The voltammetry for the reduction of oxygen at a microdisk electrode is reported in six commonly used RTILs: [C4mim][NTf2], [C4mpyrr][NTf2], [C4dmim][NTf2], [C4mim][BF4], [C4mim][PF6], and [N 6,2,2,2][NTf2], where [C4mim]+ is 1-butyl-3-methylimidazolium, [NTf2]- is bis(trifluoromethanesulfonyl)imide, [C4mpyrr]+is N-butyl-N-methylpyrrolidinium, [C4dmim]+ is 1-butyl-2,3-methylimidazolium, [BF4]- is tetrafluoroborate, [PF6]- is hexafluorophosphate, and [N6,2,2,2]+ is n-hexyltriethylammonium at varying scan rates (50-4000 mV s-1) and temperatures (293-318 K). Diffusion coefficients, D, of oxygen are deduced at each temperature from potential-step chronoamperometry, and diffusional activation energies are calculated. Oxygen solubilities are also reported as a function of temperature. In the six ionic liquids, the Stokes-Einstein relationship (D ∝ η-1 ) was found to apply only very approximately for oxygen. This is considered in relationship to the behavior of other diverse solutes in RTILs.
|Number of pages||7|
|Journal||The Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical|
|Publication status||Published - 2 Jul 2009|