DFT calculations of ammonia oxidation reactions on bimetallic clusters of platinum and iridium

Ali Estejab, Gerardine G. Botte

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

Density functional theory calculations were performed on four platinum-iridium clusters, Pt3-xIrx (x = 0-3) to examine ammonia oxidation in alkaline media. The adsorption of NH3-x (x = 0-3) on these clusters and the effect of cluster composition on the adsorption were investigated. The hybrid B3LYP level of theory was used in Gaussian 09 along with the LANL2DZ and 6-311++g basis sets.The HOMO-LUMO energy gap on bare metal clusters showed that increasing the iridium concentration decreased the energy gap, a sign of a more reactive catalyst. The relative adsorption energy showed more stability of NH3-x on the Ir3 cluster and less stability as the number of platinum atoms increased in the cluster. These results combined with activation and dissociation energy calculations of sequential dehydrogenation reactions showed that Ir3 is more active than Pt3 for ammonia oxidation, and the addition of iridium to platinum makes a more favorable pathway for the ammonia oxidation reaction. The computational calculations suggest the possibility of two different mechanisms of ammonia oxidation on platinum and iridium electrocatalysts.

Original languageEnglish
Pages (from-to)31-40
Number of pages10
JournalComputational and Theoretical Chemistry
Volume1091
DOIs
StatePublished - Sep 1 2016

Keywords

  • Ammonia electrolysis
  • Ammonia oxidation
  • Density functional theory
  • Hydrogen production
  • Platinum and iridium bimetallic catalyst
  • Waste water remediation

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