Kinetics study of diamond electrodes at different levels of boron doping as quasi-reversible systems

Electrochemical reversibility was investigated for diamond electrodes with different boron concentrations for two redox couple. Diamond electrodes presented quasi-reversible electrochemical behavior for both electrolytes. In the range of scan rate and doping level analyzed diamond electrodes presented heterogeneous electron-transfer rate constant k(0) values of approximately 10(-4)-10(-3) cm/s for ferri/ferrocyanide and of approximately 10(-6)-10(-5) for quinone/hydroquinone. It was observed a maximum k(0) value when the electrode reaches a semi metallic behavior, associated to its higher crystalline quality and lower impurity incorporation. The acceptor concentrations were evaluated in the range of 10(18)-10(21) cm(-3) from the Mott-Schottky plot curve slope. The results were compared with platinum and glassy carbon electrodes. Scanning electron microscopy (SEM) has also shown diamond crystallites decreasing with boron doping increasing. Raman spectroscopy has evidenced a drastic decrease of 1332 cm(-1) peak, characteristic of boron-doped diamond. Atomic force microscopy (AFM) measurements have also demonstrated the electrode topography and its real active area for electrochemical response. (C) 2002 Elsevier Science B.V. All rights reserved.