Development of a new cathode material for intermediate temperature solid oxide fuel cells

Abstract

Solid oxide fuel cells (SOFCs) are electrochemical energy conversion devices that directly convert the chemical energy to electricity with high conversion efficiency and no pollution emissions. Despite their excellent advantages, the high operating temperature of a conventional SOFC leads to some challenges, such as material compatibility challenges and high costs. As a resolution, intermediate temperature (IT) SOFCs have been introduced, operating from 500 to 700 oC. The main obstacles toward IT-SOFC commercialization, however, are poor oxide-ion conductivity of an electrolyte and low catalytic activity of a conventional cathode, stemming from the reduction of operating temperature. Therefore, considerable efforts have been dedicated in the two areas for the successful performance of IT-SOFCs: improving the ionic conductivity of electrolytes and reducing the polarization resistance of cathodes.

This thesis mainly focuses on the latter one with the aim to develop a novel cathode material with high performance for IT-SOFC applications. The systematic studies for achieving high electrochemical performances and stable thermal properties are presented in the thesis as following,

1. Investigate strontium effects on the electrochemical performances for a simple perovskite oxide, Pr1-xSrxCoO3-d (x = 0.1, 0.3, 0.5, and 0.7). 2. Compare the oxygen transport kinetics between simple and double perovskite oxides in PrBa1-xSrxCo2O5+d (x = 0, 0.25, 0.5, 0.75, and 1.0) systems. 3. Study on sintering and composite effects in for PrBa0.5Sr0.5Co1.5Fe0.5O5+d cathode material for IT-SOFCs. 4. Stabilize thermal expansion of Co-based cathode material by Cu-doping in PrBa0.5Sr0.5Co2O5+d.