High Performance Low Temperature Solid Oxide Fuel Cells with Alkali Metal Carbonate Additives in Co-Doped Ceria Electrolyte

Abstract

Doped ceria-carbonates composites are a new class of electrolytes for low temperature solid oxide fuel cells, these show very high ionic conductivity due to fast interfacial transport [1-2]. As reported by Chockalingum and Basu [3], 25 wt% (LiNa)2CO3-GDC electrolyte exibited an ionic conductivity of 0.17 S cm−1 at 550 °C and lowest activation energy of 0.127 eV in the temperature range 550–800 °C. To further improve the ionic conductivity, a series of calcium gadolinium/neodymium/samarium co-doped cerium oxide, M0.2CaxCe0.8-xO2 (x = 0.01 to x = 0.1) (M= Gd, Nd, Sm) have been synthesised by solgel method. The electrolytes have been physically and electrochemically characterized with respect to their thermal behaviour, phase, microstructure, elemental analysis and electrochemical performance using thermogravimetric analysis, X-ray diffraction (XRD), scanning electron microscopy, Transmission electron microscopy (TEM), Energy-dispersive X-ray spectroscopy and electrochemical impedance spectroscopy respectively. The particle size of as synthesized electrolyte powders is ~ 20 nm as observed from the TEM. XRD results of the prepared electrolytes show that the powders are phase pure. The gadolinium calcium co-doped ceria lithium sodium carbonate (25% (LiNa)2CO3-Gd0.2Ca0.05Ce0.75O2) composite electrolytes exhibit high ionic conductivity (0.3 Scm-1 at 650°C), as it combines both the advantages of co-doping and the composite effect. Co-doped composite electrolytes show higher conductivity and stability due to the presence of calcium than the previously investigated composite electrolytes of (LiNa)2CO3-GDC [4, 5].