES; OXIDES; OXYGEN; PERFORMANCE; REACTORS; SUPPORTS; SURFACES; SYNTHESIS; VACANCIES; WATER; WATER GAS; YIELDS; national synchrotron light source

Citation Formats

Rodriguez, J, Liu, P, Wang, X, Wen, W, Hanson, J, Hrbek, J, Perez, M, and Evans, J. Water-Gas Shift Activity of Cu Surfaces and Cu Nanoparticles Supported on Metal Oxides. United States: N. p., 2009. Web. doi:10.1016/j.cattod.2008.08.022.
Rodriguez, J, Liu, P, Wang, X, Wen, W, Hanson, J, Hrbek, J, Perez, M, & Evans, J. Water-Gas Shift Activity of Cu Surfaces and Cu Nanoparticles Supported on Metal Oxides. United States. https://doi.org/10.1016/j.cattod.2008.08.022
Rodriguez, J, Liu, P, Wang, X, Wen, W, Hanson, J, Hrbek, J, Perez, M, and Evans, J. 2009. "Water-Gas Shift Activity of Cu Surfaces and Cu Nanoparticles Supported on Metal Oxides". United States. https://doi.org/10.1016/j.cattod.2008.08.022.
@article{osti_980677,
title = {Water-Gas Shift Activity of Cu Surfaces and Cu Nanoparticles Supported on Metal Oxides},
author = {Rodriguez, J and Liu, P and Wang, X and Wen, W and Hanson, J and Hrbek, J and Perez, M and Evans, J},
abstractNote = {Oxide supported Cu catalysts show significant activity for the water-gas shift reaction (WGS, CO + H{sub 2}O {yields} H{sub 2} + CO{sub 2}) but their performance is not fully understood and is highly dependent on the synthesis conditions or the nature of the oxide support. This article describes a series of new studies examining the water-gas shift activity of Cu/MgO(1 0 0) surfaces and compares it to the activities found for pure copper systems, Cu nanoparticles in contact with well-defined surfaces of TiO{sub 2}, ZnO, MoO{sub 2} and CeO{sub 2}, and Cu cations present in mixed-metal oxides. Catalytic tests performed over CuFe{sub 2}O{sub 4}, Ce{sub 1-x}Cu{sub x}O{sub 2} or CuMoO{sub 4} show significant WGS activity only when the Cu cations in the mixed-metal oxide are reduced to metallic copper. Thus, Cu nanoparticles were deposited on different oxide surfaces and their WGS activity was measured in a batch reactor (P{sub CO} = 20 Torr; P{sub H{sub 2}O} = 10 Torr; T = 575-650 K). The WGS activity of the Cu nanoparticles supported on MgO(1 0 0) was 2-3 times larger than that of Cu(1 0 0). Even better WGS catalysts were obtained when Cu was deposited on CeO{sub 2}(1 1 1) or TiO{sub 2}(1 1 0). An apparent activation energy of 13.8 kcal/mol was found for the WGS on Cu/MgO(1 0 0). This is smaller than the value of 15.2 kcal/mol observed on Cu(1 0 0), and substantially larger than the values of 7-9 kcal/mol seen for the apparent activation energies of the Cu/CeO2(1 1 1) and Cu/TiO2(1 1 0) catalysts. Post-reaction surface characterization pointed to the lack of O vacancies in the Cu/MgO(1 0 0) catalysts. This is in contrast to results found for Cu/CeO{sub 2}(1 1 1) and Cu/TiO{sub 2}(1 1 0), where the oxide support exhibits a significant concentration of O vacancies as a consequence of the WGS reaction. The oxygen vacancies present in Cu/CeO{sub 2}(1 1 1) and Cu/TiO{sub 2}(1 1 0) help in the dissociation of the water molecule and reduce the apparent activation energy for the WGS process. Such a phenomenon cannot occur on the Cu/MgO(0 0 1) catalysts, and the main steps of the WGS probably take place on the Cu nanoparticles.},
doi = {10.1016/j.cattod.2008.08.022},
url = {https://www.osti.gov/biblio/980677}, journal = {Catalysis Today},
issn = {0920-5861},
number = 1-2,
volume = 143,
place = {United States},
year = {Thu Jan 01 00:00:00 EST 2009},
month = {Thu Jan 01 00:00:00 EST 2009}
}