Effect of Cathode Functional Layer on the Electrical Performance of Tubular Solid Oxide Fuel Cell

Abstract

Development of technology related to solid oxide fuel cells at Materials Group, BARC includes synthesis of materials viz. lanthanum strontium manganite (LSM), yttria stabilized zirconia (YSZ), NiO etc. using chemical methods followed by shaping components and integrating into single cells. The indigenously prepared materials are converted to single cells for studies on material characterization and cell performances. This paper presents results of studies on electrical performances of tubular solid oxide fuel cell under hydrogen and oxygen atmospheres and correlates them with the use of cathode functional layers. Studies on symmetrical cells comprising of YSZ electrolyte sandwiched between cathode layers were carried out using electrical impedance spectroscopy (EIS). The EIS results exhibit improvement of area specific resistance (ASR) on incorporation of functional layers. Based on EIS data, double functional layers with varying compositions were incorporated in button cells as well as tubular single cells. Two types of tubular cells were fabricated, electrolyte supported and cathode supported. The electrolyte supported tubular cells were fabricated by making one-end closed tubes of YSZ, followed by coating with porous LSM inside and porous NiO-YSZ layer outside the tubes. On the other hand, tubular cathode supported cells were fabricated by one-end closed porous LSM tubes, followed by subsequent coatings of electrolyte and anode. The cells were characterized for electrical performance from 800 to 1000°C. Electrical power output from electrolyte supported cells with cathode functional layers increased from 300 mW per cell to 500 mW per cell. On the other hand, cathode supported cells exhibited improvement in ASR from ∼ 2 Ωcm2 to < 1 Ωcm2. The results were correlated with microstructure, area of triple phase boundaries and catalytic activity of cathode.