Electrochemical characteristics of electrospun La_0.6Sr _0.4Co_0.2Fe_0.8O_3-δ-Gd _0.1Ce_0.9O_1.95 cathode

The poor activity of cathode materials for electrochemical reduction of oxygen in intermediate and low temperature regime (<700 °C) is a key obstacle to reduced-temperature operation of solid oxide fuel cells (SOFCs). In our previous work, the direct methane fuel cell exhibits approximately 1 W cm^-2 at 650 °C in hydrogen atmosphere without any functional layers when the electrospun LSCF-GDC cathode was applied into the La ₂Sn₂O₇-Ni-GDC anode-supported cell, which is approximately two times higher performance than 0.45 W cm^-2 of the cell with the conventional LSCF-GDC cathode. For detailed analysis of the fibrous cathode, the symmetrical cells with the electrospun and conventional LSCF-GDC cathode are fabricated, and then their electrochemical characteristics are measured by using electrochemical impedance spectroscopy (EIS). Each resistance contribution is determined by equivalent circuit consisting of a series resistance (R_s) and three arcs to describe the polarization resistance of the cathode. Total polarization resistance of the electrospun LSCF-GDC cathode is approximately two times lower than that of the conventional LSCF-GDC cathode at 650 °C, which is attributed to fibrous microstructures and large amount of pores in 100-200 nm. The results correspond to the difference in the cell performances obtained from our previous work.