Promising Candidates For Hydrogen Storage Research Articles

Dehydrogenation of LiBH4 Destabilized with Various Oxides

Lithium borohydride is a promising candidate for hydrogen storage and fuel cell application due to its high hydrogen content. In the present work, the effect of various oxides on the dehydrogenation of LiBH4 was investigated. The MS-TG results showed that the LiBH4/oxide mixtures were able to dehydrogenate at much lower temperatures; for example, the onset of dehydrogenation was below 100 °C for a LiBH4−Fe2O3 mixture with a mass ratio of 1:2, and the majority of the hydrogen (∼6 wt %) could be released after heating to 200 °C. The order of destabilization effect for LiBH4 for the studied oxides was Fe2O3 > V2O5 > Nb2O5 > TiO2 > SiO2. XRD results revealed that the destabilization of LiBH4 by the oxides resulted from a redox reaction of LiBH4 + MOx → LiMOx + B + 2H2. Investigation of mixed metal oxides showed that a TiO2/SiO2 sample produced an even greater effect, decreasing the temperature of hydrogen release from LiBH4 by more than either TiO2 and SiO2 alone.

Li12Si60H60 Fullerene Composite: A Promising Hydrogen Storage Medium

By using the first-principles DFT calculations, we design a novel hydrogen storage material, Li(12)Si(60)H(60) composite, and validate its geometric stability. It is found that the adsorbed Li atoms do not cluster on the Si(60)H(60) fullerene unlike other metals such as Ti, owing to the relatively low Li-Li binding energy and the inhibition of Si-H bonds. Our results show that the Li-doping enhances the hydrogen adsorption ability of Si(60)H(60) significantly, owing to the charge transfer from the doped Li atoms to the host material and the polarization of the adsorbed H(2) molecules. By combining the first-principles calculation and grand canonical Monte Carlo simulation, we further investigate the hydrogen storage capacity of the simulation-synthesized exohedral Li(12)Si(60)H(60) composite at T = 77 K. As the vdW gap (i.e., the separation between the surfaces of two Li(12)Si(60)H(60) fullerenes) is equal to 8.2 A, the total hydrogen uptake of the square-arranged Li(12)Si(60)H(60) array reaches 12.83 wt % at p = 10 MPa, while the excess hydrogen uptake shows a maximum of 7.46 wt % at p = 6 MPa. Impressively, at T = 298 K and p = 10 MPa, the Li(12)Si(60)H(60) array still exhibits a total hydrogen uptake of 3.88 wt % at the vdW gap of 8.2 A. These results clearly indicate that the composite, Li(12)Si(60)H(60) fullerene, is a promising candidate for hydrogen storage.

Ab initio molecular dynamics study of the hydrogen diffusion in sodium and lithium hydrides

Light weight complex metal hydrides, sodium hydride (NaH), and lithium hydride (LiH) are the last step materials during hydrogen release process of alanates and borates, which are promising candidates for hydrogen storage. We report ab initio molecular dynamics (MD) calculations based on density functional theory to study the hydrogen-deuterium exchange in NaH and LiH. We predict the single hydrogen-deuterium exchange in NaH and LiH and calculate the self-diffusion constants, ⟨D⟩NaH≈1.46×10−9 m2 s−1 of deuterium in NaH at 420 K and ⟨D⟩LiH≈1.49×10−9 m2 s−1 of deuterium in LiH at 550 K, which are in good agreement with the experimental values.

Identification of a stable phase for the high-capacity hydrogen-storage materialZn(BH4)2from density functional theory and lattice dynamics

First-principles calculations were performed on $\text{Zn}{({\text{BH}}_{4})}_{2}$ using density functional theory (DFT) within the local density approximation and the projected augmented wave method. $\text{Zn}{({\text{BH}}_{4})}_{2}$ is a promising candidate for hydrogen storage with a capacity of 8.5 $\text{wt}\text{ }%$. A direct method lattice dynamics approach using ab initio force constants was utilized to calculate the phonon dispersion curves. This allowed us to establish the stability of the crystal structure at finite temperatures. DFT was used to calculate electronic properties and the direct method lattice dynamics was used to calculate the finite temperature thermal properties. $\text{Zn}{({\text{BH}}_{4})}_{2}$ is found to have an orthorhombic structure in the space group of ${Pmc2}_{1}$ with lattice parameters $a=4.118\text{ }\text{\AA{}}$, $b=4.864\text{ }\text{\AA{}}$, $c=7.916\text{ }\text{\AA{}}$. It is an insulating material having a DFT-calculated band gap of 3.529 eV. Analysis of the electronic structure shows strong bonding between hydrogen atoms and boron in the ${[{\text{BH}}_{4}]}^{\ensuremath{-}}$ complex and also less polar bonding between the Zn and the hydrogen atom. The reaction enthalpy was calculated for the reaction $\text{Zn}{({\text{BH}}_{4})}_{2}=\text{Zn}+2\text{B}+4{\text{H}}_{2}(g)$ to be 76.91 $\text{kJ}/\text{mol}$ of ${\text{H}}_{2}$ at 0 K without any zero point energy correction, and 59.90 $\text{kJ}/\text{mol}$ of ${\text{H}}_{2}$ including the zero point energy correction. The simulated standard enthalpy of formation for the complex $\text{Zn}{({\text{BH}}_{4})}_{2}$ was found to be $\ensuremath{-}66.003\text{ }\text{kJ}/\text{mol}$ of ${\text{H}}_{2}$ at 300 K. This suggests that the crystal structure of $\text{Zn}{({\text{BH}}_{4})}_{2}$ is stable at room temperature and this complex hydride can thus be considered a potential candidate for hydrogen storage.

Silicon Nanotube as a Promising Candidate for Hydrogen Storage: From the First Principle Calculations to Grand Canonical Monte Carlo Simulations

We employ a multiscale theoretical method, which combines the first-principle calculation and a grand canonical Monte Carlo (GCMC) simulation, to predict the adsorption capacity of hydrogen in silicon nanotube (SiNT) arrays at T = 298 K in the pressure range from 1 to 10 MPa. In the multiscale method, the binding energy obtained from the first-principle calculation is used as an input in the GCMC simulation. It is found from the first-principle calculation that the SiNT arrays exhibit much stronger attraction to hydrogen both inside and outside SiNTs, compared to the isodiameter carbon nanotubes (CNTs). The subsequent GCMC simulations indicate that the SiNT arrays present distinct improvements of 106%, 65%, and 52% in the gravimetric adsorption capacity of hydrogen at P = 2, 6, and 10 MPa, respectively, compared to the isodiameter CNTs. This suggests that the SiNT array is a promising candidate for hydrogen storage.

Using First Principles Calculations to Identify New Destabilized Metal Hydride Reactions for Reversible Hydrogen Storage.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

Using first principles calculations to identify new destabilized metal hydride reactions for reversible hydrogen storage

Hydrides of period 2 and 3 elements are promising candidates for hydrogen storage, but typically have heats of reaction that are too high to be of use for fuel cell vehicles. Recent experimental work has focused on destabilizing metal hydrides through mixing metal hydrides with other compounds. A very large number of possible destabilized metal hydride reaction schemes exist, but the thermodynamic data required to assess the enthalpies of these reactions are not available in many cases. We have used density functional theory calculations to predict the reaction enthalpies for more than 300 destabilization reactions that have not previously been reported. The large majority of these reactions are predicted not to be useful for reversible hydrogen storage, having calculated reaction enthalpies that are either too high or too low, and hence these reactions need not be investigated experimentally. Our calculations also identify multiple promising reactions that have large enough hydrogen storage capacities to be useful in practical applications and have reaction thermodynamics that appear to be suitable for use in fuel cell vehicles and are therefore promising candidates for experimental work.

Ultrafast Reaction between Li3N and LiNH2 To Prepare the Effective Hydrogen Storage Material Li2NH

Li2NH is a promising candidate for hydrogen storage. However, its performance for hydrogen absorption is strongly dependent on its preparation method. In this paper, we report that an ultrafast solid reaction between Li3N and LiNH2 provides a new synthesis approach to an effective Li2NH material, which can reversibly store 6.8 wt % hydrogen with fast kinetics and excellent stability. In contrast, Li2NH prepared via the conventional LiNH2 decomposition method absorbs less than 2 wt % hydrogen in 500 min. Scanning electron microscopy (SEM) and BET measurements demonstrated that the poor performance of Li2NH prepared via the conventional decomposition method is caused by sintering. In addition, the hydrogen capacity of Li2NH, which was prepared via the reaction between LiH and LiNH2, reached a value of only about 4 wt % after 500 min.

Identification of Destabilized Metal Hydrides for Hydrogen Storage Using First Principles Calculations

Hydrides of period 2 and 3 elements are promising candidates for hydrogen storage but typically have heats of reaction that are too high to be of use for fuel cell vehicles. Recent experimental work has focused on destabilizing metal hydrides through alloying with other elements. A very large number of possible destabilized metal hydride reaction schemes exist. The thermodynamic data required to assess the enthalpies of these reactions, however, are not available in many cases. We have used first principles density functional theory calculations to predict the reaction enthalpies for more than 100 destabilization reactions that have not previously been reported. Many of these reactions are predicted not be useful for reversible hydrogen storage, having calculated reaction enthalpies that are either too high or too low. More importantly, our calculations identify five promising reaction schemes that merit experimental study: 3LiNH(2) + 2LiH + Si --> Li(5)N(3)Si + 4H(2), 4LiBH(4) + MgH(2) --> 4LiH + MgB(4) + 7H(2), 7LiBH(4) + MgH(2) --> 7LiH + MgB(7) + 11.5H(2), CaH(2) + 6LiBH(4) --> CaB(6) + 6LiH + 10H(2), and LiNH(2) + MgH(2) --> LiMgN + 2H(2).