Sc/Ti decorated novel C24N24 cage: Promising hydrogen storage materials

Inspired by the TM?N₄ coordination environment and the promising hydrogen adsorption property of the Ti–C₄ unit, four novel TM₆C₂₄N₂₄ (TM = Sc, Ti) cages with six TM?N₄/TM?C₄ units are designed simultaneously for the first time in this paper. Their stabilities are studied by using DFT calculations and confirmed by MD simulations. Sc₆C₂₄N₂₄(N₄) and Ti₆C₂₄N₂₄(N₄) can absorb 30 hydrogen molecules and keep the original structures intact. The average hydrogen adsorption energy is 0.13–0.26 eV for Sc₆C₂₄N₂₄(N₄)-6nH₂ (n = 1–5), and 0.09–0.23 eV for Ti₆C₂₄N₂₄(N₄)-6nH₂ (n = 1–5). The hydrogen storage capacities are 6.30 wt % and 6.20 wt %, respectively. Besides, the 30H₂ can be readily adsorbed on Sc₆C₂₄N₂₄(N₄) under 160 K and 100% desorbed at 270 K under 0.1 MPa. The desorption temperature could increase if the pressure becomes higher. Sc₆C₂₄N₂₄(C₄)/Ti₆C₂₄N₂₄(C₄) complexes are higher in energy than corresponding Sc₆C₂₄N₂₄(N₄)/Ti₆C₂₄N₂₄(N₄). They are not suitable as room-temperature hydrogen storage materials due to the structural deformation in the hydrogen storage process.     

Sc/Ti-decorated and B-substituted defective C60 as efficient materials for hydrogen storage

Doping heteroatoms and producing defects are perfect methods to improve the hydrogen storage property of TM-decorated carbon materials. In this view, four novel Sc/Ti-decorated and B- substituted defective C₆₀ fullerenes (B₂₄C₂₄) are explored. The special stability, large specific surface, uniform distribution of the metal and positively charged states make these four fullerenes have high hydrogen storage capacities. Especially, each Sc atom in Sc₆B₂₄C₂₄(B₄) can adsorb up to five H₂ molecules with a storage capacity of 6.80 wt %. The adsorbed H₂ molecules in Sc₆B₂₄C₂₄(B₄)–30H₂ begin to relax at 190 K and are 100% released at 290 K. Moreover, a comparative study is carried out for hydrogen storage properties of Sc-decorated B₄, C₄, or N₄ coordination environments. These results provide a new focus on the nature of B-, and N-substituted defective carbon nanomaterials.     

A theoretical research of dihydrogen storage in ScxNy (x+y=4) compounds

The dihydrogen storage capacity of Sc_xN_y (x + y = 4) compounds have been theoretically investigated at different levels. At B3LYP-D3/6-311G(3df,3pd) level, ScN₃ has multiple isomers with similar energies, which is an interference of hydrogen storage research. Sc₂N₂ and Sc₃N has four and three isomers, respectively. For both systems, the lowest-lying isomers are planar Sc₂N₂ 01 and Sc₃N 01, which are energetically much low-lying by at least 20 kcal/mol than the other isomers, respectively. Sc₃N 01 can adsorb 8H₂ with gravimetric uptake capacity of 9.77 wt %. It satisfies the target specified by US DOE, however, some hydrogen molecules will dissociate and bond atomically on scandium atoms. The strong binding energy (0.66 eV/H₂) exceeds the reversible adsorption range (0.1–0.4 eV/H₂), which will cause high operating temperature to desorb hydrogen during the application process. Sc₂N₂ 01 can adsorb 9H₂ in the molecular form. The H₂ gravimetric uptake capacity of Sc₂N₂ 01 (9H₂) (13.33 wt %) exceeds the target set by US Department of Energy, moreover, its average adsorption energy (0.32 eV/H₂) is in the reversible adsorption range. The interaction of Sc₂N₂ 01 with H₂ molecules is considered by means of the bond critical points (bcp) in the quantum theory of atoms in molecules (QTAIM). The Gibbs free energy corrected adsorption energy points that the adsorption of Sc₂N₂ 01(9H₂) is energetically favorable below 240 K. Therefore, in Sc_xN_y (x + y = 4), the planar compound Sc₂N₂ 01 is more suitable to be a dihydrogen adsorption material.     

Hydrogen capability of bimetallic boron cycles: A DFT and ab initio MD study

Bimetallic boron cycle, B₆C₂TM₂ (TM = scandium, titanium), was recently predicted to have high stability and aromaticity. The hydrogen capabilities of these clusters were studied in the present work. Our computational results indicate that the gravimetric hydrogen uptake capacity of B₆C₂Sc₂ and B₆C₂Ti₂ and clusters are 11.7% and 11.4%, respectively. The adsorption energies of H₂ molecules on B₆C₂Sc₂ and B₆C₂Ti₂ clusters are predicted with different calculational schemes to meet the criteria of reversible hydrogen storage. The interaction of H₂ with B₆C₂Ti₂ cluster is a little stronger than that with B₆C₂Sc₂. Ab initio molecular dynamics simulations indicate that H₂ molecules can be efficiently released from the metal sites of B₆C₂TM₂ clusters at room temperature. The bulk-like B₆C₂Sc₂ and B₆C₂Ti₂ tetramer can also efficiently adsorb H₂ molecules.     

Novel sandwich-type dimetallocenes: Toward promising candidate media for high-capacity hydrogen storage

With respect to first-principles calculations, the sandwich-type dinuclear organometallic compounds as (C₅H₅)₂TM₂ (M = Sc and Ti) can adsorb up to eight hydrogen molecules. The corresponding gravimetric hydrogen-storage capacity is 6.7 wt% for (C₅H₅)₂Ti₂ and 6.8 wt% for (C₅H₅)₂Sc₂. The multimetallocenes (e.g., CpTi₃Cp and CpTi₄Cp) complexes can further increase the H₂ adsorption capacity to 8.7 wt% and 10.4 wt%, respectively. These sandwich-type organometallocenes proposed in this work are favorable for reversible adsorption and desorption of hydrogen under ambient conditions. These predictions will likely provide a new route for developing novel high-capacity hydrogen-storage materials.     

The effect of charge on the dihydrogen storage capacity of Sc2–C6H6

The effect of charge on the dihydrogen storage capacity of Sc₂–C₆H₆ has been investigated at B3LYP-D3/6-311G(d,p) level. The neutral system Sc₂–C₆H₆ can store 8H₂ with gravimetric density of 8.76 wt %, and one H₂ dissociates and bonds atomically on the scandium atom. The adsorption of 8H₂ on Sc₂–C₆H₆ is energetically favorable below 155 K. The atom-centered density matrix propagation (ADMP) molecular dynamics simulations show that Sc₂–C₆H₆ can adsorb 3H₂ within 1000 fs at 300K. Compared with Sc₂–C₆H₆, the charged systems can adsorb more hydrogen molecules with higher gravimetric density, and all the H₂ are adsorbed in the molecular form. The gravimetric densities of Sc₂–C₆H₆⁺ and Sc₂–C₆H₆²⁺ are 9.75 and 10.71 wt%. Moreover, the maximum adsorption of charged systems are favorable in wider temperature range. Most importantly, the ADMP-MD simulations indicate that Sc₂–C₆H₆²⁺ can adsorb 6 hydrogen molecules within 1000 fs at 300K. It can be found that the gravimetric density (6.72 wt%) of Sc₂–C₆H₆²⁺ still exceeds the target of US Department of Energy (DOE) under ambient conditions.     

Hydrogen trapping efficiency of Li decorated porous boron fullerene B38: The first-principles study

The demand for clean renewable energy is urgent in current. The hydrogen application is difficult mainly due to the ratively low capacity in the storage medium. In this work, the adsorption and desorption of the hydrogen molecules by the Li atoms decorated B₃₈ cage are studied by the density functional theory. The calculated largest binding energy of one Li atom (2.68 eV and 2.58 eV) is upon the hexagonal hole of the B₃₈ cage, which is much larger than the experimental cohesive energy of bulk Li (1.63 eV). Each Li atom in the outside of the B₃₈ cage can adsorb up to four H₂ molecules. The E_ad of B₃₈(Li-nH₂)₄ decreases from the 0.22 eV for n = 1 to the 0.11 eV for n = 4. The B₃₈(Li–4H₂)₄ structure achieves the 6.85 wt% hydrogen gravimetric density, which is higher than the goal of 5.5 wt% before 2017 set by the United States Department of Energy. The almost the same partial density of states for the fifth H₂ molecule as that of the isolated H₂ molecule, the longer 4.5 Å distance between the fifth H₂ molecule and the Li atom, together with the small NBO charges all reveal the weak electronic field around the Li⁺, which can interpret the weak H₂ adsorption mechanism. Finally, the B₃₈Li₄ structure can easily release 9H₂ molecules at 373 K known from the molecular dynamic simulation and practically trap about 1.08H₂ molecules at 373 K/3 atom condition calculated by the grand partition function. Thus, its reversible practical HGD of B₃₈Li₄-14.34H₂ is 6.18 wt%, which is almost the same value as the theoretical 6.85 wt% for B₃₈(Li–4H₂)₄. Our studies will be the strong theory basis for the future application in hydrogen storage material development.     

Adsorption ability of pristine C24N24 nanocage promising as high hydrogen storage material: A DFT-D3 investigation

Adsorption of eight numbers of H₂, (H₂)_n where n = 1, 2, 4, 6, 8, 12, 18, 24, adsorbed on the C₂₄N₂₄ nanocage (CNNC) surface was investigated using three different DFT methods. Adsorption energies of various numbers of H₂ adsorbed on the CNNC surface were obtained. Adsorption strength of the CNNC was found depending on the adsorbed H₂ numbers and is in order: the H₂ numbers of (H₂) > (H₂)₂ > (H₂)₄ > (H₂)₆ > (H₂)₈ > (H₂)₁₂ > (H₂)₁₈ > (H₂)₂₄. The most stable adsorption configuration of (H₂)₁₂/CNNC, all adsorbed H₂ molecules formed as the full monolayer (ML) coverage, are dissociative chemisorption. The bilayer of (H₂)₂₄/CNNC was found that the first and second layers are composed of 12H₂ as dissociative chemisorption and 12H₂ as physisorption, respectively. The high hydrogen storage capacity of the CNNC formed as (H₂)₂₄/CNNC, around 7.75 wt% was found.     

Synthesis,structural characterization and thermal decomposition studies of (N2H5)2B12H12 and its solvates

A series of salts of the B₁₂H₁₂²⁻ anion has been prepared: a solvent-free (N₂H₅)₂B₁₂H₁₂, its solvates – (N₂H₅)₂B₁₂H₁₂·H₂O, (N₂H₅)₂B₁₂H₁₂·2(CH₃CN), (N₂H₅)₂B₁₂H₁₂·(CH₃OH), and the salt of a protonated azine – [(CH₃)₂CNNHC(CH₃)₂]₂B₁₂H₁₂. These compounds have been synthesized from the commercially available precursors via one- or two-step procedures and fully identified on the basis of single-crystal and powder X-ray diffraction. At room temperature (N₂H₅)₂B₁₂H₁₂ crystallizes in C2/c space group, with a = 18.480(5) Å, b = 6.5344(19) Å, c = 13.106(4) Å and β = 131.911(16)^o, V = 1177.8(7) ų, Z = 4. While this compound nominally contains ca. 10.7 wt% of hydrogen, it thermally decomposes above 200 °C releasing mainly N₂ and NH₃, with H₂ being only the minor gaseous product. Contrary to the recently reported case of hydrazinates of borohydrides, doping with 5 mol% of FeCl₃ does not increase the relative amount of hydrogen significantly, however, it alters the ratio of N₂ and NH₃.     

Li decorated C9N4 monolayer as a potential material for hydrogen storage

Based on first−principles calculations, we investigate the possibility of the two-dimensional porous C₉N₄ material as for hydrogen storage, and find that the adsorption energy of H₂ molecules on the pristine C₉N₄ is too weak to meet the requirements of hydrogen storage, whereas the adsorption on the Li−decorated sheet is relatively moderate. Each C₉N₄ unit cell can incorporate 6 Li atoms, of which 3 Li atoms are located above the intrinsic hole and the others are below. The unit cell can hold 14 hydrogen molecules with an average adsorption energy of −0.12 eV, which meets the reversible storage condition of hydrogen, and the gravity density reaches 7.04 wt%. Particularly, 6Li@C₉N₄ maintains excellent H₂ storage performance under a tensile strain within 2%. The ab initio MD simulations performed at 300 K show that all 14 H₂ molecules remained on the double sides of 6Li@C₉N₄ in the absence and presence of strain. Therefore, we predict that Li−modified C₉N₄ could be a potential material with excellent ductility for hydrogen storage at room temperature.     

Alkali,alkaline earth and transition metal doped B6H6 complexes for hydrogen storage

Alkali, alkaline earth and transition metal doped B₆H₆ complexes are considered for the hydrogen storage. Density functional theory (DFT) and second order Møller–Plesset methods with 6–311++G** basis set have been used for the study. B₆H₆Li, B₆H₆Be, B₆H₆Sc, B₆H₆Li₂, B₆H₆Be₂, B₆H₆Sc₂ complexes can interact with maximum three, two, four, six, four and eight H₂ molecules respectively with respective H₂ uptake capacity of 7.2, 4.8, 6.5, 12.5, 8.3 and 9.1 wt%. This uptake capacity is well above the target set by the U.S. Department of Energy by 2020 except for the B₆H₆Be complex. Thermo chemistry calculations are carried out to estimate the Gibbs free energy corrected H₂ adsorption energy which reveals whether adsorption of hydrogen on these complexes is favourable or not at different temperature. It is observed that H₂ adsorption on all the six complexes are unfavourable at ambient conditions where as it is favourable below 150, 135, 75, and 50 K on B₆H₆Sc, B₆H₆Be, B₆H₆Li and B₆H₆Li₂ complexes respectively. Various interaction energies in H₂ adsorbed complexes are obtained using Many-body analysis approach. The H₂ desorption temperature for the B₆H₆Li, B₆H₆Be, B₆H₆Sc, B₆H₆Li₂, B₆H₆Be₂ and B₆H₆Sc₂ complexes is found to be 25, 165, 265, 10, 265 and 373 K respectively.     

The effect of Sc addition on the hydrogen storage capacity of Ti0.32Cr0.43V0.25 alloy

The effect of the addition of 4th element on the hydrogen storage capacity of Ti_0.32Cr_0.43V_0.25 alloy was evaluated by simulation and confirmed experimentally. The crystal lattice volume, phase formation energy, and hydrogen absorption energy of the alloys were calculated by ab initio calculation for the alloys containing the third-period transition metals as Sc, Cr, Mn, Fe, Co, Ni, Cu, and Zn. It was postulated that the hydrogen absorption would be favored by large crystal volume and low hydrogen absorption energy. The calculation suggested Sc as the most suitable element and the hydrogen capacities of a series of Ti_0.32Cr_0.43−xV_0.25Sc_x alloys (x = 0.02–0.1) were determined accordingly. Among the alloys, the capacities of Ti_0.32Cr_0.41V_0.25Sc_0.02 and Ti_0.32Cr_0.39V_0.25Sc_0.04 alloys were higher than that of the Ti_0.32Cr_0.43V_0.25 alloy. The capacity of both alloys could be enhanced further by the heat treatment at 1250 °C due to the elimination of the second-phase TiCr₂.     

Hydrogen storage in scandium decorated triazine based g-C3N4: Insights from DFT simulations

Hydrogen is being considered a ‘fuel of the future,’ a viable alternative to fossil fuels in fuel cell vehicles. Using Density Functional Theory simulations, reversible, onboard hydrogen storage in Sc-decorated triazine-based graphitic carbon nitride (g-C₃N₄) has been explored. Sc atom binds strongly on the g-C₃N₄ structure with a binding energy of ?7.13 eV. Each Sc atom can reversibly bind 7 molecules of hydrogen, giving a net gravimetric storage capacity of 8.55 wt%, an average binding energy of ?0.394 eV per H₂, and a corresponding desorption temperature of 458.28 K, fulfilling the criteria prescribed by the US Department of Energy. The issue of transition metal clustering has been investigated by computing the diffusion energy barrier (2.79 eV), which may be large enough to hinder the clustering tendencies. The structural integrity of Sc-g-C₃N₄ has been verified through ab-initio Molecular Dynamics simulations. The interaction mechanism of Sc over g-C₃N₄ and H₂ over Sc-g-C₃N₄ has been explored using density of states and charge transfer analysis. A flow of charge from valence 3d orbitals of Sc towards vacant orbitals of g-C₃N₄ during the binding of Sc over g-C₃N₄ is observed. The binding of H₂ on Sc-g-C₃N₄ may be via Kubas type of interactions which is stronger than physisorption due to net charge gain by H 1s orbital from Sc 3d orbital. Our systematic investigations indicate that Sc-decorated g-C₃N₄ may be a high-performance material for reversible hydrogen storage applications.     

First principle study of reversible hydrogen storage in Sc grafted Calix[4]arene and Octamethylcalix[4]arene

The use of hydrogen as a sustainable clean energy source has several benefits, such as reduction in dependency on petroleum fuel and emission of green house gases, and enhanced energy security. The H₂ storage properties of Sc grafted calix[4]arene (CX) and octamethylcalix[4]arene (MCX) are investigated by using density functional theory with M06/6-311G(d,p) level of theory. It is observed that Sc strongly binds with benzene rings of CX and MCX through Dewar coordination with average Sc binding energy of 1.09 and 1.25 eV, respectively for CXSc₄ and MCXSc₄. Each Sc atom adsorbs 4 H₂ molecules on both the Sc grafted systems and H₂ molecules are bound by Kubas interaction with H₂ interaction energy in the range of 0.2–0.5 eV. The calculated conceptual reactivity index shows the stability of the systems increases with number of hydrogen molecules. Hirshfeld charge analysis shows the charge transfer mechanism during H₂ adsorption. Born-Oppenheimer molecular dynamics simulations of CXSc₄-16H₂ and MCXSc₄-16H₂ systems, show that these systems are stable up to 273 K and all the adsorbed H₂ releases at 373 K. The hydrogen storage capacity of Sc grafted CX system is found to be 8.9 wt % and for MCX system is 9.7 wt %. The energy and storage capacity meets the US Department of Energy target, which makes them a propitious hydrogen storage material.     

Modification of graphenylene nanostructure with transition metals (Fe,Sc and Ti) to promote hydrogen storage ability: A DFT-D3 study

Hydrogen, as a clean alternative to fossil fuels, has received much attention in recent years. But its utilizing requires to overcome storage problems. Here, we investigated the hydrogen adsorption behavior of graphenylene (GPY), a 2D carbon nanostructure, and Sc, Fe and Ti transition metal (TM) decorated GPY by spin-polarized DFT calculations. For TM-decoration of GPY, seven different sites and various distances from carbon sheet were investigated, carefully. Structural and electronic properties of the structures, adsorption energies, band gap values, and the most stable configurations were considered and discussed. Results showed that 6-membered ring (H2 site) is the best site for Sc, Fe, and Ti-decoration and corresponding E_ads was −3.95, −2.66, and −3.65 eV, respectively. Also, pristine GPY and Sc and Ti-decorated GPY have not magnetic character, unlike Fe-GPY. As well, entrance of Sc, Fe and Ti atoms in H2 site of the GPY structure causes its band gap increases from 0.033 eV to of 0.491, 0.080, and 0.372 eV, respectively. E_ads of the H₂ molecule onto pristine GPY is low (−0.160 eV), and must be improved for practical hydrogen storage applications. Sc, Fe, and Ti-decoration improves it about 2.23, 5.69 and 3.63 times. Because of this improvement, we could store up to 20H₂ molecules on TM-decorated GPY systems. These results indicate that TM-decorated GPY can be a suitable option for H₂ storage applications in the future.     

Hydrogen storage in scandium doped small boron clusters (BnSc2, n=3–10): A density functional study

In this work, we present the hydrogen adsorption capacity of Sc doped small boron clusters (B_nSc₂, n = 3–10) using density functional theory. Almost no structural change was observed in the host clusters after hydrogen adsorption. Stabilities of the studied clusters were confirmed by various reactivity parameters such as hardness (η), electrophilicity (ω), and electronegativity (χ). The average adsorption energies was found in the range of 0.08–0.19 eV/H₂ inferring physisorption process, and the fact is also supported by the average distance from Sc to H₂ molecules which was in the range of 2.13 Å-2.60 Å. All the clusters were found to have gravimetric density satisfying the target set by the U.S. Department of Energy (US-DOE) (5.5 wt% by 2020). From Bader's topological analysis, it was confirmed that the nature of interaction was likely to be somewhat closed shell type. ADMP molecular dynamics simulations study was performed at different temperatures to understand the adsorption and dissociation of H₂ from the complexes.     

Effects of different substitution concentration and configuration on some properties of magnesium hydrides substituted with titanium; Ab initio study

We investigated hydrogen some properties of magnesium hydrides substituted with titanium by a first principles calculation. In order to evaluate effect of different substitution concentration and configuration on desorption temperature and bulk modulus, we constructed five systems such as Mg₄Ti₂H₁₂, Mg₈Ti₂H₂₀, Mg₁₆Ti₂H₃₆, Mg₁₄Ti₄H₃₆ and Mg₁₂Ti₆H₃₆ by using 1 × 1 × 3, 1 × 1 × 5 and 3 × 3 × 1 super cell of pure magnesium hydride. Among the investigated systems, Mg₁₄Ti₄H₃₆ system showed the best performance as hydrogen storage material in the complex viewpoints of substitution energy, desorption temperature and bulk modulus. In addition to, our results demonstrated that not only substitution concentration but also configuration plays vital effect on material's property of magnesium hydrides. Bader charge analysis explained the reason why desorption temperature is fallen down by substitution with titanium.     

The theoretical research of hydrogen storage capacities of Cu3Bx (X=1–4) compounds under ambient conditions

The hydrogen adsorption and storage of Cu₃B_x (X = 1–4) compounds have been computationally investigated at B3LYP-D3/6-311G (3df, 3pd) level. The most stable compounds of Cu₃B_x (X = 1–4) can adsorb 16, 11, 15, and 9 hydrogen molecules with H₂ gravimetric densities of 13.80, 9.46, 11.94, 7.20 wt%, respective. Their average adsorption energies are in the range of 0.26–0.43 eV/H₂. The Gibbs free energy corrected adsorption energies indicate that the maximum adsorption of Cu₃B_x (X = 1–4) are energetically favorable under ambient conditions. Atom-centered density matrix propagation (ADMP) molecular dynamics simulations are used to analyzed the real time dynamics of H₂ and Cu₃B_x (X = 1–4). We can find that Cu₃B_x (X = 1–4) can bind with 4–5 H₂ within 1000 fs at 200 K.     

Cesium hydrazinidoborane,the last of the alkali hydrazinidoboranes,studied as potential hydrogen storage material

Alkali hydrazinidoboranes MN₂H₃BH₃ (M = Li, Na, K, Rb) have been developed for hydrogen storage. To complete the family of MN₂H₃BH₃, we focused on cesium hydrazinidoborane CsN₂H₃BH₃ (CsHB). It has been synthesized by reaction of cesium with hydrazine borane (N₂H₄BH₃) at −20 °C under inert atmosphere, and it has been characterized. A crystalline solid (monoclinic, s.g. P2₁ (No. 4)) has been obtained. Its potential for hydrogen storage has been studied by combining different techniques. It was found that, under heating at constant heating rate (5 °C min⁻¹) or at constant temperature (e.g. 120 °C), CsHB decomposes rather than it dehydrogenates. It releases several unwanted gaseous products (e.g. NH₃, B₂H₆) together with H₂, and transforms into a residue that poses safety issues because of shock-sensitivity and reactivity towards O₂/H₂O. Though the destabilization brought by Cs⁺ onto the anion [N₂H₃BH₃]⁻ has been confirmed, the effect is not efficient enough to avoid the aforementioned drawbacks. All of our results are presented herein and discussed within the context of solid-state hydrogen storage.     

Effect of boron substitution on hydrogen storage capacity of Li and Ti decorated naphthalene

Interaction of molecular hydrogen with Li and Ti doped boron substituted naphthalene viz. C₆B₄H₈Ti₂ and C₆B₄H₈Li₂ has been studied using density functional theory (DFT) method. The C₆B₄H₈Li₂ complex can interact with maximum of four hydrogen molecules, whereas three H₂ molecules are adsorbed on C₁₀H₈Li₂ complex. The C₆B₄H₈Ti₂ complex can interact with maximum of eight hydrogen molecules. The gravimetric hydrogen uptake capacity of C₆B₄H₈Ti₂ and C₆B₄H₈Li₂ complex is found to be 6.85 and 5.55 wt % respectively, which is higher than that of unsubstituted C₁₀H₈Ti₂ and C₁₀H₈Li₂ complexes. The boron substitution has significantly affected the hydrogen adsorption energies. The H₂ adsorption energy and Gibb's free energy corrected H₂ adsorption energy are found to be more prominent after boron substitution. The C₆B₄H₈Ti₂ and C₆B₄H₈Li₂ complexes are more stable than the respective unsubstituted C₁₀H₈Ti₂ and C₁₀H₈Li₂ complexes due to their higher binding energies. According to the atom-centered density matrix propagation (ADMP) molecular dynamics simulations C₆B₄H₈Li₂ complex retain not a single adsorbed hydrogen molecule during the simulation at room temperature, whereas five hydrogen molecules at 300 K and eight at 100 K are remain absorbed on C₆B₄H₈Ti₂ complex. The C₆B₄H₈Ti₂ complex is found to be more promising material for hydrogen storage than C₁₀B₄H₈Li₂.