Distribution measurements in an operating polymer electrolyte fuel cell

The water balance between the flow channels, gas diffusion layer, and electrolyte membrane is a critical phenomenon affecting polymer electrolyte fuel cell (PEFC) performance. This paper presents data on the in situ water distribution within the gas channel of an operating PEFC. Following careful calibration and instrumentation, a gas chromatograph (GC) was interfaced directly to the fuel cell at various locations along the serpentine anode and cathode flow paths of a specially designed fuel cell. The 50 cm ² active area instrumented fuel cell also permits simultaneous current distribution measurements via the segmented collector plate approach. The on-line GC method allows discrete measurements of the water vapor content of the flow about every two minutes. Water distribution data are shown at several inlet relative humidities and cell operating voltages. For the thin electrolyte membranes used (51 μm), there is little functional dependence of anode gas channel water distribution on current output. For thin membranes, this indicates that there is little gradient in the water activity between anode and cathode, for the conditions tested (i < 1 A/cm ²).