Dependence of Gas Stoichiometry on the Uniformity and Stability of a Segmented Proton Exchange Membrane Fuel Cell

This study developed an eight-segmented fuel cell for investigating local current distribution and stability along channel with six-pass serpentine flow field. The stoichiometry of anode was 1.2 and cathode was 4 as the benchmark for comparison. When the stoichiometry flow rate of cathode was 4 and anode decreased to 1.05, which caused the hydrogen starvation on the downstream. The decrease of cathode stoichiometry from 4 to 2 resulted in less water diffusing to membrane and slight decrease of the conductivity on the gas-inlet segment. The cathode stoichiometry of 1.2 showed better performance than the stoichiometry of 2 at 8^th segment. The reason is the hydration of membrane by water produced. When the fuel cell was operating under full humidity at 0.5V constant voltage, the current density would oscillate with time at different cathode stoichiometry. This result indicated that the location causes channel water flooding and draining alternately. The oscillation decreased at lower cathode stoichiometry.