Preparation, Optimization And Oxygen Reduction Mechanism Of Sm_0.5Sr_0.5CoO₃/La_0.8Sr_0.2Ga_0.8Mg_0.15Co_0.05O₃

Sm0.5Sr0.5CoO3 (SSC) is one kind of excellent cathode materials for intermediate temperature solid oxide fuel cells (ITSOFC) reported recently. There are growing interests in developing high performance SSC supported on doped LaGaO3 electrolytes, and illustrating the mechanism of oxygen reduction over SSC. Multiple techniques, including SEM, XRD, EDAX, Impedance spectrometry, polarization, were applied to study the SSC electrode supported on La0.8Sr0.2Ga0.8Mg0.15Co0.05O3 (LSGMC5) in this thesis. The composition of the electrode and the structure of the SSC/LSGMC5 assembly were optimized, and the oxygen reduction mechanism over corresponding electrodes was studied systematically.The addition of LSGMC5 powders into SSC electrode was effective in improving the performance and the stability of SSC electrode supported on LSGMC5. Both the sintering temperature and the amount of LSGMC5 added into SSC have strongly effect on the performance of the electrode. SSC-LSGMC5 composite electrodes consisted of 15 wt % LSGMC5 sintered at 1473K exhibited the highest activity and stability for electrochemical oxygen reduction.The performance of SSC-LSGMC5 electrode was further improved dramatically by the addition of an LSGMC5 interlayer between an SSC-LSGMC5 electrode and an LSGMC5 electrolyte pellet due to the improved microstructure of the electrode/electrolyte interface. The addition of the interlayer resulted in the shift of the active reaction zone from the electrode/electrolyte interface to the electrode/interlayer interface, which increased the length of the gas/electrode/electrolyte three-phase boundary and the area of the electrode/electrolyte two-phase boundary. The results of electrochemical measurements showed that the polarization resistance of cathode decreased from...