Redox systems boron-doped diamond

Fig. 24. Energy diagram of the boron-doped diamond/aqueous redox electrolyte solution interface (a) at the flat-band potential (b) at the equilibrium potential of Fe(CN)63, 4 system. Ec is the energy of conduction band bottom, Ev is the energy of valence band top, F is the Fermi level, Eft, is the flat-band potential. Shown are the electrochemical potential levels of the Fe(CN)63, 4 and quinone/hydroquinone (Q/H2Q) systems in solution. The electrode potential axis E is related to the standard hydrogen electrode (SHE). Reprinted from [110]. Copyright (1997), with permission from Elsevier Science.

Figure 8(a) shows a cyclic voltammetric curve obtained at BDD electrode in 0.5 M H2SO4. The fact that the separation between the cathodic and the anodic peaks (AEp) is very high (about 0.9 V) indicates that the Q/H2Q system is irreversible at the boron-doped diamond electrode. Furthermore, the apparent equilibrium redox potential of the couple Q/H2Q(Eo = 0.65 V) is much closer to the anodic peak potential than to the cathodic one. 

A subsequent one-electron transfer occurs at more positive potentials, 0.9 V, to form the dication, CPZ", which is quickly hydrolyzed [179]. The electrode reaction kinetics for this redox system (CPZ/CPZ ) at diamond are mainly influenced by the density of electronic states at the formal potential [22,30]. Rapid electrode-reaction kinetics have been observed for boron-doped diamond electrodes, with no evidence of any molecular adsorption [22,30]. The QS jQp ratio for the CPZ/CPZ redox reaction is ca. 1. The ip and ip values varied linearly with the scan rate, while Qp and Qp were independent of scan rate. These trends are predicted for thin-layer voltammetric behavior. 

Cyclic Voltammetric and Heterogeneous Electron Transfer Rate Constant Data for Four Aqueous-Based Redox Systems at Boron-Doped Microcrystalline Diamond Thin-Film Electrodes... 

Figure 11 shows cyclic voltammetric i-E curves for (A) Fe(CN)e ", (B) Ru(NH3)e (C) IrCl6 / (D) methyl viologen (MV ) in 1 M KCl, and (E) 4-tert-butylcatechol, and (F) Fe in 0.1 M HCIO4 at a boron-doped nanocrystalline diamond thin film electrode. The potential scan rate (v) was 0.1 V/s. The Ep for these redox systems ranges from... 

Cyclic Voltammetric Data for Aqueous-Based Redox Systems at a Boron-Doped Nanocrystalline Diamond Thin-Film Electrode... 

---