In Situ Study of PEMFC Start-Up Degradation Using a Novel Through-Plate Reference Electrode Array
In order to meet cost and durability targets for polymer electrolyte membrane fuel cells (PEMFCs), there is an urgent need for improved in situ measurement techniques to enhance understanding of degradation mechanisms and to facilitate design optimisation. A highly innovative reference electrode design has recently been developed at NPL that makes use of a standard hydrogen electrode (SHE) connected to the active area of the cell via a fine Nafion tube salt bridge inserted through the end plates of the fuel cell. The ion conducting path through the gas diffusion layer is achieved by Nafion impregnation at the point of contact with the Nafion tubing. Use of an array of such electrodes has for the first time enabled mapping of the spatial distribution of electrode potential in an operating PEMFC while minimising the perturbation of the measurement that occurs with conventional fuel cell reference electrode designs. Here we demonstrate application of this technique to the investigation of catalyst support corrosion during fuel cell start-up, when fuel is introduced to the cell without a nitrogen purge. In this situation an air/fuel boundary progresses through the anode flow-field causing a transient mixed potential at the cathode of >1.4 V versus SHE, which enables carbon oxidation to occur. The NPL reference electrode array allows unprecedented time-resolved measurement of this potential spike as it progresses through the cell. The influence of flow-field design on the potential transient behaviour during start-up is investigated, supported by measurements of CO2 evolution from corrosion of the carbon catalyst support.
KeywordsFuel cells PEMFC In situ Reference electrode
List of Abbreviations
Gas diffusion layer
Johnson Matthey Fuel Cells Ltd
Membrane electrode assembly
National Physical Laboratory, UK
Polymer electrolyte membrane fuel cell
Standard hydrogen electrode
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This work was supported by the UK National Measurement System and an Industrial Group comprising Acal Energy, AFC Energy, C Tech Innovation, CMR Fuel Cells, Intelligent Energy and Johnson Matthey. The authors are grateful to Johnson Matthey for supply of fuel cell components.
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