A cobalt-free Ba(0.5)Sr(0.5)FeO(3-delta)-Ce(0.8)Sm(0.2)O(2-delta) (BSF-SDC) composite is employed as a cathode for an anode-supported proton-conducting solid oxide fuel cells (H-SOFCs) using BaZr(0.1-)Ce(0.7)Y(0.2)O(3-delta) (BZCY) as the electrolyte. The chemical compatibility between BSF and SDC is evaluated. The XRD results show that BSF is chemically compatible with SDC after co-fired at 1000 degrees C for 6 h. A single cell with a 20-mu m-thick BZCY electrolyte membrane exhibits excellent power densities as high as 792 and 696 mW cm(-2) at 750 and 700 degrees C, respectively. To the best of our knowledge, this is the highest performance reported in literature up to now for BZCY-based single cells with cobalt-free cathode materials. Extremely low polarization resistances of 0.030 and 0.044 Omega cm(2) are achieved at 750 and 700 degrees C respectively. The excellent performance implies that the cobalt-free BSF SDC composite is a promising alternative cathode for H-SOFCs. Resistances of the tested cell are investigated under open circuit conditions at different operating temperatures by impedance spectroscopy. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.