Synthesis and Application of Heteroatom-Doped Graphite as the Electrode Material: Influences of Defect Density and Heteroatom on Heterogeneous Electron Transfer Rate

Abstract

Thermal method was applied for the synthesis of O-doped and N-doped graphite materials using melamine and glucose as the sources of O and N, respectively. Graphite paste electrodes were prepared with the synthesized O-doped and N-doped graphite materials. The route of synthesis was explored by cyclic voltammetry using the fabricated paste electrodes and [Fe(CN)6]3–/4– as a simple outer-sphere redox probe. The results of structural and electrochemical investigations clearly showed that doping of O and N as heteroatom in the synthesized materials not only increased the defect density, the ratio of edge to basal plane sites, of graphite materials but also enhanced the rate of heterogeneous electron transfer at their corresponding paste electrodes. The heterogeneous electron transfer rate constant (k0) for [Fe(CN)6]3–/4– at the fabricated O-doped and N-doped graphite paste electrodes were about 51 and 46 times that observed for graphite paste electrode, respectively. The values of electroactive surface area calculated for both O-doped and N-doped graphite materials were about 5 times that obtained for graphite paste electrode. Thereafter, electrochemical behaviors of isoniazid, ascorbic acid, dopamine, and uric acid as the models of biologically relevant molecules were investigated at the prepared heteroatom-doped graphite paste electrodes, and the obtained results were compared with those obtained using paste electrodes prepared by pristine graphite, pristine multiwalled carbon nanotubes, and oxidized multiwalled carbon nanotubes and also by glassy carbon electrode.