Artifacts in measuring electrode catalyst area of fuel cells through cyclic voltammetry

Robert N. Carter, Shyam S. Kocha, Frederick T. Wagner, Matthew Fay, Hubert A. Gasteiger

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

97 Scopus citations

Abstract

Cyclic Voltammetry (CV) is a well-established technique to measure the electrochemically active surface area (ECA) of a catalyst in an electrode through hydrogen adsorption/desorption (HAD). In the field of proton exchange membrane fuel cells this method can be applied to scales ranging from rotating disc electrodes (RDE) to single-cell and even multiple-cell stacks where the working electrode (WE) is part of a membrane-electrode assembly (MEA). In this paper, it is shown for MEA tests that molecular hydrogen evolution can create significant artifacts in the shape of the HAD curve, which impacts the calculated ECA. This artifact is related to the rate of mass transfer of molecular hydrogen away from the WE and depends on the nitrogen purge flow rate used for the WE during the voltage sweep. A brief discussion of spatially resolved CV measurements is also provided where it is shown that this same artifact can create the appearance of spatial variation in a cell's ECA. The impact of hydrogen evolution on ECA measurements can be mitigated by reducing the purge rate to below ca. 1 sccm/cm2 of electrode active area, whereupon the ECA measured for an MEA agrees to that of the same catalyst in an RDE experiment to within 10-15%. Additionally, it is shown that the same ECA as measured for a catalyst in RDE can be obtained for an MEA-based one if the WE is filled with liquid water.

Original languageEnglish
Title of host publicationECS Transactions - 7th Symposium Devoted to Proton Exchange Membrane Fuel Cells
Pages403-410
Number of pages8
Edition1 PART 1
DOIs
StatePublished - 2007
Externally publishedYes
Event7th Symposium Devoted to Proton Exchange Membrane Fuel Cells - 212th ECS Meeting - Washington, DC, United States
Duration: 7 Oct 200712 Oct 2007

Publication series

NameECS Transactions
Number1 PART 1
Volume11
ISSN (Print)1938-5862
ISSN (Electronic)1938-6737

Conference

Conference7th Symposium Devoted to Proton Exchange Membrane Fuel Cells - 212th ECS Meeting
Country/TerritoryUnited States
CityWashington, DC
Period7/10/0712/10/07

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