On the Co solubility in Ce0.9Zr0.1O2 nanoparticles studied by EXAFS

Abstract

The Co solubility in the (Ce0.9Zr0.1)1-xCoxO2-δ system have been studied varying the Co content, 0 ​≤ ​x ​≤ ​0.15, and the heat treatment temperature, 600 ​≤ ​T ​≤ ​1000 ​°C, on samples prepared by the citrate method, by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray absorption spectroscopy (XAS). XRD data shows no significant variation in the lattice parameter of the fluorite crystal structure and reveals the presence of Co3O4 oxide as secondary phase in most samples with the exception of those with x ​= ​0.03 and 0.05 annealed at 600 ​°C. The analysis of the extended X-ray absorption fine structure (EXAFS) zone of the K-edge of Co of these two samples clearly indicates Co oxide is in amorphous state. These results indicate the incorporation of Co in Ce0.9Zr0.1O2-δ at T ​≥ ​600 ​°C is negligible. This is an important result, mainly for catalytic applications, where the characterization of the active centre is a key factor for understanding the performance of the catalyst.