Cr-poisoning of a LaNi0.6Fe0.4O3 cathode under current load

This study demonstrates the significant impact of Cr-poisoning on the performance of the $LaNi_{0.6}Fe_{0.4}O_3$ (LNF) SOFC cathode under current load. Volatile Cr-species, originating from a porous metallic foam, enter the working electrode and modify both the LNF cathode layer and the $Gd_{0.4}Ce_{0.6}O_{1.8}$ (GDC) barrier layer, causing increasing overpotential and cell impedance. The increase of the ohmic resistance is caused by a decrease of the in-plane electronic conductivity of the LNF layer (due to Cr incorporation and Ni removal from the LNF perovskite lattice) combined with a deterioration of the ionic conductivity of the GDC barrier layer due to reactivity with Cr resulting in formation of a $GdCrO_{3}$-phase. The increase of the polarisation resistance is caused by a decrease of the electrochemical activity of the LNF surface towards oxygen reduction reaction at the triple phase boundary (TPB) due to Cr-incorporation in the outer shell of the LNF grains. Chemical reaction and electrochemically driven reaction of volatile Cr-species with LNF and GDC contributes to the extrinsic degradation of the LNF cathodes under current load.