Degradation mechanism of Ni-based anode in low concentrations of dry methane

Degradation mechanism of Ni0.5Cu0.5-Gd0.2Ce0.8O1.9 (CGO) bimetallic anode in low concentrations of dry methane is studied with a (La0.25Sr0.25)(0.95)MnO3-delta-CGO cathode supported SOFC. Leakage tests suggested that as-prepared cells are well-sealed by glass ring at elevated temperatures. OCV of as-prepared cell in each concentration of CH4 is over 1.2 V. indicating that the ScSZ electrolyte film prepared by a dual drying pressing method is dense enough. It is found that rapid degradation phenomenon easily occurred at relatively high current density in 7.4 and 14.8% of dry methane in the performance test. XRD and EIS analyses indicated that the degradation of the Ni0.5Cu0.5-CGO anode at high current density could be mainly attributed to the re-oxidation of Ni. GC results showed that the re-oxidation of Ni always occurred at a relatively high p(H2O), which always appeared at a relatively high current density. The degraded cell is successfully recovered by burning the anode with O-2 and re-reducing with H-2. (C) 2011 Elsevier B.V. All rights reserved.