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ABSTRACT: Nitrogen-doped graphene was recently synthesized and was reported to be a catalyst for hydrogen dissociative adsorption under a perpendicular applied electric field (F). In this work, the diffusion of H atoms on N-doped graphene, in the presence and absence of an applied perpendicular electric field, is studied using density functional theory. We demonstrate that the applied field can significantly facilitate the binding of hydrogen molecules on N-doped graphene through dissociative adsorption and diffusion on the surface. By removing the applied field the absorbed H atoms can be released efficiently. Our theoretical calculation indicates that N-doped graphene is a promising hydrogen storage material with reversible hydrogen adsorption/desorption where the applied electric field can act as a switch for the uptake/release processes.
Physical Chemistry Chemical Physics 12/2011; 14(4):1463-7. · 3.57 Impact Factor
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[show abstract]
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ABSTRACT: Nitrogen-doped graphene was recently synthesized and was reported to be a
catalyst for hydrogen dissociative adsorption under a perpendicular applied
electric field (F). In this work, the diffusion of H atoms on N-doped graphene,
in the presence and absence of an applied perpendicular electric field, is
studied using density functional theory. We demonstrate that the applied field
can significantly facilitate the binding of hydrogen molecules on N-doped
graphene through dissociative adsorption and diffusion on the surface. By
removing the applied field the absorbed H atoms can be released efficiently.
Our theoretical calculation indicates that N-doped graphene is a promising
hydrogen storage material with reversible hydrogen adsorption/desorption where
the applied electric field can act as a switch for the uptake/release
processes.
11/2011;
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ABSTRACT: The thermal stability of graphene/graphane nanoribbons (GGNRs) is
investigated using density functional theory. It is found that the energy
barriers for the diffusion of hydrogen atoms on the zigzag and armchair
interfaces of GGNRs are 2.86 and 3.17 eV, respectively, while the diffusion
barrier of an isolated H atom on pristine graphene was only ~0.3 eV. These
results unambiguously demonstrate that the thermal stability of GGNRs can be
enhanced significantly by increasing the hydrogen diffusion barriers through
graphene/graphane interface engineering. This may provide new insights for
viable applications of GGNRs.
11/2010;
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ABSTRACT: Graphane, hydrogenated graphene, was very recently synthesized and predicted to have great potential applications. In this work, we propose a new promising approach for hydrogenation of graphene based on density functional theory (DFT) calculations through the application of a perpendicular electric field after substitutionally doping by nitrogen atoms. These DFT calculations show that the doping by nitrogen atoms into the graphene layer and applying an electrical field normal to the graphene surface induce dissociative adsorption of hydrogen. The dissociative adsorption energy barrier of an H2 molecule on a pristine graphene layer changes from 2.7 to 2.5 eV on N-doped graphene, and to 0.88 eV on N-doped graphene under an electric field of 0.005 au. When increasing the electric field above 0.01 au, the reaction barrier disappears. Therefore, N doping and applying an electric field have catalytic effects on the hydrogenation of graphene, which can be used for hydrogen storage purposes and nanoelectronic applications.
08/2010;
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ABSTRACT: Due to the importance of hydrogenation of graphene for several applications, we present an alternative approach to hydrogenate graphene based on density functional theory calculations. We find that a negative perpendicular electric field F can act as a catalyst to reduce the energy barrier for molecular H2 dissociative adsorption on graphene. Increasing −F above 0.02 a.u. (1 a.u. = 5.14×1011 V/m), this hydrogenation process occurs smoothly without any potential barrier.
Applied Physics Letters 06/2010; 96(25):253106-253106-3. · 3.84 Impact Factor
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ABSTRACT: A promising material for hydrogen storage at room temperature–Al doped graphene is proposed theoretically by using density functional theory calculation. Hydrogen storage capacity of 5.13 wt % is predicted at T=300 K and P=0.1 GPa with an adsorption energy E<sub>b</sub>=-0.260 eV / H <sub>2</sub> . This is close to the target specified by U.S. Department of Energy with a storage capacity of 6 wt % and a binding energy of -0.2 to -0.4 eV / H <sub>2</sub> at ambient temperature and modest pressure for commercial applications. It is believed that the doped Al alters the electronic structures of both C and H <sub>2</sub> . The bands of H <sub>2</sub> overlapping with those of Al and C simultaneously are the underlying mechanism of hydrogen storage capacity enhancement.
Journal of Applied Physics 05/2009; · 2.17 Impact Factor
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ABSTRACT: The thermal stability of interaction between CO molecules and Al doped graphene is studied using ab initio molecular dynamics calculations to reveal the adsorption/desorption behavior of the system. With these results, an adsorption-desorption phase diagram was established with atomic thermodynamics. The temperature (T) dependent desorption time tau(T) was determined with a thermal desorption method. The results show that the optimal desorption temperature is 400 K. The effect of T on atomic structure parameters and electrical properties were analyzed. It shows that the maximum variation of electrical conductivity induced by the adsorption occurs at 400 K, indicating that the best sensing performance of the devices should be at this particular temperature.
Physical Chemistry Chemical Physics 04/2009; 11(11):1683-7. · 3.57 Impact Factor
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ABSTRACT: This review covers interface properties and adsorption behaviors of graphene underlying density functional theory (DFT) simulations and their relevance in evaluation, developing and discovering new materials for gas sensors and hydrogen storage materials. It is intended to be of interest for both experimentalists and theorists to expand application fields of graphene.
The Open Nanoscience Journal 01/2009; 3:34-55.
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ABSTRACT: The origin of the size and temperature dependent Young’s modulus (Y) in noble metal nanowires with fcc structure was investigated by considering the size effects on surface bond contraction and melting temperature (T<sub>m</sub>) variation. The results show that Y decreases with a shrinking disparity between T<sub>m</sub> and the material’s application temperature, while the surface bond contraction results in increase in Y with size reduction. Thus, the variation in Y is the consequence of the subtle interplay and competition between these two factors. This finding indicates that Y of nanowires can be controlled by manipulating the size and the application temperature.
Applied Physics Letters 09/2008; · 3.84 Impact Factor
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ABSTRACT: The atomic structure of the graphene/α-SiO(2)(0001) interface under electric field F with different intensities is studied using the density functional theory method. Simulation results indicate that the atomic structure of the graphene/α-SiO(2)(0001) interface has only a slight change under the condition of F≤0.02 au. However, the distance between substrate and graphene d(0) changes evidently. Moreover, as F reaches 0.03 au, the formation of a C-O covalent bond on the interface is present, which would destroy the excellent electronic properties of graphene. Thus, there exists a maximum for F in application of the graphene.
Nanotechnology 07/2008; 19(27):275710. · 3.98 Impact Factor
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ABSTRACT: A principle of enhancement CO adsorption was developed theoretically by using density functional theory through doping Al into graphene. The results show that the Al doped graphene has strong chemisorption of CO molecule by forming Al-CO bond, where CO onto intrinsic graphene remains weak physisorption. Furthermore, the enhancement of CO sensitivity in the Al doped graphene is determined by a large electrical conductivity change after adsorption, where CO absorption leads to increase of electrical conductivity upon via introducing large amount of shallow acceptor states. Therefore, this newly developed Al doped graphene would be an excellent candidate for sensing CO gas. Comment: 16 pages and 4 figures
06/2008;
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ABSTRACT: Based on the Sutton–Chen many-body potential function, several thermodynamic parameters of Ag are simulated by molecular dynamics. The parameters simulated are size dependences of the Kauzmann temperature TK and melting temperature Tm, and size and temperature dependences of melting enthalpy Hm and melting entropy Sm. The simulation results and the results of the thermodynamic theory models of TK and Tm show good agreement, indicating that as the size of the Ag particles decreases, the TK and Tm functions decrease. However, the ratio of TK and Tm of Ag nanoparticles is size-independent.
Nanotechnology 05/2007; 18(25):255706. · 3.98 Impact Factor
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ABSTRACT: Molecular hydrogen storage at room temperature in Al-doped bulk graphite with wider layer distances was studied using density functional theory calculation. Hydrogen storage capacity of 3.48 wt% or volume density of 51 kg/m3 was predicted at T=300 K and P=0.1 GPa with adsorption energy Eb=−0.264 eV/H2. This is close to the target of volume density 62 kg/m3 and satisfies the requirement of immobilization hydrogen with binding strength of 0.2–0.7 eV/H2 at ambient temperature and modest pressure for commercial applications specified by the U.S. Department of Energy.
Solid State Communications 149:1363-1367. · 1.65 Impact Factor
