Oxygen transport, thermal and electrochemical properties of NdBa0.5Sr0.5Co2O5+δ cathode for SOFCs

In this study, the crystal structure, thermal, oxygen transport, electrical conductivity and electrochemical properties of the perovskite NdBa0.5Sr0.5Co2O5+delta (NBSC55) are investigated. In the temperature range of 250 degrees C-350 degrees C, the weight loss upon heating was due to a partial loss of lattice oxygen and along with a reduction of Co(4+ )to Co3+. The tend of weight-loss slows down as temperature increased above 350 degrees C indicating a reduction of Co3+ to Co2+ during this stage. The oxygen migration is dominated by surface exchange process at high temperature range (650-800 degrees C); however, the bulk diffusion process prevails at low temperature range (500-600 degrees C). For long-term testing, the polarization resistance of NBSC55 increases gradually form 3.13 Omega cm(2) for 2 h to 3.34 Omega cm(2) for 96 h at 600 degrees C and an increasing-rate for polarization resistance is around 0.22% h(-1). The power density of the single cell with NBSC55 cathode reached 341 mW cm(-2) at 800 degrees C.