Patent ID: 8003278

Claim:
A fuel cell formed by stacking a membrane electrode assembly and first and second separators sandwiching the membrane electrode assembly, said membrane electrode assembly including a pair of electrodes and an electrolyte membrane interposed between said electrodes, a reactant gas passage for passing a reactant gas therethrough and extending through said separator in the stacking direction, said first and second separators each comprising: a reactant gas flow field formed at a position corresponding to a power generation area of said electrode for supplying the reactant gas to said electrode, wherein the reactant gas flow field comprises a fuel gas field formed on the first separator to supply a fuel gas to one of the electrodes, and an oxygen-containing gas flow field formed on the second separator to supply an oxygen-containing gas to the other electrode; and a buffer area provided between said reactant gas flow field and said reactant gas passage for stirring the reactant gas, said membrane electrode assembly comprising a humidification section facing said buffer area, wherein water permeates through said humidification section from said buffer area, the buffer area of said first separator and the buffer area of said second separator facing each other through said membrane electrode assembly, the water in the fuel gas permeating from the fuel gas flow field to the oxygen-containing gas flow field through a first humidification section, the water in the oxygen-containing gas permeating from the oxygen-containing gas flow field to the fuel gas flow field through a second humidification section, the fuel gas and the oxygen-containing gas flowing in a counterflowing manner.