Potential dependence of segregation and surface alloy formation of a Ru modified carbon supported Pt catalyst

Rose, Abigail and Crabb, Eleanor M. and Qian, Yangdong and Ravikumar, M. K. and Wells, Peter P. and Wiltshire, Richard J. K. and Yao, Jun and Bilsborrow, Robert and Mosselmans, Fred and Russell, Andrea E. (2007) Potential dependence of segregation and surface alloy formation of a Ru modified carbon supported Pt catalyst. Electrochimica Acta, 52 ( 19). pp. 5556-5564. ISSN 0013-4686

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Official URL: http://dx.doi.org/10.1016/j.electacta.2007.02.023

Abstract

Ruthenium modified carbon supported platinum catalysts have been shown to have a similar activity towards carbon monoxide oxidation as conventionally prepared bimetallic PtRu alloy catalysts. In this study the effect of the applied electrode potential and potential cycles on the location and oxidation state of the Ru species in such Ru modified Pt/C catalysts was investigated using in situ EXAFS collected at both the Ru K and Pt L3 absorption edges. The as prepared catalyst was found to consist of a Pt core with a Ru oxy/hydroxide shell. The potential dependent data indicated alloying to form a PtRu phase at 0.05 V versus RHE and subsequent dealloying to return to the Ru oxy/hydroxide decorated Pt surface at potentials greater than 0.7 V. The Ru–O distances obtained indicate that both Ru3+ and Ru4+ species are present on the surface of the Pt particles at oxidising potentials; the former is characteristic of the as prepared Ru modified Pt/C catalyst and following extensive periods at potentials above 0.7 V and the latter of the Ru oxide species on the PtRu alloy.

Item Type:Article
Additional Information:Ruthenium modified carbon supported platinum catalysts have been shown to have a similar activity towards carbon monoxide oxidation as conventionally prepared bimetallic PtRu alloy catalysts. In this study the effect of the applied electrode potential and potential cycles on the location and oxidation state of the Ru species in such Ru modified Pt/C catalysts was investigated using in situ EXAFS collected at both the Ru K and Pt L3 absorption edges. The as prepared catalyst was found to consist of a Pt core with a Ru oxy/hydroxide shell. The potential dependent data indicated alloying to form a PtRu phase at 0.05 V versus RHE and subsequent dealloying to return to the Ru oxy/hydroxide decorated Pt surface at potentials greater than 0.7 V. The Ru–O distances obtained indicate that both Ru3+ and Ru4+ species are present on the surface of the Pt particles at oxidising potentials; the former is characteristic of the as prepared Ru modified Pt/C catalyst and following extensive periods at potentials above 0.7 V and the latter of the Ru oxide species on the PtRu alloy.
Keywords:Platinum, Fuel cell catalysts, EXAFS, CO oxidation, Ruthenium
Subjects:F Physical Sciences > F200 Materials Science
F Physical Sciences > F342 Quantum Mechanics
F Physical Sciences > F170 Physical Chemistry
Divisions:College of Science > School of Engineering
ID Code:5427
Deposited By: Jun Yao
Deposited On:07 May 2012 20:43
Last Modified:07 May 2012 20:43

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