| Titre : | Thermal stability and dispersion behavior of nanostructured CexZr1-xO2 mixed oxides over anatase-TiO2 : a combined study of CO oxidation and characterization by XRD, XPS, TPR, HREM, and UV-Vis DRS (2009) |
| Auteurs : | Benjaram M. Reddy, Éditeur scientifique ; Pankaj Bharali, Éditeur scientifique ; Pranjal Saikia, Éditeur scientifique |
| Type de document : | Article : texte imprimé |
| Dans : | Industrial & engineering chemistry research (Vol. 48 N°1, Janvier 2009) |
| Article en page(s) : | P. 453-462 |
| Note générale : | Chemical engineering |
| Langues : | Anglais |
| Tags : | Nanostructured CexZr1− ; xO2 Thermal stability Oxides Anatase-TiO2 |
| Résumé : | A study has been undertaken on the thermal stability and dispersion behavior of nanostructured CexZr1−xO2 mixed oxides over anatase-TiO2 support, synthesized by a deposition coprecipitation method and subjected to heat treatments at different temperatures. An unsupported CexZr1−xO2 mixed oxide was also synthesized by coprecipitation method for the purpose of comparison. The structural/morphological characterization was performed using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HREM), X-ray photoelectron spectroscopy (XPS), UV−visible diffuse reflectance spectroscopy (UV−vis DRS), and temperature-programmed reduction (TPR) techniques. XRD measurements revealed the presence of cubic Ce0.75Zr0.25O2 phase at 773 K and incorporation of more zirconium into the ceria lattice at higher temperatures. HREM analysis conformed highly dispersed Ce−Zr nano-oxides over anatase-TiO2 support having the sizes in the range of 3−5 nm at 773 K. At higher temperatures, a slight increase in the crystallite size (5−10 nm) has been observed. The XPS measurements revealed the stabilization of Ce3+ at higher temperatures and presence of Zr and Ti in 4+ oxidation states. UV−vis DRS studies showed that oxygen to metal (Ce4+/Ce3+) charge-transfer transitions occur at lower wavelengths in the case of CexZr1−xO2/TiO2 compared to pure CexZr1−xO2. TPR experiments revealed that the surface reduction of CexZr1−xO2/TiO2 takes place at lower temperatures, which facilitates better CO oxidation activity in comparison to the unsupported CexZr1−xO2. |
| En ligne : | http://pubs.acs.org/doi/abs/10.1021/ie8012677 |
