Deposition of chromium species at Sr-doped LaMnO3 electrodes in solid oxide fuel cells -: II.: Effect on O2 reduction reaction

The O-2 reduction reactions on Sr-doped LaMnO3 (LSM) electrodes in solid-oxide fuel cells in the absence and presence of a chromia-forming alloy metallic interconnect have been investigated. Similar to those in the absence of the chromia-forming alloy, the O-2 reduction reactions on LSM electrodes in the presence of chromia-forming alloys are limited by two electrode processes, the diffusion of oxygen species on the LSM surface and the migration of oxygen ions into zirconia electrolyte. In the presence of chromia;forming alloy, the dissociative adsorption and diffusion of oxygen on the LSM electrode surface are inhibited by the gaseous Cr species (e.g.:, CrO3), and the migration processes of oxygen ions into zirconia electrolyte are inhibited by the solid Cr species [e.g., Cr2O3/(Cr, Mn)(3)O-4] deposited on the electrolyte surface. The inhibiting effect of the solid Cr species becomes increasingly dominant on the O-2 reduction with the polarization time. The mechanism and kinetics of the O-2 reduction on the LSM electrodes in the absence and presence of chromia-forming alloy are discussed. (C) 2000 The Electrochemical Society. S0013-4651(00)02-114-5. All rights reserved.