Use of Metal Sulfides as Anode Catalysts in H[sub 2]S-Air SOFCs

Anode catalysts comprising MoS 2 and composite metal sulfides have been investigated for electrochemical oxidation of hydrogen sulfide in solid oxide fuel cells (SOFCs) at temperatures up to 850°C. All catalysts exhibited good electrical conductivity and catalytic activity at all temperatures. MoS 2 and composite catalysts were found to be more active than Pt, an established catalyst for high-temperature H 2 S -air fuel cells at 650-830°C. However, MoS 2 itself sublimes above 450°C. In contrast, composite catalysts (M-Mo-S) derived from a mixture of sulfides of Mo and other transition metals (Fe, Co, Ni) have been shown to be stable and effective for electrochemical conversion of H 2 S in SOFCs up to 850°C. Electrical contact is poor between platinum current collecting layers and metal sulfide anode catalysts. This problem has been overcome by mechanically mixing conductive Ag powder into the anode layer, instead of applying a thin layer of platinum to the anode.