Hydrogen Storage Ability Research Articles

A Route for Phase Control in Metal Nanoparticles: A Potential Strategy to Create Advanced Materials.

There is untapped potential for materials whose crystal structures are unobtainable in the bulk state. Several examples of such structures have been found in nanomaterials, and these materials exhibit unique properties that arise from their unique electronic states and surface structures. Here, recent developments in the syntheses of these nanomaterials and their unique properties, such as hydrogen-storage ability and catalytic activity, are summarized. Firstly, the syntheses and properties of novel solid-solution alloy nanoparticles in immiscible alloy systems such as Ag-Rh and Pd-Ru are introduced. Following this, the crystal structure control of nanoscale Ru is discussed. These unique alloy materials show enhanced properties and highlight the potential of phase control to be a new strategy for nanomaterial development.

The study of the hydrogen storage capacity of the Ti atoms coated Si@Ga12 clusters

The generalized gradient approximation based on the density functional theory method is used to investigate the hydrogen storage abilities of the transition metal Ti atoms coated Tim-Si@Ga12 (m = 1, 2) clusters. The average binding energy of the Ti atom to the hollow site on the Si@Ga12 surface and the distance between the neighboring two Ti atoms are 5.20 eV and 2.8 Å, respectively larger than the experimental cohesive energy of bulk Ti (4.85 eV/atom) and the experimental bond length of the Ti2 dimer (1.97 Å), so the clustering of Ti atoms can be prevented, this is critical for large amount hydrogen storage. Ti-Si@Ga12 and Ti2-Si@Ga12 can adsorb 6 and 12H2 molecules separately with the average adsorption energy of 0.37 eV and 0.30 eV, which would allow hydrogen storage at near-ambient conditions. The Dewar–Kubas interaction mechanism dominates the adsorption of H2 by the Ti-Si@Ga12 and Ti2-Si@Ga12 structures. The average desorption temperature analysis and the molecular dynamic simulation demonstrate that the structures reported here are favorable for the reversible hydrogen storage at near-ambient conditions.

The properties of hydrogenated derivatives of the alkali atom coated clusters C6M6 (M = Li, Na): A density functional study

The generalized gradient approximation based on density functional theory is used to study the geometric structures, electronic properties and hydrogen storage abilities of alkali metal atom decorated C6M6 (M=Li, Na). The most stable site for the Li and Na atoms is above the bridge site of the C–C bond of the C6 ring. It is calculated that C6Li6 and C6Na6 can most adsorb 24 and 12 H2 molecules respectively. The average adsorption energy for H2 of C6 (M–nH2)6 (M=Li, Na) are from 0.15eV to 0.6eV, which are between physical adsorption and chemical adsorption (0.1–0.8eV), so they can realize the reversible adsorption of hydrogen. However, the average adsorption energy of H2 and the hydrogen gravimetric density of C6(Li–4H2)6 are larger than those of C6(Na–2H2)6. Therefore, C6Li6 exhibits better hydrogen storage ability than that of C6Na6. The atomic orbital hybridization mechanism dominates the adsorption of H2 by C6M6 (M=Li, Na). However, the desorption of H2 by C6(Li–4H2)6 can be realized easier than that by C6(Na–2H2)6 at the room temperature. The dynamic simulation, electronegativity, hardness, electrophilicity, and aromaticity of all the structures explore that C6M6 (M=Li, Na) and their hydrogenation structures have considerable stabilities.

Hydrogen storage property of materials composed of Mg nanoparticles and Ni nanoparticles fabricated by gas evaporation method

We have fabricated the materials composed of the Mg and the Ni nanoparticles and clarified the hydrogen storage property by using TEM, XPS and QCM. The Mg and the Ni nanoparticles have been fabricated by gas evaporation method and been mixed. The diameters of the Mg and the Ni nanoparticles have been estimated as 20.0 ± 8.4 and 4.7 ± 2.0 nm, respectively. And the Mg and the Ni nanoparticles as prepared sample possess almost clean surface. This sample can absorb the hydrogen under atmospheric pressure at 30 °C before completely oxidized. However, the hydrogen storage ability of this sample has been lost by the adsorption of residual gases even under vacuum condition in several hours after the end of fabrication. Due to the Mg oxide shell on the surface of the Mg nanoparticles is formed by the residual gases, the hydrogenation of the Mg nanoparticles are hindered.

A first principles study of hydrogen storage on lithium decorated two dimensional carbon allotropes

Graphene has been intensively investigated as a possible hydrogen storage medium due to the spectacular properties granted by its two-dimensional nature. Since graphene's discovery, several new two-dimensional carbon allotropes have been theorized and synthesized. We investigated the hydrogen storage ability of six such allotropes: C65, C64, C63, C62, C31 and C41. The ability to anchor lithium metal atoms over each allotrope and the hydrogen binding energies for each lithium decorated allotrope were studied with density functional theory using LDA, GGA and vdW-DF2 (for describing van der Waals interactions) functionals. All the allotropes were able to achieve double sided lithium decoration and hydrogen adsorption. Every allotrope other than C31 possesed lithium binding energies stronger than bulk lithium's cohesive energy which indicates that adsorbed lithium atoms will not cluster on the allotrope surface. Furthermore, every structure produced hydrogen binding energies stronger than that of lithium decorated graphene, suggesting the potential of use of these structures in practical hydrogen storage media. The C41 structure was able to adsorb far more hydrogen molecules than any other structure with a maximum hydrogen gravimetric density of 7.12 wt.% using the vdW-DF2 functional.

Effect of modified linkers of MOF-5 on enhancing interaction energies: A theoretical study

The performance of modified organic linkers on improving the interaction energies between H2 and MOF-5 with alkyl ether chains of different lengths has been investigated by density functional calculations at both DFT-D and M06-2X levels of theory. All results show that the interaction energies for modified organic linkers are larger than those for unmodified organic linker (BDC), indicating that organic linker modification is an effective strategy to improve the adsorption energy between the linker and a hydrogen molecule. This paper provides an easy but effective idea on improvement of hydrogen storage ability of the MOFs.

Non-conventional processing routes and applications of intermetallics

Intermetallics are materials offering wide variety of interesting properties, such as high hardness, high chemical resistance, shape memory or hydrogen storage ability. However, the synthesis and processing of intermetallic compounds by common metallurgical techniques is often very problematic. In this paper, the modern techniques involving non-conventional processes of powder metallurgy, reactive sintering and mechanical alloying, are presented. In the field of application, novel directions are linked – the use of intermetallic-based materials as surgical implants or tool materials.

Porous BN for hydrogen generation and storage

Hydrogen is a highly appealing renewable energy resource, while hydrogen generation and storage for practical applications remain a great challenge at present. The proposed porous p-BN has both good hydrogen generation and storage ability which can be dramatically enhanced by C-dopant and Li-decoration.

Computational investigation of hydrogen storage on scandium–acetylene system

The hydrogen storage capacities of synthesized Scandium–Acetylene systems (Sc–η2–(C2H2) and HCC–ScH) are tested by using density functional theory (DFT) and the coupled-cluster theory (CCSD (T)) with 6–311++G (3df, 3pd) basis sets. Both the energy profile and natural bond orbital analysis predict that Sc–η2–C2H2 and HCC–ScH complexes are promising hydrogen storage materials. The Sc–η2–(C2H2) and HCC–ScH complexes can trap up to six hydrogen molecules, reaching gravimetric uptake capacities as high as 14.56 wt%. Thermo-chemistry calculations indicate two H2 in Sc–η2–C2H2(H2)6 and four H2 in HCC–ScH(H2)6 can be readily adsorbed at 77 K and desorbed at 298.15 K under atmospheric pressure, corresponding to the maximal reversible hydrogen storage abilities of 5.37 and 10.20 wt%, respectively. The further comparison between HCC–ScH(H2) and HCC–ScH− (2H) reveals that the charged state of Sc atom has a great influence on the hydrogen adsorption state and adsorption energy. Moreover, dimers may form in case of scandium-acetylene systems. The most stable (C2H2Sc)2 can adsorb ten H2 molecules, reaching the hydrogen storage capacity of 12.43 wt%. Thermo-chemistry calculations indicate the maximal reversible hydrogen storage capacities of Sc(C2H2)2 and (C2H2Sc)2 are 7.67 and 7.85 wt%, respectively.

不同金属外掺杂富勒烯C20M(M=Li, Ti, Fe)的储氢性能

使用密度泛函理论（DFT）中的广义梯度近似（GGA）对经碱金属原子Li、 过渡金属原子Ti和Fe修饰的富勒烯C 20 M（M=Li，Ti，Fe）的储氢性能进行研究. 结果表明，C 20 Li（C 20 Ti 和C 20 Fe）能够吸附H 2 的最大数目为6，6和4，与18电子规则相吻合；C 20 M（M=Li，Ti，Fe）对H 2 的平均吸附能在0.25~0.80 eV范围内，介于物理吸附和化学吸附之间（0.1~0.8 eV），因此可以实现常温下对氢的可逆吸附. C 20 Li主要通过正负电荷形成的偶极矩作用进行储氢，而C 20 Ti和C 20 Fe主要通过Dewar-Kubas作用进行储氢.

Synthesis of novel hollow microflowers (NHMF) of Nb3O7F, their optical and hydrogen storage properties

A two step, facile surfactant free hydrothermal route was adopted to synthesize Nb3O7F novel hollow microflowers (NHMF). Time dependent experiments were performed which suggested Nb3O7F-NHMF were formed due to Ostwald-ripening process. Raman spectroscopy was conducted to understand different vibrational modes of Nb3O7F-NHMF. Its characteristic band at 692 cm−1 was observed which is associated to NbO6 octahedron sharing. The bandgap of 3.2 eV was calculated by using UV-VIS-NIR absorption spectrum. Considering importance of layered structures in energy storage applications, hydrogen storage ability of Nb3O7F-NHMF were measured for the first time. The maximum values of hydrogen absorption for Nb3O7F-NHMF at 373 K and 473 K were 0.789 wt.% and 1.08 wt.%, respectively. The hydrogen storage measurements revealed the potential of Nb3O7F-NHMF as prospective material for energy storage applications.

The Effect of Nickel and Graphite on the Hydrogen Storage Ability of Magnesium in the First Cycle

AbstractMagnesium can serve as a solid‐state hydrogen‐storage material, and over recent years it has been taken into consideration owing to its high storage capacity. The effect of 10 wt % nickel and graphite (G) on hydrogen sorption of magnesium was compared. The powder mixture was mechanically milled for 35 h under an argon atmosphere. A Sievert apparatus was used for hydrogen sorption analysis. Scanning electron microscopy and X‐ray diffraction were used for morphological characterization. Hydrogen sorption analysis was performed at 3.5 MPa and 473 K. The results showed that graphite had a better effect than nickel on the hydrogen storage properties of magnesium owing to a greater reduction in the particle size of magnesium and the physisorption of hydrogen by graphite. The hydrogen adsorption of Mg+10 wt % G was also investigated at 2.0, 3.5, and 4.0 MPa, and it was found that the compound adsorbed 5.7 wt % hydrogen at 4.0 MPa because hydrogen could penetrate into the inner parts of the magnesium powder at higher pressure.

The influence of stacking faults on hydrogen storage in TiCx

The hydrogen storage ability of TiCx with stacking faults (SFs) is studied in this work. It is found that the absorption of hydrogen atoms is possible in both TiCx with and without SFs. And, besides the carbon vacancy sites, the hydrogen atoms can also occupy the tetrahedral sites in the SFs layers. More importantly, it is confirmed that the diffusion of hydrogen in TiCx with SFs is much easier than that in TiCx without SFs, especially the diffusion around the SFs layers. The energy barrier for diffusion of the hydrogen atom in the SFs layers and diffusion from the SF layer to the next layer is only 0.099 eV and 0.185 eV, respectively. Therefore, bringing in the SFs in TiCx with ordered carbon vacancies will be an effective method to solve the diffusion problem during the processes of hydrogen storage.

Mechanical Ball-Milling Preparation of Fullerene/Cobalt Core/Shell Nanocomposites with High Electrochemical Hydrogen Storage Ability

The design and synthesis of new hydrogen storage nanomaterials with high capacity at low cost is extremely desirable but remains challenging for today's development of hydrogen economy. Because of the special honeycomb structures and excellent physical and chemical characters, fullerenes have been extensively considered as ideal materials for hydrogen storage materials. To take the most advantage of its distinctive symmetrical carbon cage structure, we have uniformly coated C60's surface with metal cobalt in nanoscale to form a core/shell structure through a simple ball-milling process in this work. The X-ray diffraction (XRD), scanning electron microscope (SEM), Raman spectra, high-solution transmission electron microscopy (HRTEM), energy-dispersive X-ray spectrometry (EDX) elemental mappings, and X-ray photoelectron spectroscopy (XPS) measurements have been conducted to evaluate the size and the composition of the composites. In addition, the blue shift of C60 pentagonal pinch mode demonstrates the formation of Co-C chemical bond, and which enhances the stability of the as-obtained nanocomposites. And their electrochemical experimental results demonstrate that the as-obtained C60/Co composites have excellent electrochemical hydrogen storage cycle reversibility and considerably high hydrogen storage capacities of 907 mAh/g (3.32 wt % hydrogen) under room temperature and ambient pressure, which is very close to the theoretical hydrogen storage capacities of individual metal Co (3.33 wt % hydrogen). Furthermore, their hydrogen storage processes and the mechanism have also been investigated, in which the quasi-reversible C60/Co↔C60/Co-Hx reaction is the dominant cycle process.

Ball-milling preparation of one-dimensional Co–carbon nanotube and Co–carbon nanofiber core/shell nanocomposites with high electrochemical hydrogen storage ability

Owing to the special honeycomb structures and excellent electrical characters of carbon nanotube (CNT) and carbon nanofiber (CNF), they are extensively considered as ideal cornerstones for hydrogen storage materials. Herein, metal cobalt has been uniformly coated on CNT's and CNF's surfaces in nanoscale through a simple ball milling process. Accordingly their X-ray diffraction, scanning electron microscope and transmission electron microscopy measurements clarify the satisfying composite structures. And their electrochemical experimental results demonstrate that the as-obtained CNT/Co and CNF/Co composites have excellent electrochemical hydrogen storage reversibility and considerably high storage capacities of 717.3 mAh g−1 (2.62 wt% hydrogen) and 739.4 mAh g−1 (2.70 wt% hydrogen) under room temperature and ambient pressure, which are much higher than the capacities of individual CNT (29.9 mAh g−1, 0.11 wt% hydrogen) and CNF (49.0 mAh g−1, 0.18 wt% hydrogen) measured in this work. Furthermore their hydrogen storage processes and the mechanism have also been investigated, in which the quasi-reversible CNT (CNF)/Co ↔ CNT (CNF)/Co–Hx reaction is the dominant cycle process.

Uniform Bi2S3 nanorods-assembled hollow spheres with excellent electrochemical hydrogen storage abilities

Hierarchical Bi2S3 hollow spheres have been synthesized by a facile solvothermal process in the presence of sodium tartrate. The hollow spheres are composed of numerous ultrathin nanorods with the average diameter of 15 nm. Based on the time dependent electron microscope observations, the formation mechanism of such hierarchical structures has been proposed as a sodium tartrate directed self-assembled process and oriented attachement mechanism. The morphology and size of the subunits can be controlled by adjusting the amount of sodium tartrate. The Nitrogen adsorption-desorption measurements suggest that mesopores exist in these hollow spheres. The as-derived Bi2S3 hollow spheres exhibit excellent electrochemical hydrogen storage properties.

Compositional effects on the hydrogen storage properties of Mg(NH2)2–2LiH–xKH and the activity of KH during dehydrogenation reactions

Potassium hydride (KH) was directly added to a Mg(NH2)2-2LiH system to improve the hydrogen storage properties; the corresponding mechanisms were elucidated. The Mg(NH2)2-2LiH-0.08KH composite displays optimized hydrogen-storage properties, reversibly storing approximately 5.2 wt% hydrogen through a two-stage reaction and a dehydrogenation onset at 70 °C. The 0.08KH-added sample fully dehydrogenated at 130 °C begins to absorb hydrogen at 50 °C, and takes up approximately 5.1 wt% of hydrogen at 140 °C. Adding KH significantly enhances the de-/hydrogenation kinetic properties; however, an overly rapid hydrogenation rate enlarges the particle size and raises the dehydrogenation temperature. A cycling evaluation reveals that the KH-added Mg(NH2)2-2LiH system possesses good reversible hydrogen storage abilities, although the operational temperatures for de-/hydrogenation increase during cycling. Detailed mechanistic investigations indicate that adding KH catalytically decreases the activation energy of the first dehydrogenation step and reduces the enthalpy of desorption during the second dehydrogenation step as a reactant, significantly improving the hydrogen storage properties of Mg(NH2)2-2LiH.

Hydrogen Storage Capacity Study of a Li+Graphene Composite System with Different Charge States

Based on first-principles plane-wave calculations, we firstly reconfirm that the Li+graphene complex can be taken as a hydrogen storage medium with capacity of 12.8wt%. Then metal adsorption properties of this Li+graphene system with different charge states are investigated. Finally, the hydrogen storage ability of the charging system is calculated. Our calculations show that adding positive charge on a Li+graphene composite results in a conspicuous reduction of Li2s and Li2p orbital occupation with respect to the C2p state. As a result, a stronger bonding between Li and graphene is formed, and a special double-layer hydrogen adsorption structure has been found. Compared to the neutral system, utilizing the positive charged Li+graphene to store hydrogen molecules can solve the issue of clustering of metal atoms after releasing hydrogen, and can improve hydrogen storage capacity up to a gravimetric density of 20.4wt%, correspondingly one adsorbed Li atom can effectively absorb up to seven H2 molecules.

The high-capacity hydrogen storage abilities of the Ti atoms coated Si@Al12 clusters

The storage of hydrogen molecules by Ti atoms coated Si@Al12 clusters is investigated using the density functional method. Ti atoms are bonding strongly to the surface of Si@Al12 and are not clustered. Ti–Si@Al12 and Ti2–Si@Al12 can adsorb 6 and 12 H2 molecules with the adsorption energy per H2 of 0.53 and 0.44eV respectively. The hydrogen gravimetric density of Ti2–Si@Al12·12H2 is 6.6wt%, exceeding the 5.5wt% at 2015 specified by US Department of Energy. Therefore, the stable Si@Al12 can be applied as one candidate for hydrogen storage materials at near-ambient conditions.

D-penicillamine assisted hydrothermal synthesis of Bi2S3 nanoflowers and their electrochemical application

Single crystalline flower-like Bi2S3 nanostructures were successfully synthesized via a simple, facile and green hydrothermal method, with the assistance of D-penicillamine. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), and found their morphologies mainly depend on the ratios of Bi3+ to D-penicillamine, as well as the reaction temperature and time. And the possible growth mechanism has been discussed in some detail. In addition, the as-prepared Bi2S3 nanoflowers show good hydrogen storage ability. This strategy can be potentially expanded to prepare other metal chalcogenides materials.