Internal reforming of SOFCs - Carbon deposition on fuel electrode and subsequent deterioration of cell

Several cermet anode materials were investigated for direct internal reforming operation of solid oxide fuel cells. The effects of steam and discharge conditions were examined for internal reforming operation with propane as a hydrocarbon fuel. Even at high steam-to-carbon (S/C) ratio, power generation characteristics with Ni-yttria-stabilized zirconia (YSZ) were deteriorated during internal reforming operation with propane at 1000 degrees C, possibly due to carbon formation at low current densities, whereas stable generation behavior was observed for the cells with Ni-scandia-stabilized zirconia (ScSZ) or Ni-samaria-doped ceria (SDC) anode by feeding propane at low S/C = 0.8. The carbon deposition rate was measured for several cermet anode materials by feeding dry or humidified methane by the gravimetric technique. The carbon deposition rate over Ni-ScSZ was lower than Ni-YSZ, leading to better generation performance with propane at low S/C. Ni-SDC showed the highest carbon deposition rate among the cermets investigated, even for humidified methane. This implies that carbon formed over Ni-SDC could be effectively removed upon power generation. (c) 2006 The Electrochemical Society. All rights reserved.