Heterogeneous electron-transfer rate constants for ferrocene and ferrocene carboxylic acid at boron-doped diamond electrodes in a room temperature ionic liquid

Doo Young Kim, Ju Chan Yang, Hyoun Woo Kim, Greg M. Swain

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

Heterogeneous electron-transfer rate constants were determined for ferrocene and ferrocene carboxylic acid (FCA) in the room temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF 4), at boron-doped microcrystalline diamond thin-film electrodes. Comparison data for FCA in 1 M KCl were also obtained. The apparent heterogeneous electron-transfer rate constant, kapp0, for FCA was 10× lower in the RTIL 1.5 (± 1.1) × 10-3 cm s-1 as compared to KCl 4.6 (± 1.3) × 10-2 cm s-1. The kapp0 for ferrocene was also 10x lower in the RTIL 5.0 (± 1.2) × 10-3 cm s-1 as compared to a common organic electrolyte solution 5.5 (± 1.2) × 10-2 cm s -1. The diffusion coefficient for FCA (Dred) was determined by chronoamperometry to be 1.3 × 10-7 cm2 s-1, ca. 100× lower than the value (1.9 × 10 -5 cm2 s-1) in KCl. The lower diffusion coefficient is consistent with the 100× greater viscosity of the RTIL. The lower kapp0 values for these outer-sphere redox systems is attributed, at least in part, to a reduced number of attempts to surmount the activation barrier (i.e., a reduced nuclear frequency factor, νn) due to the more viscous medium.

Original languageEnglish
Pages (from-to)49-56
Number of pages8
JournalElectrochimica Acta
Volume94
DOIs
StatePublished - Apr 1 2013

Bibliographical note

Funding Information:
This work was generously supported by grants from the Army Research Office (W911NF-09-1-0451) and the Natural Science Foundation (CHE-0911383). The authors thank Yan Zhu for her assistance performing some of the cyclic voltammetric measurements.

Keywords

  • Cyclic voltammetry
  • Diamond electrodes
  • Electrode kinetics
  • Room temperature ionic liquids

ASJC Scopus subject areas

  • General Chemical Engineering
  • Electrochemistry

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