Rotating disk electrode measurements on the CO tolerance of a high-surface area Pt/Vulcan carbon fuel cell catalyst

T. J. Schmidt, H. A. Gasteiger, R. J. Behm

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Abstract

We examine the electrocatalytic properties of a Pt/Vulcan carbon catalyst toward the electro-oxidation of CO and CO/H2 mixtures under proton exchange membrane fuel cell (PEMFC) relevant conditions (60 to 80°C, continuous reactant flow), employing rotating disk electrode (RDE) measurements. We demonstrate that our recently introduced thin-film RDE technique can be applied to predict the performance of real fuel cell anodes operating on CO-contaminated H2. The method involves attaching the catalyst particles to a glassy carbon RDE via a thin Nafion film. The thin-film RDE technique opens the possibility for the mass-transport-free determination of the electrode kinetics at 100% catalyst utilization. At identical mass-specific current densities, the overpotentials for CO/H2 oxidation measured with the thin-film RDE technique are in excellent agreement with performance data from PEMFC anodes. The kinetics of pure CO oxidation were investigated with CO/N2 mixtures, revealing that the CO oxidation activity increases with decreasing CO partial pressure (negative reaction order). The observed ignition potential for CO oxidation was the same for both the CO/N2 and the CO/H2 mixtures. Two H2 oxidation mechanisms in the presence of CO can be distinguished: (i) a high Tafel slope region at low overpotentials, where H2 oxidation occurs in vacancies of the CO adlayer; and (ii) a low Tafel slope region at high overpotentials where H2 and CO oxidation occur simultaneously.

Original languageEnglish
Pages (from-to)1296-1304
Number of pages9
JournalJournal of the Electrochemical Society
Volume146
Issue number4
DOIs
StatePublished - Apr 1999
Externally publishedYes

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