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Redox-reversible electrode material for direct hydrocarbon solid oxide fuel cells.

Solid oxide fuel cells (SOFCs) have the potential to directly operate on hydrocarbon fuels such as natural gas, however, the state-of-the-art nickel-based anodes have significant issues such as coking, sulfur poisoning and redox instability. We report a novel double perovskite oxide Sr2Co0.4Fe1.2Mo0.4O6-δ (SCFM) that possesses excellent redox reversibility, and can be used as both the anode and cathode. At 900 oC in a reducing environment, double perovskite phase SCFM transforms into a composite of the Rud-dlesden-Popper structured oxide Sr3Co0.1Fe1.3Mo0.6O7-δ (RP-SCFM) with the Co-Fe alloy nanoparticles homogeneously distribut-ed on the surface of RP-SCFM. At 900 oC in an oxidizing atmosphere, the composite transforms back into the double perovskite phase SCFM. The mixed ionic-electronic conductivity and excellent oxygen reduction reaction catalytic activity make SCFM an excellent cathode material for SOFCs. When SCFM is used as the anode, excellent performance and stability are achieved on ei-ther direct oxidation of methane as fuel or operation with sulfur-containing fuels. The excellent redox reversibility coupled with outstanding electrical and catalytic properties manifested by SCFM will enable a broad application in energy conversion and stor-age devices.