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 deposit ring around the edge of the LSM electrode coating. The width of the ring was about 60 mu m for an LSM electrode polarized for about 50 h. Overpotential (eta) increases with polarization time. In contrast to eta electrode interface resistance (R-E) measured under open circuit conditions decreases initially after passing the current and remains almost constant with polarization. The results indicate that the deposition process of chromium species may not be dominated by electrochemical reduction processes in competition with O-2 reduction at an early stage of polarization. (C) 1999 Elsevier Science S.A. All rights reserved.