Effect of Chromium Poisoning on Performance of Sr-Doped LaMnO 3 (LSM)-Based Cathode in Anode-Supported Solid Oxide Fuel Cells

Ni-YSZ anode-supported planar solid oxide fuel cells (SOFCs), comprised of a Sr-doped LaMnO 3 (LSM) + yttria-stabilized zirconia (YSZ) cathode active layer and a LSM cathode current collector layer, are fabricated. Electrochemical performance tests of the cells with and without chromia-forming alloy interconnect in the temperature range 700 - 800°C are conducted. Humidified hydrogen (97% H 2 - 3% H 2 O) is used on the anode side, and oxygen and water vapor contents on the cathode side are varied, in order to control the rate of Cr vaporization. The cathode performances with and without the Cr environment are analyzed by estimating the polarization losses at the cathode. This is done with the help of impedance spectroscopy measurements and curve-fitting the experimentally measured voltage vs current density (V-i) plots to a polarization model. Microstructures of the cathode cross sections are observed before and after the tests to quantify the effects of Cr deposition. Based on these experimental and analytical results, the effects of Cr poisoning on performance of LSM-based cathode under various conditions are evaluated, and mechanisms of Cr poisoning are proposed.