Local current measurement in PEFC
Major barriers for a successful commercialization of Polymer Electrolyte Fuel Cells (PEFCs) are insufficient lifetime and high cost of platinum catalyst. A comprehensive understanding of aging and transport phenomena on all relevant length scales is a key to improve durability and to reduce precious metal loading. Flow fields as used in PEFCs for the distribution of the reactant gases over the electrode area cause inhomogeneities. The importance of down the channel inhomogeneities has been realized. Inhomogeneities in the perpendicular to the flow channel direction, however, have not received adequate attention to date, possibly due to the lack of direct experimental evidence. A novel approach allows for the first time the direct measurement of the local cell current in channel and land areas of PEFCs with sub-millimeter resolution. The high potential of our method is demonstrated here in the evaluation of in-plane current transients during start-up of a PEFC and in transient flooding experiments in combination with neutron radiography for liquid water detection. The method provides key information that is badly needed for the understanding of transport and degradation phenomena and for the assessment of mitigation strategies.