Surface structure and electrical conductivity of natural and artificial graphites

Marchand, D.; Frétigny, Christian; Laguës, M.; Legrand, A. P.; McRae, E.; Marêché, J.F.; Lelaurain, M.

doi:10.1016/0008-6223(84)90082-4

Cited by 19 publications

(7 citation statements)

References 24 publications

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“…4C. We find a significant change in conductivity anisotropy with porosity, increasing from~25 at P~0.7 to >1000 at very low porosity, with the latter value in line with that expected for HOPG [71]. This increase in anisotropy as porosity is decreased is, of course, a direct result of the platelet alignment observed in Fig.…”

Section: Conductivity Anisotropysupporting

confidence: 87%

On the relationship between morphology and conductivity in nanosheet networks

Barwich

Araújo

Rafferty

et al. 2021

Carbon

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It is well-known that the morphology of nanostructured networks is closely linked to network properties. However, controlling and characterizing the morphology of networks of 2D nanosheets has not been explored. In this work, we use networks of liquid-exfoliated graphene nanosheets as a model system to examine the relationship between network morphology and conductivity in nanosheet networks. We use a combination of heat and pressure to controllably alter the morphology of the network, resulting in the annihilation of large pores (>40 nm) and improved nanosheet alignment within the sample. Such compression can result in a tenfold increase in network conductivity. Analysis shows both in-plane and out-of-plane conductivities to scale with porosity in line with percolation theory. The conductivity anisotropy was~3000 at low-porosity and was projected to fall to 1 in the limit of high porosity. Computational studies link the conductivity increase to an increase in network connectivity and a reduction in junction resistance as the porosity is decreased.

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Section: Conductivity Anisotropysupporting

confidence: 87%

On the relationship between morphology and conductivity in nanosheet networks

Barwich

Araújo

Rafferty

et al. 2021

Carbon

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“…However, the isolation of graphene initiated significant advances in preparation of high-quality graphite samples using mechanical exfoliation. [35][36][37] Surprisingly, the fundamental electrochemistry of natural crystalline graphite has barely been explored (with the exception of ionic intercalation) and much of what is understood about basal/edge plane electroactivity has been learned from experiments on HOPG. Mechanical exfoliation of natural graphite, however, can now yield single-crystal monoand multi-layer flakes reaching millimetre lateral dimensions.…”

Section: Introductionmentioning

confidence: 99%

“…Specific dissimilarities are the high step edge density, imperfect layer stacking and rotational disorder of polycrystalline HOPG, 6,34 in comparison to the large crystallite sizes and ordered stacking of the highest-quality natural graphite crystals. [35][36][37] Surprisingly, the fundamental electrochemistry of natural crystalline graphite has barely been explored (with the exception of ionic intercalation) and much of what is understood about basal/edge plane electroactivity has been learned from experiments on HOPG.…”

Section: Introductionmentioning

confidence: 99%

Electron transfer kinetics on natural crystals of MoS₂ and graphite

Velický

Bissett

Tóth

et al. 2015

Phys. Chem. Chem. Phys.

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Here, we evaluate the electrochemical performance of sparsely studied natural crystals of molybdenite and graphite, which have increasingly been used for fabrication of next generation monolayer molybdenum disulphide and graphene energy storage devices. Heterogeneous electron transfer kinetics of several redox mediators, including Fe(CN)6(3-/4-), Ru(NH3)6(3+/2+) and IrCl6(2-/3-) are determined using voltammetry in a micro-droplet cell. The kinetics on both materials are studied as a function of surface defectiveness, surface ageing, applied potential and illumination. We find that the basal planes of both natural MoS2 and graphite show significant electroactivity, but a large decrease in electron transfer kinetics is observed on atmosphere-aged surfaces in comparison to in situ freshly cleaved surfaces of both materials. This is attributed to surface oxidation and adsorption of airborne contaminants at the surface exposed to an ambient environment. In contrast to semimetallic graphite, the electrode kinetics on semiconducting MoS2 are strongly dependent on the surface illumination and applied potential. Furthermore, while visibly present defects/cracks do not significantly affect the response of graphite, the kinetics on MoS2 systematically accelerate with small increase in disorder. These findings have direct implications for use of MoS2 and graphene/graphite as electrode materials in electrochemistry-related applications.

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“…(= 0.22 S cm À1 )] of electric conductivity of a layered graphite monocrystal exceeding 10 5 . [1] Consequently, it has remained a significant challenge to develop large dielectric anisotropy (defined as De = e k Àe ? or Fe = e k /e ?…”

Section: Introductionmentioning

confidence: 99%

“…The relative dielectric constant ε r varies little with anisotropy, with the largest known anisotropic ratio approaching a value less than 10 2 and which either sharply drops to 1–2 orders of magnitude or almost vanishes between two different directions with increasing phase‐transition temperature. In contrast, conductivity is a strong function of direction and the best known example of this is the large anisotropic ratio [ δ ∥ (=222 700 S cm −1 )/ δ ⊥(=0.22 S cm −1 )] of electric conductivity of a layered graphite monocrystal exceeding 10 5 1. Consequently, it has remained a significant challenge to develop large dielectric anisotropy (defined as Δ ε = ε ∥ − ε ⊥ or Φε = ε ∥ / ε ⊥ , in which ε ∥ or ε ⊥ is the real part of the complex permittivity ε = ε r + iε a , and one of the most important physical properties of liquid crystalline compounds that in essence determine the lower threshold voltage of liquid crystal displays (LCDs) 2.…”

Section: Introductionmentioning

confidence: 99%

Homochiral Laminar Europium Metal–Organic Framework with Unprecedented Giant Dielectric Anisotropy

Zhao

et al. 2008

Chemistry A European J

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Hydrothermal (deuteratothermal) reaction of L-ethyl lactate (Lig-Et) with Eu(ClO(4))(3)6 H(2)O gives colorless block crystals of [Eu(Lig)(2)(X(2)O)(2)][ClO(4)] (1, X=H; 2, X=D) both of which possess a two-dimensional laminar homochiral framework. Single-crystal dielectric measurements reveal that 1 and 2 display a giant dielectric anisotropy approximately exceeding 100 and large isotopic effect with about 54 % enhancement along the a axis. Their ferroelectric features further confirm this respect. Crystal parameters: 1, C(6)H(14)ClO(12)Eu, M(r)=465.58, monoclinic, C(2), a=8.6786(6), b=8.3965(6), c=10.2153(7) A, beta=92.040(1) degrees , V=743.92(9) A(3), Z=2, rho(calcd)=2.079 Mg m(-3), R(1)=0.0508, wR(2)=0.1239, mu=4.448 mm(-1), S=1.043; Flack=0.04(5). 2: C(6)H(10)D(4)ClO(12)Eu, M(r)=469.61, monoclinic, C(2), a=8.689(2), b=8.410(2), c=10.224(3) A, beta=92.057(4) degrees , V=746.7(3) A(3), Z=2, rho(calcd)=2.089 Mg m(-3), R(1)=0.0465, wR(2)=0.1150, mu=4.432 mm(-1), S=1.058; Flack=0.02(5).

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Surface structure and electrical conductivity of natural and artificial graphites

Cited by 19 publications

References 24 publications

On the relationship between morphology and conductivity in nanosheet networks

On the relationship between morphology and conductivity in nanosheet networks

Electron transfer kinetics on natural crystals of MoS₂ and graphite

Homochiral Laminar Europium Metal–Organic Framework with Unprecedented Giant Dielectric Anisotropy

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Surface structure and electrical conductivity of natural and artificial graphites

Cited by 19 publications

References 24 publications

On the relationship between morphology and conductivity in nanosheet networks

On the relationship between morphology and conductivity in nanosheet networks

Electron transfer kinetics on natural crystals of MoS2 and graphite

Homochiral Laminar Europium Metal–Organic Framework with Unprecedented Giant Dielectric Anisotropy

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Electron transfer kinetics on natural crystals of MoS₂ and graphite