Graphane Research Articles

Aqueous Proton Transportation in Graphene-Based Nanochannels.

Graphene oxide (GO) has been unveiled to exhibit high proton conductivity in a humidified or aqueous environment, making it a promising candidate to construct proton conduction nanochannels. In this work, we systematically investigate how the confinement effect and surface chemistry influence the proton transportation behavior in graphene-based nanochannels via extensive ReaxFF MD simulations. Graphene (GE), graphane (GA), and hydroxygraphane (HG) sheets were employed to mimic the graphitic and functionalized region of GO and construct nanochannels with different interlayer distances. We find that confined water molecules are stratified and their orientation is influenced by the surface chemistry, thus impacting the distribution of protons. Surface chemistry makes the compression of the hydrogen-bond network induced by the confinement effect more variable. The hydrogen-bond network between GE slabs is crushed by extreme confinement and ultrafast proton transportation behavior mainly achieved via vehicle mechanism. Meanwhile, the hydrogen-bond network and solvation structure can be kept more complete with the existence of functional groups. The hydrogen bonds formed with surface functional groups impede the transportation of water molecules but allow more Grotthuss hopping of protons to different extents. Our work clarified the proton transportation mechanism in graphene-based nanochannels with different interlayer distances and surface chemistry and can guide the future design of proton conduction devices such as proton exchange membranes.

Механофизика и механохимия графена и графана

Механофизика и механохимия графена и графана

Effect of polymer matrix and nanofiller on non-bonding interfacial properties of nanocomposites

To investigate the effect of polymer matrix and nanofiller on interfacial mechanical properties of their resulting nanoreinforced composites, pull-out tests of different nanofillers, such as graphene (GE), graphane (GA) and carbon nanotube (CNT), from various polymer matrix including polyethylene (PE), poly(methyl methacrylate) (PMMA), polytetrafluoroethylene (PTFE) and poly(vinylidene chloride) (PVDC), are simulated using molecular dynamics method (MD). The velocity-load model is applied in MD simulations, and the variation of non-bonding energy (van der Waals interaction), pull force and the average interfacial shear strength (ISS) in the pull-out process are obtained and presented graphically. Under the same mass density, when PE is used as polymer matrix for GE and CNT nanofillers, the resulting nanoreinforced composite possesses the highest non-bonding interfacial energy and the strongest ISS, and the pull force required for pulling out the nanofiller is the largest. For GA nanofiller, the GA-PMMA produces the highest non-bonding interfacial energy and the ISS. With the increase of diameter of CNT, the effect of its reinforcement becomes weak gradually. The chirality of GE does not influence the interfacial mechanical property of GE-reinforced nanocomposite. The (3, 3) CNT nanofiller produces the almost identical interfacial characteristic compared with GE nanofiller. However, when the GA nanofiller is used, the non-bonding energy, pull force and the average ISS of nanocomposite increases by nearly 100%.

Electronic Structures and Photocatalytic Responses of SrTiO3(100) Surface Interfaced with Graphene, Reduced Graphene Oxide, and Graphane: Surface Termination Effect

The enhanced photocatalytic activity of SrTiO3(STO), a promising photocatalyst for decomposing organic compounds and overall water splitting for H2/O2 evolution, has been experimentally demonstrated by coupling the graphene (GR) sheet. Here, we reveal the mechanism of the enhanced photocatalytic activity of STO/GR composites using ab initio calculations. Due to C 2p states forming the bottom of the conduction band or the top of the valence band, the band gap is reduced to about 0.6 eV, resulting in a strong absorption in the visible region. The composites of STO coupled with reduced graphene oxide (RGO) and graphane (GRH) are also explored to investigate their potential photocatalytic activity. We demonstrate that the surface termination layer of the STO(100) surface plays an important role in determining the formation energy, interfacial distance, band gap, and optical absorption of these composites. Moreover, the GR sheet is a sensitizer for STO with a termination layer of TiO2; on the contrary, it is a...

A DFT-D study of hydrogen adsorption on functionalized graphene

In this paper, we use density functional theory with dispersion correction functional (DFT-D) as implemented in the Vienna ab initio simulation package in order to investigate hydrogen adsorption on graphane (GH) and fluorographene (GF).

Wrinkling deformation and thermal conductivity of one graphane sheet under shear

Molecular dynamics simulations were performed to investigate the wrinkling deformation of one single-layer graphane (GA) sheet under shear, and the shear deformation was compared with that of the macromembrane under shear. Furthermore, the thermal conductivity of the wrinkled GA sheet at 300 K was calculated. Moreover, the differences of anti-shear capability and thermal conductance between the GA and another corresponding graphene sheet are discussed. The results show that the solutions of the macromembrane are applicable to predict the wrinkling deformation of the GA sheet under shear and that both the GA and the graphene sheet under shear have comparable anti-buckling capability, whereas the GA sheet has much lower post-buckling load-carrying capacity. By increasing the shear strain, the thermal conductivity of both the GA and the graphene sheets decreases, and under the same shear strain the graphene sheet has higher thermal conductivity than the GA sheet.

Thermal properties of fluorinated graphene

Large scale atomistic simulations using the reactive force field approach (ReaxFF) are implemented to investigate the thermomechanical properties of fluorinated graphene (FG). A new set of parameters for the reactive force field potential (ReaxFF) optimized to reproduce key quantum mechanical properties of relevant carbon-fluor cluster systems are presented. Molecular dynamics (MD) simulations are used to investigate the thermal rippling behavior of FG and its mechanical properties and compare them with graphene (GE), graphane (GA) and a sheet of BN. The mean square value of the height fluctuations $< h^2>$ and the height-height correlation function $H(q)$ for different system sizes and temperatures show that FG is an un-rippled system in contrast to the thermal rippling behavior of graphene (GE). The effective Young's modulus of a flake of fluorinated graphene is obtained to be 273 N/m and 250 N/m for a flake of FG under uniaxial strain along arm-chair and zig-zag direction, respectively.

TWO DIMENSIONAL AND NOVEL QUASI TWO DIMENSIONAL QUANTUM LIQUIDS

In this thesis we have used Quantum Monte Carlo techniques to study two systems that can be regarded as the archetype for neutral strongly interacting systems: 4He, and its fermionic counterpart 3He.More specifically, we have used the Path Integral Ground State and the Path Integral Monte Carlo methods to study a system of two dimensional 3He (2d-3He) and a system of 4He adsorbed on Graphene-Fluoride (GF) and Graphane (GH) at both zero and finite temperature. The purpose of the study of 4He on GF (GH) was the research of new physical phenomena, whereas in the case of 2d-3He it was the application of novel methodologies for the ab-initio study of static and dynamic properties of Fermi systems. In the case of 2d-3He we have computed the spin susceptibility as function of density which turned out to be in very good agreement with experimental data; we have also obtained the first ab-initio evaluation of the zero-sound mode and the dynamic structure factor of 2d-3He that is in remarkably good agreement with experiments. In the case of 4He adsorbed on GF (GH), we determined the zero temperature equilibrium density of the first monolayer of 4He showing also that the commensurate sqrt(3) x sqrt(3) R30 phase is unstable on both substrates; at equilibrium density we found that 4He on GF (GH) is a modulated superfluid with an anisotropic phono-rotonic spectrum; at high coverages we found an incommensurate triangular solid and, on both GF and GH, a commensurate phase at filling factor x= 2/7 that is locally stable or at least metastable. Remarkably, in this commensurate solid phase and for both GF and GH, our computations show preliminary evidence of the presence of a superfluid fraction.

Thermodynamic Aspects of the Graphene/Graphane/Hydrogen Systems: Relevance to the Hydrogen On-Board Storage Problem

The present analytical review is devoted to the current problem of thermodynamic stability and related thermodynamic characteristics of the following graphene layers systems: 1) double-side hydrogenated graphene of composition CH (theoretical graphane) (Sofo et al. 2007) and experimental graphane (Elias et al. 2009); 2) theoretical single-side hydrogenated graphene of composition CH; 3) theoretical single-side hydrogenated graphene of composition C2H (graphone); 4) experimental hydrogenated epitaxial graphene, bilayer graphene and a few layers of graphene on SiO2 or other substrates; 5) experimental and theoretical single-external side hydrogenated single-walled carbon nanotubes, and experimental hydrofullerene C60H36; 6) experimental single-internal side hydrogenated (up to C2H or CH composition) graphene nanoblisters with intercalated high pressure H2 gas inside them, formed on a surface of highly oriented pyrolytic graphite or epitaxial graphene under the atomic hydrogen treatment; and 7) experimental hydrogenated graphite nanofibers-multigraphene with intercalated solid H2 nano-regions of high density inside them, relevant to solving the problem of hydrogen on-board storage (Nechaev 2011-2012).

Novel substrates for Helium adsorption: Graphane and Graphene—Fluoride

The discovery of fullerenes has stimulated extensive exploration of the resulting behavior of adsorbed films. Our study addresses the planar substrates graphene—fluoride (GF) and graphane (GH) in comparison to graphene. We present initial results concerning the potential energy, energy bands and low density behavior of 4He and 3He films on such different surfaces. For example, while graphene presents an adsorption potential that is qualitatively similar to that on graphite, GF and GH yield potentials with different symmetry, a number of adsorption sites double that on graphene/graphite and a larger corrugation for the adatom. In the case of GF, the lowest energy band width is similar to that on graphite but the He atom has a significantly larger effective mass and the adsorption energy is about three time that on graphite. Implications concerning the monolayer phase diagram of 4He are explored with the exact path integral ground state method. A commensurate ordered state similar to the R30° state on graphite is found the be unstable both on GF and on GH. The ground states of submonolayer 4He on both GF and GH are superfluids with a Bose Einstein condensate fraction of about 10%.

Publisher's Note: “Wettability of pristine and alkyl-functionalized graphane” [J. Chem. Phys. 137, 034707 (2012)

Publisher's Note: “Wettability of pristine and alkyl-functionalized graphane” [J. Chem. Phys. 137, 034707 (2012)

Here comes graphane?

Here comes graphane?