An H2S-Tolerant Ni-GDC Anode with a GDC Barrier Layer

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, H 2 S 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 H 2 S at 800°C under constant current conditions. Some SOFC prototypes contained a ∼5 μm 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 H 2 S 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 H 2 S 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 H 2 S.