In the present study, the surface of La0.6Sr0.4CoO3 (LSC) was modified via atomic layer deposition (ALD) using CoOx as the modification material. The effect of the ALD CoOx treatment on the LSC-based anode-supported solid oxide fuel cell was analyzed and the ALD CoO5-treated cell was found to exhibit lower power density than that of the bare cell. Based on the electrochemical impedance spectroscopy measurements, it was concluded that this degradation stems mainly from the increased polarization loss, which results from the deterioration of the oxygen surface exchange property. Similarly, examining the bode plot revealed that the impedance at frequencies lower than 1 kHz increased mainly after the CoOx treatment; this increased impedance is believed to be associated with the limitation of O-2 adsorption and dissociation. (C) The Author(s) 2015. Published by ECS. All rights reserved.