Structural modifications of nanostructured ceria CeO2,xH2O during dehydration process

Hydrated nanostructured cerium dioxide CeO2, xH2O (hydrated nanoceria) has been synthesized in room conditions via a precipitation route. This hydrated nanoceria phase has been subjected to thermal decomposition in the temperature range from 25 °C to 800 °C. At least three decomposition steps have been observed in thermal and thermogravimetric analyses. Three different samples of cubic nanoceria respectively obtained at room temperature (RT-nanoceria), 80 °C (80-nanoceria) and 600 °C (600-nanoceria) have been studied by X-Ray diffraction, Raman spectroscopy and scanning electron microscopy analyses. The analyses of X-ray diffraction profiles and Raman vibrational bands have clearly shown that dehydration is accompanied by increasing crystallite size, lattice parameter contraction. The cubic structure of hydrated RT-nanoceria might be associated with a complex chemical formula unit involving Ce4+, Ce3+ mixed valences, oxygen vacancies, lattice and surface water and OH− proton species.

Graphical abstractX-ray diffraction and Raman spectroscopy analyses. (Left): X-ray diffraction pattern of hydrated nanoceria CeO2,xH2O at room temperature; (Right): Evolution of Raman spectra of nanoceria (room temperature, heated at 80 °C and at 600 °C).Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We analyze the dehydration process of a ceria precursor CeO2,xH2O. ► Thermal analyses show water elimination in at least three steps. ► The lattice parameter of dehydrated cubic ceria is subjected to contraction. ► X-ray diffraction and Raman spectroscopy show structural modifications. ► A correlation between Raman frequency shift and profile broadening is established.