Voltammetry at graphite electrodes: The oxidation of hexacyanoferrate (II) (ferrocyanide) does not exhibit pure outer-sphere electron transfer kinetics and is sensitive to pre-exposure of the electrode to organic solvents

Through theoretical modelling based upon a diffusion domain approach, we show that for a basal plane pyrolytic graphite electrode with a 10-20% surface coverage of edge plane sites, minimal differences in the voltammetric response should be expected from that of an edge plane pyrolytic graphite electrode. Further through the use of organic solvents, for the modification of the electrode surface, it is demonstrated that the voltammetry of the oxidation of ferrocyanide in aqueous solution is surface sensitive and we infer that it likely occurs through the formation of a bridging ion complex with the electrode surface. Accordingly it is suggested that the electron transfer mechanism for the oxidation of ferrocyanide at a graphite electrode should not be viewed as being outer-sphere in nature. These results have implications for voltammetric experimentation with both graphite and carbon nanotube modified electrodes. (C) 2011 Elsevier B.V. All rights reserved.