Potential oscillations during galvanostatic overoxidation of graphite in aqueous sulphuric acids

Beck, F.; Jiang, Junmei; Krohn, H.

doi:10.1016/0022-0728(95)03870-m

Cited by 76 publications

(53 citation statements)

References 16 publications

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“…This section covers the studies in which poten tiometric and calorimetric measurements were used to study the intercalation dynamics in binary and ternary 29 Thus, it was first demonstrated convincingly that the formation of GB upon the chemical (using K 2 Cr 2 O 7 or KMnO 4 ) and electrochemical oxidation involves consecu tive transformation of higher stages into lower ones, which confirms the domain model of the GIC.…”

Section: Study Of Formation Of Intercalation Compounds By Potentiometmentioning

confidence: 84%

Acceptor-type graphite intercalation compounds and new carbon materials based on them

et al. 2005

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The problems of synthesis and study of the physicochemical properties of graphite interca lation compounds (GIC) formed upon insertion of various molecules into the interplanar space of graphite are considered. Binary and ternary intercalation compounds with protonic acids (HNO 3 , CH 3 COOH, H 3 PO 4 , H 2 SO 4 , etc.) are described. The results of systematic research into graphite intercalation by potentiometry, calorimetry, powder X ray diffraction, conduc tivity measurements, DTA, chemical analysis, and other methods are given. These results underlie elucidation of the characteristic and peculiar features of acid insertion into graphite. The physicochemical properties and practical applications of GIC and low density carbon materials are analyzed.

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Section: Study Of Formation Of Intercalation Compounds By Potentiometmentioning

confidence: 84%

Acceptor-type graphite intercalation compounds and new carbon materials based on them

et al. 2005

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“…Beck et al [2,3] investigated the behavior of graphite in dilute H 2 SO 4 solutions. According to their results, reducing the acid concentration increases the stage index, causes a linear increase in the potential of formation of the corresponding stage (56 mV/mol), and raises the fraction of the corrosion current related to side reactions [4].…”

Section: Introductionmentioning

confidence: 99%

Graphite intercalation in the graphite-H2SO4-R (R = H2O, C2H5OH, C2H5COOH) systems

et al. 2005

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The electrochemical behavior of graphite in polar solvent-H 2 SO 4 electrolytes is studied in a wide range of H 2 SO 4 concentrations. The results demonstrate that, with decreasing H 2 SO 4 concentration, the charging curves become smoother and shift to higher potentials, the stage index increases, and intercalation compounds are more difficult to obtain. At H 2 SO 4 concentrations of 50% and lower, graphite polarization is accompanied by a significant overoxidation, as evidenced by the anomalously small intercalate layer thicknesses: 7.75-7.85 Å. Anodic polarization of graphite in electrolytes consisting of H 2 SO 4 and a polar solvent (H 2 O and C 2 H 5 OH) follows the same mechanism as in the case of the formation of graphite bisulfate. In going from water to C 2 H 5 OH, a less polar solvent, the intercalation threshold increases from 30 to 70% H 2 SO 4 . It is shown using a set of characterization techniques that, in the graphite-H 2 SO 4 -R (R = H 2 O, C 2 H 5 OH) systems, the solvent is not intercalated into graphite. Stage I-III ternary graphite intercalation compounds (TGICs) are synthesized for the first time in the graphite-H 2 SO 4 -C 2 H 5 COOH system: stage I TGICs at H 2 SO 4 concentrations above 70%, stage II in the range 30-70% H 2 SO 4 , and stage III at H 2 SO 4 concentrations down to 10%. The intercalate layer thickness in the TGICs is 7.94 Å. The mechanism of TGIC formation in this system is shown to differ from those in mixtures of H 2 SO 4 and other organic acids. Thermal analysis in combination with spectroscopic analysis of gaseous products provides clear evidence for intercalation of propionic acid into the TGIC and indicates that the thermal stability of this compound is lower than that of graphite bisulfate.

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“…Water molecules can be transported to the next zone. A more detailed description of this mechanism is given in the original reference [161]. Also, Harrach et al [162] have described potential oscillations during the galvanostatic oxidation of highly oriented pyrographite (HOPG) intercalated with H 2 SO 4 .…”

Section: Other Oscillatory Oxidation Reactionsmentioning

confidence: 98%

“…Beck et al [161] have described potential oscillations during galvanostatic overoxidation of graphite electrode in aqueous solution of sulfuric acid to yield electrochemical graphite oxide (EGO). The period of these oscillations was as long as about one hour.…”

Section: Other Oscillatory Oxidation Reactionsmentioning

confidence: 99%

Temporal Instabilities in Anodic Oxidation of Small Molecules/Ions at Solid Electrodes

Orlik

2012

Monographs in Electrochemistry

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Oscillations and multistability in oxidation processes at solid electrodes are important for several reasons. First, they were reported for species that are (or can appear) important in chemical engineering of fuels, including the fuel cells: hydrogen, carbon monoxide, formaldehyde, formic acid/formate ions, 2-propanol, 1-butanol, hydrazine, or ethylene glycol. It can be useful to know how to avoid instabilities involving these species or, on the contrary, to profit from them. Second, electrooxidation of these molecules exhibits rich variety of nonlinear dynamic behaviors which can be treated in a model way for the sake of generalization. Third, some of these processes, under appropriate conditions, can become a source of spatial or spatiotemporal patterns on electrodes which phenomena only recently gained satisfactory explanation and description. In this chapter, we shall summarize the temporal phenomena associated with the oxidation of the above-mentioned molecules, while pattern formation will be discussed in separate Chap. 2 of volume II.Current research data indicate that such processes should be qualified as electrocatalytic, i.e., the electrode surface is actively engaged in the kinetics of the electron transfer reaction, usually involving the process taking place via the adsorbed intermediate. As in the case of other types of electrochemical oscillators, one can observe the evolution of the understanding of the source of chemical instabilitiesfrom early, sometimes oversimplified explanations oriented exclusively on the properties of the electrode/electrolyte interface toward more recent concepts, involving the analysis of the system's stability in terms of nonlinear dynamics. In particular, oscillations under galvanostatic conditions could be understood only recently in terms of the concept of the HN-NDR oscillator [1] (cf. Chap. 3).The anodic oxidation of H 2 on Pt electrode is an electrocatalytic process, in which the electron transfer is preceded by the adsorption of H 2 molecule on the active surface site. Hence, the oscillatory course of this process can be associated M. Orlik, Self-Organization in Electrochemical Systems I, Monographs in Electrochemistry,

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Potential oscillations during galvanostatic overoxidation of graphite in aqueous sulphuric acids

Cited by 76 publications

References 16 publications

Acceptor-type graphite intercalation compounds and new carbon materials based on them

Acceptor-type graphite intercalation compounds and new carbon materials based on them

Graphite intercalation in the graphite-H2SO4-R (R = H2O, C2H5OH, C2H5COOH) systems

Temporal Instabilities in Anodic Oxidation of Small Molecules/Ions at Solid Electrodes

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