The effects of palladium introduction on the catalytic activity of LSCF composite cathodes are investigated by comparing the performance of LSCF-GDC and Pd-LSCF-GDC cathodes. Pd-LSCF-GDC cathodes were prepared by impregnation of Pd and LSCF precursor into GDC scaffold separately in two steps. The electrochemical results show that the introduction of Pd promotes the catalytic activity of LSCF-GDC cathodes under the condition of both heating and cooling processes. The promotion is related to the existing state of Pd with LSCF under different conditions. According to in-situ high temperature XRD and XPS results, the PdO phase is stable at temperature below 700 degrees C, and decomposed to Pd metal at 700-800 degrees C during heating process. Combination XRD with TG-DSC analysis confirms that some Pd changes into Pd0 phase at 837 degrees C. Correspondingly, the phase composition changed little and the coexistence of Pd and tiny PdO is stable in the cooling process from 850 to 25 degrees C. Copyright (C) 2016, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.