Deposition of chromium species at Sr-doped LaMnO3 electrodes in solid oxide fuel cells - II. Effect on O-2 reduction reaction

The O-2 reduction reactions on Sr-doped LaMnO3 (LSM) electrodes in solid-ox ide fuel cells in the absence and presence of a chromia-forming alloy metal lic interconnect have been investigated. Similar to those in the absence of the chromia-forming alloy, the O-2 reduction reactions on LSM electrodes i n the presence of chromia-forming alloys are limited by two electrode proce sses, the diffusion of oxygen species on the LSM surface and the migration of oxygen ions into zirconia electrolyte. In the presence of chromia;formin g alloy, the dissociative adsorption and diffusion of oxygen on the LSM ele ctrode surface are inhibited by the gaseous Cr species (e.g.:, CrO3), and t he migration processes of oxygen ions into zirconia electrolyte are inhibit ed by the solid Cr species [e.g., Cr2O3/(Cr, Mn)(3)O-4] deposited on the el ectrolyte surface. The inhibiting effect of the solid Cr species becomes in creasingly dominant on the O-2 reduction with the polarization time. The me chanism and kinetics of the O-2 reduction on the LSM electrodes in the abse nce and presence of chromia-forming alloy are discussed. (C) 2000 The Elect rochemical Society. S0013-4651(00)02-114-5. All rights reserved.