Synthesis and Stability of SrxNiyOz Chromium Getter for Solid Oxide Fuel Cells

Abstract

Stability of SrO-NiO solid solution synthesized from low cost alkaline earth and transition metal nitrate salts is studied for application as a gaseous chromium getter in solid oxide fuel cells (SOFC). Phase identification and its evolution has been examined using high temperature in-situ X-ray diffraction (HT-XRD) whereas thermal stability and morphology of compounds have been studied using XRD in combination with scanning electron microscopy (SEM). Synthesized SrxNiyOz powder remains stable up to 900°C in air, whereas exposure above 950°C leads to its dissociation into separate SrO and NiO phases. Presence of SrO in powder reacts with H2O and CO2, present in atmospheric air, resulting into pulverization due to volume change and the formation of hydroxides and carbonates. Thermogravimetric analysis (TGA) of the pulverized powders show approximately 20% weight loss due to the evaporation of hydroxyl and carbonate groups. Chemical stability of SrxNiyOz is considered essential in order to prevent pulverization and flaking of the getter coating applied over ceramic honeycomb or foam substrates. Chromium getter is considered a cost effective and reliable means to mitigate cathode poisoning in high temperature electrochemical systems such as solid oxide fuel cells, solid oxide electrolysis cell (SOEC) and oxygen transport membranes (OTM).