Characterization of thermodynamic, electrical, and electrochemical properties of Sm0.5Sr0.5Co1-xNbxO3-δ (x=0, 0.1) as cathode for IT-SOFCs

Abstract

The thermodynamic and electrical characteristics of the Sm0.5Sr0.5CoO3-δ (SSC) have been studied as a competitive candidate of cathode material for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Some researchers reported that the relationship between cation substitution and stability of perovskite structure based on mixed conductors, and found that Nb doped perovskite exhibits the most stable perovskite structure and it has also the highest electrical conductivity. In this study, we have investigated the structural, electrical, electrochemical, and redox properties of Sm0.5Sr0.5Co1-xNbxO3-δ (SSCNbx) cathodes under conditions relevant to IT-SOFC operation. The SSCNbx (x = 0, 0.05, and 0.1) oxides show gradually decreasing electrical conductivity with increasing Nb doping at the same temperature. The maximum power density of SSCNbx (x = 0.05, 0.1) is lower than that of SSC; however, SSCNbx (x = 0.1) is more stable than SSC considering the thermodynamic behaviour, as determined through redox isotherms. These results suggest that a Nb doped SSC perovskite is suitable, considering its high power density and reasonable redox stability, as an IT-SOFC cathode material.