Author(s):
Rocha, Leandro Silva Rosa [UNESP] ; Amoresi, Rafael Aparecido Ciola [UNESP] ; Duarte, Thiago Marinho ; Marana, Naiara Letícia [UNESP] ; Sambrano, Julio Ricardo [UNESP] ; Aldao, Celso Manuel ; Simões, Alexandre Zirpoli [UNESP] ; Ponce, Miguel Adolfo ; Longo, Elson [UNESP]
Date: 2021
Persistent ID: http://hdl.handle.net/11449/213656
Origin: Oasisbr
Subject(s): Defeitos; Espectroscopia de raio X; Monóxido de carbono; Lantânio; Defects; Lanthanum; Cerium oxide; Carbon monoxide; X-ray photoelectron spectroscopy; Defeitos; Defeitos; Espectroscopia de raio X; Espectroscopia de raio X; Monóxido de carbono; Monóxido de carbono; Lantânio; Lantânio; Defects; Defects; Lanthanum; Lanthanum; Cerium oxide; Cerium oxide; Carbon monoxide; Carbon monoxide; X-ray photoelectron spectroscopy; X-ray photoelectron spectroscopy
Description
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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.
Faculty of Engineering of Guaratingueta, São Paulo State University, UNESP
LACOM/INCTMN, Federal University of Paraiba, João Pessoa
INTEMA - National University of Mar del Plata, Mar del Plata, Argentina
Federal University of Sao Carlos (UFSCar), Department of Chemistry, São Carlos, SP, Brazil
FAPESP: 2013/07296-2. 2016/25500-4. 2017/19143-7
Capes - 001
