Insight into the Reaction Mechanism of (La0.58Sr0.40)(Co0.20Fe0.80)O3-delta Cathode with Volatile Chromium Species at High Current Density in a Solid Oxide Fuel Cell Stack

Anode-supported solid oxide fuel cells with different Cr protection layers on the metallic interconnect were operated in a short stack at 700 degrees C for 1240 h. The current density was raised sequentially from 0.5 A cm(-2) during the first 240 h of operation to 0.75 A cm(-2) for a further 1000 h. After operation, the (La,Sr)(Co,Fe)O3-delta (LSCF) cathode layers were analyzed with respect to Cr interaction by both wet chemical and microstructural methods. For cells equipped with interconnects coated with a dense APS protection layer, the amount of Cr on the cathode was in the range of a few mu g. For cells with a porous WPS coating on the interconnect, the amount of Cr was in the range of 110-160 mu g cm(-2) and Cr-containing phases were detected by SEM analysis both on top of the cathode layer and also at the LSCF/GDC interface, which has rarely been observed before. In addition, a deterioration of the cathode microstructure near the LSCF/GDC interface was observed. With respect to the high current density during operation, a theory was developed which explains both the Cr deposition at the LSCF/GDC interface and also the deterioration of the cathode. (C) The Author(s) 2017. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.