Solid oxide fuel cells (SOFCs) are promising energy conversion systems for the next generation. High-temperature operation of this electrochemical device offers high fuel flexibility as well as high energy conversion efficiency. Currently, methane is widely utilized as the main fuel source for the residential SOFC cogeneration system, and the pre-reformed gas is supplied to the anode chamber. In this case, the anode is requested to be active for the reforming reaction of hydrocarbons as well as the electrochemical oxidation of fuels. The tolerance to carbon deposition is also an important property to provide against accidents of the reforming system because the hydrocarbon will be directly introduced to the anode.

Recently, Kubota has reported the strong chemical interaction between Ni and GDC (Gd₂O₃‒CeO₂) for the Ni‒GDC cermet anode in solid oxide fuel cells [1]; CeO₂ species migrated on the Ni surface after the exposure to the reducing atmosphere. Generally, such a chemical interaction is promoted by the redox treatment. In this study, then, the influence of redox treatment on the chemical interaction between Ni and doped ceria was studied to design the cermet anode with high tolerance to carbon deposition.

The Ni‒GDC cermet subjected to the redox treatment showed high tolerance to carbon deposition in dry methane. Furthermore, the redox treatment did not affect the mechanism of electrochemical hydrogen oxidation in wet hydrogen atmospheres. We also demonstrated the stable power generation of the single cell with the optimized Ni‒GDC anode in a wet methane atmosphere.

Acknowledgements

This study was supported by Japan Science and Technology Agency (JST), CREST.

Reference [1] J. Kubota, The 23th Symposium on Solid Oxide Fuel Cells in Japan, Extended Abstract, p34-37 (2014).