Surface Reactivity of Ag-Modified Ceria to Hydrogen: A Combined Experimental and Theoretical Investigation

Stefania Benedetti, Giulia Righi, Paola Luches, Sergio D'Addato, Rita Magri, Annabella Selloni

Research output: Contribution to journalArticle

Abstract

We investigate the mechanism of H2 activation on Ag-modified cerium oxide surfaces, of interest for different catalytic applications. The study is performed on thin epitaxial cerium oxide films, investigated by X-ray photoemission spectroscopy to assess the changes of both the Ag oxidation state and the concentration of Ce3+ ions, O vacancies, and hydroxyl groups on the surface during thermal reduction cycles in vacuum and under hydrogen exposure. The results are interpreted using density functional theory calculations to model pristine and Ag-modified ceria surfaces. Although the reactivity of ceria toward H2 oxidation improves when a fraction of Ce cations is substituted with Ag, the concentration of reduced Ce3+ ions in Ag-modified ceria is found to be lower than in pure ceria under the same conditions. This behavior is observed even though the number of surface oxygen vacancies caused by the thermal treatment under hydrogen exposure is larger for the Ag-modified surface. These results are explained in terms of a change of the oxidation state of the surface Ag, which is able to acquire some of the extra surface electrons created by the oxygen vacancies and the adsorbed hydrogen atoms. Our findings provide new insights into the reactivity of Ag-modified ceria, which has been proposed as a promising alternative to platinum electrodes in electrochemical devices.

Original languageEnglish (US)
Pages (from-to)27682-27690
Number of pages9
JournalACS Applied Materials and Interfaces
Volume12
Issue number24
DOIs
StatePublished - Jun 17 2020

All Science Journal Classification (ASJC) codes

  • Materials Science(all)

Keywords

  • X-ray photoemission spectroscopy
  • ceria
  • density functional theory
  • hydrogen dissociation
  • metal dopants
  • reaction kinetics
  • silver
  • surface reduction

Fingerprint Dive into the research topics of 'Surface Reactivity of Ag-Modified Ceria to Hydrogen: A Combined Experimental and Theoretical Investigation'. Together they form a unique fingerprint.

  • Cite this