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Title: Hydrogen activation, diffusion, and clustering on CeO{sub 2}(111): A DFT+U study

Abstract

We present a comprehensive density functional theory+U study of the mechanisms underlying the dissociation of molecular hydrogen, and diffusion and clustering of the resulting atomic species on the CeO{sub 2}(111) surface. Contrary to a widely held view based solely on a previous theoretical prediction, our results show conclusively that H{sub 2} dissociation is an activated process with a large energy barrier ∼1.0 eV that is not significantly affected by coverage or the presence of surface oxygen vacancies. The reaction proceeds through a local energy minimum – where the molecule is located close to one of the surface oxygen atoms and the H–H bond has been substantially weaken by the interaction with the substrate –, and a transition state where one H atom is attached to a surface O atom and the other H atom sits on-top of a Ce{sup 4+} ion. In addition, we have explored how several factors, including H coverage, the location of Ce{sup 3+} ions as well as the U value, may affect the chemisorption energy and the relative stability of isolated OH groups versus pair and trimer structures. The trimer stability at low H coverages and the larger upward relaxation of the surface O atoms withinmore » the OH groups are consistent with the assignment of the frequent experimental observation by non-contact atomic force and scanning tunneling microscopies of bright protrusions on three neighboring surface O atoms to a triple OH group. The diffusion path of isolated H atoms on the surface goes through the adsorption on-top of an oxygen in the third atomic layer with a large energy barrier of ∼1.8 eV. Overall, the large energy barriers for both, molecular dissociation and atomic diffusion, are consistent with the high activity and selectivity found recently in the partial hydrogenation of acetylene catalyzed by ceria at high H{sub 2}/C{sub 2}H{sub 2} ratios.« less

Authors:
 [1];  [2];  [3];  [1]
  1. Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, E-28049 Madrid (Spain)
  2. CIC Energigune, Albert Einstein 48, 01510 Miñano, Álava (Spain)
  3. Instituto de Catálisis y Petroleoquímica, CSIC, C/ Marie Curie 2, E-28049 Madrid (Spain)
Publication Date:
OSTI Identifier:
22308757
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 141; Journal Issue: 1; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-9606
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ACETYLENE; ADSORPTION; ALLOCATIONS; CERIUM IONS; CERIUM OXIDES; CHEMISORPTION; DISSOCIATION; HYDROGEN; INTERACTIONS; MOLECULES; RELAXATION; SCANNING TUNNELING MICROSCOPY; STABILITY; SUBSTRATES

Citation Formats

Fernández-Torre, Delia, Instituto de Estructura de la Materia, CSIC, C/ Serrano 121, E-28006 Madrid, Carrasco, Javier, Instituto de Catálisis y Petroleoquímica, CSIC, C/ Marie Curie 2, E-28049 Madrid, Ganduglia-Pirovano, M. Verónica, Pérez, Rubén, and Condensed Matter Physics Center. Hydrogen activation, diffusion, and clustering on CeO{sub 2}(111): A DFT+U study. United States: N. p., 2014. Web. doi:10.1063/1.4885546.
Fernández-Torre, Delia, Instituto de Estructura de la Materia, CSIC, C/ Serrano 121, E-28006 Madrid, Carrasco, Javier, Instituto de Catálisis y Petroleoquímica, CSIC, C/ Marie Curie 2, E-28049 Madrid, Ganduglia-Pirovano, M. Verónica, Pérez, Rubén, & Condensed Matter Physics Center. Hydrogen activation, diffusion, and clustering on CeO{sub 2}(111): A DFT+U study. United States. doi:10.1063/1.4885546.
Fernández-Torre, Delia, Instituto de Estructura de la Materia, CSIC, C/ Serrano 121, E-28006 Madrid, Carrasco, Javier, Instituto de Catálisis y Petroleoquímica, CSIC, C/ Marie Curie 2, E-28049 Madrid, Ganduglia-Pirovano, M. Verónica, Pérez, Rubén, and Condensed Matter Physics Center. Mon . "Hydrogen activation, diffusion, and clustering on CeO{sub 2}(111): A DFT+U study". United States. doi:10.1063/1.4885546.
@article{osti_22308757,
title = {Hydrogen activation, diffusion, and clustering on CeO{sub 2}(111): A DFT+U study},
author = {Fernández-Torre, Delia and Instituto de Estructura de la Materia, CSIC, C/ Serrano 121, E-28006 Madrid and Carrasco, Javier and Instituto de Catálisis y Petroleoquímica, CSIC, C/ Marie Curie 2, E-28049 Madrid and Ganduglia-Pirovano, M. Verónica and Pérez, Rubén and Condensed Matter Physics Center},
abstractNote = {We present a comprehensive density functional theory+U study of the mechanisms underlying the dissociation of molecular hydrogen, and diffusion and clustering of the resulting atomic species on the CeO{sub 2}(111) surface. Contrary to a widely held view based solely on a previous theoretical prediction, our results show conclusively that H{sub 2} dissociation is an activated process with a large energy barrier ∼1.0 eV that is not significantly affected by coverage or the presence of surface oxygen vacancies. The reaction proceeds through a local energy minimum – where the molecule is located close to one of the surface oxygen atoms and the H–H bond has been substantially weaken by the interaction with the substrate –, and a transition state where one H atom is attached to a surface O atom and the other H atom sits on-top of a Ce{sup 4+} ion. In addition, we have explored how several factors, including H coverage, the location of Ce{sup 3+} ions as well as the U value, may affect the chemisorption energy and the relative stability of isolated OH groups versus pair and trimer structures. The trimer stability at low H coverages and the larger upward relaxation of the surface O atoms within the OH groups are consistent with the assignment of the frequent experimental observation by non-contact atomic force and scanning tunneling microscopies of bright protrusions on three neighboring surface O atoms to a triple OH group. The diffusion path of isolated H atoms on the surface goes through the adsorption on-top of an oxygen in the third atomic layer with a large energy barrier of ∼1.8 eV. Overall, the large energy barriers for both, molecular dissociation and atomic diffusion, are consistent with the high activity and selectivity found recently in the partial hydrogenation of acetylene catalyzed by ceria at high H{sub 2}/C{sub 2}H{sub 2} ratios.},
doi = {10.1063/1.4885546},
journal = {Journal of Chemical Physics},
issn = {0021-9606},
number = 1,
volume = 141,
place = {United States},
year = {2014},
month = {7}
}