Oxygenated Edge Plane Sites Slow the Electron Transfer of the Ferro‐/Ferricyanide Redox Couple at Graphite Electrodes

Abstract

The electron transfer kinetics of ferrocyanide, potassium hexachloroiridate(III), hexaammineruthenium(III) chloride, and N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) have been examined at basal plane and edge plane pyrolytic graphite electrodes which have been allowed to oxidise in air for various periods of time. It is demonstrated via voltammetric and X-ray photoelectron spectroscopy (XPS) analysis that oxygenated species formed at edge plane sites/defects decrease the electron transfer kinetics of ferrocyanide but that the rates for potassium hexachloroiridate(III), hexaammineruthenium(III) chloride and TMPD are insensitive to the oxygenated species. The behaviour of the ferro-/ferricyanide couple contrasts with that seen on single-walled carbon nanotubes where oxygenation of the tube ends is known to speed up the electron transfer kinetics (A. Chou, T. Bocking, N. K. Singh, J. J. Gooding, Chem. Commun. 2005, 842); the possible reasons for this contrasting behaviour are discussed.

Exploiting the Properties of Ti‐Doped CVD‐Grown Diamonds for the Assembling of Electrodes

“…Such values range from 10 −6 to 10 2 cm s −1 going from different carbons to metalbased electrodes. [26,[29][30][31][32] As also found in the case of BDD electrodes, the lower values of app 0 k of the Tidoped diamond electrode with respect to metal systems can be ascribed to semiconductive electronic proper ties of the diamond material that translate into a lower poten tialdependent density of electronic states and carrier density as compared to metals. [31,33] Moreover, the absence of specific functional groups on the diamond surface can be responsible for a further rate decrease since it was evidenced that some of them can be involved in the electrocatalysis process of inner sphere electron transfers, such the one occurring for Fe 2+/3+ couple.…”

Direct Electrochemistry of Redox Enzymes as a Tool for Mechanistic Studies

“…In the work of Taniguchi and co-workers, the HOPG surface was peeled off with adhesive tape to adsorb fructose dehydrogenase on a fresh basal-plane. 199 The rate of ET for the ferro/ ferricyanide redox couple is much faster at edge-plane graphite than at basal-plane graphite; 200 this can be used to test the nature of the electrode surface and the presence of edge-plane defects. 114 Glassycarbonwasalsoused,althoughlessfrequently.…”

Carbon Nanomaterials in Biosensors: Should You Use Nanotubes or Graphene?

“…[58][59][60][61] There is evidence, for example, that the favorable electrochemical properties of SWNT-modified electrodes arise from oxygenated carbon species, especially carboxyl moieties, which are produced on the tips of the nanotubes during acid purification. [40,50,62] Conversely, other work has found that increased concentrations of oxygen-containing groups on double-walled or multiwalled CNTs [63,64] and graphite [65] actually slow the rate of heterogeneous electron transfer. In fact, Pumera et al [66] consider that oxygen-containing groups play a minor role in heterogeneous electron transfer for electrochemically activated MWNTs, and suggest instead that the increased heterogeneous electron-transfer rate lies in an increase of the density of edge-like sites on the sidewalls of the tubes.…”