A dense BaZr0.8Y0.2O3-δ (BZY) proton-conducting electrolyte membrane is successfully fabricated on a NiO-BaZr0.1Ce0.7Y0.2O3-δ (NiO-BZCY) anode substrate by a co-pressing process after co-firing at 1400 °C. BZY powders are synthesized via a citric acid-nitrate gel combustion process after calcination at 1100 °C. The SEM results reveal that the BZY membrane is crack-free, very dense, and 20 μm thick. A single cell with Sm0.5Sr0.5CoO3-δ-Ce0.8Sm0.2O2-δ (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 V at 700, 650, 600, and 550 °C, respectively. A maximum power density of 170 mW cm-2 is obtained at 700 °C. Resistances of the testing cell are investigated under open circuit conditions at different operating temperatures by impedance spectroscopy. © 2010 Elsevier B.V. All rights reserved.