Edge plane, HOPG

It is important to clarify that there have been, in the literature, some examples of electrochemical processes on CNT-modified electrodes on which an apparent electrocatalytic process associated to the CNTs seems to take place (that is from the edge-plane-like sites) where in fact that was not the case. An example is the apparent electrocatalytic oxidation ofhydrazine at MWNTelectrodes [64,65]. Such electrochemical behavior has been demonstrated to be a consequence of iron impurities contained in the CNTs that were responsible for the observed electrocatalytic effects (Figure 3.7). Therefore, caution is needed when reporting catalytic effects of CNTs under a given redox system and a careful comparison vdth, for instance, edge HOPG is mandatory to make sure that the CNTs are the responsible for the electrochemical enhancement. 

Fig. 13.12 ESED of noble metals is a tri-potential sequence (inset), (a) Eirst the HOPG step edges are oxidized to form carboxyl groups, disrupting edge sp bond, (b) deposition is initiated with nucleation sites at the edge plane from a low potential pulse, (c) followed by a low overpotential step for subsequent growth of the nucleation sites to the coalescing point...

Figure 14.6 Cyclic voltammetry in 1.0 mM K4[Fe(CN)6] and 1.0 M KCl at a scan rate of 20 mV/s with (a) HOPG basal planes (continuous line, a sample exposed in the air for several days dashed line, a freshly cleaved sample) and (b) HOPG edge planes (continuous line, end-connected dashed line, side-connected). (Adapted with permission from ref. 43. Copyright 2004 Royal Society of Chemistry.)...

Figure 2.13 CV for the reduction of 1 mM Fe(CN)g " in aqueous 0.1 M KCI solution at a scan rate of 75mVs (a) ZYH-grade HOPG electrode shows a highly irreversible process and (b) ZYH-grade HOPG electrode, which was hand-polished to create edge-plane defect sites, displays both a reversible and irreversible process, (c) Relationship of A p...

Figure 2.16 (a) Schematic of the simulation geometry model for a Nafion-coated HOPG surface (i), where the numbers are indicative of the film-solution interface (1), periodic boundaries from which the step array response can be determined (2a, 2b), step-edge plane (3), and basal plane (4a, 4b), respectively, and simulated concentration profiles for a Nafion-Ru(bpy)3 +... 

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