The solid oxide fuel cell (SOFC) can operate effectively on a variety of fuels, such as coal-syngas and hydrogen. A Ni-based cermet is a cost-effective anode material for these fuels; however, H2S in the fuel can degrade cell performance by poisoning the Ni-based anode. In this research, nickel- gadolinium doped ceria (Ni-GDC) hybrid anodes were exposed to synthesized coal-syngas and H-2 fuels with various concentrations of H2S at 800 degrees C under constant current conditions. Some SOFC prototypes contained a similar to 5 mu m thick GDC barrier layer inserted between the Ni-GDC hybrid anode and the YSZ electrolyte. A reference electrode was incorporated in the cell to monitor changes in the anode and cathode polarization resistances. The tests showed that the cells with a GDC barrier layer were resistant to H2S at levels up to 1000 ppm in wet H-2 and 100 ppm in syngas during long-term tests. Cells without the barrier layer had a significantly lower tolerance for the H2S impurity. This result, along with post-mortem analyses of the poisoned anode, lead to the hypothesis that the GDC barrier layer assists in the prevention of nickel oxidation at the anode/electrolyte interface by acting as an oxidation catalyst for the H2S. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.067111jes] All rights reserved.