First-principles vdW-DF study on the enhanced hydrogen storage capacity of Pt-adsorbed graphene (original) (raw)
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Pt-decorated graphene as superior media for H2S adsorption: A first-principles study
Applied Surface Science, 2012
The adsorption mechanism of hydrogen sulfide (H 2 S) molecules on pristine and Pt-decorated graphene sheets was studied using density functional theory calculations based on local density approximation and generalized gradient approximation methods. Our calculations show that a Pt-decorated graphene system has much higher binding energy, higher net charge transfer values and shorter connecting distances than pristine graphene due to chemisorption of the H 2 S molecule. Furthermore, the calculated density of states show that orbital hybridization is visible between the H 2 S and Pt-decorated graphene sheets, while there is no evidence for hybridization between the H 2 S molecule and the pristine graphene sheet. Interestingly, we find that up to seven H 2 S molecules can stably bind to a Pt atom on each side of the graphene sheet with desirable binding energy.
Hydrogen storage on platinum decorated graphene: A first-principles study
BIBECHANA, 2014
Adsorption of gaseous/molecular hydrogen on platinum (Pt) decorated and pristine graphene have been studied systematically by using density functional theory (DFT) level of calculations implemented by Quantum ESPRESSO codes. The Perdew-Burke-Ernzerhof (PBE) type generalized gradient approximation (GGA) exchange-correlation functional and London dispersion forces have been incorporated in the DFT-D2 level of algorithm for short and long range electron-electron interactions, respectively. With reference to the binding energy of Pt on different symmetry sites of graphene supercells, the bridge (B) site has been predicted as the best adsorption site. In case of 3×3 supercell of graphene (used for detail calculations), the binding energy has been estimated as 2.02 eV. The band structure and density of states calculations of Pt adatom graphene predict changes in electronic/magnetic properties caused by the atom (Pt). The adatom (Pt) also enhances the binding energy per hydrogen molecule i...
A DFT-D study of hydrogen adsorption on functionalized graphene
RSC Adv., 2015
In this paper, we use density functional theory with dispersion correction functional (DFT-D) as implemented in Vienna Ab Initio Simulation package in order to investigate hydrogen adsorption on graphane (GH) and fluorographene (GF). The adsorption sites at different surface coverage rates were studied to determine the most stable configurations. The comparison between the results obtained using standard pure DFT functionals and dispersion corrected ones; highlight the role of the dispersion effect in the adsorption energies and the orientation of the molecules relative to the surface. The coverage rate is found to increase up to 75% on the two sides, what makes these nanoporous materials, promising candidates for hydrogen storage. Electronic properties such as density of states and band structures were calculated on both GH and GF systems. It is observed that after H 2 adsorption the band gap of GH is only slightly modified, whereas the opposite trend is observed on GF.
Understanding adsorption of hydrogen atoms on graphene
The Journal of Chemical Physics, 2009
Adsorption of hydrogen atoms on a single graphite sheet (graphene) has been investigated by rstprinciples electronic structure means, employing plane-wave based, periodic density functional theory. A reasonably large 5x5 surface unit cell has been employed to study single and multiple adsorption of H atoms. Binding and barrier energies for sequential sticking have been computed for a number of congurations involving adsorption on top of carbon atoms. We nd that binding energies per atom range from ∼ 0.8 eV to ∼ 1.9 eV, with barriers to sticking in the range 0.0 − 0.2 eV. In addition, depending on the number and location of adsorbed hydrogen atoms, we nd that magnetic structures may form in which spin density localizes on a √ 3x √ 3R30 • sublattice, and that binding (barrier) energies for sequential adsorption increase (decrease) linearly with the site-integrated magnetization. These results can be rationalized with the help of the valence-bond resonance theory of planar π conjugated systems, and suggest that preferential sticking due to barrierless adsorption is limited to formation of hydrogen pairs.
2019
We conducted theoretical investigation of the structural and electronic properties of Pt-functionalized graphene and NH-doped Pt-functionalized graphene, which are shown to be efficient materials for hydrogen storage. Nitrene radical dopant was an effective addition required for enhancing the Pt binding on the graphene sheet. We found that up to three H2 molecules could be adsorbed by Pt-functionalized graphene with an average binding energy in the range 3.049−1.731eV eV. The most crucial part of our work is measuring the effect of nitrene radical on Pt-functionalized graphene. Our calculations predicted that the addition of NH radicals on Pt-functionalized graphene enhance the binding of Pt on graphene, which helps also to avoid the desorption of Pt(H2)n (n=1-3) complexes from graphene sheet. Our results also predict Pt-functionalized NH-doped graphene is a potential hydrogen storage medium for on-board applications.
Density functional study of adsorption of molecular hydrogen on graphene layers
The Journal of Chemical Physics, 2000
Density functional theory has been used to study the adsorption of molecular H 2 on a graphene layer. Different adsorption sites on top of atoms, bonds and the center of carbon hexagons have been considered and compared. We conclude that the most stable configuration of H 2 is physisorbed above the center of an hexagon. Barriers for classical diffusion are, however, very small.
First-principles DFT levels of calculations have been carried out in order to study the structural stability and electronic properties of hydrogen passivated graphene (H-graphene) clusters. Two different shaped clusters, rectangular and circular, consisting of 6 to 160 carbon atoms and hydrogen termination at the zigzag boundary edges have been studied. The relative stability of circular shaped cluster consisting 96 C-atoms have been predicted to be around 1.5% greater than that of rectangular shape cluster consisting same number of C-atoms. In comparing circular and rectangular cluster containing same number of C-atoms, the HOMO-LUMO gap of former have been predicted to be 2.159 eV and that of later just 0.346 eV. Adsorption of oxygen atom on H-graphene with different schemes including single sided, both sided and high concentration adsorption, was also studied systematically through first-principles DFT calculations by taking four different H-graphene clusters. The calculations showed that the most stable adsorption site for oxygen adatom on Hgraphene being B-site with adsorption energy 4.011 eV on the rectangular H-graphene cluster consisting 70 carbon atoms. Moreover, on increasing the size of H-graphene cluster, the adsorption energy of oxygen atom found to be increase. The distance of adatom from the nearest carbon atom of H-graphene sheet was 1.52 Å, however, the adatom height from the H-graphene basal plane was 1.97 Å. The bonding of oxygen adatom on H-graphene was through the charge transfer about 0.40 |e| from H-graphene to adatom and includes the negligible local distortion in the underlying planner H-graphene. Charge redistribution upon adsorption induces significant dipole moment 2.356 Debye on rectangular H-graphene cluster consisting 70 carbon atoms. The adsorption energy per O-atom in case of both side adsorption (one at B site and other at opposite B site below the sheet) was found to be around 2% greater than that of single O adsorption. The calculated values of dipole moment (0.881 Debye) and HOMO-LUMO gap (0.590 eV) in this case were almost one third of that for single O adsorption. The adsorption energy per O atom for both side adsorption model such that one at the B site and other at neighboring B site below the H-graphene sheet was found to be 4.650 eV, which is around 14% greater than that of both side adsorption discussed above and 16% greater than that of single O adsorption. The adsorption energy per O-atom, dipole moment and HOMO-LUMO gap in case of three oxygen atom adsorption on the alternate B site of central benzene ring of H-graphene cluster C70H22 have been estimated to be 4.522 eV, 5.898 Debye and 0.820 eV respectively.
Diffusion, adsorption, and desorption of molecular hydrogen on graphene and in graphite
The Journal of Chemical Physics, 2013
The diffusion of molecular hydrogen (H 2) on a layer of graphene and in the interlayer space between the layers of graphite is studied using molecular dynamics computer simulations. The interatomic interactions were modeled by an Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential. Molecular statics calculations of H 2 on graphene indicate binding energies ranging from 41 meV to 54 meV and migration barriers ranging from 3 meV to 12 meV. The potential energy surface of an H 2 molecule on graphene, with the full relaxations of molecular hydrogen and carbon atoms is calculated. Barriers for the formation of H 2 through the Langmuir-Hinshelwood mechanism are calculated. Molecular dynamics calculations of mean square displacements and average surface lifetimes of H 2 on graphene at various temperatures indicate a diffusion barrier of 9.8 meV and a desorption barrier of 28.7 meV. Similar calculations for the diffusion of H 2 in the interlayer space between the graphite sheets indicate high and low temperature regimes for the diffusion with barriers of 51.2 meV and 11.5 meV. Our results are compared with those of first principles.
Influence of Electric Field in the Adsorption of Atomic Hydrogen on Graphene
2015
The influence of external electric field (EF) in the adsorption of atomic hydrogen on graphene (H/G) was studied by means of electronic structure calculations based on spin-polarized density functional theory with generalized gradient approximation (GGA). The changes in atomic hydrogen physisorption-chemisorption on graphene owed to EF (which ranged between −1.25 V/Å and 0.75 V/Å) were determined. Analysis of the electronic charge density for an H/G system explained the EF influences on the adsorption properties (analyzing changes in electronic charge density for H/G system). A decrease of more than 100% in the chemisorption barrier for an EF of −1.25 V/Å was found. The changes in the electronic charge density confirm the possibility of manipulating the physical-chemical adsorption of hydrogen on graphene by applying electric fields.