Mechanism for the water-gas shift reaction on monofunctional platinum and cause of catalyst deactivation

David W. Flaherty, Wen Yueh Yu, Zachary D. Pozun, Graeme Henkelman, C. Buddie Mullins

Research output: Contribution to journalArticlepeer-review

Abstract

The behavior of monofunctional platinum, Pt(1 1 1), for the water-gas shift reaction has been investigated using experimental and theoretical methods. Kinetic and isotopic measurements performed from 525 to 675 K are consistent with an associative mechanism for the water-gas shift reaction in which carbon monoxide is oxidized by a hydroxyl group. The kinetically-relevant step consists of the unimolecular decomposition of an adsorbed carboxylate intermediate. The turnover frequency of Pt(1 1 1) is five times greater than that observed on Cu(1 1 1) under identical conditions (612 K, 26 Torr CO, 10 Torr H2O); however, Pt(1 1 1) loses activity over time due to the formation of carbonaceous deposits, a process not observed in similar studies of Cu(1 1 1). Our experimental and theoretical results suggest that CO dissociates via two pathways: the Boudouard reaction and through a COH intermediate. Nucleation of carbon at step-edges and subsequent oligomerization deactivate the catalyst. These results provide insight into the synergistic roles of noble metal clusters and active supports for the water-gas shift reaction.

Original languageEnglish (US)
Pages (from-to)278-288
Number of pages11
JournalJournal of Catalysis
Volume282
Issue number2
DOIs
StatePublished - Sep 1 2011
Externally publishedYes

Keywords

  • Copper
  • Hydrogen
  • Model catalyst
  • Noble metal
  • Poisoning
  • Reaction mechanism
  • Reforming

ASJC Scopus subject areas

  • Catalysis
  • Physical and Theoretical Chemistry

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