Incipient Electrochemical Oxidation of Highly Oriented Pyrolytic Graphite: Correlation between Surface Blistering and Electrolyte Anion Intercalation

Hathcock, Kevin W.; Brumfield, Jay C.; Goss, Charles A.; Irene, E. A.; Murray, Royce W.

doi:10.1021/ac00109a045

Cited by 92 publications

(87 citation statements)

References 19 publications

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“…21,23 Considering the relationship between intercalation and electrowetting that we have described, we found that similar effects to those reported above for ClO4 -were found with SO4 This study further confirms that ion-intercalation/de-intercalation of specific ions (ClO4 -), rather than the anodic formation of graphite oxide or, water oxidation is responsible for the electrowetting of graphite that we observe. …”

Section: Anion Effect On Electrowettingsupporting

confidence: 91%

“…However, there is no intercalation of PO4 3-ions into graphite. 21,22,23 In the studies herein, we control the potential to avoid exfoliation and explore the factors that promote electrowetting and its associated timescale. Our work provides intriguing insights into the effect of step edge density on electrowetting, with the highest quality HOPG samples that have low step edge density (but monolayer steps) leading to more facile ion intercalation/de-intercalation and thus extensive electrowetting.…”

Section: Introductionmentioning

confidence: 99%

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Low-Voltage Voltammetric Electrowetting of Graphite Surfaces by Ion Intercalation/Deintercalation

2016

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We demonstrate low-voltage electrowetting at the surface of freshly cleaved highly oriented pyrolytic graphite (HOPG). Using cyclic voltammetry (CV), electrowetting of a droplet of sodium perchlorate solution is observed at moderately positive potentials on high-quality (low step edge coverage) HOPG, leading to significant changes in contact angle and relative contact diameter that is comparable to the widely studied electrowetting on dielectric (EWOD) system, but over a much lower voltage range. The electrowetting behavior is found to be reasonably fast, reversible and repeatable for at least 20 cyclic scans (maximum tested). In contrast to classical electrowetting, e.g. EWOD, the electrowetting of the droplet on HOPG occurs with the intercalation/de-intercalation of anions between the graphene layers of graphite, driven by the applied potential, observed in the CV response, and detected by X-ray photoelectron spectroscopy. The electrowetting behavior is strongly influenced by those factors that affect the extent of the intercalation/de-intercalation of ions on graphite, such as scan rate, potential polarity, quality of the HOPG substrate (step edge and step height), and type of anion in the solution. In addition to perchlorate, sulfate salts also promote electrowetting, but some other salts do not. Our findings suggest a new mechanism for electrowetting based on ion intercalation and the results are of importance to fundamental 2 electrochemistry, as well as diversifying the means by which electrowetting can be controlled and applied.3

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Section: Anion Effect On Electrowettingsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Low-Voltage Voltammetric Electrowetting of Graphite Surfaces by Ion Intercalation/Deintercalation

2016

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“…previous studies. 30 The mechanism of blister formation on HOPG is shown schematically in Figure 2d. [30][31][32] Anion intercalation starts close to, or at, surface defects ( Figure 2d …”

Section: Resultsmentioning

confidence: 99%

“…graphite), which ultimately leads to delamination, followed by fracturing into a bubble-like blister structure (hollow interior), that is presented on the graphite surface. [30][31][32] These are interesting structures, but their electrocatalytic properties have not been widely studied.…”

Section: Introductionmentioning

confidence: 99%

Nanoscale Electrocatalysis of Hydrazine Electro-Oxidation at Blistered Graphite Electrodes

Kim

Perry

et al. 2016

ACS Appl. Mater. Interfaces

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“…HOPG is rather unusual in that it cannot readily be encapsulated for study, nor can it be cycled to extreme potentials for cleaning without disrupting the surface 27 and promoting ion intercalation. 28 For the studies reported herein, voltammetry was performed on freshly cleaved HOPG surfaces initially using a droplet arrangement. 14a,29 This avoided any possible mechanical strain on the HOPG surface.…”

Section: Cells For Voltammetry On Hopgmentioning

confidence: 99%

A New View of Electrochemistry at Highly Oriented Pyrolytic Graphite

et al. 2012

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Major new insights on electrochemical processes at graphite electrodes are reported, following extensive investigations of two of the most studied redox couples, Fe(CN) 6 4−/3− and Ru(NH 3 ) 6 3+/2+ . Experiments have been carried out on five different grades of highly oriented pyrolytic graphite (HOPG) that vary in step-edge height and surface coverage. Significantly, the same electrochemical characteristic is observed on all surfaces, independent of surface quality: initial cyclic voltammetry (CV) is close to reversible on freshly cleaved surfaces (>400 measurements for Fe(CN) 6 4−/3− and >100 for Ru(NH 3 ) 6 3+/2+ ), in marked contrast to previous studies that have found very slow electron transfer (ET) kinetics, with an interpretation that ET only occurs at step edges. Significantly, high spatial resolution electrochemical imaging with scanning electrochemical cell microscopy, on the highest quality mechanically cleaved HOPG, demonstrates definitively that the pristine basal surface supports fast ET, and that ET is not confined to step edges. However, the history of the HOPG surface strongly influences the electrochemical behavior. Thus, Fe(CN) 6 4−/3− shows markedly diminished ET kinetics with either extended exposure of the HOPG surface to the ambient environment or repeated CV measurements. In situ atomic force microscopy (AFM) reveals that the deterioration in apparent ET kinetics is coupled with the deposition of material on the HOPG electrode, while conducting-AFM highlights that, after cleaving, the local surface conductivity of HOPG deteriorates significantly with time. These observations and new insights are not only important for graphite, but have significant implications for electrochemistry at related carbon materials such as graphene and carbon nanotubes.

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Incipient Electrochemical Oxidation of Highly Oriented Pyrolytic Graphite: Correlation between Surface Blistering and Electrolyte Anion Intercalation

Cited by 92 publications

References 19 publications

Low-Voltage Voltammetric Electrowetting of Graphite Surfaces by Ion Intercalation/Deintercalation

Low-Voltage Voltammetric Electrowetting of Graphite Surfaces by Ion Intercalation/Deintercalation

Nanoscale Electrocatalysis of Hydrazine Electro-Oxidation at Blistered Graphite Electrodes

A New View of Electrochemistry at Highly Oriented Pyrolytic Graphite

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