CO oxidation over titanate nanotube supported Au

T. A. Ntho, James Arthur Anderson, M. S. Scurrell

Research output: Contribution to journalArticle

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Abstract

New experimental findings, which offer further information concerning the deactivation mechanism of CO oxidation over titania nanotube (TN) supported gold, are reported. Contrary to earlier reports by others, we have observed that the formation of bicarbonate species during CO oxidation on the Au/TN catalyst is a competing reaction that leads to catalyst deactivation. We regard the formation of bicarbonate species not as an intermediate step but rather a product of the CO2 produced during CO oxidation. The bicarbonate species detected at 1290 cm(-1) was very stable and only desorbed at relatively high temperatures. In the presence of water the bicarbonate species (1290 cm(-1)) did not form under reaction conditions. CO2-TPD results implied that water possibly reacted with and removed the already formed bicarbonate species and prevented its further formation and in the process promoted the reaction and prevented deactivation. The possible reactions of how water (OH) might remove the gold associated bicarbonate and hence reactivate and promote the oxidation of CO are discussed. The mechanisms for the formation of the observed bicarbonate may account for the deactivation of the Au/TN catalyst during CO oxidation; this reaction would consume the CH groups on Au which have been reported as essential in the mechanism of CO oxidation. The above hypothesis Of CO2 being able to chemisorb on gold nanoparticles is not Unique. Based on IR studies [N.M. Schubert, A. Venugopal, M.J. Kalich, V. Plazk, R.J. Behm, J. Catal. 222 (2004) 32; B. Schumacher, Y. Denkwitz, V. Plzak, M. Kinne, R.J. Behm, J. Catal. 224 (2004) 449], evidence was provided which pointed to the fact that CO and CO2 competed for adsorption on the same site on Au surfaces. To the best of our knowledge, this is the first time that DRIFTS and CO2-TPD have been combined to show that CO2 is adsorbed on the gold-nanoparticles in the form of bicarbonate to the detriment of the oxidation of CO. (C) 2008 Elsevier Inc. All rights reserved.

Original languageEnglish
Pages (from-to)94-100
Number of pages7
JournalJournal of Catalysis
Volume261
Issue number1
Early online date4 Dec 2008
DOIs
Publication statusPublished - 1 Jan 2009

Keywords

  • Gold
  • Titania
  • Nanotubes
  • Deactivation
  • CO oxidation
  • Bicarbonate
  • Infrared
  • TPD
  • CO2
  • carbon-monoxide oxidation
  • gold nanoparticles
  • catalytic-activity
  • AU/TIO2 catalyst
  • temperature
  • adsorption
  • AU/ALPHA-FE2O3
  • mechanism
  • oxides
  • water

Cite this

Ntho, T. A., Anderson, J. A., & Scurrell, M. S. (2009). CO oxidation over titanate nanotube supported Au. Journal of Catalysis, 261(1), 94-100. https://doi.org/10.1016/j.jcat.2008.11.009

CO oxidation over titanate nanotube supported Au. / Ntho, T. A.; Anderson, James Arthur; Scurrell, M. S.

In: Journal of Catalysis, Vol. 261, No. 1, 01.01.2009, p. 94-100.

Research output: Contribution to journalArticle

Ntho, TA, Anderson, JA & Scurrell, MS 2009, 'CO oxidation over titanate nanotube supported Au', Journal of Catalysis, vol. 261, no. 1, pp. 94-100. https://doi.org/10.1016/j.jcat.2008.11.009
Ntho, T. A. ; Anderson, James Arthur ; Scurrell, M. S. / CO oxidation over titanate nanotube supported Au. In: Journal of Catalysis. 2009 ; Vol. 261, No. 1. pp. 94-100.
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N2 - New experimental findings, which offer further information concerning the deactivation mechanism of CO oxidation over titania nanotube (TN) supported gold, are reported. Contrary to earlier reports by others, we have observed that the formation of bicarbonate species during CO oxidation on the Au/TN catalyst is a competing reaction that leads to catalyst deactivation. We regard the formation of bicarbonate species not as an intermediate step but rather a product of the CO2 produced during CO oxidation. The bicarbonate species detected at 1290 cm(-1) was very stable and only desorbed at relatively high temperatures. In the presence of water the bicarbonate species (1290 cm(-1)) did not form under reaction conditions. CO2-TPD results implied that water possibly reacted with and removed the already formed bicarbonate species and prevented its further formation and in the process promoted the reaction and prevented deactivation. The possible reactions of how water (OH) might remove the gold associated bicarbonate and hence reactivate and promote the oxidation of CO are discussed. The mechanisms for the formation of the observed bicarbonate may account for the deactivation of the Au/TN catalyst during CO oxidation; this reaction would consume the CH groups on Au which have been reported as essential in the mechanism of CO oxidation. The above hypothesis Of CO2 being able to chemisorb on gold nanoparticles is not Unique. Based on IR studies [N.M. Schubert, A. Venugopal, M.J. Kalich, V. Plazk, R.J. Behm, J. Catal. 222 (2004) 32; B. Schumacher, Y. Denkwitz, V. Plzak, M. Kinne, R.J. Behm, J. Catal. 224 (2004) 449], evidence was provided which pointed to the fact that CO and CO2 competed for adsorption on the same site on Au surfaces. To the best of our knowledge, this is the first time that DRIFTS and CO2-TPD have been combined to show that CO2 is adsorbed on the gold-nanoparticles in the form of bicarbonate to the detriment of the oxidation of CO. (C) 2008 Elsevier Inc. All rights reserved.

AB - New experimental findings, which offer further information concerning the deactivation mechanism of CO oxidation over titania nanotube (TN) supported gold, are reported. Contrary to earlier reports by others, we have observed that the formation of bicarbonate species during CO oxidation on the Au/TN catalyst is a competing reaction that leads to catalyst deactivation. We regard the formation of bicarbonate species not as an intermediate step but rather a product of the CO2 produced during CO oxidation. The bicarbonate species detected at 1290 cm(-1) was very stable and only desorbed at relatively high temperatures. In the presence of water the bicarbonate species (1290 cm(-1)) did not form under reaction conditions. CO2-TPD results implied that water possibly reacted with and removed the already formed bicarbonate species and prevented its further formation and in the process promoted the reaction and prevented deactivation. The possible reactions of how water (OH) might remove the gold associated bicarbonate and hence reactivate and promote the oxidation of CO are discussed. The mechanisms for the formation of the observed bicarbonate may account for the deactivation of the Au/TN catalyst during CO oxidation; this reaction would consume the CH groups on Au which have been reported as essential in the mechanism of CO oxidation. The above hypothesis Of CO2 being able to chemisorb on gold nanoparticles is not Unique. Based on IR studies [N.M. Schubert, A. Venugopal, M.J. Kalich, V. Plazk, R.J. Behm, J. Catal. 222 (2004) 32; B. Schumacher, Y. Denkwitz, V. Plzak, M. Kinne, R.J. Behm, J. Catal. 224 (2004) 449], evidence was provided which pointed to the fact that CO and CO2 competed for adsorption on the same site on Au surfaces. To the best of our knowledge, this is the first time that DRIFTS and CO2-TPD have been combined to show that CO2 is adsorbed on the gold-nanoparticles in the form of bicarbonate to the detriment of the oxidation of CO. (C) 2008 Elsevier Inc. All rights reserved.

KW - Gold

KW - Titania

KW - Nanotubes

KW - Deactivation

KW - CO oxidation

KW - Bicarbonate

KW - Infrared

KW - TPD

KW - CO2

KW - carbon-monoxide oxidation

KW - gold nanoparticles

KW - catalytic-activity

KW - AU/TIO2 catalyst

KW - temperature

KW - adsorption

KW - AU/ALPHA-FE2O3

KW - mechanism

KW - oxides

KW - water

U2 - 10.1016/j.jcat.2008.11.009

DO - 10.1016/j.jcat.2008.11.009

M3 - Article

VL - 261

SP - 94

EP - 100

JO - Journal of Catalysis

JF - Journal of Catalysis

SN - 0021-9517

IS - 1

ER -