In order to simplify solid oxide fuel cell (SOFC) system, a single-compartment cell, which can avoid the need for a high temperature gas sealing and can be operated in the flow of a mixture of CH4 and air, has been studied. This cell consisted of Pt | BaCe0.8Y0.2O3-α | Au, in which both electrodes were exposed to the CH4+air mixture with a CH4/O2 ratio of 2 at 950 °C , and it generated an electric power density of 0.166 W cm−2 producing hydrogen and carbon monoxide (synthetic gas) with a H2/CO ratio of about 2. A large difference in catalytic activity for the partial oxidation of CH4 between the Pt and Au electrode materials led to an oxygen concentration cell which could generate an electric power between them.