Cyclic voltammetry can provide interface information of the electrode surface in dependence of the modification process. The
cyclic voltammetric behavior of 1.0 mM K3[Fe(CN)6] containing
0.1 M KCl at different electrodes was studied at a potential scan rate
of 100 V s1 (Fig. 3A). On the bare SPCE (curve a), a pair of weak
redox peaks with the peak-to-peak separation (DEp) of 0.31 V was
observed, indicating the lethargic electron transfer rate at the
interface. On the G/SPCE (curve b), a pair of well-defined peaks
appeared with a peak potential separation DEp of 0.28 V. On the N/
G/CPE (curve c), a higher peak current than that on both SPCE and
G/SPCE was observed, but DEp extended to 0.39 V which is due to
the presence of a membrane which deteriorates the diffusion
process. The presence of the ionic liquid in IL/G/SPCE (curve d)
causes well-defined and enhanced redox peaks with a small DEp of
0.22 V, which could be ascribed to the high ionic conductivity and
maybe an electrocatalytic activity of the IL. After N was added to the
IL/G/SPCE, the anodic and cathodic peaks current even improved
showing a DEp of 0.20 V, indicating that the ionic liquid slightly
overcompensates and synergically improves the otherwise negative
influence of the Nafion membrane in the N/IL/G/SPCE (curve e).
The relative peak separations, c0 ¼ (Epa Epc)/0.058, and anodic
to cathodic peak current density ratios (Ipa/Ipc) are given in Table 1.
The theoretical c0
-values for this redox reaction is 1.