PNNL

Abstract

Abstract: Ceria particles with different specific surface areas were contaminated with chloride and water, then heat treated at 500 and 900 °C, to investigate the sorption behaviour onto the metal oxide. The association of chloride with the particles was investigated using electron microscopy and energy dispersive x-ray analysis. Results from xray photoelectron spectroscopy, x-ray absorption spectroscopy (XAS) and infrared spectroscopy show that the amount of chloride and water adsorbed on the particles increases with surface area. These species are mostly removed upon heat treatment, from 6.3 to 0.8 at% Cl- on high specific surface area, and 1.4 to 0.4 at% on low specific surface area particles. Lattice parameters determined by x-ray diffraction reveal that chloride is not incorporated into the bulk ceria structure, but crystal size does increase upon contamination. Sintering of contaminated high specific surface area particles occurs with heat treatment at 900 °C, until they resemble low specific surface area particles synthesised at this temperature. The Ce L-edge XAS of ceria particles shows that chloride is not present in the first co-ordination sphere around Ce(IV) ions, so is not directly bonded to Ce as a chloride in the bulk structure.