High-capacity Hydrogen Storage Medium Research Articles

Potential reversible and high-capacity hydrogen storage medium: Li-decorated B3S monolayers

The potential application of the B3S monolayer with and without Li decorated as hydrogen storage materials (HSMs) were studied using DFT calculations. We found that the interactions between H2 molecule and the pure B3S monolayer is too tiny to meet the requirements of optimal HSMs. The large binding energy (3.00–3.30 eV) of Li atoms on the B3S monolayer effectively hinders Li clustering. The adsorption energy per H2 for H2 molecules on the Li-decorated B3S monolayer is as moderate as between 0.167 and 0.208 eV, and the electrostatic nature of the interactions between H2 and Li-decorated monolayers is found. The Li-decorated B3S monolayers have high gravimetric and volumetric capacity of 7.7 wt% and 94.8 g/L, respectively. The desorption temperature indicates that the Li-decorated B3S monolayers as HSMs have high reversibility over the temperature of 224 K, and AIMD simulations show that H2 molecules have no kinetic hindrance for desorption. Therefore, the Li-decorated B3S monolayers are reversible and high capacity materials for hydrogen storage meeting the targets of U.S. DOE.

The optimal adsorption pathway of H2 molecules on Ti-Acetylene/ ethylene compounds: A DFT study

Ti-Acetylene/Ethylene complexes were used to be considered as a potential high capacity hydrogen storage media by physisorption. Here, special attentions have been paid to the optimal adsorption pathway of H2 molecules on TiC2H2/TiC2H4 compounds by using CCSD(T) and B3LYP functionals. An interesting result is that some most stable configurations of TiC2H2(nH2)(n = 1–7) complexes are not the structures coordinated by H2 molecules but plausible hydrogenation intermediates. Based on the potential energy profiles and MD simulations, the optimal adsorption pathway is considered as TiC2H2(T) → 1b → 2c → 2b → 2a → 3b → 3a → 4a → 5a → 5b → 6d → C2H6 + Ti(H2)5 for TiC2H2 and TiC2H4(1c) → 2a → 3b → 3a → 4a → 5a → 5b → 6d → C2H6+Ti(H2)5 for TiC2H4. It indicates that the adsorptions of H2 molecules on TiC2H2/TiC2H4 contain chemisorption and physisorption. The product C2H6+Ti(H2)5 exhibits 14 wt% uptake of H2, which is completely consistent with the experimental results.

Hydrogen storage in Na-decorated H4,4,4-graphyne: A density functional theory and Monte Carlo study

To find appropriate hydrogen storage materials, Na-decorated H4,4,4-graphyne has been investigated by combing a density functional theory (DFT) and grand canonical Monte Carlo simulations (GCMC). From DFT, we find that the most priority adsorption site for Na atom is the acetylenic ring center of the H4,4,4-graphyne. The Na atoms are adsorbed on two sides of the acetylenic ring named 4Na-decorated H4,4,4-graphyne, with the average binding energy of 2.33 eV. With H2 molecules are introduced into the surface of 4Na-decorated H4,4,4-graphyne continuously, it is found that up to 9 H2 molecules are adsorbed around each Na atom and the adsorbed H2 molecules are split into two layers with the average hydrogen adsorption energy of 0.12 eV/H2, corresponding to a huge gravimetric density of 16.03 wt%. From GCMC simulations, the gravimetric H2 uptake of Na-decorated H4,4,4-graphyne reaches to the maximum value of 16.97 wt% at 77 K and 100 bar which echoes the results attained by DFT. So, our findings suggest that the Na-decorated H4,4,4-graphyne can be a high-capacity hydrogen storage medium.

Lithium and calcium decorated triphenylene-graphdiyne as potential high-capacity hydrogen storage medium: A first-principles prediction

Recently, a novel layered two-dimensional carbon nanomaterial was synthesized named triphenylene-graphdiyne (TpG). The acetylenic ring and triphenylene are included in primitive cell of this structure. In this work, many different strategies have been adopted to investigate hydrogen storage capacity of Li- and Ca-decorated pristine and B-doped TpG by first-principles calculations. The maximum three H2 molecules are captured around every one Li atom by Li-decorated on the acetylenic ring only for TpG. The hydrogen storage gravimetric capacity of 8.17 wt% with an approximate ideal average H2 adsorption energy of 0.18 eV/H2. Moreover, both acetylenic ring and triphenylene are decorated by Li and two H2 molecules are adsorbed for each Li atom. The hydrogen storage capacity reaches to 9.70 wt% with an ideal average hydrogen adsorption energy of 0.27 eV/H2. After two C atoms are doped by B atoms, two more Li atoms are introduced to the triphenylene. Here, maximum 20 H2 molecules are adsorbed on Li-decorated B-doped TpG. The hydrogen storage capacity reaches to 8.77 wt%, with ideal average hydrogen adsorption energy of 0.24 eV/H2. Four H2 molecules can be adsorbed effectively by Ca-decorated pristine TpG with the average hydrogen adsorption energy of 0.19 eV/H2. We also calculated the H2 storage of Ca-decorated B-doped TpG and 5.51 wt% of gravimetric with ideal average hydrogen adsorption energy of 0.25 eV/H2 can be obtained. Our calculation indicates that the Li- and Ca-decorated B-doped TpG and Li-decorated pristine TpG can be a very promising material for reversible hydrogen storage.

Exploring the possibility of GaPNTs as new materials for hydrogen storage

The possibility of hydrogen storage in gallium phosphate nanotubes (GaPNTs) as a high-capacity hydrogen storage media is studied by employing ab-initio density functional theory (DFT) calculations with a van der Waals (VdW) correction. The binding energy, the distance of the adsorbed hydrogen molecules and the charge transfer were particularly calculated. The obtained results indicate that hydrogenation of the GaPNTs is sensitive to the curvatures and chiralities of the nanotubes. It is found that the binding energy of hydrogen physisorption on GaP nanotubes is higher that on carbon nanotubes. These results are useful in the search for a proper media for hydrogen storage at ambient conditions.

Li adsorption on monolayer and bilayer MoS2 as an ideal substrate for hydrogen storage**Project supported by the National Key Basic Research Program of China (Grant No. 2012CB932304), the National Natural Science Foundation of China (Grant No. 21763007), the Innovation Team Foundation of the Education Department of Guizhou Province, China (Grant No. [2014]35), and the Key Laboratory of Low Dimensional Condensed

Based on the first-principles plane wave calculations, we show that Li adsorbed on monolayer and bilayer MoS2 forming a uniform and stable coverage can serve as a high-capacity hydrogen storage medium, and Li-coated MoS2 can be recycled by operations at room temperature due to Li having strength binding, big separation and is stable against clustering. The full Li coverage MoS2 system (2*2 hexagonal MoS2 supercell) can reach up to eight H2 molecules on every side, corresponding to the gravimetric density of hydrogen storage up to 4.8 wt% and 2.5 wt% in monolayer and bilayer MoS2, respectively. The adsorption energies of hydrogen molecules are in the range of 0.10eV/H2–0.25 eV/H2, which are acceptable for reversible H2 adsorption/desorption near ambient temperature. In addition, compared with light metals decorated low dimension carbon-based materials, the sandwiched structure of MoS2 exhibits the greatly enhanced binding stability of Li atoms as well as slightly decreased Li-Li interaction and thus avoids the problem of metal clustering. It is interesting to note that the Li atom apart from the electrostatic interaction, acts as a bridge of hybridization between the S atoms of MoS2 and adsorbed H2 molecules. The encouraging results show that such light metals decorated with MoS2 have great potential in developing high performance hydrogen storage materials.

Li-decorated carbon ene-yne as a potential high-capacity hydrogen storage medium.

Based on comprehensive first-principles calculations, we predict that Li-decorated carbon ene-yne (CEY) can serve as a reversible and high density hydrogen storage medium. The adsorption structures, charge transfer, electronic properties and energy storage characteristics of Li-decorated CEY are investigated. It is established that Li can bind strongly to sp and sp2 hybridized CEY without the formation of Li clusters. The strong interaction between Li and CEY is attributed to the sp binding C px/py states which hybridize heavily with the Li 2s/2p states. After Li decoration, CEY undergoes a transition from a semiconductor to a metal. Each Li atom anchors seven H2 molecules with the average adsorption energy falling in a suitable range (-0.2 to -0.4 eV per H2). The adsorption mechanism of H2 molecules has also been discussed. Two Li atom decorated CEY can obtain up to a 9.96 wt% hydrogen storage capacity.

Ti functionalized carbon and boron nitride chains: a promising material for hydrogen storage

The geometries, electronic structures, thermochemical properties, polarizabilities, and hyperpolarizabilities of high capacity hydrogen storage media consisting of alkali metal such as Li or transition metal as Ti, that is, functionalized at the end of C and BN chains have been investigated theoretically using density functional theory (DFT). Fundamental aspects such as interaction energy, natural bond orbital (NBO), charge transfer, energy gap, and the projected density of states (PDOS) are elucidated to analyze the adsorption properties of H2 molecules. Our results revealed that H2 is introduced sequentially on the Ti-C7, Ti(B)-B4N3, and Ti(N)-B3N4 complexes and the H2 uptake capacity are found to be 10.89, 10.80, and 10.58 wt%, respectively. Moreover, two Ti atoms can be adsorbed concomitantly to the ends of C7, B4N3, and B3N4 chains where Ti sites can accommodate 16 H2 molecules, with 8 per Ti center, leading to a storage capacity of up to 26.40, 26.28, and 25.94 wt%, respectively. In addition, two binding mechanisms contribute to the adsorption of hydrogen molecules: polarization of the H2 under the electric field produced by the Ti–chain dipole and hybridization of the 3d orbitals of Ti with σ orbitals of H2. These lead to the hydrogen binding energies within the range of 0.22–0.56 eV/H2, open a prospect of a promising material system for hydrogen storage at ambient temperature. The large difference in charge transfer and interaction between the metal and chains is responsible for the large hyperpolarizability. Moreover, the C and BN chains can be stabilized effectively by C20 fullerene termination and store 8 H2 with an average binding energy of 0.22 eV/H2. The hydrogen desorption energies and temperatures indicate that the Ti-C7,Ti(B)-B4N3, Ti(N)-B3N4, Ti-C7-Ti, Ti(B)-B4N3-Ti(B), Ti(N)-B3N4-Ti(N), Ti-C7-C20, Ti(B)-B4N3-C20, and Ti(N)-B3N4-C20 complexes are easy to desorb H2 molecules.

Magnetic Moment Controlling Desorption Temperature in Hydrogen Storage: A Case of Zirconium-Doped Graphene as a High Capacity Hydrogen Storage Medium

For the first time, we predict through density functional theory that a single Zr atom attached on graphene surface can adsorb maximum of 9 H2 molecules with average binding energy of 0.34 eV and average desorption temperature of 433 K leading to a wt % of 11, higher than the DoE’s requirement of 6.5 wt %.The dependency of desorption temperature (TD) of H2 molecule with the magnetic moment (μ) of the system was exclusively studied by formulating the empirical relation TD = T0 + aμb (with T0 = 399 K, a = 302.38 J–1 T K and b = 0.5). For a system with a large magnetic moment, the charge transfer to the hydrogen molecule is higher, leading to higher desorption temperature (may be higher than prescribed limit for hydrogen storage by DoE). As the magnetic moment reduces, TD comes into the desired window for fuel cell applications. It can be inferred from this study that controlling the magnetic character of the system through doping may be an effective way to bring TD in to the desired window. We qualitatively...

Si20H20 cluster modified by small organic molecules and lithium atoms for high-capacity hydrogen storage

By using first-principles calculations based on density functional theory, we design a potential high-capacity hydrogen storage medium by exohedrally functionalizing a stable inorganic Si20H20 nanocage with small organic molecules and Li atoms. The perhydrogenated Si20H20 nanocage was functionalized by replacing H atoms with –CN2H3 (or –CONH2) and Li atoms, and the resulting functionalized complexes show high structural stabilities. Our calculation reveals that Si20H10(CONHLi)10, Si20H10(CONLi2)10, Si20H10(CN2H2Li)10, and Si20H10(CN2HLi2)10 possess an adequate hydrogen binding energy that is suitable for practical storage and usage at ambient temperature. When these complexes reach their maximum H2 uptake capacity, the gravimetric hydrogen percentage is 11.57 wt% for Si20H10(CONHLi)10, 12.40 wt% for Si20H10(CONLi2)10, 10.17 wt% for Si20H10(CN2H2Li)10, and 12.50 wt% for Si20H10(CN2HLi2)10. These complexes can be dispersed into metal–organic frameworks (MOFs) to improve their hydrogen storage properties further.

Li-decorated graphyne as high-capacity hydrogen storage media: First-principles plane wave calculations

Taking into account the van der Waals correction, the characteristics of the Li-decorated graphyne as the hydrogen storage medium have been explored using first-principles plane wave calculations. We find that Li atom can be adsorbed not only over the center of large hexagon (HL site) but also over the center of small hexagon (HS site). For double-side Li decorations, there are 14H2 molecules can be adsorbed on Li-decorated graphyne primitive cell with the adsorption energy of 0.19 eV/H2. As a result, the hydrogen storage capacity of 13.0 wt% can be obtained. This suggests that the Li-decorated graphyne system can serve as a high-capacity hydrogen storage medium.

Metal adatoms-decorated silicene as hydrogen storage media

Hydrogen storage properties of 10 different adatom decorated silicene are carried out using density functional theory calculations with long-range van der Waals dispersion correction. It is found that the binding energy between metal adatoms and the silicene is greater than the cohesive energy of bulk metal so that clustering of adatom will not occur once it is bonded with silicene. The adsorption of H2 on Li, Na, K, Mg, Ca, and Au decorated silicene is a weak physisorption. Differently, a weaker chemisorption is responsible for the adsorption of H2 on Be, Sc, Ti, and V decorated silicene. In particular, silicene with Na, K, Mg, and Ca decorating on both sides leads to 7.31–9.40 wt% hydrogen storage capacity with desirable adsorption energy, indicating that the metal-decorated silicene can serve as a high capacity hydrogen storage medium.

Tuning hydrogen storage in lithium-functionalized BC2N sheets by doping with boron and carbon.

First-principles calculations are used to explore the strong binding of lithium to boron- and carbon-doped BC2N monolayers (BC2NBC and BC2NCN, respectively) without the formation of lithium clusters. In comparison to BC2N and BC2NCB, lithium-decorated BC2NBC and BC2NCN systems possess stronger s-p and p-p hybridization and, hence, the binding energy is higher. Lithium becomes partially positively charged by donating electron density to the more electronegative atoms of the sheet. Attractive van der Waals interactions are responsible for binding hydrogen molecules around the lithium atoms. Each lithium atom can adsorb three hydrogen molecules on both sides of the sheet, with an average hydrogen binding energy of approximately 0.2 eV, which is in the range required for practical applications. The BC2NBC-Li and BC2NCN-Li complexes can serve as high-capacity hydrogen-storage media with gravimetric hydrogen capacities of 9.88 and 9.94 wt %, respectively.

Yttrium-dispersed C60 fullerenes as high-capacity hydrogen storage medium

Interaction between hydrogen molecules and functionalized C60 is investigated using density functional theory method. Unlike transition metal atoms that tend to cluster on the surface, C60 decorated with 12 Yttrium atoms on each of its 12 pentagons is extremely stable and remarkably enhances the hydrogen adsorption capacity. Four H2 molecules can be chemisorbed on a single Y atom through well-known Dewar-Chatt-Duncanson interaction. The nature of bonding is a weak physisorption for the fifth adsorbed H2 molecule. Consequently, the C60Y12 complex with 60 hydrogen molecules has been demonstrated to lead to a hydrogen storage capacity of ∼6.30wt.%.

Ti–η2-(C2H2) and HC[tbnd]C–TiH as high capacity hydrogen storage media

The hydrogen storage capacities of π complex (Ti–η2-(C2H2)) and the corresponding ethynyl metal hydrides (HCC–TiH) complex were tested using second order Møller Plesset method with 6-311++G(3df,3pd) basis sets. Both on Ti–η2-(C2H2) and HCC–TiH, up to six hydrogen molecules can be absorbed with a binding energy of 0.20–0.42 eV/H2, corresponding the maximal retrievable hydrogen storage density of 14.06 wt%. A comparative study of various density functional theory calculations showed that the averaged H2 adsorption energy is not only considerably affected by the level of theory used but also dependent on the complex of the material dealing with. Dimerizations of the Ti–acetylene complexes were also discussed.

Molecular hydrogen uptake by zigzag graphene nanoribbons doped with early 3d transition-metal atoms

We performed ab initio density-functional calculations to investigate the structural, electronic and magnetic properties of nanostructures comprising single-adatoms of Sc, Ti or V adsorbed on a hydrogen-passivated zigzag graphene nanoribbon (GNR). We also investigated the affinity of the resulting doped nanostructures for molecular hydrogen. In all cases, the most stable structures featured the adatom at positions near one of the edges of the GNR. However, whereas in the most stable structures of the systems Sc/GNR and V/GNR the adatom was located above a bay of the zigzag edge, Ti/GNR was found to be most stable when the adatom was at a first-row hole site. Adsorption at sites near one of the ribbon edges reduced drastically the average magnetic moment of the carbon atoms at that edge. On the other hand, the magnetic moments of the adatoms on the GNR, as the electronic character of the doped nanostructures, depended on the adsorption site and on the adatom species, but their absolute values were in all cases, except when Sc was at an edge bay site, greater than those of the corresponding free atoms. Our results showed that, of the three systems investigated in this paper, Ti/GNR (except when Ti is adsorbed at an edge bay site) and V/GNR appear to satisfy the criterion specified by the U. S. Department of Energy for efficient H2 storage, as far as binding energy is concerned. We discussed in detail the differences between the adsorption of H2 on the system Ti/GNR and the adsorption of H2 on Ti-adsorbed carbon nanotubes, which have been proposed as a high-capacity hydrogen storage media.

Light metals decorated covalent triazine-based frameworks as a high capacity hydrogen storage medium

The structural stability and hydrogen adsorption capacity of an alkali (Li, Na and K) and alkali earth (Mg and Ca) metal atom decorated covalent triazine-based framework (CTF-1) are studied using ab initio density functional calculations. The calculation results revealed that Li, Na, K and Ca atoms can be adsorbed on the CTF-1 with the formation of a uniform and stable coverage due to the charge transfer between the metal atoms and the CTF-1 substrate, thus avoiding the clustering problem that occurs for the decoration of metal atoms on other substrates. The metal decorated CTF-1 could adsorb up to 30 hydrogen molecules with an average binding energy of ∼0.16–0.26 eV/H2, corresponding to a gravimetric density of 12.3, 10.3 and 8.8 wt% for the CTF–Li6, CTF–Na6 and CTF–Ca6 complexes, respectively, thereby enabling the Li, Na and Ca decorated covalent triazine-based frameworks to be very promising materials for effective reversible hydrogen storage at near ambient conditions.

High-capacity hydrogen storage of Na-decorated graphene with boron substitution: First-principles calculations

Based on density-functional theory, we found that a boron-substituted graphene uniformly decorated with Na atoms on double sides can serve as a high-capacity hydrogen storage medium. Otherwise, the semimetallic boron-substituted graphene change into conductor after the adsorption of Na atoms. While the adsorbed Na atoms forming a (2×2) pattern can capture nine H2 molecules corresponding to a storage capacity of 11.7wt.% at T=300K and without external pressure.

Ultra-high hydrogen storage capacity of Li-decorated graphyne: A first-principles prediction

Graphyne, consisting of sp- and sp2-hybridized carbon atoms, is a new member of carbon allotropes which has a natural porous structure. Here, we report our first-principles calculations on the possibility of Li-decorated graphyne as a hydrogen storage medium. We predict that Li-doping significantly enhances the hydrogen storage ability of graphyne compared to that of pristine graphyne, which can be attributed to the polarization of H2 molecules induced by the charge transfer from Li atoms to graphyne. The favorite H2 molecules adsorption configurations on a single side and on both sides of a Li-decorated graphyne layer are determined. When Li atoms are adsorbed on one side of graphyne, each Li can bind four H2 molecules, corresponding to a hydrogen storage capacity of 9.26 wt. %. The hydrogen storage capacity can be further improved to 15.15 wt. % as graphyne is decorated by Li atoms on both sides, with an optimal average binding energy of 0.226 eV/H2. The results show that the Li-decorated graphyne can serve as a high capacity hydrogen storage medium.

Metal decorated monolayer BC2N for hydrogen storage

Using first-principles density functional calculations, we show that metal decorated monolayer BC2N can serve as a high-capacity hydrogen storage medium with the gravimetric density of 7.69–10.0wt.%. In particular, Li and Ca decorated BC2N are systematically investigated and found to be feasible for hydrogen storage without metal clustering owing to the Coulomb repulsion between the metal adatoms. Both the polarization mechanism and the orbital hybridizations contribute to the adsorption of H2 molecules and the average adsorption energies are 0.24 and 0.26eV/H2, respectively.