Electrochemical Operation of La(Ni,Fe)O 3 under Cr-Poisoning Conditions

Abstract

This study demonstrates the significant impact of Cr-poisoning on the electrochemical operation 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 combined with a deterioration of the ionic conductivity of the GDC barrier layer. 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.