Oxygen reduction on strontium-doped LaMnO 3 cathodes in the absence and presence of an iron–chromium alloy interconnect

Abstract

Oxygen reduction on a Sr-doped LaMnO 3 (LSM) electrode of a solid oxide fuel cell (SOFC) is investigated in the absence and the presence of a Fe–Cr alloy interconnect. The results show that oxygen reduction is controlled by a surface exchange reaction that involves dissociative adsorption and diffusion of oxygen on the LSM electrode surface, and migration of oxygen ions from the LSM to the yttria stabilized zirconia (YSZ) electrolyte lattice at the three-phase boundary (TPB). In the presence of Fe–Cr alloy, the reaction order and activation energy of the surface exchange process are similar to those in the absence of Fe–Cr alloy. This indicates that the presence of gaseous chromium species simply reduces the active sites for the surface exchange reaction by blocking oxygen vacancy formation on the LSM electrode surface. On the other hand, the Cr 2O 3/(Cr,Mn) 3O 4 solid species deposited on the YSZ electrolyte surface primarily inhibits the migration of oxygen ions into the YSZ electrolyte, as indicated by a significant increase in the activation energy of the migration process of the oxygen ions into YSZ electrolyte.