First-principles study of hydrogen storage on Li12C60 (original) (raw)
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A density functional study of hydrogen storage in Li decorated C20 fullerene
INTERNATIONAL CONFERENCE ON MULTIFUNCTIONAL MATERIALS (ICMM-2019)
Molecular adsorption of hydrogen in lithium decorated smallest fullerene (C 20 Li 2) has been carried out within the framework of density functional theory (DFT) at B3LYP/6311+G(d,p) level. Hydrogen molecules were added sequentially till maximum number of hydrogen molecules could be accommodate by the C 20 Li 2. The kinetic stabilities of the hydrogenated clusters were confirmed through global reactivity descriptors and electronic band gaps. It was observed that the C 20 Li 2 clusters could hold maximum up to eight hydrogen molecule with average adsorption energy in the range 0.11-0.06 eV/H 2 resulting in gravimetric density of 5.98 wt% which was in accordance with the target set by US Department of Energy (US-DOE) for optimal hydrogen adsorption. The average adsorption energy value and the distance between Li atom and hydrogen molecules indicated the process to be physisorption type. Topological analysis using Bader's quantum theory of atoms in molecules (QTAIM) concluded that the interaction between H 2 and Li atom to be closed shell type with ρ < 0.20 a.u with positive ∇ 2 ρ corresponding to ionic or van der Walls bonds.
The interaction of hydrogen with Li-coated C70 fullerene: A DFT study
International Journal of Hydrogen Energy, 2018
We have applied density functional calculations to study the structure, stability and hydrogen storage properties of Li-coated C 70 fullerenes. Our results show that among different possibilities for the geometry of Li-coated C 70 fullerenes, Li atoms prefer to occupy exohedral and endohedral positions on top of the pentagons. Among isomers of Li 2 C 70 and Li 6 C 70 , those in which one of the Li atoms occupy the endohedral position of one of the polar pentagonal rings and the other ones situate on the top of the pentagons around the opposite polar pentagon, have higher binding energies. Charge transfer is occurred from Li to C 70 , putting extra electrons in the vicinity of the Li atom. This results in the binding of hydrogen in atomic form to the on-top C site that is nearest to the Li atom in the preferred configuration of hydrogenated Li-coated C 70 fullerene. Therefore, there are two types of hydrogen binding in Li 6 C 70. One group of hydrogen bind to Li atoms in quasi-molecular form, which will desorb at a lower temperature, and the other group of H atoms bind to C in atomic form, which will desorb at higher temperatures.
Physical Review Letters, 2008
We explore theoretically the feasibility of functionalizing carbon nanostructures for hydrogen storage, focusing on the coating of C 60 fullerenes with light alkaline-earth metals. Our first-principles density functional theory studies show that both Ca and Sr can bind strongly to the C 60 surface, and highly prefer monolayer coating, thereby explaining existing experimental observations. The strong binding is attributed to an intriguing charge transfer mechanism involving the empty d levels of the metal elements. The charge redistribution, in turn, gives rise to electric fields surrounding the coated fullerenes, which can now function as ideal molecular hydrogen attractors. With a hydrogen uptake of >8:4 wt % on Ca 32 C 60 , Ca is superior to all the recently suggested metal coating elements.
Extending the hydrogen storage limit in fullerene
Carbon, 2017
Li 6 C 60 has been chosen as the most representative system to study the hydrogenation mechanism in alkali-cluster intercalated fullerides. We present here a muon spin relaxation (µSR) experiment that hints the chance to achieve a higher storage capacity on fullerene with respect to the values suggested in literature. Moreover, a linear relationship between the muonium adduct radical hyperfine frequency and the level of C 60 hydrogenation was found and it can be exploited to probe the C 60 hydrogenation level, giving more credit to this technique in the field of hydrogen storage materials.
Theoretical investigation on the alkali-metal doped BN fullerene as a material for hydrogen storage
Chemical Physics, 2010
First-principles calculations have been used to investigate hydrogen adsorption on alkali atom doped B 36 N 36 clusters. The alkali atom adsorption takes place near the six tetragonal bridge sites available on the cage, thereby avoiding the notorious clustering problem. Adsorption of alkali atoms involves a charge transfer process, creating positively charged alkali atoms and this polarizes the H 2 molecules thereby, increasing their binding energy. Li atom has been found to adsorb up to three hydrogen molecules with an average binding energy of 0.189 eV. The fully doped Li 6 B 36 N 36 cluster has been found to hold up to 18 hydrogen molecules with the average binding energy of 0.146 eV. This corresponds to a gravimetric density of hydrogen storage of 3.7 wt.%. Chemisorption on the Li 6 B 36 N 36 has been found to be an exothermic reaction, in which 60 hydrogen atoms chemisorbed with an average chemisorption energy of À2.13 eV. Thus, the maximum hydrogen storage capacity of Li doped BN fullerene is 8.9 wt.% in which 60 hydrogen atoms were chemisorbed and 12 hydrogen molecules were adsorbed in molecular form.
Alkali-metal clusters encapsulated into fullerenes: Computations on Lix@C60
Journal of Computational Methods in Sciences and Engineering, 2008
Li@C60 and Li@C70 can be now produced by the low-energy bombardment method in bulk amounts and thus, their computations at higher levels of theory are also of interest. In the report, the computations are carried out on Li@C60, Li2@C60 and Li3@C60 with the B3LYP density-functional treatment in the standard 3-21G and 6-31G* basis sets. In all three species Li atoms exhibit non-central locations relatively close to the cage. The computed energetics suggests that Lix@C60 species could be produced for several small x values if the Li pressure is enhanced sufficiently. This type of metallofullerenes also belongs among potential candidate agents for nanoscience applications including molecular electronics.
2014
We report an innovative synthetic strategy based on the solid state reaction of fullerene C 60 with lithium-transition metals alloys (platinum and palladium), which provides transition metal-decorated lithium intercalated fullerides, with improved hydrogen storage properties. Compounds with Li 6 Pt 0.11 C 60 and Li 6 Pd 0.07 C 60 stoichiometry were obtained and investigated with manometric/calorimetric techniques which showed an 18% increase of the final H 2 absorbed amount with respect to pure Li 6 C 60 (5.9 wt% H 2 ) and an improved absorption process kinetic. The absorption mechanism was investigated with X-rays diffraction which allowed to identify the formation of the hydrofullerides. Scanning Electron Microscopy was applied to gain information on transition metal distribution and detected the presence of platinum and palladium aggregates which are shown to perform a surface catalytic activity towards hydrogen molecule dissociation process.
Applied Surface Science, 2021
Using first principles density functional theory simulations, we have observed that the scandium decorated C24 fullerene can adsorb up to six hydrogen molecules with an average adsorption energy of-0.35 eV per H2 and average desorption temperature of 451 K. The gravimetric wt % of hydrogen for the scandium decorated C24 fullerene system is 13.02%, which is sufficiently higher than the Department of Energy, United States demand. Electronic structure, orbital interactions, and charge transfer mechanisms are explained using the density of states, spatial charge density difference plots, and Bader charge analysis. A total amount of 1.44e charge transfer from the 3d and 4s orbitals of scandium to the 2p carbon orbitals of C24 fullerene. Hydrogen molecules are attached to scandium decorated C24 fullerene by Kubas type of interactions. Diffusion energy barrier calculations predict that the existence of a sufficient energy barrier will prevent metal-metal clustering. Ab-initio molecular dynamics (A.I.M.D.) simulations confirm the solidity of structure at the highest desorption temperature. Therefore, 2 we believe that the scandium decorated C24 fullerene system is a thermodynamically stable, promising reversible high-capacity hydrogen storage device.
Hydrogen storage mechanism and lithium dynamics in Li12C60 investigated by μSR
Carbon, 2015
The lithium cluster intercalated fulleride Li 12 C 60 was investigated by means of Muon Spin Relaxation (lSR) spectroscopy with the intent of unveil its hydrogen storage mechanism. Thanks to the well-known propensity of positive muons to form Muonium, a light isotope of the hydrogen atom, the final stages of the absorption process can be probed. The appearance of a slow oscillating signal in the time evolution of the muon polarization indicates the presence of Li-Mu covalent pair, never observed before in lower doped Li fullerides, which mimics the formation of LiH at the first stage of hydrogen chemisorption in the material. In addition, the lSR signal shows a clear transition above 150 K, compatible with a thermally activated Li cluster rearrangement. The combined Inelastic Neutron Scattering analysis suggests that tetrahedral Li clusters may undergo a progressive melting upon heating, which could favour room temperature ionic diffusion. (M. Riccò ). C A R B O N 9 0 ( 2 0 1 5 ) 1 3 0 -1 3 7 Av ai la bl e at w w w . s c i e n c e di r e c t .c om ScienceDirect j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c a r b o n C A R B O N 9 0 ( 2 0 1 5 ) 1 3 0 -1 3 7
Journal of Alloys and Compounds, 2021
By employing the state-of-the-art density functional theory, we report the hydrogen storage capability of yttrium decorated C24 fullerene. Single Y atom attached on C24 fullerene can reversibly adsorb a maximum number of 6 H2 molecules with average adsorption energy-0.37 eV and average desorption temperature 477 K, suitable for fuel cell applications. The gravimetric weight content of hydrogen is 8.84 %, which exceeds the target value of 6.5 wt % H by the department of energy (DoE) of the United States. Y atom is strongly bonded to C24 fullerene with a binding energy of-3.4 eV due to a charge transfer from Y-4d and Y-5s orbitals to the C-2p orbitals of C24 fullerene. The interaction of H2 molecules with Y atom is due to the Kubas type interaction involving a charge donation from the metal d orbital to H 1s orbital, and back donation causing slight elongation of H-H bond length. The stability of the system at the highest desorption temperature is confirmed by ab-initio molecular dynamics simulations, and the metal-metal clustering formation has been investigated by computing the diffusion energy 2 barrier for the movement of Y atoms. We have corrected all the calculated energies for the van der Waals (vdW) interactions by applying the dispersion energy corrections, in addition to the contribution of the GGA exchange-correlation functional. The C24+Y system is stable at room temperature, and at the highest desorption temperature, the presence of a sufficient diffusion energy barrier prevents metal-metal clustering. Furthermore, binding energies of H2 are within the target value by DoE (-0.2-0.7 eV/H2), while H2 uptake (8.84 % H) is higher than DoE's criteria. Therefore, we propose that Y decorated C24 fullerene can be tailored as a practically viable potential hydrogen storage candidate.