Properties Of Hydrides Research Articles

An ab-initio study of the physical properties of Ge-based perovskites (XGeH3: X=Mg, Ca, and Sr) for potential H2 storage application

Mainstreaming hydrogen (H2) energy demands a paradigm shift in storage technologies. Solid-state H2 storage stands out as a beacon of hope, but its universal acceptance hinges on a meticulous exploration of its intricacies. This study harnesses density functional theory (DFT) via the WIEN2k code to compute the physical properties (e.g., structural, thermodynamic, thermoelectric, mechanical, and electronic) and H2 storage properties of Ge-based perovskite hydrides (i.e., XGeH3: X=Mg, Ca, and Sr). Current investigation yields remarkable insights for these hydrides that are: (i) exceptional gravimetric H2 storage capacities: 3.02, 2.61, and 1.85 wt%, (ii) favorable thermodynamic formation energies: -82.01, -91.66, and -101.30 kJ/mol, (iii) optimal hydrogen desorption temperatures: 627.47, 701.30, and 775.06 K, respectively, (iv) validated mechanical stability through elastic constant analysis, (v) inclusive elastic properties (e.g., bulk modulus, Young's modulus, shear modulus, Poisson's ratios) are examined by 3D visualization of anisotropic elastic properties and anisotropic factor using ELATE software), (vi) calculation of thermodynamic and thermoelectric properties, and (vii) confirmed of metallic solid essence through electronic properties and 0 eV band gap values. These results favor a frontier in sustainable energy storage solutions, revealing the widespread adoption of solid-state H2 storage and to unlock the full potential of H2 energy, paving the way for a cleaner and greener future.

Catalytic effects of multiple heterointerfaces on the hydrogen storage properties of magnesium hydride

Catalytic effects of multiple heterointerfaces on the hydrogen storage properties of magnesium hydride

Role of solute elements in Mg-Mg2Ni hydrogen storage alloys: A first-principles calculation study

The effects of various alloying elements on the performance of Mg-Mg2Ni hydrogen storage alloys were investigated by performing first-principles density functional theory calculations. We examined the important characteristics of hydrogen storage alloys by considering both Mg-based solid solution and Mg2Ni-based intermetallic compound phases, where the hydride forms are MgH2 and Mg2NiH4, respectively. In particular, qualitatively valid information for predicting changes in plateau pressures in the pressure-composition-temperature (PCT) curve was provided by calculating changes in the energy of related hydrogenation reactions. The effects of alloying elements on volume changes due to hydrogenation reactions were also obtained to provide additional criteria for the practical use of hydrogen storage alloys. For the Mg2Ni-based intermetallic compound, we examined the site preference of each alloying element, considering the designated stoichiometry of the base alloy. Based on the revealed site preferences, the effects of various possible alloying elements on the properties of Mg2Ni-based hydrides were also examined. Electronic structure analyses were further conducted to elucidate the detailed mechanisms underlying the role of the additional solute elements.

Performance investigations on thermochemical energy storage system using cerium, aluminium, manganese, and tin-substituted LaNi5 hydrides

The necessity to store solar thermal energy draws attention to the development of energy storage systems (ESS), which can be addressed by the implementation of metal hydride (MH) energy storage systems (MHESS). The successful operation of metal hydride energy storage systems depends on the properties of the metal hydrides employed, which vary with compositional changes. Therefore, in the present work, the influence of the substitution of Aluminium (Al), Manganese (Mn), and Tin (Sn) for Nickel (Ni) and Cerium (Ce) for Lanthanum (La) on LaNi5 properties is studied in terms of hydrogen storage capacity (HSC), reaction enthalpy, working temperature, and pressure, and consequently on metal hydride energy storage system performance. The metal hydride properties were measured through the volumetric method using an in-house Sievert's Apparatus, and it was observed that the hydrogen storage capacity and equilibrium pressure are higher in the case of Cerium (1.48 wt%, 6.26 bar) substitution than those for Aluminum (1.43 wt%, 0.81 bar), Manganese (1.44 wt%, 0.9 bar), and Tin (1.4 wt%, 0.17 bar) at 20 °C. In contrast, the opposite trend was observed for reaction enthalpies. These metal hydride properties are applied to estimate the thermodynamic performance of metal hydride energy storage systems operating at 25 °C, 100 °C, 130 °C, and 150 °C using the metal hydride combination of La0.9Ce0.1Ni5 – LaNi4.7Al0.3, LaNi4.7Mn0.3 – LaNi4.7Sn0.3 and La0.9Ce0.1Ni5 – LaNi4.7Sn0.3. The coefficient of performance (COP) is observed to be 0.49, 0.46, and 0.54, respectively. Based on available driving pressure and thermodynamic performance, the combination of La0.9Ce0.1Ni5 – LaNi4.7Sn0.3 is observed to be more suitable for metal hydride energy storage systems with energy storage of 2439.69 kJ for 10 kg of metal hydrides.

Unlocking the Origin of High‐Temperature Superconductivity in Molecular Hydrides at Moderate Pressures

AbstractThe current pressing challenge in the field of superconducting hydride research is to lower the stable pressure of such materials for practical applications. Molecular hydrides are usually stable under moderate pressure, but the underlying metallization mechanism remains elusive. Here, the important role of chemical interactions in governing the structures and properties of molecular hydrides is demonstrated. A new mechanism is proposed for obtaining high‐temperature and even room‐temperature superconductivity in molecular hydrides and report that the ternary hydride NaKH12 hosts Tc values up to 245 K at moderate pressure of 60 GPa. Both the excellent stability and superconductivity of NaKH12 originate from the fact that the localized electrons in the interstitial region of the metal lattice occupying the crystal orbitals well matched with the hydrogen lattice and forming chemical templates to assist the assembly of H2 units. These localized electrons weaken the H─H covalent bonds and improve the charge connectivity between the H2 units, ensuring the strong coupling between electrons and hydrogen‐dominated optical phonons. The theory provides a key perspective for understanding the superconductivity of molecular hydrides with various structural motifs, opening the door to obtaining high‐temperature superconductors from molecular hydrides at moderate pressures.

Synthesis of Laves phase hydrides YFe2H6 and YFe2H7 at high pressure: Reaching a limit of interstitial hydrogen uptake

The C15 Laves phase compound YFe2 has been extensively studied for its significant hydrogen absorption in its tetrahedral interstitial sites. It can stably hold up to five hydrogen atoms per formula unit under ambient conditions. However, the maximum hydrogen capacity in such Laves phase materials remains an open question. The use of high pressure is a tool that facilitates the formation of polyhydrides with high hydrogen-to-metal ratios. By subjecting YFe2H4.2 to hydrogen pressures up to 50 GPa in a diamond anvil cell without any heating, two new interstitial compounds, YFe2H6 and YFe2H7, were synthesized. Synchrotron X-ray diffraction and ab initio calculations reveal that these new compounds have ordered hydrogen atoms occupying two types of tetrahedral interstitial sites, A2B2 and B4 (for YFe2H7), and a new triangular interstitial site AB2, in an orthorhombic structure distorted from the C15 Laves phase. The magnetic properties of YFe2Hx hydrides have to be taken into account to reproduce experimental volumes, identify stable compounds on the convex hull of the YFe2-H system, and explain deviations from Vegard’s law regarding volume expansion with hydrogen concentration. These compounds cannot be retrieved at ambient pressure upon pressure release.

Impact of Calcium Doping on the Electronic and Optical Characteristics of Strontium Hydride (SrH2): A DFT Study

This study investigates the electronic and optical properties of calcium-doped strontium hydride (SrH2) using first-principles density functional theory (DFT) calculations via the CASTEP code with generalized gradient approximation (GGA). We explore the impact of calcium (Ca) doping on the electronic band structure, density of states (DOS), and optical absorption spectra of SrH2. Our results show that Ca doping significantly alters the electronic properties of SrH2, notably increasing the indirect bandgap from 1.3 eV to 1.6 eV. The DOS analysis reveals new states near the Fermi level, primarily from Ca 3d orbitals. Moreover, the optical absorption spectra display enhanced absorption in the visible range, suggesting the potential for optoelectronic applications. This research highlights the feasibility of tuning the electronic and optical characteristics of SrH2 through Ca doping, thus opening the way for the generation of advanced materials with tailored properties.

Enhancements in Hydrogen Storage Properties of Magnesium Hydride Supported by Carbon Fiber: Effect of C–H Interactions

Carbon-based materials with excellent catalytic activity provide new ideas for the development of magnesium-based hydrogen storage. C-H bonding interactions may play a key role in performance improvement. In this work, we comprehensively compare the magnesium-carbon cloth composites (CC) prepared by method of dry ball milling and wet impregnation. The results were that the hydrogen release activation energy (Ea) of MgH2@CC composites prepared by wet immersion method was 175.1 ± 19.5 kJ·mol−1, which was lower than that of pure MgH2 (Ea = 213.9 ± 6.4 kJ·mol−1), and the activation energy of MgH2-CC composites prepared by ball milling method was 137.3 ± 8.7 kJ·mol−1, which provided better results. The kinetic enhancement should be attributed to C-H interactions. The presence of carbon carriers and electron transfer to reduce the activation energy of Mg-H bond fracture. These results will provide further insights into the promotion of hydrogen ab-/desorption from metal hydrides.

Equation of State, Structure, and Transport Properties of Iron Hydride Melts at Planetary Interior Conditions

AbstractIron hydrides are a potentially dominant component of the metallic cores of planets, primarily because of hydrogen's ubiquity in the universe and affinity for iron. Using ab initio molecular dynamics, we examine iron hydrides with 0.1, 0.33, 0.5, and 0.6 mol fraction hydrogen up to 100 GPa between 3,000 and 5,000 K to describe how hydrogen content affects the melt structure, hydrogen speciation, equation of state (EOS), atomic diffusivity, and melt viscosity. We find that the addition of hydrogen decreases the average Fe–Fe coordination number and lengthens Fe–Fe bonds, while Fe–H coordination number increases. The pair distribution function of hydrogen at low pressure indicates the presence of molecular hydrogen. By tracking chemical speciation, we show that the amount of molecular hydrogen increases and the number of iron in Hx≥1Fey≥0 clusters decreases as the hydrogen concentration increases. We parameterize a pressure, volume, temperature, and composition EOS and show that the molar volume and Grüneisen parameter of the melts decrease while the compressibility and thermal expansivity increase as a function of hydrogen concentration. We find that hydrogen acts as a lubricant in the melts as the iron and hydrogen become more diffusive and the melts become more inviscid as the hydrogen concentration increases. We estimate 2.7 wt% hydrogen in the Martian core and 0.49–1.1 wt% hydrogen in Earth's outer core based on comparisons to seismic models, with the assumption that the cores are pure liquid iron‐hydrogen alloy, and we compare the small exoplanet population with mass‐radius curves of iron hydride planets.

Diagnostic study on laser-produced metal hydride plasmas

The characteristics of laser-produced metal hydride plasmas have been investigated in this work. The charge state and velocity of ions were determined by employing a time-of-flight technique in conjunction with an electrostatic deflection method. The ion velocities were found to be supersonic with values in the range of 104 to 105 m/s. The proportion of hydrogen ions was found to be lower than that of titanium ions. The ion emission behavior was studied by using a Faraday cup. When the total integrated space was taken into account, the ns pulsed laser was capable of producing hydrogen ion currents greater than one hundred mA. In order to understand the plasma generation process, we performed a comparative analysis between laser-generated plasma and arc plasma, and also investigated the effect of laser power density on the composition and velocity of the ions, the ablation properties of metal hydrides, and the maintainability of hydrogen ion emission.

First principles investigation for the hydrogen storage properties of novel lithium-based XLiH3 (X=K, Rb) perovskite-type hydrides for advance hydrogen storage system

In this work, the density functional theory is used to investigate the structural, mechanical, electronic, dynamic, thermodynamic, optical and hydrogen storage properties of XLiH3 (X = K, Rb) for the first time. Both KLiH3 and RbLiH3 materials exhibit dynamic, mechanical and thermodynamic stability. The lattice parameters of KLiH3 and RbLiH3 are 3.908 and 4.070 Å, respectively. The investigation of Cauchy pressure, Poisson's ratio and B/G ratio shows that KLiH3 and RbLiH3 are brittle materials. Moreover, the electronic properties of XLiH3 hydrides demonstrate that KLiH3 and RbLiH3 show metallic nature. Optical properties of these compounds are studied and reveal that they have very high refractive indexes and dielectric functions. The thermodynamic properties, including heat capacity, entropy, enthalpy, and free energy of XLiH3, are investigated as well. The hydrogen storage capacities of KLiH3 and RbLiH3 are 5.805 and 3.071 wt%, respectively, confirming that KLiH3 has a high hydrogen storage capacity and is more suitable as a hydrogen storage material. Our study opens up a new-pathway for designing novel hydrogen storage materials.

Superconducting properties of rare-earth boron hydrides at high pressure studied by first-principles calculations

Superconducting properties of rare-earth boron hydrides at high pressure studied by first-principles calculations

Effects of H vacancies on photochromic properties of oxygen-containing yttrium hydride

We present in-situ studies of H loss from YHO films using ion beam analysis and its effect on the photochromic properties. The film evaporates loosely bound H under exposure to a beam of 3056 keV He2+ without a concomitant increase of O. Annealing at 145 °C decreases both the photochromic contrast and the bleaching speed indicating the importance of mobile H for the photochromic reaction.

Effect of phase composition and cluster structure on de-/hydriding kinetics of as-cast and heat-treated Ti33V37Mn30-xCrx alloys

To enhance the hydrogen storage property, elements Mn in Ti33V37Mn30 alloy were partially substituted with varying concentrations of elements Cr. The Ti33V37Mn24Cr6 variant, which exhibited superior performance, was selected for further analysis. Ti33V37Mn24Cr6 samples were first heat-treated separately at 773K, 973K and 1173K for 2h, and then water-quenched. The effect of Cr substitution and heat treatment on the microstructure and de-/hydriding properties of Ti33V37Mn30-xCrx alloys were investigated. As-cast alloys were composed of BCC phases mainly, along with some C14 Laves phases and Ti-rich phases. The lattice parameter of BCC phases in Ti33V37Mn24Cr6 increased to 3.053 Å. Cr substitution changed the tetrahedral gap of the alloy. At 298K, the initial hydrogen absorption capacity and the maximum hydrogen desorption capacity of Ti33V37Mn24Cr6 were raised to 3.07 wt% and 1.81 wt%, respectively. The lattice parameter of Ti33V37Mn24Cr6 alloys heat-treated at 773K also enlarged to 3.056 Å. Elevating the heat treatment temperature to 973K and 1173K significantly raised the proportion of C14 Laves phases in the alloy. Hydrogen storage performance of heat-treated alloys was examined at 298K. The results suggested that the heat-treated alloys could be fully activated after one hydrogen ab-/desorption cycle. Ti33V37Mn24Cr6 alloy heat-treated at 773K achieved the maximum hydrogen desorption capacity of 1.83 wt%, with an accelerated hydrogen ab-/desorption rate.

Ball Milling Innovations Advance Mg-Based Hydrogen Storage Materials Towards Practical Applications.

Mg-based materials have been widely studied as potential hydrogen storage media due to their high theoretical hydrogen capacity, low cost, and abundant reserves. However, the sluggish hydrogen absorption/desorption kinetics and high thermodynamic stability of Mg-based hydrides have hindered their practical application. Ball milling has emerged as a versatile and effective technique to synthesize and modify nanostructured Mg-based hydrides with enhanced hydrogen storage properties. This review provides a comprehensive summary of the state-of-the-art progress in the ball milling of Mg-based hydrogen storage materials. The synthesis mechanisms, microstructural evolution, and hydrogen storage properties of nanocrystalline and amorphous Mg-based hydrides prepared via ball milling are systematically reviewed. The effects of various catalytic additives, including transition metals, metal oxides, carbon materials, and metal halides, on the kinetics and thermodynamics of Mg-based hydrides are discussed in detail. Furthermore, the strategies for synthesizing nanocomposite Mg-based hydrides via ball milling with other hydrides, MOFs, and carbon scaffolds are highlighted, with an emphasis on the importance of nanoconfinement and interfacial effects. Finally, the challenges and future perspectives of ball-milled Mg-based hydrides for practical on-board hydrogen storage applications are outlined. This review aims to provide valuable insights and guidance for the development of advanced Mg-based hydrogen storage materials with superior performance.

Detection and Characterization of Hydride Ligands in Copper Complexes by Hard X-Ray Spectroscopy.

Transition metal complexes, particularly copper hydrides, play an important role in various catalytic processes and molecular inorganic chemistry. This study employs synchrotron hard X-ray spectroscopy to gain insights into the geometric and electronic properties of copper hydrides as potential catalysts for CO2 hydrogenation. The potential of high energy resolution X-ray absorption near-edge structure (HERFD-XANES) and valence-to-core X-ray emission (VtC-XES) is demonstrated with measurement on Stryker's reagent (Cu6H6) and [Cu3(μ3-H)(dpmppe)2](PF6)2 (Cu3H), alongside a non-hydride copper compound ICu(dtbppOH) (Cuy-I). The XANES analysis reveals that coordination geometries strongly influence the spectra, providing only indirect details about hydride coordination. The VtC-XES analysis exhibits a distinct signal around 8975 eV, offering a diagnostic tool to identify hydride ligands. Theoretical calculations support and extend these findings by comparing hydride-containing complexes with their hydride-free counterparts.

Large impact of phonon lineshapes on the superconductivity of solid hydrogen

Phonon anharmonicity plays a crucial role in determining the stability and vibrational properties of high-pressure hydrides. Furthermore, strong anharmonicity can render phonon quasiparticle picture obsolete questioning standard approaches for modeling superconductivity in these material systems. In this work, we show the effects of non-Lorentzian phonon lineshapes on the superconductivity of high-pressure solid hydrogen. We calculate the superconducting critical temperature TC ab initio considering the full phonon spectral function and show that it overall enhances the TC estimate. The anharmonicity-induced phonon softening exhibited in spectral functions increases the estimate of the critical temperature, while the broadening of phonon lines due to phonon-phonon interaction decreases it. Our calculations also reveal that superconductivity emerges in hydrogen in the Cmca − 12 molecular phase VI at pressures between 450 and 500 GPa and explain the disagreement between the previous theoretical results and experiments.

Microstructure and interaction in aluminum hydrides@polydopamine composites and interfacial improvement with GAP adhesive.

The reduction of interfacial interaction and the deterioration of processing properties of aluminum hydrides (AlH3) is the main challenges preventing its practical application. Here, a simple and effective core-shell structure aluminum hydrides@polydopamine (AlH3@PDA) complex was constructed through in-situ polymerization. The evolution of element states on the surface of AlH3 conducted by X-ray photoelectron spectroscopy indicated the successful introduction of PDA to form the core@shell structure, the thickness of the PDA coated layer increased with the increasing PDA dosage from 0.1 to 1.6% in mass fraction, and the maximum of thickness is 50nm in TEM testing. Py GC/MS results proved that the increase of dopamine concentration leads to higher proportions of self-assemble units, whereas lower dopamine concentrations favor higher levels of chemical bonded components. Regarding whether PDA is a covalent polymer or a noncovalent aggregate of some species, the formation of intermediates, such as dopaminechrome and 5,6-dihydroxyindole played an important role to coordination interaction with AlH3 in FTIR, Raman, and UV-Vis spectra testing. Compared with pure AlH3, the formation of organic PDA coating improved AlH3 heat resistance. The adhesion work with GAP adhesive was also improved from 107.02J/m2 of pure AlH3 to 111.13mJ/m2 of AlH3@PDA-5 complex. This paper provides well support for further practical application of AlH3 in solid propellants.

First-principles analysis of physical properties of the novel calcium-based hydrides for hydrogen storage application

The current work aims to investigate the physical properties of the new calcium-based perovskite hydride CaXH3 (X=Cu, and Zn) for hydrogen storage applications using DFT studies. Both materials were found to be thermodynamically and mechanically stable owing to their negative formation enthalpies, cohesive energy, and elastic constants. The absence of negative frequencies in the phonon dispersion curve reveals the dynamic stability of the structure. The optimized structure lattice constants were found 3.62Å, and 3.78Å with a bulk modulus of 117.40, and 82.39 GPa, respectively. The Poisson and Pugh ratios were confirmed to have ionic bonding, while the Cauchy difference and Pugh ratio (B/G) results exhibited the brittle behavior of both materials. In addition, both materials have anisotropic characteristics, and CaCuH3 is stiffer than CaZnH3. The electronic properties confirmed that both compounds have a metallic nature owing to the zero band gap and high contribution of the Ca and X (Cu, Zn) d states near the Fermi level. These compounds were found non-magnetic by the investigation of magnetic properties. The optical results indicate that CaZnH3 plays a significant role in optoelectronics, solar cells, and photonics applications because of its higher conductivity, refractive index, dielectric function, and reflectivity, as well as its higher adsorption than CaCuH3.The hydrogen storage capacities of CaCuH3 and CaZnH3 hydrides were calculated to be 2.88 wt. % and 2.75 wt.%, respectively, and it was predicted that both compounds have the potential to store hydrogen, as evidenced by storage application.

High temperature superconductivity of quaternary hydrides XM3Be4H32 (X, M = Ca, Sr, Ba, Y, La, Ac, Th) under moderate pressure

The compressed hydrogen-rich compounds have received extensive attention as promising candidates for room temperature superconductivity, however, the high pressure required to stabilize such materials hinders their wide practical application. In order to search for potential superconducting hydrides that are stable at low pressures, we have investigated the crystal structures and properties of quaternary hydrides, XM3Be4H32 (X, M = Ca, Sr, Ba, Y, La, Ac, Th) via first-principles calculations. We identified nine dynamically stable quaternary hydrides at 20 GPa. Strikingly, their superconducting transition temperatures (Tc) are much higher than that of liquid nitrogen, especially CaTh3Be4H32 (124 K at 5 GPa), ThLa3Be4H32(134 K at 10 GPa), LaAc3Be4H32 (135 K at 20 GPa) and AcLa3Be4H32 (153 K at 20 GPa) exhibit outstanding superconductivity at mild pressures. Metal atoms acting as pre-compressors donate abundant electrons to hydrogen, weakening the H–H covalent bond and thus facilitating the metallization of the hydrogen sublattice. At the same time, the appropriate combination of metal elements with different ionic radius and electronegativity can effectively tune the electronic structure near the Fermi level and improve the superconductivity. Molecular dynamics simulations reveal that these quaternary hydrides remain thermodynamically stable in the experimental acceptable pressure range (above 50 GPa). These findings fully reveal the great promise of hosting high-temperature superconductivity of quaternary hydrides at moderate pressures and will further promote related exploration.