A mechanistic study on the activation process of (La, Sr)MnO3 electrodes of solid oxide fuel cells

The mechanism of the activation process for the O2 reduction on (La0.8Sr0.2)0.9MnO3 (LSM) electrodes is investigated by examining the electrochemical behavior of LSM under cathodic and anodic polarization conditions and the relaxation behavior of LSM under open circuit. A comparative study is also performed on a LSM electrode after dilute acid etching treatment. It has been shown that the segregated SrO has a significant inhibiting effect on the surface exchange process such as dissociative adsorption, incorporation and diffusion of oxygen species on the LSM surface, resulting in the initially very high impedance for the O2 reduction on LSM electrodes. A mechanism involving the incorporation of SrO into LSM lattice with the concomitant removal of cation vacancies is proposed for the activation effect of cathodic current passage/polarization in solid oxide fuel cells.