Effect of hydration and thermal treatment on ceria surface using non-intrusive techniques

The evolution of plutonium dioxide surface due to water adsorption seems to influence H2 generation through the radiolysis of adsorbed water. Surface evolution of ceria, a non-radioactive surrogate for plutonium dioxide, was investigated using Inverse Gas Chromatography (IGC), Raman spectroscopy, Environmental Scanning Electronic Microscopy (ESEM) and Atomic Force Microscopy (AFM). IGC highlights the complexity of ceria surface revealing three different adsorption sites on surface and indicate a surface evolution upon hydration. Thermal treatment appears to regenerate at least partially the initial surface state before hydration. IGC points out the influence of calcination temperature of ceria precursor on surface reactivity. The nature of surface modification was investigated by Raman spectroscopy which suggests formation of superficial hydroxide layer. ESEM and AFM were used to study potential surface topology modification upon superficial layer formation. Cerium hydroxide forms as a superficial layer with a nanostructure differing from the one of the oxide.