Design Of Hydrogen Storage Materials Research Articles

Machine learning accelerates design of bilayer-modified graphene hydrogen storage materials

To accelerate the exploration of modified graphene hydrogen storage materials, this paper proposes a Data-Driven Exploration Framework (DDEF) based on the best-fitting machine learning (ML) algorithms (Random Forest: Recall = 0.83, Accuracy = 0.83, Gradient boosted regression: R2 = 0.90, RMSE = 0.06) and density functional theory (DFT). The hydrogen storage capacity of bilayer double-deficient graphene (BDG[Li]) doped with B atoms and modified with Li and Ti atoms was predicted using ML, which shortens the design cycle of hydrogen storage materials. The interlayer composite hydrogen storage mechanism of the BDG[Li] structure is revealed by electronic property analysis. For the first time, the calculation method of the interlayer electrostatic force energy (Ej) is proposed, and the equation for calculating the interlayer H2 adsorption energy is optimized. The hydrogen storage data of BDG[Li] and the construction of Ej provide new feature data for subsequent ML calculations. Both DDEF and Ej are computationally verified to have high accuracy and generalizability, which is of research significance for accelerating the design of hydrogen storage materials.

Enhancing the hydrogen storage properties of (Ti, M)C1−x materials (M = W, Mg, Ni, and Al) depends on the carbon vacancies: Potential for the recycling of scraps

New energy storage systems and recycling schemes are required to solve the increasing environmental and energy problems. Owing to the increasing cost of raw materials, scraps need to be recycled. Carbides can be used as hydrogen storage materials; however, their mechanical properties remain unclear. To fabricate high-quality carbides from scraps as potential candidates for hydrogen storage materials, it is necessary to understand the mechanical properties of the carbides when absorbing hydrogen atoms. In this study, we evaluated the thermodynamic stabilities, mechanical properties, and electronic structures of (Ti, M)C1-x materials (M = W, Mg, Ni, and Al, x=0–1. The effects of the carbon vacancies were examined using density functional theory calculations. Based on the results, the TiC0.625 composition was stable at ambient temperature and pressure. Titanium carbides have shown potential for use in hydrogen storage applications at 0≤x≤0.375, as the hardness decreases rapidly when x≥0.375. In addition, the results indicate that (Ti, Al)C should mainly be used in the target hydrogen storage materials at a composition below x=0.25. These findings support the design of hydrogen storage materials based on recycled carbides.

Exploration and design of Mg alloys for hydrogen storage with supervised machine learning

Hydrogen storage is an essential technology for the development of a sustainable energy system. Magnesium (Mg) and its alloys have been identified as promising materials for hydrogen storage due to their high hydrogen storage capacity, low cost, and abundance. However, the use of Mg alloys in hydrogen storage materials requires a thorough understanding of the material properties and their behavior under different conditions. In this study, we established a database of Mg alloys properties and their hydrogen storage performance, which was then used to train various machine learning (ML) regression models with maximum hydrogen storage (Ab_max) and maximum hydrogen release (De_max) as outputs. These models possess excellent prediction accuracy. The GBR model for Ab_max and MLP model for De_max present highest accuracy with the R2 of the test set reaching 0.947 and 0.922, respectively. The Shapley additive explanations (SHAP) algorithm was then used to interpret the best ML models, and the critical values of important descriptors were obtained to guide the design of hydrogen storage materials. Finally, based on the best ML models, the Ab_max and De_max were predicted for the Mg-based binary alloys with other 16 metal elements and Mg–Ni-based ternary alloys with other 15 metal elements, respectively. Among them, 96Mg-4Sm and 95Mg–1Ni-4Sm have higher Ab_max and De_max of 6.31 wt% and 5.69 wt%, 6.64 wt% and 5.63 wt%, respectively, meeting the requirement of high Ab_max/De_max at the operating temperature below 300 °C.

A review on BCC-structured high-entropy alloys for hydrogen storage

Recently, high entropy alloys (HEAs) with body-centred cubic (BCC) single phase structures have attracted wide attention in many fields including hydrogen storage, due to their unique structural characteristics and excellent performance. Its novel design concept provides more possibilities for the investigation of advanced hydrogen storage materials, in which several remarkable research works have been published, providing opportunities for the design of hydrogen storage materials with unprecedented properties. In this review, we combed through the definition and criteria of high entropy alloys, and summarized the current research status of body-centred cubic-structured high entropy alloys for hydrogen storage from multiple perspectives of composition designs, synthesis processes, and hydrogen storage properties. Moreover, the possible application scenarios and future research directions are analysed.

Analysis of hydrogen storage mechanism in bilayer double-vacancy defective graphene modified using transition metals: Insights from Ti-BDVG(Ti)-Ti

In this study, using the first principles calculation and analysis, we found that the B-doping in double-vacancy defective graphene could effectively increase the binding energy of Ti atoms in each adsorption site, especially in the H2 adsorption site with a maximum binding energy of 8.3 eV. However, N-doped bilayer graphene (N-BLG) reduced the binding energy of Ti atoms by 88% of the adsorption sites. Given these two findings, a B- and N-doped bilayer double-vacancy-defective graphene (Ti-BDVG(Ti)-Ti) was constructed. Our findings also showed that the Ti-BDVG(Ti)-Ti outer surface and inner surface could adsorb 32 and 12H2 molecules, respectively, of which 22, 20 and 2H2 molecules are adsorbed by Kubas, electrostatic interactions and chemisorption, respectively. The hydrogen storage mechanism of Ti-BDVG(Ti)-Ti involves multiple adsorption modes, and this hydrogen storage mechanism provides a theoretical basis for the rational design of hydrogen storage materials with maximum effective hydrogen storage capacity.

In Situ Observation of Electron-Beam-Induced NaH Decomposition in Graphene Nanoreactors by Transmission Electron Microscopy

Sodium hydride (NaH) was unprecedently embedded inside graphene nanobubbles via the discovered reaction between NaH and CO. With the graphene nanobubble as a nanoreactor for NaH, we directly observed the electron-beam-induced decomposition process of graphene-covered NaH by in situ high-resolution transmission electron microscopy with energy dispersive spectrometry and electron energy loss spectroscopy, revealing its decomposition mechanism. This can provide guidance for the design of hydrogen storage materials.

Experimental investigation and thermodynamic modeling of the ternary Ti–Fe–Mn system for hydrogen storage applications

The Ti–Fe–Mn alloys have attracted extensive interests due to the excellent hydrogen storage properties of the TiFe and TiMn2 (i.e. the C14 Laves phase) intermetallic compounds. The phase equilibria involving these two phases are essential for the design of hydrogen storage materials. In order to accelerate the design process, a thermodynamic description of the ternary Ti–Fe–Mn system was developed by experimental phase diagram study, ab initio calculations and CALPHAD-type thermodynamic modeling in the present work. The phase equilibria involving TiFe and C14 Laves phases were investigated by using electron probe microanalysis (EPMA). The partial isothermal sections at 1273 and 1373 K were established. Ab initio calculations were carried out to assist the determination of the thermodynamic parameters for the C14 Laves phase. The Ti-Mn system was re-assessed to reproduce the phase diagram data over the entire composition range. The Ti-Fe-Mn system was modeled and optimized based on reliable binary descriptions and experimental data. The TiFe and C14 Laves phases were well described to reproduce the phase equilibria with other phases in the ternary system. Moreover, the developed thermodynamic description of the Ti-Fe-Mn system was successfully applied for the prediction of phase constitutions of hydrogen storage alloys, demonstrating evidently the reliability of the practical use of present model parameters.

Fingerprinting diverse nanoporous materials for optimal hydrogen storage conditions using meta-learning.

Adsorptive hydrogen storage is a desirable technology for fuel cell vehicles, and efficiently identifying the optimal storage temperature requires modeling hydrogen loading as a continuous function of pressure and temperature. Using data obtained from high-throughput Monte Carlo simulations for zeolites, metal-organic frameworks, and hyper-cross-linked polymers, we develop a meta-learning model that jointly predicts the adsorption loading for multiple materials over wide ranges of pressure and temperature. Meta-learning gives higher accuracy and improved generalization compared to fitting a model separately to each material and allows us to identify the optimal hydrogen storage temperature with the highest working capacity for a given pressure difference. Materials with high optimal temperatures are found in close proximity in the fingerprint space and exhibit high isosteric heats of adsorption. Our method and results provide new guidelines toward the design of hydrogen storage materials and a new route to incorporate machine learning into high-throughput materials discovery.

Large entropy derived from low-frequency vibrations and its implications for hydrogen storage

Adsorption and desorption are driven by the energy and entropy competition, but the entropy effect is often ignored in hydrogen storage and the optimal adsorption strength for the ambient storage is controversial in the literature. This letter investigated the adsorption states of the H2 molecule on M-B12C6N6 (M = Li, Na, Mg, Ca, and Sc) and analyzed the correlation among the zero point energy (ZPE), the entropy change, and the adsorption energy and their effects on the delivery capacities. The ZPE has large correction to the adsorption energy due to the light mass of hydrogen. The computations show that the potential energies along the spherical surface centered at the alkali metals are very flat and it leads to large entropy (∼70 J/mol·K) of the adsorbed H2 molecules. The entropy change can compensate the enthalpy change effectively, and the ambient storage can be realized with relatively weak adsorption of ΔH = −12 kJ/mol. The results are encouraging and instructive for the design of hydrogen storage materials.

(Invited) Core-Shell Hydride Nanoarchitectures for Reversible Hydrogen Storage

The properties of nanomaterials are known to be size depend. Such size depend effects could offer powerful means to finally control both the thermodynamic and kinetic properties of hydride materials at the molecular level [1] and thus enable the practical design of hydrogen storage materials from these effects. However, investigations through such an approach require new strategies to both synthesise and stabilise nanoparticles of highly reactive hydride materials and the understanding to control the key parameters that will allow reversibility with high storage capacity. The use of porous host structures offers such a route, however the storage capacity usually remains limited by the intrinsic difficulty of entirely fill the porosity. Herein, the potential of a new core-shell confinement approach and recent progress we have made through this nanosizing method will be discussed [2]. Since, complex hydrides still undergo phase transitions including melting at the nanoscale, this core-shell approach has proven to be an very effective strategy to stabilise and simultaneously catalyse the reversible storage of hydrogen with hydrides including borohydrides and alanates (Figure 1). It also provides us with new means to stabilise against oxidation highly reactive nanoparticles of elements such as lithium.

Simulation, Modelling and Design of Hydrogen Storage Materials

Simulation, Modelling and Design of Hydrogen Storage Materials

The Structural and Hydrogen Storage Properties of Al-Doped Boron Nitride Nanotube

The geometrical structures and electronical properties, as well as hydrogen storage of Al-doped boron nitride nanotube have been investigated using first principles based on density functional theory. The results show that the symmetry of boron nitride nanotube is destroyed slightly by doping one Al atom. Furthermore, physical absorption is found due to the small average absorption energy of Al-BNNT-nH2, which indicates that this hydrogen absorption will occurs at room temperature. In addition, some novel structures presenting almost same absorption behaviors are predicted, which will offer useful information to future experimental investigation on the design of hydrogen storage materials.

Phase Transitions in Borohydride Perovskites

A series of complex hydrides based on the highly dynamic tetrahydroborate anion BH4-and crystallizing in theABX3type lattice has recently been discovered. They present a rare case of a family of iono-covalent hydrides that has a genuine tunable host lattice, making them an interesting new class of host compounds for not only the design of hydrogen storage materials but also hydride-properties related to heavy metals. Amongst these, preliminary results onREE-based luminescence will be discussed in the neat and doped compounds, the Ln2+excited states surprisingly not being subject to significant quenching by B-H vibrations. Unlike oxide- or halide-perovskites some members of theAB(BH4)3group do not evolve to higher symmetries as a function of temperature. We show by means ofin-situsynchrotron X-ray powder diffraction, vibrational spectroscopy andab initiocalculations in the solid state, that temperature-induced structural distortions in perovskite-typeACa(BH4)3(A= K, Rb, Cs) have their origin in close hydridic di-hydrogen contacts of repulsive nature. Coupling between internal B-H vibrations and phonons results in lattice distortions that are identical in symmetry to well-known instabilities (soft modes) in perovskites, which generally condense to lower temperatures. Anion-substitution BH4-<->X-(X= Halide) calculated on ordered models can relax distortions caused by repulsive effects. High temperature phase-transitions inACa(BH4)3can be of first or second-order, including 2-fold superlattices, simple cubic-cubic transitions accompanied by volume expansion or complex modulated superstructures accompanied by negative volume expansion, as is the case in RbCa(BH4)3. Close di-hydrogen contacts may be suggested as a tool to tailor the crystal symmetry in complex hydride perovskites in the future.

Graphical Abstract: Eur. J. Inorg. Chem. 11/2011

AbstractThe cover picture shows an allegoric representation of the dawning hopes of a hydrogen energy transition, which would alleviate the foreseeable shortage of fossil fuels for the transportation sector. Metal‐organic frameworks (MOFs), represented by the honeycomb structure, have become a main focus in the current search for economically viable materials for hydrogen storage and delivery. The signpost at the left of the picture is a reminder that thermodynamics of the hydrogen uptake and delivery process is ruled by the corresponding enthalpy and entropy changes, which are shown to be interrelated. Both of these thermodynamic quantities have to be taken into account for intelligent design of hydrogen storage materials. Details are discussed in the article by C. O. Areán et al. on p. 1703 ff.

Enthalpy–Entropy Correlation for Hydrogen Adsorption on MOFs: Variable‐Temperature FTIR Study of Hydrogen Adsorption on MIL‐100(Cr) and MIL‐101(Cr) (Eur. J. Inorg. Chem. 11/2011)

AbstractThe cover picture shows an allegoric representation of the dawning hopes of a hydrogen energy transition, which would alleviate the foreseeable shortage of fossil fuels for the transportation sector. Metal‐organic frameworks (MOFs), represented by the honeycomb structure, have become a main focus in the current search for economically viable materials for hydrogen storage and delivery. The signpost at the left of the picture is a reminder that thermodynamics of the hydrogen uptake and delivery process is ruled by the corresponding enthalpy and entropy changes, which are shown to be interrelated. Both of these thermodynamic quantities have to be taken into account for intelligent design of hydrogen storage materials. Details are discussed in the article by C. O. Areán et al. on p. 1703 ff.

Nanoporous Polymers for Hydrogen Storage

The design of hydrogen storage materials is one of the principal challenges that must be met before the development of a hydrogen economy. While hydrogen has a large specific energy, its volumetric energy density is so low as to require development of materials that can store and release it when needed. While much of the research on hydrogen storage focuses on metal hydrides, these materials are currently limited by slow kinetics and energy inefficiency. Nanostructured materials with high surface areas are actively being developed as another option. These materials avoid some of the kinetic and thermodynamic drawbacks of metal hydrides and other reactive methods of storing hydrogen. In this work, progress towards hydrogen storage with nanoporous materials in general and porous organic polymers in particular is critically reviewed. Mechanisms of formation for crosslinked polymers, hypercrosslinked polymers, polymers of intrinsic microporosity, and covalent organic frameworks are discussed. Strategies for controlling hydrogen storage capacity and adsorption enthalpy via manipulation of surface area, pore size, and pore volume are discussed in detail.

Hydrogen storage properties of clathrate hydrate materials

The design of hydrogen storage materials that achieve all of the U.S. Department of Energy's 2015 goals (storage capacity, operating conditions, reversibility, cost, etc.) has proved to be a challenge. Recent progress in the area of clathrate hydrates suggests many potential advantages when compared with other “conventional” materials. In this work, the hydrogen storage potential of several clathrate systems (including sII, semi-clathrates, and Jeffrey's structures) has been investigated by high-pressure Raman spectroscopy, by direct gas release measurements, and by theoretical storage considerations. Some key findings of this work include new insights into the spectral properties of hydrogen molecules within hydrate cavities and the maximum possible hydrogen storage capacity of different clathrate structures. Ultimately, these findings will aid in the design and production of new hydrogen storage materials.