An oxygen-ion conducting electrolyte such as yttria-stabilized zirconia has been traditionally used for the fabrication of solid oxide fuel cells (SOFCs). Due to a high activation energy for conduction, SOFCs based on stabilized zirconia are normally operated at temperatures approaching 1000°C. The high operating temperature leads to the corrosion and incompatibility of materials, severely limits the selection of materials that might be suitable as the interconnect, and increases the difficulty of forming seals and manifolding. In order to overcome these problems, efforts are being made to develop electrolytes that can perform at intermediate temperatures. Most of the studies on intermediate temperature SOFCs are based on the development of doped cerates and gallates as oxygen-ion conducting electrolytes. In SOFCs whose electrolyte is an oxygen-ion conductor, water is formed at the fuel-side electrode, which dilutes the fuel. An SOFC that uses a proton conductor as the electrolyte eliminates this problem, because water is generated at the air electrode, and not at the fuel electrode. The operating temperature of the SOFC can be reduced to ≈600°C using proton conductors. We have fabricated an SOFC using BaCe0.8Y0.2Ox (BCY) proton conductor as the electrolyte. An ≈15-μm-thick dense BCY film was prepared on a porous Ni/BCY cermet (i.e., ceramic/metal composite) substrate by a colloidal spray deposition technique. The gas permeable Ni/BCY cermet substrate backed with nickel mesh was used as the anode, and platinum paste backed with platinum mesh served as cathode. The current-voltage characteristics of the BCY-based SOFC were measured in the temperature range 600-800°C using wet air on the cathode side and wet hydrogen on the anode side. The open circuit voltage was close to the theoretical value at all operating temperatures. The power density of the fuel cell was ≈240 and ≈875 mW/cm2 at 600 and 800°C, respectively. The development at our laboratory of SOFCs based on proton conductors will be presented in this talk.

*Work supported by U.S. Department of Energy under Contract W-31-109-ENG-38.