Stabilization of platinum anode catalyst in a H2S-O2 solid oxide fuel cell with an intermediate TiO2 layer

The performance of supported platinum as an anode catalyst in a hydrogen sulfide solid oxide fuel cell with yttria-stabilized zirconia (YSZ) as the electrolyte has been examined in the temperature range of 700-900degreesC. The highest current density achieved at 800degreesC was 100 mA/cm(2) and the highest power density was 15.4 mW/cm(2), when operated with 5% H2S feed. Increasing the concentration of H2S in the anode feed did not improve the performance of the cell, due to corruption of the platinum anode; the reversible formation and decomposition of PtS on the platinum-YSZ interface led to instability of the electrochemical interface of the Pt catalyst with the YSZ electrolyte. The membrane structure and performance were both stabilized by interposing a thin layer of TiO2 between the Pt anode and YSZ electrolyte. The stabilized open-circuit voltage value depended on flow rates of the anode and cathode feeding gases. This behavior is attributed to the crossover of reactants, which change the partial pressures of product SO2 and H2O. (C) 2002 The Electrochemical Society.