Development of Solid Oxide Fuel Cells and the Component Materials

In addition to the high conversion efficiency, the solid oxide fuel cell (SOFC) is quite attractive from the viewpoint of fuel flexibility, especially the possibility of internal reforming of methane and other hydrocarbons for power generation. The systems with several kW to tens kW-class modules have been successfully operated and tested in Japan. The SOFC systems with internal steam reforming reaction over a Ni-YSZ anode or pressurized condition have been tested as a suitable operation mode. Methane internal reforming proceeded without deterioration with time, whereas the power generation with ethane and ethylene suffered from carbon deposition even at high steam-to-carbon ratio. Carbon deposition region and equilibrium partial pressure of oxygen in the C-H-O diagram were estimated from the thermodynamic data. Reduced temperature SOFC operation is another approach, especially for small scale applications, in which scandia-stabilized zirconia, lanthanum gallate, or rare earth-doped ceria were employed as candidate for the electrolyte.