Electrochemical behaviour of graphite- and molybdenum electrodes modified with thin-film diamond

Films of undoped polycrystalline diamond were deposited on molybdenum or graphite substrates by hot filament chemical vapour deposition (HFCVD), using a precursor gas mixture of methane in excess hydrogen. The morphology and quality of the as-deposited films were monitored by scanning electron microscopy, Raman spectroscopy, and X-ray diffraction, and the electrochemical activity monitored with cyclic voltammetry. The results suggest a direct correlation between electrochemical activity, film thickness, and quality. Analysis of the ferrocyanide–ferricyanide couple at a diamond-modified molybdenum or graphite electrode suggest some extent of electrochemical reversibility, but the rates of charge transfer across the diamond– substrate interface varied with the methane concentration and substrate type. The ratio of the anodic and cathodic peak currents was always close to unity. Ex situ studies with energy dispersive spectroscopy show that some Prussian Blue was deposited on the graphite-modified electrode, grown using 0.5% CH in H . 2002 Elsevier Science B.V. All rights reserved. 4 2