High temperature proton conductors (HTPCs) based fuel cells directly fed with methane mixtures were investigated. Doped barium zirconate was chosen as electrolyte because of its good chemical stability in CO2 and H2O containing atmosphere. The sintering temperature of doped barium zirconate was decreased down to 1350 degrees C by doping with 1wt.% ZnO. A co-pressing method was used for fabricating anode supported single cell. Flat and reproducible bottom cell of NiO-BZYZn / BZYZn / Pt were produced. OCV measurements, I-V curves, and impedance spectra were recorded in the 600-750 degrees C temperature range. The addition of carbon dioxide to methane improved SOFC stability by suppressing coking in Ni anodes. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.042111jes] All rights reserved.