Surface structural and electrochemical investigations of pyrolytic carbon film electrodes prepared by chemical vapour deposition using ethene as carbon source

Abstract

Pyrolytic carbon film electrodes (PCFEs) prepared from ethene by chemical vapour deposition (CVD) have been characterized electrochemically. The residual currents and potential limits of the electrodes were determined in various aqueous solutions, and the kinetics of the electron transfer reaction of K 4Fe(CN) 6 in 1 M KCl were studied by cyclic voltammetry. The apparent heterogeneous rate constant for the ferro/ferricyanide system was determined to be about 5 × 10 −3 cm s −1 and the electrode capacitances were of the order of 5–10 μF cm −2. The useful potential window in neutral phosphate buffer was determined to be +1.2 to −1.5 V vs. SCE. The surface composition was examined, both before and after the electrochemical experiments, using X-ray photoelectron spectroscopy (XPS) and scanning Auger microscopy (SAM), while the electrode surface topography was monitored ex situ with a scanning tunnelling microscope (STM). The surface topography was shown to be dependent on the deposition temperature used. There was also some evidence that prolonged electrochemical experiments resulted in a surface reorganization. Such a process might explain the observed decrease in the rate constant for the ferro/ferricyanide system and the structural changes observed with STM.