In accordance with various embodiments of the invention, a fuel cell assembly (100) may comprise a flow passageway (130) having a region of graduated cross sectional area along the flow passageway (130) for maintaining a reaction equilibrium. The region may be defined be the arrangement of stacked fuel cell elements (110) alone or in combination with additional shaped spacers (160). The spacers are provided with a textured surface which may simply be irregular or may have some type of designed grooves or ridges. This irregular surface produces turbulences in the reactant flow increasing the probability of the reactant gas stream interacting with the electrode material.
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