Fuel Cell

A fuel cell comprising a proton-conducting solid electrolyte, a fuel electrode provided on one side of the solid electrolyte, and an oxidant electrode provided on the other side of the solid electrolyte, the solid electrolyte including at least one internal electrode therein characterized in that the fuel cell further comprises a polarizing means for electrochemically polarizing the at least one internal electrode for oxidizing, or reducing, a fuel, or an oxidant, passing through an inside of the solid electrolyte.