Effect of A-site deficiency in BaCe0.8Sm0.2O3-δ on the electrode performance for proton conducting solid oxide fuel cells

The effect of A-site deficiency in BaCe0.8Sm0.2O3-delta on the electrode performance is investigated using Ba1-xCe0.8Sm0.2O3-delta (x= 0.00, 0.02 and 0.05) to constitute composite anode and cathode with NiO and Sm0.5Sr0.5CoO3 (SSC), respectively. Two overlapped arcs are observed in impedance spectra of the cells with those composite electrodes under open circuit conditions. The low frequency resistances reduce first and then increase with the value of A-site deficiency of BaCe0.8Sm0.2O3-delta in both anode and cathode, while the high frequency resistances keep almost stable with activation energy of 0.65 eV. These results suggest that the high frequency resistances are mainly dominated by the conductivity of electrolyte, while the low frequency resistances are more apt to the electrode activity. With Ba0.98Ce0.8Sm0.2O3-delta substituting for BaCe0.8Sm0.2O3-delta in both anode and cathode, the polarization resistance is 0.339 Omega cm(2) at 650 degrees C, only 421% of that with BaCe0.8Sm0.2O3-delta based electrodes. Meanwhile, maximum power density about 271.0 mWcm(-2) at 650 degrees C is achieved with the modified electrode compositions. (C) 2010 Elsevier B.V. All rights reserved.