Electrochemical Characterization of Binderless, Recompressed Exfoliated Graphite Electrodes:  Electron-Transfer Kinetics and Diffusion Characteristics

Abstract

Exfoliated graphite (EG) is prepared by the thermal exfoliation of graphite intercalation compounds at different temperatures. Surface and bulk physicochemical properties of EG are followed by spectroscopic and analytical methods and are observed to be a function of exfoliation temperature. EG particles can be recompressed without any binder and used as surface-renewable electrodes. Surface preparation is accomplished by either polishing or roughening the electrode surface using emery sheets. Effects of exfoliation temperature and the surface preparation on the electron-transfer kinetics and on the diffusion characteristics have been followed by electrochemical methods using several benchmark redox systems. It is found that the electron-transfer kinetics and the diffusion of K(4)[Fe(CN)(6)] are affected by the nature of the EG surface while that of iron(II)(1,10-phenanthroline)(3) and cobalt(II)(1,10-phenanthroline)(3) are not affected by the surface preparation. The redox systems are classified into different groups according to their kinetic sensitivity. Diffusion of electroactive species toward the EG electrodes is found to nonlinear. Current-time plots suggest that the recompressed EG electrodes can be modeled as fractals.

Electron Transfer Processes at Aryl‐Modified Glassy Carbon Electrode

“…Due to the uncertainty of the electron transfer mechanism, several assumptions can be found in literature, ranging from outer -sphere [13,14] to inner -sphere electron transfer [5,6,8]. However, it seems unambiguous to us that Fe(CN) 3À=4À 6 rather follows an inner -sphere mechanism, involving chemisorption.…”

“…It has been found that surface oxides, introduced by polishing of the GC [13,14], do not show any effect on ferricyanide [5,6], however, surface oxides are expected to play a prominent role in the electron transfer kinetics of Fe(CN) 3À=4À 6 [12]. The Frumkin effect for this redox system will be further discussed in the Section 3.5, since the pH is assumed to have an important influence on it.…”

“…Even though, Ramesh and Sampath [14] have employed an exfoliated graphite electrode in their study, we can use their observations for a simplified comparison with our results. Their polished electrode can be assimilated to a grafted GC, namely implying covered edge sites.…”

Enhanced Thermal Conductivity in a Hybrid Graphite Nanoplatelet – Carbon Nanotube Filler for Epoxy Composites

“…GNPs are typically prepared by intercalation and exfoliation of graphite; [24][25][26][27][28][29] and by control of the exfoliation conditions we were able to obtain GNPs comprised of 2 to 8 graphene layers with a lateral dimension of 200-1000 nm and an aspect ratio in the range of 50 to 300. [16] This was achieved by thermal shock exfoliation of natural graphite flakes at 800 8C [25,26] followed by high shear mixing and sonication in order to separate the exfoliated graphite flakes into nanoplatelets.[16] A series of composites were prepared with a hybrid filler loading between 5 wt % and 40 wt % in the epoxy (EPON 682/ EPIKURE) matrix. The ratio of SWNTs and GNPs in the hybrid filler was varied in order to study their efficiency in enhancing the thermal conductivity of the composite.…”

Direct electrochemistry of glucose oxidase assembled on graphene and application to glucose detection

“…Several forms of carbon materials such as graphite [1,2], highly ordered mesoporous carbon [3], carbon nanofiber [4], carbon nanotube [5][6][7][8], etc. have been studied to immobilize redox enzymes and used for developing enzyme-based electrochemical devices.…”