Properties of Ni/YSZ cermet as anode for SOFC

As the anode of a solid oxide fuel cell, Ni/YSZ cermet material was investigated. We measured the power output, IR resistance and polarization resistance as a function of the Ni/YSZ volume ratio. IR resistance decreased as the Ni/YSZ ratio was increased. The linear relationship between IR resistance and the reciprocal values of the nickel surface area indicates that the contact resistance between the electrolyte and the anode dominated IR resistance. On the other hand, polarization resistance increased as the Ni/YSZ ratio was increased. Analysis of AC impedance plots indicated that polarization resistance contributed to the number of reaction sites which were ascribed to the triple boundary layer. Moreover, the boundary between nickel particles and zirconia particles in the anode worked as the triple boundary layer. Furthermore, we proposed the double layer anode, which consisted of the interfacial layer and the bulk layer. A cell with a double layer anode exhibited high performance. The interfacial layer and the bulk layer had a strong effect on IR resistance and polarization resistance, respectively. (C) 2000 Elsevier Science B.V. All rights reserved.