A dense BaZr0.8Y0.2O3-delta (BZY) proton-conducting electrolyte membrane is successfully fabricated on a NiO-BaZr0.1Ce0.7Y0.2O3-delta (NiO-BZCY) anode substrate by a co-pressing process after co-firing at 1400 degrees C. BZY powders are synthesized via a citric acid-nitrate gel combustion process after calcination at 1100 degrees C. The SEM results reveal that the BZY membrane is crack-free, very dense, and 20 mu m thick. A single cell with Sm0.5Sr0.5CoO3-delta-Ce0.8Sm0.2O2-delta (SSC-SDC) as the cathode is assembled and tested with wet hydrogen (2% H2O) as the fuel and static air as the oxidant. The open circuit voltages (OCVs) are 0.953, 0.987, 1.014, and 1.039 Vat 700, 650, 600, and 550 degrees C, respectively. A maximum power density of 170 mW cm(-2) is obtained at 700 degrees C. Resistances of the testing cell are investigated under open circuit conditions at different operating temperatures by impedance spectroscopy. (C) 2010 Elsevier B.V. All rights reserved.