A fuel cell includes a membrane electrode assembly and a separator. The separator includes a reactant gas inlet manifold, a reactant gas outlet manifold, a reactant gas channel, an inlet connection channel, an inlet buffer portion, an outlet buffer portion, and an outlet connection channel. A pressure drop through the inlet buffer portion is less than a pressure drop through the reactant gas channel when a reactant gas flows from the reactant gas inlet manifold to the reactant gas channel. A pressure drop through the outlet buffer portion is less than a pressure drop through the outlet connection channel when the reactant gas flows from the reactant gas channel to the reactant gas outlet manifold.