Effect of oxide on carbon deposition behavior of CH4 fuel on Ni/ScSZ cermet anode in hihh temperature SOFCs

This work investigated the effect of oxide in Ni-zirconia cermets on the carbon deposition behavior in internal reforming SOFCs. Within 800-1000 degrees C, carbon deposition was found to decrease with increasing temperature on Ni/ScSZ cermet anodes at a low oxygen/carbon ratio (O/C=0.03) during anodic oxidation of methane. On the contrary, an opposite trend was observed on Ni/YSZ under the same conditions, consisting with the temperature dependence of carbon deposition predicted by a thermodynamic equilibrium calculation. Results of temperature-programmed-reduction (TPR) of NiO mixed with YSZ or ScSZ indicated that interaction of Ni with ScSZ is stronger than that with YSZ. The stronger interaction was corroborated by observed tendency of inhibiting Ni agglomeration by both BET specific surface area analysis and SEM observation. It was also found that the dependence of CO2 production rate monitored by GC on current density showed a similar dependence trend of the equilibrium CO2 content on O/C ratio. A model in which H2Oad enrichment effects on Ni surface by anodic current depend on the interaction between Ni and the oxide in Ni cermet was proposed to explain the different carbon deposition behaviors between Ni/YSZ and Ni/ScSZ cermets. (c) 2005 Elsevier B.V. All rights reserved.