Simultaneous Measurements of Species and Current Distributions in a PEFC under Low-Humidity Operation

An experimental technique has been developed to conduct simultaneous measurements of species concentration and current density distributions using a segmented cell of 50 cm2. Twelve segmented subcells in conjunction with a multichannel potentiostat were employed to measure the current distribution, and two sets of multiposition microactuators and micro gas chromatographs were used to measure gas concentration distributions on the anode and cathode sides simultaneously. Distribution data are shown systematically for a polymer electrolyte fuel cell (PEFC) operated under low-humidity cathode conditions and at 80DGC and 2 atm. The O2 concentration profile for the PEFC is generally linear and can be well predicted by a simple mass balance analysis, the anode water concentration profile is closely tied to the net water transport rate through the membrane, and the net water transport coefficient ranges between 0.05 and 0.30 even under very dry cathode conditions, suggesting the presence of strong back-diffusion of water from the cathode to the anode despite rather dry cathode gas.