PEM fuel cell stacks operated under dry-reactant conditions

A double-path-type flow-field design that has two gas inlets and two gas outlets is presented for PEM fuel cells. The two paths are arranged in such a way that the inlet of one flow-field is adjacent to the outlet of the other flow-field and, within any section of the electrode active area, there are always adjacent channels with reactant flowing in opposite directions. Such a design enables the dry entering gas to become hydrated by acquiring some moisture from the exiting moist gas; and, within any section of the active area, the drier gas in one flow-field can share the moisture in the wetter gas flowing in the other flow-field. Such a design effectively uses the water produced by the stack to hydrate the membrane and the catalyst layers. The effectiveness of this design was demonstrated by running multiple-cell stacks where the stack could run stably at a current density up to 0.33 A/cm2 using dry hydrogen and dry air.