Single chamber anode-supported fuel cells are investigated under several methane-oxygen-nitrogen atmospheres at intermediate temperatures (500 degrees C-700 degrees C). Ce-0.9Gd0.1O1.95 (CGO) is chosen as electrolyte and deposited by screen-printing onto NiO-CGO anode pellets. A cathode composed of 70 wt% La0.6Sr0.4Co0.2Fe0.8O3-delta (LSCF) and 30 wt% of CGO is screen-printed onto the electrolyte. Thermogravimetric analyses of anode reduction are performed at 700 degrees C. Carbon deposition is observed under diluted methane but a successful reduction is obtained after an initialization under diluted methane followed by a final treatment under methane-to-oxygen ratio (R-mix) of 2. Anode-supported fuel cells are investigated regarding the working temperature and R-mix. Two types of cells are prepared with modifications of the electrolyte microstructure. For both cells tested, the Open Circuit Voltage (OCV), the power density and the fuel utilization increase when R-mix and temperature decrease. The electrolytes of both cells have a porous microstructure and the electrolyte of the second cell, with the highest thickness, brings better performances. At 600 degrees C for R-mix = 0.6, the maximum power density is improved from 60 for the first cell to 160 mW cm(-2) for the second cell. Comparing the fuel utilization, it increases from 3% for the first cell to 6% for the second one for the same testing conditions. (C) 2013 Elsevier B.V. All rights reserved.