Author(s):
Rocha, Leandro Silva Rosa ; Aparecido Ciola Amoresi, Rafael [UNESP] ; Duarte, Thiago Marinho [UNESP] ; Marana, Naiara Letícia [UNESP] ; Sambrano, Julio Ricardo [UNESP] ; Aldao, Celso Manuel ; Simões, Alexandre Zirpoli [UNESP] ; Ponce, Miguel Adolfo ; Longo, Elson
Date: 2020
Persistent ID: http://hdl.handle.net/11449/201484
Origin: Oasisbr
Subject(s): Carbon monoxide; Cerium oxide; Defects; Lanthanum; X-ray photoelectron spectroscopy; Carbon monoxide; Carbon monoxide; Cerium oxide; Cerium oxide; Defects; Defects; Lanthanum; Lanthanum; X-ray photoelectron spectroscopy; X-ray photoelectron spectroscopy
Description
Made available in DSpace on 2020-12-12T02:33:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-04-30
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
A spectroscopic study of nanostructured lanthanum-doped cerium oxide samples showed that a mild decrease by 5.3% in the surface concentration of Ce(III) species and, a reduction by 0.2 eV in the so-called energy-gap (EF – Ev) after lanthanum addition was sufficient to create the previously reported significant dual behavior when exposed to carbon monoxide at 653 K. The observed X-ray diffraction patterns indicated the presence of a pure fluorite-type crystalline structure. A higher presence of paramagnetic defects clusters, indicated by electron paramagnetic resonance spectroscopy measurements and confirmed by the X-ray photoelectron spectroscopy, was attributed as being responsible for its dual behavior in a CO(g) atmosphere. Theoretical studies have shown the band structure and density of state of the pure and doped material, illustrating the orbitals that participate in the valence band and conduction band. The addition of a small quantity of La3+ converted some Ce3+ into Ce4+, narrowed the “effective band-gap” by 0.2 eV, and created a singly ionized oxygen vacancy species, thus changing the total electrical resistance and creating its dual behavior. The exposure to a reducing atmosphere such as carbon monoxide resulted in a significant increase in defects and converted some Ce4+ into Ce3+ and vice-versa with oxygen atmosphere exposure.
Federal University of Sao Carlos (UFSCar) Department of Chemistry
Sao Paulo State University (UNESP) School of Engineering
LACOM/INCTMN Federal University of Paraiba
Sao Paulo State University (UNESP) School of Sciences
Institute of Materials Science and Technology (INTEMA), Mar del Plata
Sao Paulo State University (UNESP) School of Engineering
Sao Paulo State University (UNESP) School of Sciences
