National Physical Laboratory

In situ mapping of potential transients during start-up and shut-down of a polymer electrolyte membrane fuel cell.

Author(s):
Brightman, E J, Hinds, G
Source:
J. Power Sources, 2014, 267, 160-170
ISSN:
ISBN:
NPL Doc. Ref:
PDB: 7163 | DDB: 6155
Document Type:
Periodical article
DOI:
http://dx.doi.org/10.1016/j.jpowsour.2014.05.040

Note: An asterisk after an author's name indicates a non-NPL author.

Abstract:

The progression of a fuel/air front through the anode flow-field during start-up or shut-down of a polymer electrolyte membrane fuel cell (PEMFC) is known to cause a transient high potential at the cathode, leading to corrosion of the carbon catalyst support. Here we present spatially resolved measurements of such potential transients in an operating fuel cell using an innovative reference electrode array, combined with quantification of carbon corrosion by measurement of CO2 in the cathode outlet. A systematic study of the effect of relative humidity on start-up/shut-down potential transients and carbon corrosion rates was carried out both under open circuit conditions and with the application of a small external load. Under all operating conditions, carbon corrosion was more severe during start-up than during shut-down, with the highest cathode potentials measured opposite the anode outlet during start-up and opposite the anode inlet during shut-down. The carbon corrosion rate was least severe under the driest conditions, which was attributed to the increased membrane resistivity. The results are discussed in the context of a schematic framework for the reverse current decay mechanism expressed in terms of local electrode potential. This new technique provides a powerful diagnostic tool for evaluation of SU/SD-tolerant catalyst layers and optimisation of fuel cell hardware design.

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