A novel cathode material for proton conducting electrolyte based solid oxide fuel cells (SOFCs) of A-site deficient Ba0.9Co0.7Fe0.2Nb0.1O3-delta (BCFN) has been synthesized and characterized. The A-site deficient BCFN has demonstrated a thermal expansion coefficient (TEC) similar to that of BaZr0.1Ce0.7Y0.2O3-delta (BZCY) electrolyte, enhanced oxygen reduction activity and chemical stability. The application of BCFN in proton-conducting electrolyte-based SOFCs has been investigated, and the SOFCs with Ni-BZCY vertical bar BZCY vertical bar BCFN configuration demonstrate maximum cell power outputs of 180, 240 and 300 mW cm(-2) at 600, 650 and 700 degrees C, respectively. The cell polarization resistance is as low as 0.951, 0.387 and 0.201 Omega cm(2) under open circuit voltage (OCV) at 600, 650 and 700 degrees C, respectively. The cell maximum power density increases from 300 to 356 mW cm(-2) at 700 degrees C after over 118 h operating under a constant current of 300 mA cm(-2). Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.