Intermediate Temperature Solid Oxide Fuel Cells Using a New LaGaO3 Based Oxide Ion Conductor: I. Doped as a New Cathode Material

Abstract

LaGaO,-based perovskite oxides doped with Sr and Mg exhibit high ionic conductivity over a wide range of oxygen partial pressure. In this study, the stability of LaGaO,-based oxide was investigated. The LaGaO,-based oxide was found to be very stable in reducing, oxidizing, and CO2 atmospheres. Solid oxide fuel cells (SOFCs) using LaGaO,-based perovskite-type oxide as the electrolyte were studied for use in intermediate-temperature SOFCs. The power-generation characteristics of cells were strongly affected by the electrodes. Both Ni and LnCoO, (Ln:rare earth) were suitable for use as anode and cathode, respectively. Rare-earth cations in the Ln site of the Co-based perovskite cathode also had a significant effect on the power-generation characteristics. In particular a high power density could be attained in the temperature range 973-1273 K by using a doped SmCoO, for the cathode. Among the examined alkaline earth cations, Srdoped SmCoO, exhibits the smallest cathodic overpotential resulting in the highest power density. The electrical conductivity of SmCoO3 increased with increasing Sr doped into the Sm site and attained a maximum at Sm0 ,Sr,,CoO3. The cathodic overpotential and internal resistance of the cell exhibited almost the opposite dependence on the amount of doped Sr. Consequently, the power density of the cell was a maximum when Sm0 ,Sr,,CoO, was used as the cathode. For this cell, the maximum power density was as high as 0.58 W/cm2 at 1073 K, even though a 0.5 mm thick electrolyte was used. This study revealed that a LaGaO,-based oxide for electrolyte and a SmCoO,-based oxide for the cathode are promising components for SOFCs operating at intermediate temperature.

Low-temperature solid-oxide fuel cells

“…In contrast, Sm 0.6 Sr 0.4 CoO 3 shows reasonably high stability and surface activity. 32 Recently, many new materials have been reported that show high activity and stability, such It is also reported that the layered interface of LaCoO 3 /La 2 CoO 4 shows extremely high activity to oxygen dissociation. 35 , 36 To gain a fundamental understanding of the ORR mechanism on these materials, several techniques are being used, such as conductivity relaxation 37 and in situ 38 and ex situ 39 oxygenisotope exchange.…”

High Temperature Fuel Cell

“…Among innumerable oxygen ion conductors viz. ceria, La-gallate (Ishihara et al, 1998) (Manner and Ivers-Tiffee, 1991) are the promising candidates. Fully stabilized zirconia offers the best choice of electrolyte having satisfied criteria of conductivity, chemical stability, durability, etc.…”

Aqueous electrophoretic deposition of YSZ electrolyte layers for solid oxide fuel cells

“…There are basically two approaches to solve this difficulty. One is to employ new electrolyte materials possessing higher ionic conductivity, such as CeO 2 and Bi 2 O 3 [2][3][4]. However, the redox behavior of the former and the insufficient strength and toughness of the latter remain to be solved before they can be practically utilized.…”