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 LaNi0.6Fe0.4O3 (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 Gd0.4Ce0.6O1.8 (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 GdCrO3-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.

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► Volatile Cr-species cause degradation of LNF cathodes under current load conditions.
► Overpotential and impedance increase is due to reaction of LNF and GDC with Cr.
► Cr-reactivity is chemically and electrochemically driven.
► Rohmic increases due to the LNF conductivity drop and the GDC ionic transport loss.
► Rpol increases due to the loss of LNF electrochemical activity at TPB.