The oxygen incorporation process is investigated in a new insight based on the electrical conductivity relaxation (ECR) technique. A theoretical method is proposed to qualitatively evaluate the electrochemical performance for the oxygen reduction reaction on the electrocatalyst for solid oxide fuel cells (SOFCs). In this method, the change in oxygen partial pressure to conduct the ECR process corresponds to an electromotive force while the surface reaction rate to a current density. Accordingly, the polarization resistance as well as the current voltage relation can be derived for the oxygen reduction reaction occurred on the electrocatalyst-gas two-phase interface and at the electrocatslyst-electrolyte-gas three-phase boundary. The method is demonstrated with our previously experimental results on the composite system consisting of lanthanum strontium cobalt ferrite and samaria-doped ceria, which is a typical composite cathode for intermediate-temperature SOFCs. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.