Flow of quasi-two dimensional water in graphene channels

Fang, Chao; Wu, Xinke; Yang, Fengchang; Qiao, Rui

doi:10.1063/1.5017491

Cited by 19 publications

(12 citation statements)

References 43 publications

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“…The nonconducting model surface consists of a single layer of 5600 charge-free carbon atoms on a graphene lattice, interacting with water via the Lennard-Jones potential. ,, The conductor behavior of graphene is captured by the addition of fluctuating Gaussian charges on carbon atoms as outlined in the Results and Discussion section. We mitigate finite size effects by periodically replicating the surface in the lateral ( x , y ) directions.…”

Section: Models and Methodsmentioning

confidence: 99%

Solvent–Solvent Correlations across Graphene: The Effect of Image Charges

et al. 2020

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Wetting experiments show pure graphene to be weakly hydrophilic, but its contact angle (CA) also reflects the character of the supporting material. Measurements and molecular dynamics simulations on suspended and supported graphene often reveal a CA reduction due to the presence of the supporting substrate. A similar reduction is consistently observed when graphene is wetted from both sides. The effect has been attributed to transparency to molecular interactions across the graphene sheet; however, the possibility of substrate-induced graphene polarization has also been considered. Computer simulations of CA on graphene have so far been determined by ignoring the material's conducting properties. We improve the graphene model by incorporating its conductivity according to the constant applied potential molecular dynamics. Using this method, we compare the wettabilities of suspended graphene and graphene supported by water by measuring the CA of cylindrical water drops on the sheets. The inclusion of graphene conductivity and concomitant polarization effects leads to a lower CA on suspended graphene, but the CA reduction is significantly bigger when the sheets are also wetted from the opposite side. The stronger adhesion is accompanied by a profound change in the correlations among water molecules across the sheet. While partial charges on water molecules interacting across an insulator sheet attract charges of the opposite sign, apparent attraction among like charges is manifested across the conducting graphene. The change is associated with graphene polarization, as the image charges inside the conductor attract equally signed partial charges of water molecules on both sides of the sheet. Additionally, using a nonpolar liquid (diiodomethane), we affirm a detectable wetting translucency when liquid−liquid forces are dominated by dispersive interactions. Our findings are important for predictive modeling toward a variety of applications including sensors, fuel cell membranes, water filtration, and graphene-based electrode materials in high-performance supercapacitors.

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Section: Models and Methodsmentioning

confidence: 99%

Solvent–Solvent Correlations across Graphene: The Effect of Image Charges

et al. 2020

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“…The effective channel height ( h eff ), which considers the atomic size of carbon atoms, is estimated by subtracting the van der Waals size of carbon atoms from the nominal channel height, h , such that h eff = h – 3.4 Å . The number of water molecules inside the channel is selected in such a manner that it reproduces an internal pressure of 1 bar , (see Section S3 in the Supporting Information). The simulations are conducted as follows: first, water molecules and carbon atoms are heated from 10 to 300 K over 50 ps.…”

Section: Computational Methodsmentioning

confidence: 99%

Quantifying Water Friction in Misaligned Graphene Channels under Ångström Confinements

Wagemann

Misra

Das

et al. 2020

ACS Appl. Mater. Interfaces

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Two-dimensional (2D) materials, such as graphene (GE), hold great potential to be employed as the fundamental building blocks of novel nanofluidic devices for a wide range of applications. Recent advances in experimental techniques are materializing such prospects by enabling the assembly of 2D material-based fluidic channels with heights as small as few Ångstroms. Here, we conduct molecular dynamics simulations to probe the effect of the relative misalignment between the walls of the GE fluidic channel with Ångstroms height on the resistance to water transport through the channel. Two types of misalignments are studied, namely, translational and rotational misalignments. Our results show that the relative misalignment of the GE lattices can lead to a substantial reduction in the friction between water and the channel walls. Moreover, a dependence of the friction on the degree of misalignment and flow direction is found for the cases with translational misalignment. In contrast, the resistance exerted by the channels with rotational misalignment is found to be independent of the rotation angle (θ) for 0°< θ < 60°but always lower than the perfectly aligned case. We associate such lowering of the resistance to water transport to the corrugation and the anisotropy in the corresponding potential energy landscape associated with each degree of misalignment. The findings, therefore, point to an unprecedented possibility of significantly enhancing the water transport in Ångstroms height GE channels by engineering the misalignments of the GE channel walls.

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“…It has been recognized that for nanopores with hydrophilic surfaces, the confined fluid viscosity increases by decreasing the confinement size; however, for nanopores with hydrophobic surfaces, the viscosity decreases by reducing the pore size. Nevertheless, recently, it has also been reported that the hydrophobic carbon surface could lead to an enhanced confined viscosity. − These different phenomena and results might suggest that the surface nature is not the critical factor determining the confined fluid viscosity within the nanopore, and instead, the surface-induced molecular structure and interfacial interaction will control the viscosity.…”

Section: Introductionmentioning

confidence: 99%

Viscosity and Structure of Water and Ethanol within GO Nanochannels: A Molecular Simulation Study

Chen

Zhan

et al. 2020

J. Phys. Chem. B

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The behavior of liquids in two-dimensional (2-D) graphene oxide (GO) nanopores is important for developing GObased nanoscience and nanofluidics. Herein, molecular dynamics simulation was carried out to study the equilibrium structures and shear viscosity for water and ethanol confined within 2-D GO nanochannels. It was observed that both species obviously exhibit structured features near GO surfaces. The confined viscosities are anisotropic with axial shear viscosity larger than vertical viscosity. The axial shear viscosities of water and ethanol are greatly enhanced for the 2-D GO nanochannels, wherein the viscosity features a decreased pattern with the pore width. Compared with water molecules, the confinement of GO channels has more effect on the viscosity of ethanol molecules. The confined shear viscosity can be described by combining contributions of the interfacial layer viscosity and the bulk-like viscosity. The influences of oxidation degrees and pore widths on the structure and transport properties have been systematically investigated, in which the interlayer viscosity is the critical determining factor. The confined structures and surface interaction were applied to interpret the transport properties of confined liquids. The enhanced interfacial layer viscosity can be attributed to the surface hydrogen-bonding interaction arising from the oxygen-containing functional groups.

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Flow of quasi-two dimensional water in graphene channels

Cited by 19 publications

References 43 publications

Solvent–Solvent Correlations across Graphene: The Effect of Image Charges

Solvent–Solvent Correlations across Graphene: The Effect of Image Charges

Quantifying Water Friction in Misaligned Graphene Channels under Ångström Confinements

Viscosity and Structure of Water and Ethanol within GO Nanochannels: A Molecular Simulation Study

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