A fuel cell stack having a plurality of fuel cells arranged adjacent one another
and compressed together. At least one of the fuel cells has an electrode plate
with a flow field formed therein, a proton exchange membrane and a compressible
fluid-permeable diffusion media that is disposed adjacent the electrode plate.
A compressing member is operable to vary a compression of the fuel cells during
operation which varies an intrusion of the compressible diffusion media into the
flow field in the adjacent electrode plate. The variation of the intrusion of the
diffusion media into the flow fields allows the control of the pressure drop across
the fuel cell stack and enables the fuel cell stack to be dynamically controlled
so that a desired operational state is achieved.