Ceria-based catalysts for the production of H2 through the water-gas-shift reaction: Time-resolved XRD and XAFS studies

Xianqin Wang, José A. Rodriguez, Jonathan C. Hanson, Daniel Gamarra, Arturo Martínez-Arias, Marcos Fernández-García

Research output: Contribution to journalArticlepeer-review

30 Scopus citations

Abstract

Hydrogen is a potential alternate energy source for satisfying many of our energy needs. In this work, we studied H2 production from the water-gas-shift (WGS) reaction over Ce1-xCuxO2 catalysts, prepared with a novel microemulsion method, using two synchrotron-based techniques: time-resolved X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS). The results are compared with those reported for conventional CuOx/CeO2 and AuOx/CeO 2 catalysts obtained through impregnation of ceria. For the fresh Ce1-xCuxO2 catalysts, the results of XAFS measurements at the Cu K-edge indicate that Cu is in an oxidation state higher than in CuO. Nevertheless, under WGS reaction conditions the Ce 1-xCuxO2 catalysts undergo reduction and the active phase contains very small particles of metallic Cu and CeO2-x. Time-resolved XRD and XAFS results also indicate that Cuδ+ and Auδ+ species present in fresh CuOx/CeO2 and AuOx/CeO2 catalysts do not survive above 200 °C under the WGS conditions. In all these systems, the ceria lattice displayed a significant increase after exposure to CO and a decrease in H2O, indicating that CO reduced ceria while H2O oxidized it. Our data suggest that H2O dissociation occurred on the Ovacancy sites or the Cu-Ovacancy and Au-Ovacancy interfaces. The rate of H2 generation by a Ce0.95Cu0.05O 2 catalyst was comparable to that of a 5 wt% CuOx/CeO 2 catalyst and much bigger than those of pure ceria or CuO.

Original languageEnglish (US)
Pages (from-to)81-88
Number of pages8
JournalTopics in Catalysis
Volume49
Issue number1-2
DOIs
StatePublished - Jul 2008
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)

Keywords

  • Ceria catalysts
  • Copper catalysts
  • Gold catalysts
  • Hydrogen
  • In situ characterization
  • Water-gas shift reaction
  • X-ray absorption fine structure
  • X-ray diffraction

Fingerprint Dive into the research topics of 'Ceria-based catalysts for the production of H<sub>2</sub> through the water-gas-shift reaction: Time-resolved XRD and XAFS studies'. Together they form a unique fingerprint.

Cite this