Solid oxide fuel cells (SOFC) can be operated with a variety of fuels. In anode-supported SOFC, these fuels may decompose or react catalytically in the anode compartment resulting in mixtures that, in most cases, include high concentrations of H-2 and CO. In this study, the formation of carbon from CO and H-2 mixtures on Ni/YSZ anodes at 1073 K has been investigated using electrochemical and carbon characterization techniques. More carbon is deposited when Ni/YSZ anodes are exposed to CO/H-2 mixtures than to pure CO. Polarization of the anodes reduced the amount of carbon deposited but the extent of the reduction depended on the gas composition. (C) 2009 Elsevier B.V. All rights reserved.