Pd catalyzed Sr_0.92Y_0.08TiO_3-δ/ Sm_0.2Ce_0.8O_2-δ anodes in solid oxide fuel cells

The effects of palladium (Pd) on Sm_0.2Ce_0.8O _2-δ coated Sr_0.92Y_0.08TiO _3-δ (SDC/SYT) anodes were investigated for H₂ and CH₄ fuels. The electrochemical oxidations of both H₂ and CH₄ were accelerated by Pd impregnation. Moreover, Pd in the SDC/SYT (Pd-SDC/SYT) anode improved the cell performance by a factor of approximately 2 for H₂ and 1.5 for CH₄. The open circuit voltage (OCV) of the wet CH₄ fuel increased with increasing temperature for both the SDC/SYT anode cell and Pd-SDC/SYT anode cell, which differs from that of the H₂ fuel. Notably, the OCV values of the Pd-SDC/SYT anode cell using wet CH₄ were much higher than those using wet H₂. We observed differing potentials for the reformed gases after the out-of-cell catalyst experiment, and the CH₄ fuel with the Pd-SDC catalyst layer agreed well with the OCVs of the Pd-SDC/SYT anode cell with directly introduced wet CH₄ fuel. These results indicate the OCVs were higher than the theoretical values based on electrochemical hydrogen oxidation at increased temperatures in the Pd-SDC/SYT anode cell because of the lower water partial pressure caused by the increased steam reformation activity of Pd.