The effect of adding Ce_1-xSm_xO_2-x/2 with Different Sm contents on the electrochemical performance of GdBaCo ₂O_5+δ based composite cathode

In this paper, the Ce_1-xSm_xO_2-x/2 (x = 0.025, 0.05, 0.1, 0.2) samples were synthesized and then mixed with GdBaCo ₂O_5+δ (GBCO) to form GBCO-Ce_1-xSm _xO_2-x/2 composite cathodes. The electrochemical performance of the composite cathodes was investigated by the electrochemical impedance spectroscopy (EIS) as a function of temperature and oxygen partial pressure. The impedance spectra results demonstrated that the introduction of proper Ce_1-xSm_xO_2-x/2 phase remarkably enhanced the electrochemical performance of GBCO cathode and caused a reduction in the total polarization resistance (Rp). Furthermore, as the amount of Ce _1-xSm_xO_2-x/2 in composite cathode was fixed, the variation of Sm content in Ce_1-xSm_xO_2-x/2 also had a significant influence on the electrochemical performance of the GBCO-Ce_1-xSm_xO_2-x/2 cathodes. For example, the Rp of GBCO cathodes containing 10 wt.% Ce_1-xSm_xO _2-x/2 considerably reduced from 0.37 to 0.17 Ω cm² at 600 °C with the decreasing Sm content x from 0.2 to 0.025. The improvement in performance of the GBCO-Ce_1-xSm_xO _2-x/2 cathodes compared to pure GBCO cathode could be mainly attributed to the catalytic activity of Ce_1-xSm_xO _2-x/2 towards the surface diffusion related processes, which was an elementary step in oxygen reduction reaction at cathode.