INTEC   05402
INSTITUTO DE DESARROLLO TECNOLOGICO PARA LA INDUSTRIA QUIMICA
Unidad Ejecutora - UE
artículos
Título:
Surface Reduction Mechanism of Cerium-Gallium Mixed Oxides with Enhanced Redox Properties
Autor/es:
J. VECCHIETTI; S. COLLINS; W. XU; L. BARRIO; D. STACCHIOLA; M. CALATAYUD; F. TIELENS; J.J. DELGADO; A. BONIVARDI
Revista:
JOURNAL OF PHYSICAL CHEMISTRY C
Editorial:
AMER CHEMICAL SOC
Referencias:
Lugar: Washington; Año: 2013 vol. 117 p. 8822 - 8831
ISSN:
1932-7447
Resumen:
The doping of CeO2 with different cations has been recognized as a significant factor in controlling the oxygen vacancies and improving the oxygen mobility. Thus, the catalytic properties of these materials might be determined by modifying the redox properties of ceria. A combined experimental and theoretical study of the redox properties of gallium-doped cerium dioxide is presented. Infrared spectroscopy and time-resolved X-ray diffraction were used for temperature programmed reduction (H2) and oxidation (with O2 and H2O) studies. Additionally, X-ray absorption near edge spectroscopy shows that only Ce4+ is reduced to Ce3+ in the ceria-gallia mixed oxides when annealed up to 623 K. The oxygen storage capacity (OSC) measurements show a pronounced enhancement on the reduction of ceria by gallium doping. Theoretical calculations by density functional theory (DFT) confirm the higher reducibility of gallium-doped ceria oxides and give a molecular description of the stabilization of the doped material. Based on infrared spectroscopic measurements, a novel mechanism is proposed for the surface reduction of Ce4+ to Ce3+ where Ga-H species are suggested to be directly involved in the process. In addition, the reoxidation by H2O was precluded in the gallium-doped ceria oxide.