Mechanistic studies of the electro-oxidation pathway of ammonia in several room-temperature ionic liquids

X.B. Ji, D.S. Silvester, Leigh Aldous, Christopher Hardacre, R.G. Compton

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37 Citations (Scopus)

Abstract

A mechanistic study of the direct oxidation of ammonia has been reported in several room-temperature ionic liquids (RTILs), namely, [C(4)mim][BF4], [C(4)mim][OTf], [C(2)mim][NTf2], [C(4)mim][NTf2], and [C(4)mim][PF6], on a 10 mu m diameter Pt microdisk electrode. In four of the RTILs studied, the cyclic voltammetric analysis suggests that ammonia is initially oxidized to nitrogen, N-2, and protons, which are transferred to an ammonia molecule, forming NH4+ via the protonation of the anion(s) (A(-)). In contrast, NH4+ is formed first in [C(4)mim][PF6], followed by the protonated anion(s), HA. In all five RTILs, both HA and NH4+ are reduced at the electrode surface, forming hydrogen gas, which is then oxidized. The effect of changing the RTIL anion is discussed, and this may have implications in the defining of pK(a) in RTIL media. This work also has implications in the possible amperometric sensing of ammonia gas.
Original languageEnglish
Pages (from-to)9562-9572
Number of pages11
JournalJournal of Physical Chemistry C
Volume111 (26)
Issue number26
DOIs
Publication statusPublished - 05 Jun 2007

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Energy(all)
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films

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