Chromium poisoning of the porous composite cathode effect of cathode thickness and current density

Electrochemical behavior of the {La0.65Sr0.3MnO3(LSM)/porous functional layer(FL)/8 mol % Y2O3-stabilized ZrO2(8YSZ) electrolyte} half cell in the presence of a Cr source was studied by dc method and impedance spectroscopy. The porous FL was made of a LSM and 8YSZ powder mixture. The degradation rate of the cell was found to depend strongly on the FL thickness. The increase in the thickness of the FL up to 13 mu m leads to a significant reduction of the Cr poisoning of the cathode. The effect of high current density (up to 0.5 A/cm(2)) on the long-term performance of half cells in the presence of chromium source was investigated. A few processes occur near the {LSM/8YSZ/gas} contact under current load in the presence of a chromium source: chemical transformations of this contact accompanied by the formation of chromium oxide under a relatively high current load, destruction of the electrolyte and penetration of chromium into the electrolyte along the grain boundaries. The chemical nature and rate of the transformations taking place near the {LSM/8YSZ/gas} contact under current load, most probably, determine the electrochemical performance of the cell for the initial operation period whereas the two other processes could contribute to the degradation during long-term performance. (c) 2007 The Electrochemical Society.