In-Cell Chromium Getters to Mitigate Cathode Poisoning in SOFC Stack

Abstract

Incorporation of a porous and electrically conducting chromium getter layer consisting of a mixture of complex metal oxide getter and electrically conducting perovskite phases has been examined as a potential cost effective approach for the capture of gaseous chromium species originating from the metallic interconnect alloys conventionally used in SOFC stacks. Screen printed/ brush coated SrxNiyOz and conventional LSM/LSCF containing porous layer, deposited on the cathode surface, was electrically tested in a half cell configuration (3%H2O-Air/Pt//YSZ//LSM/Getter/3% H2O-Air-CrOx) at 850 °C for 100 hours. Cell current at 0.5 V bias was monitored and electrochemical impedance spectra (EIS) in frequency range of 0.5 Hz to 200 kHz were obtained at 1-hour interval with 10 mV sinusoidal amplitude. Post tested cells were analyzed for chromium concentration profile, reaction products chemistry and morphological changes. Our observations indicate that the gaseous chromium predominantly concentrates in the getter layer. The bulk electrode and electrode-electrolyte interface remain free of chromium. The electrical performance remains largely stable as evidenced by I-t and EIS data obtained during the test. Experimental details and results will be presented and discussed.