Voltammetry of ferrocene in supercritical CO sub 2 containing water and tetrahexylammonium hexafluorophosphate

Journal Article · Thu Aug 10 00:00:00 EDT 1989 · Journal of Physical Chemistry; (USA)

DOI:https://doi.org/10.1021/j100353a052· OSTI ID:7196716

Niehaus, D; Philips, M; Michael, A; Wightman, R M ^[1]

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1. Indiana Univ., Bloomington (USA)

The voltammetric oxidation of ferrocene has been examined with microdisk electrodes in supercritical CO{sub 2} containing small-amounts of added water. Voltammograms obtained under these conditions indicate a high rate of diffusion for ferrocene but exhibit considerable ohmic drop. The ohmic distortion of the voltammograms is reduced by the addition of tetrahexylammonium hexafluorophosphate ((THA)PF{sub 6}) to the cell. However, when large amounts of (THA)PF{sub 6} are added to the cell, visual inspection indicates a two-phase system under the conditions used. Near-infrared spectra show that the upper phase is supercritical CO{sub 2} and the lower phase is liquid (THA)PF{sub 6}. This result is obtained at a temperature that is 64{degree}C below the melting point of pure (THA)PF{sub 6} at atmospheric pressure. Ferrocene is found to have a much lower diffusion coefficient in the molten salt. However, the limiting current recorded in the molten salt is not attenuated relative to that in the upper phase, because ferrocene preferentially dissolves in the molten salt. It is shown that the molten salt, when added in small amounts to the cell, acts as an electrode-surface modifier that promotes ionic conductivity and allows the oxidation of ferrocene extracted from the supercritical CO{sub 2}. This occurs even when the electrode is placed in the upper CO{sub 2} phase.

• OSTI ID: 7196716
• Journal Information: Journal of Physical Chemistry; (USA), Vol. 93:16; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
FERROCENE
VOLTAMETRY
CARBON DIOXIDE
DATA ANALYSIS
EXPERIMENTAL DATA
MEASURING INSTRUMENTS
MEASURING METHODS
SOLVENTS
SUPERFLUIDITY
WATER
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
COMPLEXES
DATA
DIENES
HYDROCARBONS
HYDROGEN COMPOUNDS
INFORMATION
IRON COMPLEXES
NUMERICAL DATA
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
POLYENES
TRANSITION ELEMENT COMPLEXES
400201* - Chemical & Physicochemical Properties
400000 - Chemistry
640400 - Fluid Physics