Promising Candidates For Hydrogen Storage Research Articles

Prediction of comprehensive properties and their hydrogen performance of Mg2XH6(X=Mn, Fe, Co, Ni) perovskite hydrides based on first principles

Hydrogen storage materials are very critical for hydrogen energy utilization. Cubic Mg2XH6(X = Mn, Fe, Co, Ni) hydrogen storage materials are investigated by first principles calculation. The structural stability are confirmed by complex consideration of phonon spectrum, formation energies and elastic constants. They are brittle and hard materials with high temperature applicable potential. Mg2MnH6 and Mg2CoH6 are magnetic compounds while Mg2FeH6 and Mg2NiH6 are non-magnetic materials. Mg2MnH6 and Mg2FeH6 are semiconductors with bandgap of 1.867 eV and 3.318 eV, respectively, indicating they are applicable in optoelectronic field, while Mg2CoH6 and Mg2NiH6 are metallic in energy band structure. They are all ionic compounds which are confirmed by Cauchy pressure, electronic density difference and electronic localization function. Their hydrogen storage capacity are all over 5.2 wt%, which are favorable in practical use. And the moderate desorption temperature of 328.9 K of Mg2MnH6 suggests it is a promising candidate for hydrogen storage.

Balancing volumetric and gravimetric capacity for hydrogen in supramolecular crystals.

The storage of hydrogen is key to its applications. Developing adsorbent materials with high volumetric and gravimetric storage capacities, both of which are essential for the efficient use of hydrogen as a fuel, is challenging. Here we report a controlled catenation strategy in hydrogen-bonded organic frameworks (RP-H100 and RP-H101) that depends on multiple hydrogen bonds to guide catenation in a point-contact manner, resulting in high volumetric and gravimetric surface areas, robustness and ideal pore diameters (~1.2-1.9 nm) for hydrogen storage. This approach involves assembling nine imidazole-annulated triptycene hexaacids into a secondary hexagonal superstructure containing three open channels through which seven of the hexagons interpenetrate to form a seven-fold catenated superstructure. RP-H101 exhibits high deliverable volumetric (53.7 g l-1) and gravimetric (9.3 wt%) capacities for hydrogen under a combined temperature and pressure swing (77 K/100 bar → 160 K/5 bar). This work illustrates the virtues of supramolecular crystals as promising candidates for hydrogen storage.

Synthesis of biochar-doped MgO catalyst for highly efficient conversion of glucose into formic acid at low temperatures

Formic acid (FA) is not only a significant platform chemical but also a promising candidate for hydrogen storage. Although homogeneous catalysts are commonly employed for the conversion of carbohydrate biomass into FA, which often come with substantial costs and inadequate reusability. It is noteworthy that there has been an increasing focus on the development of heterogeneous catalysts in this area, which aim to address these limitations and offer advantages such as easier separation and better reusability. Herein, an eco-friendly and efficient method for the catalytic conversion of glucose to FA by utilizing a biochar-MgO (BC-MgO) catalyst, which is prepared through pyrolysis of coconut husk biochar impregnated with magnesium chloride (MgCl2), is proposed. The FA yield at 74.6% is attained from glucose at 60 °C within only 3 h, utilizing a mere 0.1 g of catalyst and hydrogen peroxide (H2O2) amount of 100%. In conjunction with random forest (RF) algorithms and box-behnken experimental designs, further optimization resulted in an increased yield of 79.1%, with a selectivity of 82.7%, in only 3.8 h at 67 °C, employing 0.1 g of catalyst amount and 125% H2O2 amounts. Notably, the BC-MgO catalyst retains its catalytic efficiency over multiple cycles, only requiring a simple straightforward regeneration procedure. The mechanism underlying the glucose conversion to FA reaction system is demystified via kinetic modeling, time-gradient studies, and model compounds experiments. Life cycle assessment (LCA) indicates that when used for glucose conversion to FA, BC-MgO catalysts generate lower CO2 emissions than traditional homogeneous catalysts such as LiOH. Concurrently, an operation cost analysis indicates that operation cost of FA production from glucose is 4.1 $/kg with the BC-MgO catalyst, which is lower than LiOH catalyst (7.5 $/kg), evidencing the dual advantage of economic viability and an improved environmental impact inherent to this novel process.

Efficient hydrolytic dehydrogenation of ammonia borane catalyzed by ultrafine Pt clusters confined in Ni–Ti layered double hydroxides with closo-dodecaborate

Ammonia borane (NH3BH3, AB) is a highly promising candidate for hydrogen storage. Nevertheless, there is an urgent need to develop an efficient and stable catalyst that can control hydrogen generation under mild conditions. The use of catalysts with numerous surface atoms anchored to a carrier to achieve a synergistic effect is an appealing approach in catalysis. In this work, a series of highly dispersed metal clusters NiTi-LDH@B12H12@M (M = Au, Pd, Pt, Ag) catalysts were successfully synthesized at room temperature by leveraging the reductivity of [closo-B12H12]2- immobilized in the layered double hydroxide (LDH) laminate, along with the spatial confinement and anion exchange capabilities of LDH. Specifically, utilizing the optimal catalyst NiTi-LDH@B12H12@Pt 2.4% (wt. Pt), the AB hydrolysis reaction exhibited extraordinary catalytic activity. It exhibited a first-order reaction rate with respect to Pt and a near zero-order reaction rate with respect to AB concentration. The AB hydrolysis can be achieved in a mere 29 s at 25 °C with a conversion rate of 100%. The corresponding turnover frequency (TOF) attains a value of 454.06 molH2molPtmin−1, and the apparent activation energy (Ea) is 41.8 kJ mol−1, surpassing numerous previously reported Pt-based catalysts. The outstanding catalytic performance can be ascribed to the uniform distribution of ultrafine Pt clusters, along with the synergistic effect conferred by NiTi-LDH and intercalated anions ([closo-B12H12]2-).

Subnanometer palladium-manganese clusters in hydrophilic amino-functionalized zeolites for efficient formic acid dehydrogenation

Formic acid (FA) has emerged as a promising candidate for hydrogen storage, due to its excellent stability, low cost, and renewability. The rational design of catalysts for FA dehydrogenation is crucial for integrating FA into the hydrogen economy system. Herein, subnanometric bimetallic Pd-Mn clusters were encapsulated within hydrophilic amino-functionalized silicalite-1 (S-1) zeolite via an in-situ ligand-protection direct H2 reduction method. The graft of amino groups within zeolites not only endowed the zeolites with alkaline sites, but also significantly improved the hydrophilicity of zeolites, and enhanced the interaction between zeolite supports and encapsulated metal species, forming highly active electron-enriched Pd species. Thanks to the high dispersion of metal species and synergy between Pd and Mn species as well as the additive alkaline sites and hydrophilicity of zeolites, the optimized PdMn0.25@S-1-NH2 catalyst exhibited a superhigh H2 evolution rate from FA decomposition, with a turnover frequency value of 11,401 molH2·molPd−1·h−1 at 333 K without any additives, overcoming almost all of the state-of-the-art heterogeneous catalysts under the similar catalytic condition. This study highlights the effective synergistic effect between metal species and supports for improving catalytic efficiency in FA dehydrogenation reactions, and also opens a new paradigm for the design of functionalized zeolite-encapsulated metal catalysts for other important catalytic reactions.

Tailoring hydrogen storage performance in γ-graphyne through valence band modulation of adsorbed Li via doping and strain

Hydrogen storage is indeed fundamental to utilizing H2 effectively, and porous carbon materials have emerged as highly promising supports for this purpose. γ-Graphyne (γGy) possesses abundant chemical bonds, considerable porosity, and exceptional chemical stability, positioning it as a promising candidate for hydrogen storage and transport applications. In this study, we conducted density functional theory calculations to investigate the potential of Li- and Na-loaded γGy as hydrogen storage materials. Our findings reveal that the hydrogen storage capacity (HSC) of Na-loaded γGy falls significantly short of expectations, whereas Li-loaded γGy demonstrates a notably higher HSC. Subsequently, our calculations indicate that B-doping of γGy does not promote favorable HSC, whereas N-doping exhibits a beneficial effect. Furthermore, we observed that tensile strain favors the hydrogen storage properties of 4Li@γGy and 4Li@N-γGy, while compressive strain enhances the hydrogen storage characteristics of 4Li@B-γGy. Notably, we discovered the capacity to adjust the valence band center of Li (ɛVB), consequently influencing the hydrogen storage performance of γGy. Our investigation suggests that increased overlap between ɛVB in Li-loaded graphyne and the effective alignment of H2 and the supporting structure augments the binding force between Li and H2, thereby amplifying the HSC.

Mg-decorated CN monolayer with enhanced hydrogen storage

Current hydrogen storage confronts safety and high energy cost challenges. Solid-state hydrogen storage provides an efficient pathway with lower cost and pressure conditions. Here, we perform density functional theory (DFT) calculations measuring the hydrogen storage properties of Mg-decorated CN monolayer. 8Mg@CN structure is confirmed based on energetic and geometric criteria and it can absorb up to 40 H2 molecules, achieving a high gravimetric density of 8.92 wt% over the US Department of Energy (DOE) target. The polarized H2 molecules are proven to be physiosorbed on Mg atoms to guarantee desorption. The electronic properties are studied to illustrate the electrostatic attractions between the H2 molecules and the Mg-decorated CN monolayer. Moreover, the desorption temperatures and adsorption pressures are calculated to illustrate the reversibility of hydrogen storage applications on 8Mg@CN. These results indicate 8Mg@CN could be a promising candidate for hydrogen storage with potentially reversible application.

Thermodynamics of Reversible Hydrogen Storage: Are Methoxy-Substituted Biphenyls Better through Oxygen Functionality?

The reversible hydrogenation/dehydrogenation of aromatic molecules, known as liquid organic hydrogen carriers, is considered as an attractive option for the safe storage and release of elemental hydrogen. The recently reported efficient synthetic routes to obtain methoxy-biphenyls in high yield make them promising candidates for hydrogen storage. In this work, a series of methoxy-substituted biphenyls and their structural parent compounds were studied. The absolute vapour pressures were measured using the transpiration method and the enthalpies of vaporisation/sublimation were determined. We applied a step-by-step procedure including structure–property correlations and quantum chemical calculations to evaluate the quality of thermochemical data on the enthalpies of phase transitions and enthalpies of formation of the studied methoxy compounds. The data sets on thermodynamic properties were evaluated and recommended for calculations in chemical engineering. A thermodynamic analysis of chemical reactions based on methoxy-biphenyls in the context of hydrogen storage was carried out and the energetics of these reactions were compared with the energetics of reactions of common LOHCs. The influence of the position of the methoxy groups in the rings on the enthalpies of the reactions relevant for hydrogen storage was discussed.

Feasibility of hydrogen storage in depleted shale gas reservoir: A numerical investigation

Due to the low operation cost, high containment security, and large storage capacity, depleted shale gas reservoirs are considered as promising options for large-scale hydrogen storage. However, its feasibility has not been systematically examined yet. It is still unknown about whether the deliverability (injection/withdrawal) capacity could meet the energy supply/demand and how the depletion time, cushion gas selection, injection/withdrawal strategy will influence the performance of this scenario.Therefore, we present a numerical compositional modelling investigation on hydrogen storage in a partially depleted Fuling shale gas reservoir in China. The results demonstrated that: 1) a high injection/withdrawal capacity could be achieved through a single shale play pad in the area of interest as approximately 5.4 × 108 Sm3 hydrogen could be stored and 3 × 108 Sm3 could be recovered in each cycle (equal to 0.54 TWh of power output). 2) CH4 production is inhibited once hydrogen storage project is performed, an early depletion time could significantly reduce CH4 production but slightly improve H2 withdrawal. 3) Cushion gas injection is beneficial to reducing H2 loss and enhancing 2.8% H2 recovery, while the main drawback of this operational measure is an increase in capital cost in gas separation due to lower H2 purity in the produced gas.This work demonstrates that shale gas reservoir is a promising candidate for hydrogen storage, which is beneficial to the implementation of large-scale hydrogen economy and the operation of hydrogen supply chain.

Advances and prospects in electrocatalytic hydrogenation of aromatic hydrocarbons for synthesis of “loaded” liquid organic hydrogen carriers

Liquid organic hydrogen carriers (LOHC) are considered as the safest and most promising candidates for hydrogen storage, meeting the requirements of sufficient weight and volume capacity (over 6 wt%), hydrogenation-dehydrogenation reversibility and low cost. The prospects of catalytic hydrogenation of polycyclic hydrocarbons for the production of LOHC are considered. The comparison shows that electrocatalytic hydrogenation of aromatic LOHC is highly advantageous, since this approach eliminates the use of gaseous hydrogen in the production of "loaded" LOHC and therefore is safer than the conventional hydrogenation. The advantage of electrocatalytic hydrogenation compared to catalytic hydrogenation is that high temperatures are not required. The approaches to increase the efficiency of electrocatalytic hydrogenation are discussed.

DFT study of superlight ambient temperature reversible H2 storage media based on Li decorated on new planar BCN

A novel 2D pm-BCN monolayer with unique porous geometry, superlight mass, and superior stability is a promising candidate for hydrogen storage. However, pure 2D materials suffer from the weak Van de Waals interaction between the H2, and modification becomes necessary to improve their performance. Here, we design a new complex by decorating active Li ions on the 2D pm-BCN substrate. The decoration of Li can transfer a partial electron to the substrate pm-BCN, which enhances the original π bonding among pm-BCN and induce more active sites on it. Both Li and BCN can act as the adsorption sites. The H2 can realize reversible adsorption under an ambient condition with average adsorption energy of −0.20 eV/H2 and a gravimetric capacity of 6.34 wt%, which surpasses the targe value set by U.S. Department of Energy (DOE). Rigorous analysis of its electronic properties, including a partial density of states, charge density, and crystal orbital overlap population, illustrates that the polarization mechanism contributes to the enhancement of the hydrogen storage capacity of Li@pm-BCN.

A novel dry water with perfluorohexanone for explosion suppression of AlH3

AlH3 is a promising candidate for hydrogen storage, but has high explosion risk. To prevent the accident of AlH3, the novel dry water (DW) was applied to the suppression of AlH3 explosion, and the addition of perfluorohexone improved the suppression effect significantly. When the mass fraction of 16.70wt% perfluorohexanone-modified dry water (PMDW) was added with 700 g/m3, the maximum explosion pressure decreased by 54.37 %, and the maximum explosion pressure rising rate dropped by 98.80 %. The 3-dimensional network structure of silica, adsorbing flame radicals and preventing heat transfer, was proved to play a pivotal role in the explosion suppression by HRTEM and NMR. The evaporation and decomposition of the internal solution would greatly improve the cooling effect. CF2 captured H, O, and OH radicals in the flame and interrupted the free radical chain reaction. Our work is a step towards the application of eco-friendly DW in the field of explosion suppression.

Molecular hydrogen storage in binary H2-CH4 clathrate hydrates

Clathrate hydrate has emerged as a promising candidate for hydrogen storage, but the major challenge is the high pressure required for its formation. The addition of natural gas can significantly reduce the formation pressure, but also can improve the energy density. In this work, we estimated the hydrogen storage capacity of the H2-CH4 binary hydrate by performing the first-principles calculations and simulations. The thermodynamical and mechanical stability of the hydrate was studied as a function of the cage occupancy of both 512 and 51264 cages. For the most stable structure, the molar ratio of H2 and H2O is 0.353:1. The H2-CH4 binary hydrate can maintain its structure during dynamics under the moderate temperature and pressure. The self-preservation effect was observed at ∼270 K, which can be used for the hydrogen storage and transport. These findings provide a better understanding of the mixed hydrate as a viable hydrogen storage technology, which could enable us to achieve a sustainable hydrogen economy.

Compositional effects on the hydrogen storage properties in a series of refractory high entropy alloys

The possible combinations in the multidimensional space of high entropy alloys are extremely broad, which makes the incremental experimental research limited. As a result, establishing trends with well-known empirical parameters (lattice distortion, valence electron concentration etc.) and predicting effects of the chemical composition change are vital to guide future research in the field of materials science. In this context, we propose a strategy to rationalize the effect of chemical composition change on the hydrogen sorption properties in a series of high entropy alloys: Ti0.30V0.25Zr0.10Nb0.25M0.10 with M = Mg, Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ta and ∅ (corresponding quaternary alloy). All materials are bcc alloys and absorb hydrogen at room temperature forming fcc or pseudo-fcc dihydride phases. The maximum hydrogen storage capacity at room temperature strongly depends on the valence electron concentration (VEC) of the alloys: the capacity is high (1.5–2.0 H/M) for low values of VEC (<4.9) whereas, a drastic fading is observed for VEC ≥4.9 which is the case for alloys with M being a late 3d transition metal. The structural analysis suggests that steric effects might not be responsible for this trend and electronic reasons may be invoked. Increasing the VEC by alloying with late 3d transition metals will fill the unoccupied valence states and the electrons from interstitial hydrogens can no longer be accommodated, which is unfavorable for hydrogen storage. Moreover, the onset temperature of desorption increases almost linearly with VEC for this composition series. These findings suggest that alloys with low VEC are more likely to become promising candidates for hydrogen storage.

Ultra-high capacity of physisorption of hydrogen molecule on AlC3 monolayer: First-principles calculations

In this research, we have investigated through the first principal calculations the adsorption of hydrogen molecule on AlC3 monolayer. In the beginning, we determined the most stable positions of hydrogen molecule adsorption on AlC3 substrate. The calculations indicate that the position of greatest stability is in the center of the carbon atom hexagon when the hydrogen molecule is placed perpendicularly on AlC3 surface, and the adsorption energy Eads is near to −0,2189 eV, where the most stable distance is 2.50 Å. The hydrogen molecule adsorption at various positions on AlC3 surface maintains its semiconducting character. The examination of the diffusion paths between the various sites indicates an ability of the hydrogen molecule to migrate between the sites, which are spaced by a slight energy barrier of 0.0163 eV. It is shown that AlC3 monolayer possess the ability to adsorb 16 hydrogen molecules, with 11.8 wt% as gravimetric capacity, as well as a desorption temperature of 173.35 K. Based on the findings, the AlC3 monolayer may be a promising candidate for hydrogen storage.

Enhanced H2 Storage Capacity of Bilayer Hexagonal Boron Nitride (h-BN) Incorporating van der Waals Interaction under an Applied External Electric Field.

Lightweight two-dimensional materials are being studied for hydrogen storage applications due to their large surface area. The characteristics of hydrogen adsorption on the h-BN bilayer under the applied electric field were investigated. The overall storage capacity of the bilayer is 6.7 wt % from our theoretical calculation with Eads of 0.223 eV/H2. The desorption temperature to remove the adsorbed H2 molecules from the surface of the h-BN bilayer system in the absence of an external electric field is found to be ∼176 K. With the introduction of an external electric field, the Eads lies in the range of 0.223–0.846 eV/H2 and the desorption temperature is from 176 to 668 K. Our results show that the external electric field enhances the average adsorption energy as well as the desorption temperature and thus makes the h-BN bilayer a promising candidate for hydrogen storage.

Nickel-decorated single vacancy phosphorene – A favourable candidate for hydrogen storage

This work studies the effect of nickel decoration on the hydrogen adsorption properties of single vacancy (SV) defective phosphorene. First principles simulations of Ni decoration show that the SV defective surfaces relax to a doped-like structure with the Ni atom in the place of the vacant phosphorus atom. The functionalised surface shows excess negative charge on neighbouring P atoms, making it suitable for sensing purposes. Additionally, the chemical activity of Ni is reduced due to strong bond formation with phosphorus. Both Ni-decorated SV phosphorene systems have H2 adsorption energies more than 3 times than that of defective phosphorene, with values between −0.594 eV and −0.6 eV. The adsorption mechanism of H2 is a two-fold process involving a small charge transfer from the surface P atoms and weak dipole-dipole interactions between the H2 molecule and the Ni atom, as the reduced chemical activity of Ni prevents bond formation with H2. The results demonstrate Ni-decorated SV Phosphorene as a promising candidate for Hydrogen storage and gas sensing applications. Further, decoration on defective phosphorene surfaces can be regarded as a method to control the chemical activity of transition metals for use in applications such as catalysis.

Structure of a seeded palladium nanoparticle and its dynamics during the hydride phase transformation

Palladium absorbs large volumetric quantities of hydrogen at room temperature and ambient pressure, making the palladium hydride system a promising candidate for hydrogen storage. Here, we use Bragg coherent diffraction imaging to map the strain associated with defects in three dimensions before and during the hydride phase transformation of an individual octahedral palladium nanoparticle, synthesized using a seed-mediated approach. The displacement distribution imaging unveils the location of the seed nanoparticle in the final nanocrystal. By comparing our experimental results with a finite-element model, we verify that the seed nanoparticle causes a characteristic displacement distribution of the larger nanocrystal. During the hydrogen exposure, the hydride phase is predominantly formed on one tip of the octahedra, where there is a high number of lower coordinated Pd atoms. Our experimental and theoretical results provide an unambiguous method for future structure optimization of seed-mediated nanoparticle growth and in the design of palladium-based hydrogen storage systems.

Tunable NaBH4 Nanostructures Revealing Structure‐Dependent Hydrogen Release

Borohydrides are promising candidates for hydrogen storage and generation assuming these can be tuned to reversibly deliver hydrogen under practical conditions. Nanostructuring of borohydrides has the potential to enable such control but this has remained elusive due to the lack of approaches to effectively prepare and stabilize borohydride nanostructures. Herein, a simple and straightforward method to assemble NaBH4, as a model borohydride, into sphere, cube, and bar‐like shapes using tetrabutylammonium bromide (TBAB), octadecylamine (ODA), and tridecanoic acid (TDA), respectively, is demonstrated. More importantly, the shape of the NaBH4 nanostructures could be tuned from one morphology to another by simply adjusting the ratio of surfactants and this is found to lead to distinct hydrogen properties. In particular, remarkable shifts in the melting points and hydrogen desorption temperatures are observed depending on the NaBH4 morphologies, i.e., spheres, cubes, or bars. For example, for the NaBH4 spheres, hydrogen release starts at ≈50 °C compared to the >500 °C of bulk NaBH4 without any transition metal dopant or catalyst. Observation of such structure‐dependent relationships finally enables new avenues to deliberately tune borohydrides toward nanostructures with specific hydrogen properties otherwise difficult to control.

Improvement of hydrogen dehydrogenation performance of lithium amide pyrolysis by ball milling with magnesium

Li–N–H system is one of the promising candidates for hydrogen storage. However, with the heat treatment, LiNH2 can release not only H2 but N2 and NH3. To improve the purity and amount of H2 in the products, LiNH2–Mg composite is prepared by ball milling. In the composite, Mg can absorb the gaseous byproducts, e.g. NH3 and N2, effectively when the LiNH2 pyrolysis. Finally, H is desorbed in the form of H2 and N is absorbed by Mg and forms Mg3N2. Besides, LiNH2 reacts with Mg directly to form LiMgN and release H2. After re-hydrogenation of the composite, H2 is stored into Li2MgN2H2 and LiH, thus the cyclic mechanism is different with the first dehydrogenation of the LiNH2–Mg composite. First-principles calculation shows that the NH3 molecule can be captured by Mg when it is adsorbed on top and bridge positions. After captured by Mg, the molecular structure of NH3 is changed and the barrier energy of NH3 dissociation is dramatically reduced. In addition, the barrier energy of NH3 and N2 dissociation on Mg (0001) plane is lower than that of H2, which means NH3 and N2 can be absorbed by Mg before Mg react with H2.