A process for converting hydrocarbons and water vapor into hydrogen, carbon monoxide, and carbon dioxide; a fuel cell device; and a process of utilizing the fuel cell to convert chemical energy to electrical energy is described. The fuel cell comprises a metallic and/or mixed conducting anode, a metallic and/or mixed conducting cathode, a proton-conducting ceramic electrolyte between the anode and the cathode, and an external load connecting the anode and the cathode. The fuel cell also includes systems for bringing gaseous hydrocarbon fuels into contact with the anode and for bringing oxygen and water vapor into contact with the cathode. Water vapor in the fuel cell passes through the ceramic electrolyte membrane from the cathode side to the anode side by ambipolar diffusion, called "steam permeation" without conducting current, under the influence of a water vapor concentration gradient.