Deposition of chromium species on Sr-doped LaMnO3 cathodes in solid oxide fuel cells

The system of chromia-forming alloy/Sr-doped LaMnO3 (LSM) electrode/3 mol% Y2O3-ZrO2 (TZ3Y) electrolyte has been investigated at 900 degrees C in air under cathodic polarization conditions. Deposition of chromium species was found to occur preferentially at the TZ3Y electrolyte surface, forming a de posit ring around the edge of the LSM electrode coating. The width of the r ing was about 60 mu m for an LSM electrode polarized for about 50 h. Overpo tential (eta) increases with polarization time. In contrast to eta electrod e interface resistance (R-E) measured under open circuit conditions decreas es initially after passing the current and remains almost constant with pol arization. The results indicate that the deposition process of chromium spe cies may not be dominated by electrochemical reduction processes in competi tion with O-2 reduction at an early stage of polarization. (C) 1999 Elsevie r Science S.A. All rights reserved.