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Thermal reduction of ceria nanostructures on rhodium(111) and re-oxidation by CO2

Schaefer, Andreas LU ; Hagman, Benjamin LU ; Höcker, Jan; Hejral, Uta LU ; Flege, Jan Ingo and Gustafson, Johan LU (2018) In Physical Chemistry Chemical Physics 20(29). p.19447-19457
Abstract

The thermal reduction of cerium oxide nanostructures deposited on a rhodium(111) single crystal surface and the re-oxidation of the structures by exposure to CO2 were investigated. Two samples are compared: a rhodium surface covered to ≈60% by one to two O-Ce-O trilayer high islands and a surface covered to ≈65% by islands of four O-Ce-O trilayer thickness. Two main results stand out: (1) the thin islands reduce at a lower temperature (870-890 K) and very close to Ce2O3, while the thicker islands need higher temperature for reduction and only reduce to about CeO1.63 at a maximum temperature of 920 K. (2) Ceria is re-oxidized by CO2. The rhodium surface promotes the re-oxidation by... (More)

The thermal reduction of cerium oxide nanostructures deposited on a rhodium(111) single crystal surface and the re-oxidation of the structures by exposure to CO2 were investigated. Two samples are compared: a rhodium surface covered to ≈60% by one to two O-Ce-O trilayer high islands and a surface covered to ≈65% by islands of four O-Ce-O trilayer thickness. Two main results stand out: (1) the thin islands reduce at a lower temperature (870-890 K) and very close to Ce2O3, while the thicker islands need higher temperature for reduction and only reduce to about CeO1.63 at a maximum temperature of 920 K. (2) Ceria is re-oxidized by CO2. The rhodium surface promotes the re-oxidation by splitting the CO2 and thus providing atomic oxygen. The process shows a clear temperature dependence. The maximum oxidation state of the oxide reached by re-oxidation with CO2 differs for the two samples, showing that the thinner structures require a higher temperature for re-oxidation with CO2. Adsorbed carbon species, potentially blocking reactive sites, desorb from both samples at the same temperature and cannot be the sole origin for the observed differences. Instead, an intrinsic property of the differently sized CeOx islands must be at the origin of the observed temperature dependence of the re-oxidation by CO2.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physical Chemistry Chemical Physics
volume
20
issue
29
pages
11 pages
publisher
Royal Society of Chemistry
external identifiers
  • scopus:85050951004
ISSN
1463-9076
DOI
10.1039/c8cp01505h
language
English
LU publication?
yes
id
90271180-8ff5-4c20-a892-a35ccb082b28
date added to LUP
2018-10-01 12:07:51
date last changed
2019-01-06 14:06:44
@article{90271180-8ff5-4c20-a892-a35ccb082b28,
  abstract     = {<p>The thermal reduction of cerium oxide nanostructures deposited on a rhodium(111) single crystal surface and the re-oxidation of the structures by exposure to CO<sub>2</sub> were investigated. Two samples are compared: a rhodium surface covered to ≈60% by one to two O-Ce-O trilayer high islands and a surface covered to ≈65% by islands of four O-Ce-O trilayer thickness. Two main results stand out: (1) the thin islands reduce at a lower temperature (870-890 K) and very close to Ce<sub>2</sub>O<sub>3</sub>, while the thicker islands need higher temperature for reduction and only reduce to about CeO<sub>1.63</sub> at a maximum temperature of 920 K. (2) Ceria is re-oxidized by CO<sub>2</sub>. The rhodium surface promotes the re-oxidation by splitting the CO<sub>2</sub> and thus providing atomic oxygen. The process shows a clear temperature dependence. The maximum oxidation state of the oxide reached by re-oxidation with CO<sub>2</sub> differs for the two samples, showing that the thinner structures require a higher temperature for re-oxidation with CO<sub>2</sub>. Adsorbed carbon species, potentially blocking reactive sites, desorb from both samples at the same temperature and cannot be the sole origin for the observed differences. Instead, an intrinsic property of the differently sized CeO<sub>x</sub> islands must be at the origin of the observed temperature dependence of the re-oxidation by CO<sub>2</sub>.</p>},
  author       = {Schaefer, Andreas and Hagman, Benjamin and Höcker, Jan and Hejral, Uta and Flege, Jan Ingo and Gustafson, Johan},
  issn         = {1463-9076},
  language     = {eng},
  number       = {29},
  pages        = {19447--19457},
  publisher    = {Royal Society of Chemistry},
  series       = {Physical Chemistry Chemical Physics},
  title        = {Thermal reduction of ceria nanostructures on rhodium(111) and re-oxidation by CO<sub>2</sub>},
  url          = {http://dx.doi.org/10.1039/c8cp01505h},
  volume       = {20},
  year         = {2018},
}