Dry methane with different concentrations is directly fed to solid oxide fuel cells (SOFCs) with a Ni-yttria-stabilized zirconia (Ni-YSZ) anode and a Ni-scandia-stabilized zirconia (Ni-ScSZ) anode. The anode outlet gases are measured in situ by gas chromatography (GC) to study the reactions of dry methane at different current densities. The comparison between the measured open-circuit voltages (OCVs) and theoretical values, the quantitative analysis of components under different current densities and the activation energy analysis of elementary reactions of CH4 are investigated to identify the types of reactions occurring to methane in SOFCs. It is found that reactions of partial oxidation, CH4 + 2O(2-) -> CO + H2O + H-2 + 4e(-), CH4 + 3O(2-) -> CO + 2H(2)O + 6e(-). and complete oxidation occur to CH4 at the Ni-based anodes in sequence while the current density increasing. (C) 2010 Elsevier B.V. All rights reserved.