Oxidation of several p-phenylenediamines in room temperature ionic liquids: Estimation of transport and electrode kinetic parameters
Journal
Journal of Physical Chemistry C
Journal Volume
112
Journal Issue
17
Start Page
6993
End Page
7000
ISSN
19327455
Date Issued
2008
Author(s)
Long, Jenny S.
Silvester, Debbie S.
Barnes, Alexander S.
Rees, Neil V.
Hardacre, Christopher
Compton, Richard G.
Abstract
The electrochemical oxidation of N,N,N′,N′-tetramethyl-p- phenylenediamine (TMPD) has been studied by cyclic voltammetry and potential step chronoamperometry at 303 K in five ionic liquids, namely [C 2mim][NTf2], [C4mim][NTf2], [C 4mpyrr][NTf2], [C4mim][BF4], and [C4mim][PF6] (where [Cnmim]+ = 1-alkyl-3-methylimidazolium, [C4mpyrr]+ = N-butyl-N-methylpyrrolidinium, [NTf2]- = bis(trifluoromethylsulfonyl)-imide, [BF4]- = tetrafluoroborate, and [PF6]- = hexafluorophosphate). Diffusion coefficients, D, of 4.87, 3.32, 2.05, 1.74, and 1.34 × 10 -11 m2 s-1 and heterogeneous electron-transfer rate constants, k0, of 0.0109, 0.0103, 0.0079, 0.0066, and 0.0059 cm s-1 were calculated for TMPD in [C2mim][NTf2], [C4mim][NTf2], [C4mpyrr][NTf2], [C4mim][BF4], and [C4mim][PF6], respectively, at 303 K. The oxidation of TMPD in [C4mim] [PF 6] was also carried out at increasing temperatures from 303 to 343 K, with an activation energy for diffusion of 32.3 kJ mol-1. k 0 was found to increase systematically with increasing temperature, and an activation energy of 31.4 kJ mol-1 was calculated. The study was extended to six other p-phenylene-diamines with alkyl/phenyl group substitutions. D and k0 values were calculated for these compounds in [C2mim][NTf2], and it was found that k0 showed no obvious relationship with the hydrodynamic radius, r. © 2008 American Chemical Society.
SDGs
Type
journal article