Microstructural and chemical characterization of chromium transport from interconnects in intermediate temperature solid oxide electrolysis (IT-SOE)

摘要

Ferritic stainless steels (FSS) are known to form volatile chromium species at elevated temperatures in oxidizing atmospheres, thus leading to chromium poisoning of SOEC electrodes. We have studied chromium transport from FSS interconnects (ThyssenKrupp VDM Crofer~R 22 APU, Aperam K41X) coated with (La_(0.8)Sr_(0.2))(Mn_(0.5)Co_(0.5))O_(3-δ) (LSMC) or La(Ni_(0.6)Fe_(0.4))O_(3-δ) (LNF) electrode contact layers at a temperature of 700°C in pure oxygen. While the contact layers significantly decreased the emission of Cr vapors from the alloys, up to 4 atom% of Cr were detected throughout the contact coatings by energy dispersive x-ray spectroscopy after 3000h (Fig.1a). The emission of Cr from various combinations of interconnect materials and contact layers has also been analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES). The introduction of a dense (Co,Mn)3O4 coating on the steel surface prevented the diffusion of Cr into the contact layers (Fig 1b) and is expected to lead to extended lifetimes of interconnects and SOE cells by reducing Cr transport to the electrode by up to 75%.