Structural analysis and electrochemical properties of cobalt-doped Sr0.9Ce0.1MnO3-δ cathode for IT-SOFCs

Cobalt was doped into the Ce-doped SrMnO3 system to enhance the low ionic conductivity of Ce-doped SrMnO3 (SCM) for solid oxide fuel cell cathode application. Structural and conductivity changes as a function of the Co content were investigated. Sr0.9Ce0.1Mn1-xCoxO3-delta (SCMCo, x = 0.1, 0.2, 0.3) cathode materials were synthesized by an EDTA citrate complexing process, which yielded a single perovskite structure, and the lattice volume was expanded by substituting Ce and Co ions. The increased lattice volume was attributed to a decrease in the valence state of the manganese and cobalt and an increase in the oxygen vacancy concentration. An increase in the concentration of oxygen vacancies with increasing Co content was identified by thermogravimetric analysis. The electrical conductivity decreased with increasing Co content, which was attributed to an increase in the activation energy for polaron hopping. Although the electrical conductivity was decreased by cobalt-doping, the polarization resistance of SCMCo also decreased significantly (from 5.611 to 1.171 Omega cm(2) at 800 degrees C). The decreased polarization resistance is attributed to enhanced oxygen-ion transfer kinetics with cobalt-doping. We conclude that cobalt substitution leads to enhancement in the electrochemical properties of the cathode due to an increase in oxygen vacancy concentration.