Tradeoff optimization of electrochemical performance and thermal expansion for Co-based cathode material for intermediate-temperature solid oxide fuel cells

Solid oxide fuel cell (SOFC) is a new electric power generation system with the advantages of high efficiency, no emissions of pollutant, and a wide range of fuels. Layered perovskite oxides have received extensive attention as promising cathode materials for SOFCs because of their faster diffusion coefficient and transport kinetics of oxygen compared to those of ABO3-type perovskite oxides. With the goals of lowering the thermal expansion coefficient (TEC) and maximizing electrochemical properties, this study focuses on the copper (Cu) effect in PrBa0.5Sr0.5Co2-xCuxO5+δ (x = 0, 0.5, and 1.0) layered perovskite oxides by investigating their structural characteristics, electrical properties, and electrochemical performance. The electrical conductivity decreases with increasing Cu content, mainly due to the decreasing amount of Co3+/4+. The average TEC values are also identified and the substitution of Cu for Co is beneficial to lower the TEC by suppression of the spin state transitions of Co3+ and reduction of Co4+. To better understand the thermodynamic behavior of the materials while checking redox stability, coulometric titration experiment is performed. We also investigate the electrochemical performance of PrBa0.5Sr0.5Co2-xCuxO5+δ cathode materials using a Ni-GDC anode-supported cell. All samples show sufficiently high power density around over 1.0 W cm−2 at 600 °C.