Ionic transport in (nano)composites for fuel cells

Abstract

Several composite materials were produced using ceria nanoparticles (<25 nm) and LiAlO2 (particle size >1 mu m). The oxides were combined with a mixture of Na2CO3 and Li2CO3 (eutectic composition), and fired at temperatures in the 600-700 degrees C range (vacuum assisted in a few cases). The composites were characterized by scanning electron microscopy, X-ray diffraction and impedance spectroscopy, in air, in the 300-600 degrees C range. Irrespective of composition or grain size all samples exhibited the same type of conductivity dependence on temperature, with a steep change close to the carbonates eutectic temperature. At T > 500 degrees C all materials have identical conductivity, indicating that molten carbonates dominate the electrical performance. However, at low temperature (300-450 degrees C) significant differences can be noticed in all composites, with the best performance observed for ceria based composites with larger grain size (close to 135 nm). Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.