Ni/Ceria cermet as anode of reduced-temperature solid oxide fuel cells

Anode characteristics of a Ce0.8Sm0.2O1.9/Ni cermet on the Ce0.8Sm0.2O1.9 electrolyte were studied by a three-probe ac impedance method combined with dc polarization, instead of the conventional current-voltage curve measurement. The experimentally obtained Cole-Cole plots of ac impedance showed a shift with added dc voltage. Both bulk resistance and electrode reaction resistance increased with increasing anodic dc current. The shift of bulk resistance is explained by the electronic conduction of the electrolyte. The increase of electrode reaction resistance is thought to be a result of discrepancy between the ionic and the external current, differing from Ni/yttria-stabilized zirconia anode. An interface resistance lower than 0.1 Omega/cm(2) was obtained below 700degrees C by using a coprecipitation method to prepare the anode precursor and cofiring it with the electrolyte to improve the contact. (C) 2002 The Electrochemical Society.