Influence of Metal Sulfides as Anode Catalysts on Performance of H_2S SOFC

摘要

Two anode catalysts with Pt, MoS2 and composite metal sulfides (MoS_2+NiS), are investigated for electrochemical oxidation of hydrogen sulfide in solid oxide fuel cell (SOFC) at temperatures 750―850℃. The catalysts comprising MoS_2 and MoS_2+NiS exhibited good electrical conductivity and catalytic activity. MoS_2 and composite catalysts were found to be more active than Pt, a widely used catalyst for high temperature H_2S/O_2 fuel cell at 750―850℃. However, MoS_2 itself sublimes above 450℃. In contrast, composite catalysts containing both Mo and transition metal (Ni) are shown to be stable and effective in promoting the oxidation of H_2S in SOFC up to 850℃. However, electric contact is poor between the platinum current collecting layer and the composite metal sulfide layer, so that the cell performance becomes worse. This problem is overcome by adding conductive Ag powder into the anode layer (forming MoS_2+NiS+Ag anode material) to increase anode electrical conductance instead of applying a thin layer of platinum on the top of anode.