Time-Resolved Water Measurement in a PEM Fuel Cell Using High-Resolution Neutron Imaging Technique

The dynamic process of water transport along the through-plane direction in the membrane electrode assembly of a proton exchange membrane fuel cell was investigated using the high-resolution neutron imaging. Four different membrane/gas diffusion layer or membrane/gas diffusion electrode assemblies were tested by measuring the through-plane water thickness profiles. The results indicate that proper design and assembly of the test fixture are critical for accurate water measurement; the accumulation speed of liquid water inside an assembly varies with time; the ionomer in catalyst layers could facilitate water management in the membrane; the time constants for wetting and drying processes are functions of gas diffusion layer thickness, inlet flow rate, and gas dew point; and the time constant for the wetting process is about 1.4 times longer than the corresponding drying process.