Potential Hydrogen Storage Material Research Articles

Ultrafine Pt nanoparticles anchored on core-shell structured zeolite-carbon for efficient catalysis of hydrogen generation.

Ammonia borane (AB) is a potential hydrogen storage material with high-efficiency hydrolytic dehydrogenation under a suitable catalyst. Noble metal catalysts have drawn a lot of attention. In this study, a carbon-coated zeolite was obtained by calcination at high temperatures using glucose as a carbon source. Pt nanoparticles were fixed on a core-shell composite support by a simple chemical reduction method. A series of catalysts were prepared with different synthesis parameters. The results show that PSC-2 has excellent catalytic performance for hydrolytic dehydrogenation of AB in alkaline solution at room temperature, and the turnover frequency (TOF) is 593 min-1. The excellent catalytic performance is attributed to the carbon layer on the zeolite surface which inhibits the aggregation or deformation of metals in the catalytic reaction. The metal-support interaction activates the water and accelerates the rate-limiting step of hydrolysis. The activation energy (E a = 44 kJ mol-1) was calculated based on the reaction temperature. In addition, the kinetics of AB hydrolysis was studied, and the effects of catalyst concentration, AB concentration and NaOH concentration on AB hydrolysis rate were further investigated. The high-efficiency catalyst prepared in this work provides a new strategy for the development of chemical hydrogen production in the field of catalysis.

Lithium decorated Ѱ-graphene as a potential hydrogen storage material: Density functional theory investigations

In the present scenario, hydrogen has become a prominent alternative of fossil fuel that motivated us to develop more advanced nanomaterials to store efficient hydrogen for future use. This paper studies the hydrogen storage performance of Li-decorated Ѱ-graphene by conducting density functional theory simulations involving van der Waals corrections. Psi (Ѱ)-graphene is an advanced two-dimensional carbon allotrope that comprises pentagon, hexagon, and heptagon carbon rings. The simulation outcome reveals that the Li atom is bounded strongly to Ѱ-graphene with −2.63 eV binding energy through 0.89e charge transfer from Li-2s orbital to C-2p orbitals. Ѱ-graphene system decorated with the Li atom can bind seven hydrogen molecules with a suitable average binding energy of −0.31 eV/H2, high H2 gravimetric capacity of 15.15 wt%, and optimal average desorption temperature of 384 K. As per the Bader charge portioning, ∼0.09e charge is transferred from the Li-2s orbital to the H-1s orbital after hydrogen adsorption on Li + Ѱ-graphene. The hydrogen molecules are adsorbed on Li + Ѱ-graphene via a polarization mechanism. The high Li diffusion barrier of 0.78 eV and structural integrity of Li + Ѱ-graphene configuration at high temperature predicts that the system is a suitable candidate for high-capacity hydrogen storage applications.

XPS Investigation on Improving Hydrogen Sorption Kinetics of the KSiH3 System by Using Zr-Based Catalysts.

The superior hydrogen storage properties makes the KSiH3 system a potential hydrogen storage material for practical applications. A theoretical capacity of 4.3 wt% bring this material to the front line of all the available hydrogen storage materials; however, the activation barrier of the reaction restricts the system to absorb and desorb hydrogen reversibly at elevated temperatures even if the thermodynamics suggest its room temperature operation. Several catalysts have already been tested to enhance its kinetic properties. In this work, the efforts were made to reduce the activation energy by using Zr-based catalysts to the KSi/KSiH3 system. The value of activation energy was found to be lowest (i.e., 87 kJ mol-1) for the ZrH2-added KSiH3 system. The mechanism of this improvement was investigated by using X-ray photoelectron spectroscopy (XPS).

Improved hydrogen storage properties of Li-Mg-N-H system by lithium vanadium oxides

The Mg(NH2)2-2LiH system is considered as one of the most potential hydrogen storage materials due to its high hydrogen storage capacity (5.6 wt%) and excellent reversible hydrogen adsorption and desorption performance. However, its poor kinetic characteristics of hydrogen absorption and desorption limit its practical application. In this work, Li3VO4 @LiVO2 was synthesized by a hydrothermal method, and was then introduced into Mg(NH2)2-2LiH system to enhance the hydrogen absorption and desorption kinetic characteristics. The results show that the hydrogen storage properties were greatly improved with addition of 10 wt% Li3VO4 @LiVO2 addition. As for the hydrogen absorption and desorption kinetics, the average hydrogen absorption rate of 10 wt% Li3VO4 @LiVO2 modified Li-Mg-N-H sample within 20 min at 200 ℃ increased by 95.2% compared with that of the pristine Li-Mg-N-H sample, and the average hydrogen desorption rate of 10 wt% Li3VO4 @LiVO2 modified sample within 30 min at 180 ℃ increased by 42% compared with that of the pristine sample. The Ea of hydrogen desorption decreased from 117.86 kJ/mol to 99.43 kJ/mol, which also indicates that Li3VO4 @LiVO2 catalyst effectively improved the kinetic performance of hydrogen desorption and desorption of Li-Mg-N-H. Moreover, the hydrogen desorption capacity and hydrogen absorption capacity of 10 wt% Li3VO4 @LiVO2 modified Li-Mg-N-H increased by 18.4% and 13.8% compared with that of the pristine sample. The catalytic mechanism of Li3VO4 @LiVO2was discussed based on XRD, XPS and FTIR analysis results.

Room-temperature hydrogen storage performance of metal-organic framework/graphene oxide composites by molecular simulations

Metal-organic framework/graphene oxide (MOF/GO) composites have been regarded as potential room-temperature hydrogen storage materials recently. In this work, the influence of MOF structural properties, GO functional group contents and different amounts of doped lithium (Li+) on hydrogen storage performance of different MOF/GO composites were investigated by grand canonical Monte Carlo (GCMC) simulations. It is found that MOF/GO composites based on small-pore MOFs exhibit enhanced hydrogen storage capacity, whereas MOF/GO based on large-pore MOFs show decreased hydrogen storage capacity, which can be ascribed to the novel pores at MOF/GO interface that favors the enhanced hydrogen storage performance due to the increased pore volume/surface area. By integrating the small-pore MOF-1 with GO, the hydrogen storage capacity was enhanced from 9.88 mg/go up to 11.48 mg/g. However, the interfacial pores are smaller compared with those in large-pore MOFs, resulting in significantly reduced pore volume/surface area as well as hydrogen storage capacities of large-pore MOF/GO composite. Moreover, with the increased contents of hydroxyl, epoxy groups as well as carboxyl group modification, the pore volumes and specific surface areas of MOF/GO are decreased, resulting in reduced hydrogen storage performance. Furthermore, the room-temperature hydrogen storage capacities of Li+ doped MOF/GO was improved with increased Li+ at low loading and decrease with the increased Li+ amounts at high loading. This is due to that the introduced Li+ effectively increases the accessible hydrogen adsorption sites at low Li+ loading, which eventually favors the hydrogen adsorption capacity. However, high Li+ loading causes ion aggregation that reduces the accessible hydrogen adsorption sites, leading to decreased hydrogen storage capacities. MOF-5/GO composites with moderate Li+ doping achieved the optimum hydrogen storage capacities of approximately 29 mg/g.

Hydrogen Adsorption and Isotope Mixing on Copper-Functionalized Activated Carbons

High-specific surface area (SSA) carbons were functionalized with copper nanoclusters and evaluated as potential hydrogen storage materials. The adsorption and desorption behaviors of the copper-functionalized material and pristine high-SSA carbon are compared between 77 and 400 K using adsorption isotherms up to 10 MPa and by temperature-programmed desorption of isotopic hydrogen. The high-SSA activated carbon with copper nanoclusters exhibited two desorption behaviors. (1) A desorption peak at 120 K, which was associated with physisorption on carbon, and (2) a desorption peak at 310 K, which was associated with a chemisorption process involving copper. The desorption from copper was strongly dependent on the hydrogen pressure used for loading, and dissociation of the hydrogen could be avoided by loading at low temperature and pressure. An enhancement of hydrogen uptake in the low-coverage (Henry’s law) regime at ambient temperatures with copper nanoclusters was observed, demonstrating an increased adsorption enthalpy with the copper-modified material. Binding site energies of 6 and 20 kJ/mol for H2 physisorption and H chemisorption, respectively, were obtained from fits to isotherms.

Structures and Electronic and Hydrogen Storage Properties of Magnesium Scandium Hydrides.

MgH2 is well known as a potential hydrogen storage material. However, its high thermodynamic stability, high dissociation temperature, slow absorption, and desorption kinetics severely limit its application. Aiming at these shortcomings, we try to improve the hydrogen storage property of MgH2 by doping with transition metal Sc atoms. The structures and electronic and hydrogen storage properties of Mg-Sc-H systems have been systematically studied by combining the crystal structure analysis by particle swarm optimization and density functional theory method. The results show that the structure of MgScH8 with the R3 space group is the most stable one, which is proved to be a wide-band gap (2.96 eV) semiconductor. The possible decomposition pathways, which are crucial for the applicability of R3-MgScH8 as a hydrogen storage material, are studied, and the pathway of MgScH8 → ScH6 + Mg + H2 is found to be the most favorable one under 107.8 GPa pressure, while above 107.8 GPa, MgScH8 → Mg + Sc + 4H2 becomes the most thermodynamically stable pathway and releases the maximum amount of hydrogen. Based on the root mean square deviation calculation, it is found that R3-MgScH8 begins to melt at 400 K. The result of ab initio molecular dynamics simulations shows that the hydrogen release capacity (4.04 wt %) can be easily achieved at 500 K, thus making MgScH8 a potential hydrogen storage material.

Ultrasound assisted synthesis of attapulgite-PdO nanocomposite using palladium complex for hydrogen storage: Kinetic studies

• 3,4,5-trimethoxybenzoic acid was used to synthesis new palladium complexes in the presence of triphenylephosphine as mixed ligand ([Pd(TMB) 2 (Pph 3 ) 2 ]). • [Pd(TMB) 2 (Pph 3 ) 2 ] was used as a palladium precursor for the ultrasound synthesis of attapulgite-PdO nanocomposite. • Attapulgite-PdO nanocomposite was used for hydrogen storage application with a maximum storage of 3.81 wt%. This research included the synthesis and characterization of new complex by in-situ method using two mole equivalent from 3,4,5-trimethoxybenzoic acid (TMB) and triphenylphosphine (Pph 3 ) in the presence of triethylamine (NEt 3 ). This complex was characterized using FTIR, 1 H NMR, 31 P NMR, CHN, molar conductivity. The results prove that TMB ligand behave as monodentate through the protonated oxygen atom of the carboxylic. This complex was used as a precursor for the synthesis of PdO@attapulgite nanocomposite which was characterized using TEM and XRD. The measurement proved that the palladium oxide nanoparticles had a positive effect in reducing the diameter of the attapulgite channels from 160 nm to the range 90–95 nm. This nanocomposite was used as a potential material for hydrogen storage. The results of hydrogen storage showed that the composite has the ability to store hydrogen even at low pressures, as it was noted that the composite had the ability to store approximately 1 wt% at 30 bar and reached 3.81 wt% at 90 bar. The kinetic studies prove that the storage fit to the pseudo-second order with coefficient factor equal to 0.9278 and the hydrogen storage was reached the maximum (3.81 wt%) after only 200 s.

Titanium-Decorated Planar Aluminene for Hydrogen Storage Using Density Functional Theory

As green technology becomes a greater focus in our society, alternative energy like hydrogen fuel begins to have significance. Current technology has allowed the use of hydrogen as a fuel in fuel cells. However, a more efficient and safer means of storage would make hydrogen fuel more practical. Investigations on two-dimensional systems have already shown them to be potentially viable hydrogen storage devices. This study investigated one such 2-D system, a planar hexagonal aluminene decorated with titanium using density functional theory. Three possible adsorption sites for Ti atoms were chosen on aluminene: top, bridge, and hollow. This study showed that the Ti atom can be adsorbed at distances of 2.25 Å, 1.99 Å, and 0.00295 Å with binding energies of-2.356 eV, -4.219 eV, and-6.084 eV at the top, bridge, and hollow site, respectively. The density of states showed the Ti-decorated aluminene to be non-magnetic when the Ti atom was adsorbed at the top and bridge sites while adsorption at the hollow site resulted in a magnetic material. The charge density difference also showed chemisorption between the Ti and Al atoms which was consistent with the binding energies and the density of states. The hydrogen molecule was adsorbed on to the decoration at the top and hollow sites with binding energies of-1.41 eV and-0.494 eV, respectively. The H2 molecule dissociated at the top site with a dissociation barrier of 0.0266 eV and an imaginary frequency of 976.99 cm-1 in the vibrational spectrum. The results of the study showed that Ti-decorated aluminene can be a potential hydrogen storage material.

The surface and encapsulated storage of H2 on Ga12N12

Ga12N12 is a fullerene cage and particularly stable. The surface adsorption and encapsulated storage of H2 on the Ga12N12 are thoroughly explored by applying a genetic algorithm combined with DFT calculations. The results reveal that one H2 can form physical adsorption on the surface sites of Ga12N12 with ideal adsorption intensities (−0.227∼-0.303 eV) and the mode of H2 adsorption on a Ga atom is the most energy favored. Interestingly, the Ga12N12 can adsorb a maximum of 38H2 molecules with mass density of 7.01 wt%. The electronic structure analysis indicates that the charge transferring between H2 and Ga12N12 is observed. Meanwhile, H2 is also effectively polarized, and thus the electrostatic interaction is improved. When H2 is adsorbed on the Ga atom, weak covalent interactions are also induced. The encapsulation of H2 in the Ga12N12 is an endothermic process and six H2 molecules can be encapsulated in the Ga12N12 with the moderate encapsulation and releasing energy barrier of 3.286∼4.508 eV and 0.390∼3.008 eV, respectively. Our results suggest that Ga12N12 is regarded as a potential hydrogen storage material.

Grand canonical Monte Carlo simulation study of hydrogen storage by Li-decorated pha-graphene

Grand canonical Monte Carlo simulation (GCMCs) is utilized for studying hydrogen storage gravimetric density by pha-graphene at different metal densities, temperatures and pressures. It is demonstrated that the optimum adsorbent location for Li atoms is the center of the seven-membered ring of pha-graphene. The binding energy of Li-decorated pha-graphene is larger than the cohesive energy of Li atoms, implying that Li can be distributed on the surface of pha-graphene without forming metal clusters. We fitted the force field parameters of Li and C atoms at different positions and performed GCMCs to study the absorption capacity of H2. The capacity of hydrogen storage was studied by the differing density of Li decoration. The maximum hydrogen storage capacity of 4Li-decorated pha-graphene was 15.88 wt% at 77 K and 100 bar. The enthalpy values of adsorption at the three densities are in the ideal range of 15 kJ⋅mol−1–25 kJ⋅mol−1. The GCMC results at different pressures and temperatures show that with the increase in Li decorative density, the hydrogen storage gravimetric ratio of pha-graphene decreases but can reach the 2025 US Department of Energy’s standard (5.5 wt%). Therefore, pha-graphene is considered to be a potential hydrogen storage material.

Potential hydrogen storage materials from Li decorated N‐doped Me‐graphene

Potential hydrogen storage materials from Li decorated N‐doped Me‐graphene

High-capacity hydrogen storage in yttrium-decorated Ψ-graphene: Acumen from density functional theory

Employing density functional theory simulations, we have predicted Y-decorated Ψ-graphene as a potential hydrogen storage material for fuel cell vehicle (FCV) applications. The system is stable at ambient and higher temperatures as substantiated by ab initio molecular dynamics simulations and is capable of holding 8.31 wt. % of hydrogen, higher than the U.S. Department of Energy (DOE) target. Each Y atom attached on Ψ-graphene can adsorb seven H2 molecules with a mean binding energy of −0.39 eV per H2 and a desorption temperature of 496.55 K—highly suitable for fuel cell applications. The Y atom binds strongly with the Ψ-graphene sheet, evident from the binding energy of −3.06 eV. The presence of a diffusion energy barrier of 0.4–0.7 eV for the diffusion of Y atom across Ψ-graphene may prevent metal–metal clustering. The flow of charge is found to be from Y atom 4d orbitals toward the C 2p orbitals of Ψ-graphene. Hydrogen molecules are found to bind reversibly by Kubas interactions involving charge donation and back donation between Y atom 4d orbitals and 1s orbitals of hydrogen, allowing for a suitable binding energy for FCV applications. Considering the stability of the system, optimum binding energy, and desorption temperature as per U.S. DOE targets; adequate barrier energy for diffusion; and excellent gravimetric hydrogen storage capability of the material, we propose Y-decorated Ψ-graphene as a potent hydrogen storage material for FCV applications.

Lithium decorated C3N as high capacity reversible hydrogen storage material: Insights from density functional theory

AbstractLithium‐decorated (Li‐decorated) C3N has been investigated as a potential material for high capacity reversible hydrogen storage. The energetic stability, dynamical stability, and thermal stability were studied. The cohesive energy of C3N (7.03 eV/atom) denotes the energetic stability, imaginary frequencies are not found from the result of phonon spectrum calculation, and the free energy vibrates slightly around −64.63 eV during the 5000 fs period and no structure reconstruction. Electronic properties showed the band gaps are 0.39 and 1.12 eV, via PBE and HSE calculations, respectively. The four probable Li‐adsorbed sites were calculated, indicating that the hollow site above the center of a hexagon ring HC site is the most likely site to absorb Li atom. Hydrogen molecules were added one by one to research the maximum hydrogen gravimetric density. Each Li atom can attach 10 hydrogen molecules within the range of physical adsorption processes (−0.1 to −0.4 eV/H2) and the hydrogen storage capacity can reach as high as 8.81 wt%. Li‐decorated C3N has great potential for on‐board reversible solid‐state hydrogen molecule storage application.

Methanolysis of ammonia borane using binder‐free hierarchical Co@Ni metal‐organic framework nanocolumn arrays catalyst for hydrogen generation

Ammonia borane (AB) is a potential material for chemical hydrogen storage because of its outstanding stability, high hydrogen density, and the development of highly effective hierarchical catalysts for AB hydrolysis. Herein, the hierarchical Co@Ni metal-organic framework (MOF) nanocolumn arrays (NCAs) on nickel foam (NF) were fabricated through a simple hydrothermal reaction, and the prepared catalysts were characterized using different techniques. The hierarchical Co@Ni-MOFNCA/NF acts as a catalyst for AB methanolysis for hydrogen production. The catalysts exhibited outstanding performance towards AB methanolysis with the TOF of TOF of 20.54 mol H2 mol catalyst−1 min−1. As a result, the activation energy of the Co@Ni-MOF NCA catalyst is 39.72 kJ mol−1 which is compared with some commercial solid support materials such as Al2O3 and AC. Additionally, the effects of nanocatalyst loading and temperatures were studied for the Co@Ni-MOF NCA catalyst. Further, a complete investigation proposes that the outstanding catalytic performance of the Co@Ni-MOF NCA catalyst could be attributed to the synergy between Co and Ni-MOF NCA.

Homogeneous First‐row Transition‐metal‐catalyzed Carbon Dioxide Hydrogenation to Formic Acid/Formate, and Methanol

AbstractDepletion of fossil fuel for global energy need emits large amount of greenhouse gas carbon dioxide into the biosphere. Carbon dioxide constitutes a sustainable C1 feedstock and cost‐effective raw material for the synthesis of bulk and fine chemicals. The catalytic hydrogenation of CO2 to formic acid, and methanol is an attractive protocol owing to their application in chemical industry and as potential renewable hydrogen storage materials. Catalytic hydrogenation reactions are atom‐economical, green and sustainable synthetic routes towards various new environmentally benign transformations. Homogeneous catalytic hydrogenation reactions based on earth‐abundant, eco‐friendly, first‐row base metals for the preparation of an assortment of organic scaffolds is currently of paramount importance in academia and industry. The surge in base metal catalysis is evident from the increase in reports available in the literature in recent years.In this review, we summarize advances on homogeneous first‐row transition metal catalysed direct and indirect reduction of carbon dioxide to formic acid/formate and methanol based on the hydrogenation strategy.

Reversible hydrogen storage capacity of Sc and Y functionalized [1,1]paracyclophane: Insights from density functional study

This work reports the hydrogen storage, and delivery capacities of Sc and Y functionalized [1,1]paracyclophane using dispersion corrected density functional theory calculations. The Sc and Y atoms are bind strongly with benzene rings of [1,1]paracyclophane. Each Sc and Y atom functionalized over [1,1]paracyclophane adsorb up to 6H2 molecules via Kubas interaction achieving maximum gravimetric density up to 8.22 wt% and 6.33 wt%, respectively. The calculated average hydrogen adsorption energy (0.36 eV) is lower than the chemisorption but higher than the physisorption process. The kinetic stabilities are verified through the HOMO-LUMO gap and different global reactive descriptors. ADMP molecular dynamics simulations reveal the reversibility of adsorbed H2 molecules at sufficiently above the room temperature and the solidity of host material at 500 K. Average Van't Hoff desorption temperature for Sc and Y decorated system was calculated to be 439 K and 412 K respectively at 1 atm of pressure. Hence, we believe that Sc and Y functionalized [1,1]paracyclophane can be considered as a thermodynamically viable, and potential reversible hydrogen storage materials at ambient environment.

Hydrogen storage properties of Li-, Sc-, Ti-decorated Ψ-graphene: A DFT study

In this paper, the hydrogen storage performance of Sc (Ti, Li)-modified [Formula: see text]-graphene ([Formula: see text]-g) is investigated by density functional theory (DFT). Sc and Ti can be stably adsorbed on [Formula: see text]-g with the binding energies of 4.78 eV and 4.83 eV, respectively. Li atoms can also be stably absorbed on B-doped [Formula: see text]-g with the binding energy of 2.51 eV. In addition, Sc and Ti atoms attached on [Formula: see text]-g can adsorb up to ten and eight hydrogen molecules, and the hydrogen gravimetric storage capacity reaches 7.93 wt.% and 6.20 wt.%, respectively. Li atoms attached on B-doped [Formula: see text]-g can adsorb up to eight hydrogen molecules with the hydrogen gravimetric storage capacity 9.32 wt.%, all meeting DOE standards. On the whole, Bader charge analysis shows that the charge is transferred from C atoms to H atoms, which is more conducive to hydrogen adsorption. All the researches prove that the Sc, Ti-decorated [Formula: see text]-g and Li-decorated B-doped [Formula: see text]-g are potential hydrogen storage materials.

Thermal conductivities of hydrogen encapsulated boron nitride and hybrid boron nitride – carbon nanotubes using molecular dynamics simulations

In this work, we investigated the thermal conductivities of boron nitride nanotubes (BNNTs) and carbon nanotubes (CNTs) as potential hydrogen storage materials using atomistic nonequilibrium molecular dynamics (NEMD) simulations. Pristine and defective (containing B/N/C single atom vacancy or B-N double atom vacancies) capped armchair BNNTs and BN-C heteronanotubes have been studied. Furthermore, thermal conduction in BNNT, CNT, and BN(50%)-C(50%) heteronanotubes with varying amounts of encapsulated H2 molecules has been evaluated. We compare the performance of the reactive forcefield ReaxFF with non-reactive Tersoff-adaptive intermolecular reactive empirical bond order (AIREBO)-Lennard-Jones (TALJ) potentials combination. The ReaxFF potential yielded consistently lower thermal conductivity (k) for all the nanotubes. However, it provides a better qualitative prediction of thermal transport in the nanotubes (in terms of k reduction due to defects and entrapped H2, and sensitivity to composition as reflected in the phonon density of states) whereas Tersoff/TALJ potentials provide a better quantitative prediction of k while failing to account for acoustic phonon details. Near-linear mixing rule for k across the CNT-BNNT composition suggested by both potentials indicates smooth interfacial heat transport at the heterojunctions.

Simultaneous preparation of sodium borohydride and ammonia gas by ball milling

Hydrogen and ammonia are both potential energy carriers being considered for large scale energy transport. Sodium borohydride (NaBH4) has been widely applied as a potential solid-state hydrogen storage material. It can produce hydrogen gas and sodium metaborate (NaBO2) after hydrolysis with water at room temperature. The regeneration of NaBH4 from NaBO2 could significantly reduce the cost of NaBH4 and enable its wide-spread industrial use. In this work, we demonstrate a simple method for regenerating NaBH4 from NaBO2·4H2O using Mg2N3, which combines NaBH4 production with NH3 gas production in a single step at room temperature. NaBH4 is successfully synthesized from NaBO2·4H2O using the Mg3N2 reducing agent via ball milling under a hydrogen atmosphere. NaBH4 is formed at a 76.6% yield by planetary ball milling at 600 rpm under 40 bar hydrogen for 12 h. NH3 gas is also formed, which can be easily separated from the solid products. Therefore, this one-step process could produce two different types of carbon-free hydrogen carriers suitable for energy export from renewable sources.