Brightman, E J; Hinds, G (2014) Feasibility study: in situ measurement of fluoride ion concentration in a polymer electrolyte membrane fuel cell. NPL Report. MAT 70

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Abstract

Metallic bipolar plates are of increasing interest to manufacturers of polymer electrolyte membrane fuel cells (PEMFCs) due to their potential to facilitate significant reductions in stack weight, volume and permeability to reactant gas, but corrosion remains a key challenge. At present the standard ex situ method of assessing the corrosion resistance of metallic bipolar plates involves electrochemical polarisation testing of specimens fully immersed in sulphuric acid, which is not representative of the real environment experienced by a bipolar plate during fuel cell operation. A range of novel in situ measurement techniques has been developed by NPL to facilitate more accurate characterisation of this environment. One critical parameter is the fluoride ion concentration in the aqueous phase, arising from degradation of the polymer membrane, which may lead to a lowering of pH in localised regions of the flow-field. In this work, a miniature fluoride ion-selective electrode was developed and combined with a reference electrode that could be inserted through a small hole in the end-plates of a fuel cell, with the capability of measuring fluoride ion concentration in water droplets in a single channel of the flow-field. The results demonstrate the feasibility of such a technique, but further work will be required to calibrate the sensor to the operating conditions of the cell. It is unlikely that the concentration of fluoride at the measurement location will be above the detection limit of the ion selective electrode, but improvements to the design and development of more sensitive ionophores may in future enable such a measurement.

Item Type:	Report/Guide (NPL Report)
NPL Report No.:	MAT 70
Keywords:	PEMFC, fluoride
Subjects:	Advanced Materials Advanced Materials > Fuels Cells
Last Modified:	02 Feb 2018 13:13
URI:	http://eprintspublications.npl.co.uk/id/eprint/6341

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