Symmetrical electrochemical cells with various electrodes, viz. La0.6Sr0.4C0.2Fe0.8O2-delta, (LSCF), LSCF-(Gd0.2Ce0.8O3) GDC, LSCF-platinum (Pt) and LSCF-GDC-Pt, were fabricated for the purpose of investigating their potential use in intermediate temperature solid oxide fuel cells (IT-SOFCs) and the relationship between the electrocatalytic characteristics and electrode microstructure of the electrochemical cells. Both the LSCF-GDC and LSCF-Pt composite electrodes seemed to perform better than the LSCF electrode for oxygen reduction. The polarization resistance was significantly reduced in the case of the composite electrodes. The incorporation of Pt particles in the LSCF electrode was found to be effective over the entire temperature range for which measurements were taken. Adding the GDC resulted in microstructural changes taking place in the LSCF electrode, and a low polarization resistance was obtained at temperatures of 600 degrees C and lower. Based on the impedance spectrum data, it was considered that Pt might accelerate the oxygen adsorption at high temperature. On the other hand, GDC seemed to serve as a fast oxygen ion diffusion path at lower temperatures. (c) 2005 Elsevier B.V. All rights reserved.