A Systematic Study of the Mass Transport, Kinetic and Thermodynamic Properties of the FeIII/II Process at Glassy Carbon and Boron-Doped Diamond Electrodes

Mingyue Lin, Jiezhen Li, Dawei Pan, Alan M Bond, Jie Zhang

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Abstract

The heterogeneous electron transfer kinetics (k0 values), mass transport and thermodynamic properties (E0 values) associated with the FeIII/II process have been determined in aqueous solutions containing 0.1 M HCl, HClO4, bis(trifluoromethanesulfonyl)imide (HNTf2) or 0.05 M silicotungstic acid (H4[α-SiW12O40]) supporting electrolytes. The diffusion coefficient (D) values for FeIII and FeII are dependent on the radius of the electrolyte anion and follow the order D(SiW12O40 4−) < D(NTf2 ) < D(ClO4 ) < D(Cl). The k0 values are found to be smaller at boron doped diamond (BDD) electrodes than glassy carbon (GC) electrodes, and influenced by the ion-pairing between electrolyte anions and FeIII and FeII. Based on the formal potential value, HNTf2 is found to be a more innocent electrolyte than commonly used HClO4 with regard to determine the true k0 values of the outer-sphere [Fe(H2O)6]3+/2+ process. Fourier transformed large amplitude alternating current voltammetry, which provides favorable signal to background ratio, was used to determine k0 values associated with the FeIII/II process in H4[α-SiW12O40] and HNTf2 electrolyte media at GC electrodes and probe the implications of the heterogeneity of the BDD electrode surface on the electrode kinetic determination in H4[α-SiW12O40] electrolyte media.

Original languageEnglish
Pages (from-to)421-430
Number of pages10
JournalElectrochimica Acta
Volume249
DOIs
Publication statusPublished - 20 Sep 2017

Keywords

  • electrode heterogeneity
  • electron transfer kinetics
  • Fe process
  • Fourier transformed alternating current voltammetry
  • medium effect

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