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Computational Insights on Functional Materials for Clean Energy Storage: Modeling, Structure and Thermodynamics
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The exponential increase in the demands of world’s energy and the devastating effects of current fossil fuels based sources has forced us to reduce our dependence on the current sources as well as finding cleaner, cheaper and renewable alternates. Being abundant, efficient and renewable, hydrogen can be opted as the best possible replacement of the diminishing and harmful fossil fuels. But the transformation towards the hydrogen-based economy is hindered by the unavailability of suitable storage medium for hydrogen. First principles calculations based on density functional theory has been employed in this thesis to investigate the structures modelling and thermodynamics of various efficient materials capable of storing hydrogen under chemisorption and physisorption mechanisms.

Thanks to their high storage capacity, abundance and low cost, metal hydride (MgH2) has been considered as promising choice for hydrogen storage. However, the biggest drawback is their strong binding with the absorbed hydrogen under chemisorption, which make them inappropriate for operation at ambient conditions. Different strategies have been applied to improve the thermodynamics including doping with light and transitions metals in different phases of MgH2 in bulk form.  Application of mechanical strain along with Al, Si and Ti doping on MgH2 (001) and (100) surfaces has also been found very useful in lowering the dehydrogenation energies that ultimately improve adsorption/desorption temperatures.

Secondly, in this thesis, two-dimensional materials with high surface area have been studied for the adsorption of hydrogen in molecular form (H2) under physisorption. The main disadvantage of this kind of storage is that the adsorption of H2 with these nanostructures likes graphane, silicene, silicane, BN-sheets, BC3 sheets are low and demand operation at cryogenic conditions. To enhance the H2 binding and attain high storage capacity the above-mentioned nanostructures have been functionalized with light metals (alkali, alkaline) and polylithiated species  (OLi2, CLi3, CLi4). The stabilities of the designed functional materials for H2 storage have been verified by means of molecular dynamics simulations.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. , 66 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1073
Keyword [en]
Density functional theory, Molecular dynamics, Hydrogen storage, Chemisorption, Physisorption, Functionalization
National Category
Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
URN: urn:nbn:se:uu:diva-206938ISBN: 978-91-554-8751-5 (print)OAI: oai:DiVA.org:uu-206938DiVA: diva2:646273
Public defence
2013-10-28, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2013-10-04 Created: 2013-09-07 Last updated: 2014-01-23
List of papers
1. Structural, electronic and thermodynamic properties of Al- and Si-doped alpha-, gamma-, and beta-MgH2: Density functional and hybrid density functional calculations
Open this publication in new window or tab >>Structural, electronic and thermodynamic properties of Al- and Si-doped alpha-, gamma-, and beta-MgH2: Density functional and hybrid density functional calculations
2012 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 37, no 11, 9112-9122 p.Article in journal (Refereed) Published
Abstract [en]

In this work, we present a detailed study of Al- and Si-doped alpha-, gamma-, and beta-MgH2 phases using the gradient corrected density functional GGA-PBE and the hybrid Hartree-Fock density functionals PBE0 and HSE06 within the framework of generalized Kohn-Sham density functional theory (DFT) using a plane-wave basis set. We investigate the structural, electronic, and thermodynamical properties of these compounds with regard to their hydrogen storage effectiveness. PBE0 and HSE06 predict cell parameters and bond lengths that are in good agreement with the GGA-PBE calculations and previously known experimental results. As expected smaller band gaps (E(g)s) are predicted by GGA-PBE for the pure magnesium hydride phases. PBE0 overcomes the deficiencies of DFT in treating these materials better than HSE06 and yields E(g)s that compare even better with previous GW calculations. Both the hybrid functionals increase the E(g)s of the Al-doped magnesium hydrides by much less magnitudes than of the Si-doped phases. This difference is interpreted in terms of charge density distributions. Best H-2 adsorption energies (Delta H-ads) are computed by HSE06 while GGA-PBE significantly overestimates them. Si-doped alpha- and beta-MgH2 exhibited the least negative Delta H-ads in close proximity to the H-2 binding energy range of -0.21 to -0.41 eV ideal for practical H-2 storage transportation applications.

Keyword
Hybrid density functionals, Magnesium hydride, Hydrogen storage, Density of states
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-177237 (URN)10.1016/j.ijhydene.2012.03.038 (DOI)000304976300021 ()
Available from: 2012-07-09 Created: 2012-07-04 Last updated: 2017-12-07Bibliographically approved
2. Transition Metals Doped MgH2 for Hydrogen Storage: A Hybrid Density Functional Calculations
Open this publication in new window or tab >>Transition Metals Doped MgH2 for Hydrogen Storage: A Hybrid Density Functional Calculations
2013 (English)In: AIP AdvancesArticle in journal (Refereed) Submitted
Abstract [en]

In this study, we have investigated the structural, electronic and thermodynamic

properties of MgH2 doped with selected transition metals (TMs) by means of hybrid

density functional theory (PBE0). On the structural side, the calculated lattice

parameters and equilibrium volumes increase in case of Sc, Zr and Y opposite to all

the other dopants indicating volumetrically increased hydrogen density. Except Fe, all

the dopants improve the kinetics of MgH2 by reducing the heat of adsorption with Cu,

Nb, Ni and V proving more efficient than others studied TM’s. The electronic

properties have been studied by density of states and correlated with hydrogen

adsorption energies.

Place, publisher, year, edition, pages
Uppsala: , 2013
Keyword
Transition metals, Desorption energy, Hydrogen Storage
National Category
Natural Sciences
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-206633 (URN)
Available from: 2013-09-02 Created: 2013-09-02 Last updated: 2014-01-23Bibliographically approved
3. Strain and doping effects on the energetics of hydrogen desorption from the MgH2 (001) surface
Open this publication in new window or tab >>Strain and doping effects on the energetics of hydrogen desorption from the MgH2 (001) surface
Show others...
2013 (English)In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 101, no 2, 27006- p.Article in journal (Refereed) Published
Abstract [en]

On the basis of first-principles calculations we have systematically investigated the energetics of hydrogen desorption from the MgH2 (001) surface. Based on total energy and electronic structure calculations, two modes namely strain and doping of selected dopants (Al, Si, Ti) and the combined effect of both on the dehydrogenation energies (Delta H) of MgH2 (001) systems have been analyzed. The maximum improvement in Delta H has been obtained with the combined effect of doping and strain. Among all the dopants, Al gives the lowest value of Delta H when the system Al-MgH2 is subjected to a 7.5% biaxial symmetric strain whereas the Si-MgH2 systems show the least improvement in Delta H. The doping of Ti on MgH2 (001) is also very beneficial even without strain. The reduction in Delta H is caused by the charge localization on the metal atoms, destabilization and the weakening of metal-hydrogen bonds.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-197485 (URN)10.1209/0295-5075/101/27006 (DOI)000314677100029 ()
Available from: 2013-03-26 Created: 2013-03-26 Last updated: 2017-12-06Bibliographically approved
4. The effects of strain and doping on the release of hydrogen fromthe MgH2(110) surface
Open this publication in new window or tab >>The effects of strain and doping on the release of hydrogen fromthe MgH2(110) surface
Show others...
2013 (English)In: Computational Material ScienceArticle in journal (Refereed) Submitted
Abstract [en]

In this letter, density functional theory has been employed to investigate the release or

desorption of hydrogen from the MgH2(110) surface. To improve upon the energetics for hydrogen

desorption from this system, the effects of strain and doping by Al, Si, Ti have been explored.

Both of these two effects have been found to be effective. The strain applied along the X direction

induces more prominent effects than along the Y direction. Regarding the doping, the system

doped with Al gives the most noticeable effect. The Si doped system shows the least improvement

while the Ti doped system lies in between as compared to the other two. The combination of

doping and strain effects is found to be more efficacious.

Place, publisher, year, edition, pages
Uppsala: Stockholm, 2013
National Category
Natural Sciences
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-206634 (URN)
Available from: 2013-09-02 Created: 2013-09-02 Last updated: 2014-01-23Bibliographically approved
5. Ab initio study of lithium-doped graphane for hydrogen storage
Open this publication in new window or tab >>Ab initio study of lithium-doped graphane for hydrogen storage
Show others...
2011 (English)In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 96, no 2, 27013- p.Article in journal (Refereed) Published
Abstract [en]

Based on the first-principle density functional calculations we predict that Li-doped graphane (prehydrogenated graphene) can be a potential candidate for hydrogen storage. The calculated Li-binding energy on graphane is significantly higher than the Li bulk's cohesive energy ruling out any possibility of cluster formations in the Li-doped graphane. Our study shows that even with very low concentration (5.56%) of Li doping, the Li-graphane sheet can achieve a reasonable hydrogen storage capacity of 3.23 wt.%. The van der Waals corrected H(2) binding energies fall within the range of 0.12-0.29 eV, suitable for practical H(2) storage applications. 

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-161557 (URN)10.1209/0295-5075/96/27013 (DOI)000295974600036 ()
Available from: 2011-11-20 Created: 2011-11-15 Last updated: 2017-12-08Bibliographically approved
6. Calcium doped graphane as a hydrogen storage material
Open this publication in new window or tab >>Calcium doped graphane as a hydrogen storage material
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2012 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, no 18, 183902- p.Article in journal (Refereed) Published
Abstract [en]

On the basis of first principle density functional theory, we have studied the stability, electronic structure, and hydrogen storage capacity of a monolayer calcium doped graphane (CHCa). The stability of CHCa was further investigated using the ab initio molecular dynamics study. The binding energy of Ca on graphane sheet was found to be higher than its bulk cohesive energy, which indicates the stability of CHCa. It was observed that with a doping concentration of 11.11% of Ca on graphane sheet, a reasonably good H-2 storage capacity of 6 wt. % could be attained. The adsorption energies of H-2 were found to be 0.1 eV, within the range of practical H-2 storage applications.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-174925 (URN)10.1063/1.4710526 (DOI)000303598600068 ()
Available from: 2012-05-30 Created: 2012-05-30 Last updated: 2017-12-07Bibliographically approved
7. Strain induced lithium functionalized graphane as a high capacity hydrogen storage material
Open this publication in new window or tab >>Strain induced lithium functionalized graphane as a high capacity hydrogen storage material
2012 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 10, 103907- p.Article in journal (Refereed) Published
Abstract [en]

Strain effects on the stability, electronic structure, and hydrogen storage capacity of lithium-doped graphane have been investigated by state-of-the-art first principles density functional theory. Molecular dynamics simulations have confirmed the stability of Li on graphane sheet when it is subject to 10% of tensile strain. Under biaxial asymmetric strain, the binding energy of Li of graphane (CH) sheet increases by 52% with respect to its bulk's cohesive energy. With 25% doping concentration of Li on CH sheet, the gravimetric density of hydrogen storage is found to reach up to 12.12wt. %. The adsorption energies of H-2 are found to be within the range of practical H-2 storage applications. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4751249]

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-183760 (URN)10.1063/1.4751249 (DOI)000309072800091 ()
Available from: 2012-11-05 Created: 2012-11-01 Last updated: 2017-12-07Bibliographically approved
8. Metal Functionalized Silicene for Efficient Hydrogen Storage
Open this publication in new window or tab >>Metal Functionalized Silicene for Efficient Hydrogen Storage
2013 (English)In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 14, no 15, 3463-3466 p.Article in journal (Refereed) Published
Abstract [en]

First-principles calculations based on density functional theory are used to investigate the electronic structure along with the stability, bonding mechanism, band gap, and charge transfer of metal-functionalized silicene to envisage its hydrogen-storage capacity. Various metal atoms including Li, Na, K, Be, Mg, and Ca are doped into the most stable configuration of silicene. The corresponding binding energies and charge-transfer mechanisms are discussed from the perspective of hydrogen-storage compatibility. The Li and Na metal dopants are found to be ideally suitable, not only for strong metal-to-substrate binding and uniform distribution over the substrate, but also for the high-capacity storage of hydrogen. The stabilities of both Li- and Na-functionalized silicene are also confirmed through molecular dynamics simulations. It is found that both of the alkali metals, Li+ and Na+, can adsorb five hydrogen molecules, attaining reasonably high storage capacities of 7.75 and 6.9 wt%, respectively, with average adsorption energies within the range suitable for practical hydrogen-storage applications.

National Category
Natural Sciences
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-206630 (URN)10.1002/cphc.201300548 (DOI)000328674000008 ()
Available from: 2013-09-02 Created: 2013-09-02 Last updated: 2017-12-06Bibliographically approved
9. Functionalization of hydrogenated silicene with alkali and alkaline earth metals for efficient hydrogen storage
Open this publication in new window or tab >>Functionalization of hydrogenated silicene with alkali and alkaline earth metals for efficient hydrogen storage
2013 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 15, no 43, 18900-18905 p.Article in journal (Refereed) Published
Abstract [en]

First principles density functional theory has been employed to investigate the electronic structure along with the stability, bonding mechanism, band gap and charge transfer of metal functionalized hydrogenated silicene (SiH), or silicane, in order to envisage the hydrogen storage capacity. Various metal adatoms including Li, Na, K, Be, Mg and Ca have been doped on the most stable chair like configuration of silicane. The corresponding binding energies and charge transfer mechanism have been discussed from the perspective of H-2 storage ability. The Li and Na metal adatoms have been found to be ideally suitable not only for their strong metal to substrate binding and uniform distribution over the substrate but also for their high capacity for storage of hydrogen. The stability of both Li and Na functionalized SiH has also been confirmed by MD simulations. It was found that both Li+ and Na+ adsorbed four H-2 molecules attaining reasonably high storage capacities of 6.30 wt% and 5.40 wt% respectively with average adsorption energies lying within the range suitable for practical H-2 storage applications, in contrast with alkaline earth metals.

Keyword
Silicane, Hydrogen Storage, Adsorption Energy
National Category
Natural Sciences
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-206631 (URN)10.1039/c3cp52830h (DOI)000325943200017 ()
Available from: 2013-09-02 Created: 2013-09-02 Last updated: 2017-12-06Bibliographically approved
10. Polylithiated (OLi2) functionalized graphane as a potential hydrogen storage material
Open this publication in new window or tab >>Polylithiated (OLi2) functionalized graphane as a potential hydrogen storage material
2012 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 24, 243902- p.Article in journal, Letter (Refereed) Published
Abstract [en]

Hydrogen storage capacity, stability, bonding mechanism, and the electronic structure ofpolylithiated molecules (OLi2) functionalized graphane (CH) has been studied by means of firstprinciple DFT. Molecular dynamics have confirmed the stability, while Bader charge analysisdescribes the bonding mechanism of OLi2 with CH. The binding energy of OLi2on CH sheet hasbeen found to be large enough to ensure its uniform distribution without any clustering. It has beenfound that each OLi2 unit can adsorb up to six H2 molecules resulting into a storage capacity of12.90 wt. % with adsorption energies within the range of practical H2storage application.

Place, publisher, year, edition, pages
USA: , 2012
Keyword
Graphane, Polylithiated
National Category
Natural Sciences
Research subject
Physics and Astronomy specializing in Theoretical Physics
Identifiers
urn:nbn:se:uu:diva-188884 (URN)10.1063/1.4772208 (DOI)000312490000108 ()
Available from: 2012-12-20 Created: 2012-12-20 Last updated: 2017-12-06Bibliographically approved
11. Functionalization of hydrogenated graphene by polylithiated species for efficient hydrogen storage
Open this publication in new window or tab >>Functionalization of hydrogenated graphene by polylithiated species for efficient hydrogen storage
2014 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 39, no 6, 2560-2566 p.Article in journal (Refereed) Published
Abstract [en]

The hydrogen (H-2) storage capacity of defected graphane (CH) functionalized by polylithiated species CLi3 and CLi4 has been investigated by means of first-principles DFT calculations. The stability and electronic structures of these potential H-2 storage materials have also been studied. The binding of these lithium rich species (CLi3, CLi4) to the CH sheet has been found to be strong enough to avoid clustering. The nature of bonding in C-Li and C-C has been revealed by Bader charge analysis. It has been found that when both sides of CH sheet are functionalized by polylithiated species, a storage capacity of more than 13 wt % can be achieved with adsorption energies of H-2 in the range of 0.25 eV-0.35 eV, which is suitable for an efficient H-2 storage.

Place, publisher, year, edition, pages
Uppsala: , 2014
National Category
Natural Sciences
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-206635 (URN)10.1016/j.ijhydene.2013.11.083 (DOI)000331920100015 ()
Available from: 2013-09-02 Created: 2013-09-02 Last updated: 2017-12-06Bibliographically approved
12. Hexagonal Boron Nitride Sheet Decorated by Polylithiated Species for Efficient and Reversible Hydrogen Storage
Open this publication in new window or tab >>Hexagonal Boron Nitride Sheet Decorated by Polylithiated Species for Efficient and Reversible Hydrogen Storage
2013 (English)In: Science of Advanced Materials, ISSN 1947-2935, Vol. 5, no 12, 1960-1966 p.Article in journal (Refereed) Published
Abstract [en]

 In the quest for promising hydrogen storage materials, we have performed first principles calculations on CLi3  and OLi2  decorated hexagonal boron nitride (h -BN), sheet. The strong binding of the polylithiated species to pristine and doped BN sheet and the large distance between these functionalized species ensure their uniform distribution over the sheet without being clustered. MD simulations have also confirmed the stabilities of both functionalized systems. Bader analysis and density of states reveals the bonding nature in the systems. A reasonably high H2  storage capacity with the adsorption energies within the desired window suggests that these systems hold promise as efficient H2  storage mediums.

Place, publisher, year, edition, pages
Uppsala: , 2013
Keyword
Polylithiated, Functionalization, Storage Capacity
National Category
Natural Sciences
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-206628 (URN)10.1166/sam.2013.1663 (DOI)000328005200020 ()
Available from: 2013-09-02 Created: 2013-09-02 Last updated: 2014-01-23Bibliographically approved
13.
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