화학공학소재연구정보센터
Journal of the Electrochemical Society, Vol.161, No.4, F551-F560, 2014
Characterization of Doped Yttrium Chromites as Electrodes for Solid Oxide Fuel Cell by Impedance Method
Redox-stable ceramic electrodes, Co and Ni doped yttrium chromites, for solid oxide fuel cell (SOFC) are characterized by electrochemical impedance spectroscopy (EIS) in various P-O2 and P-H2 atmosphere. The polarization resistances for Y0 8Ca0.2Cr0 8Co0.2O3-delta (YCCC) and Y0.8Ca0.2Cr0.9Ni0 1O3-delta (YCCN) on yttrium stabilized zirconia (YSZ) electrolyte are 0.96 and 8.4 Omega cm(2) in wet H-2, 1.2 and 36.7 Omega cm(2) in air at 850 degrees C, respectively. For the anode Application, the rate-limiting steps (RDS) are identified as charge transfer and surface diffusion for both YCCC and YCCN. The primary active zone in YCCN is three-phase boundary (3PB) but extends to a small portion of the electrode bulk in the YCCC anode. For the cathode application, O-2 dissociative adsorption or diffusion is one of the RIDS for both electrodes, and the active zone is limited to the 3PB area. The influence of electrolyte to electrode performance is investigated by replacing YSZ electrolyte with scandium stabilized zirconium (SSZ). Smaller polarization resistances are observed on each electrode in both wet H-2 and air atmospheres. Replacement of electrolyte can alter not only the rate of charge transfer process but also in some cases other surface processes not related to the electrolyte directly. It is proposed that the impact of the electrolyte on each electrode process is passed down as in a chain and the charge transfer step functions as the first ring in the chain. The best performance is obtained with the YCCC/SSZ combination, 0.49 and 1 Omega cm(2) in wet H-2 and air at 850 degrees C, respectively, making YCCC a promising electrode. (C) 2014 The Electrochemical Society.