Highly ordered pyrolytic graphite electrode

Lee, C.-Y. and Bond, A.M. (2008) Evaluation of levels of defect sites present in highly ordered pyrolytic graphite electrodes using capacitive and faradaic current components derived simultaneously from large-amplitude Fourier transformed ac voltammetric experiments. Anal. Chem., 81, 584- 594. 

Figure 1. Reflectance spectra of Fe-TsPc in 0.1 M NaOH adsorbed on the basal plane of a highly ordered pyrolytic graphite (HOPG) electrode at 0.90 V vs. a-Pd and on a Pt electrode at 0.70 V with Ar (0) and O2 ( A ) saturated solutions. Reproduced with...

On highly ordered pyrolytic graphite, HOPG(OOOl) electrodes, no UPD has been detected owing to weak carbon-lead interactions [311]. Deposition occurs by three-dimensional island growth according to Volmer-Weber mechanism. Initial steps are controlled by progressive nucleation on active sites and hemispherical diffusion. 

Figure 10.2 Fe(CN) /4 voltammetry on glassy carbon (GC) fractured in solution, and on basal plane highly ordered pyrolytic graphite (HOPG). 1 mM K4Fe(CN)6 in 1 M KC1, scan rate = 0.2 V/s. AEp for fractured GC voltammogram = 64 mV, corresponding to k° > 0.1 cm/s, AEp for HOPG = 1005 mV, k° = 1 x 10 6 cm/s. Potential scale is relative to silver quasi-reference electrode.

Cgraphite A highly-ordered pyrolytic graphite (HOPG) electrode was polished so as to expose... 

An electrochemically heterogeneous electrode is one where the electrochemical activity varies over the surface of the electrode. This broad classification encompasses a variety of electrode types [1, 2] including microelectrode arrays, partially blocked electrodes, electrodes made of composite materials, porous electrodes and electrodes modified with distributions of micro- and nanoscale electroactive particles. In this chapter, we extend the mathematical models developed in the previous chapter, in order to accurately simulate microelectrode arrays. Fbrther, we explore the applications of a number of niche experimental systems, including partially blocked electrodes, highly ordered pyrolytic graphite, etc., and develop simulation models for them. 

This chapter addresses several issues dealing with the mechanism of SEI formation on inert substrates, lithium, carbonaceous materials and tin-based alloys. Attention is currently focused on the correlation between the composition and morphology of the solid-electrolyte interphase forming on the different planes of highly ordered pyrolytic graphite (HOPG) and different types of disordered carbon electrodes in lithium-ion cells. 

Through the use of highly ordered pyrolytic graphite (HOPG) it is possible to produce an electrode which is predominantly basal in character, but even with such a surface, edge plane defects will be present in the form of steps (as indicated in Fig. 6.1). Careful preparation can lead to a surface where these edge plane defects are up to 1-10 /uM apart. 

The other major electrochemical modification approach has been that in which aromatic diazonium salts in an electrolyte solution are reduced at a diamond electrode this leads to the formation of an aryl radical, which can then attach to the diamond surface [74], This work is based on a series of papers in which the same technique was applied to the surface modification of glassy carbon and highly ordered pyrolytic graphite (HOPG) [75-78]. This approach may also be quite fruitful for tbe covalent modification of diamond surfaces, if the attachment is as robust as it is on glassy carbon surfaces. 

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