Hydrogen Storage Applications Research Articles

Advancements in Solid-State Hydrogen Storage: A Review on the Glass Microspheres.

Glass microspheres, with their unique internal structure and chemical stability, offer a promising solution for the challenges of hydrogen storage and transmission, potentially advancing the utility of hydrogen as a safe and efficient energy source. In this review, we systematically evaluate various treatment and modification strategies, including fusion, sol-gel, and chemical vapor deposition (CVD), and compare the performance of different types of glass microspheres. Our synthesis of current research findings reveals that specific low-cost and environmentally friendly modification techniques can significantly enhance the hydrogen storage efficiency of glass microspheres, with some methods increasing storage capacity by up to 32% under certain conditions. Through a detailed life-cycle and cost-benefit assessment, our study highlights the economic and sustainability advantages of using modified glass microspheres. For example, selected alternative materials used in lightweight vehicles have been shown to reduce density by approximately 10% while reducing costs. This review not only underscores the contributions of modified glass microspheres to overcoming the limitations of current hydrogen storage technologies but also provides a systematic framework for improving their performance in hydrogen storage applications. Our research suggests that modified glass microspheres could help to make hydrogen energy more commercially viable and environmentally friendly.

Challenges of Green Transition in Polymer Production: Applications in Zero Energy Innovations and Hydrogen Storage

The green transition in the sustainable production and processing of polymers poses multifaceted challenges that demand integral comprehensive solutions. Specific problems of presences of toxic trace elements are often missed and this prevents shifting towards eco-friendly alternatives. Therefore, substantial research and the development of novel approaches is needed to discover and implement innovative, sustainable production materials and methods. This paper is focused on the most vital problems of the green transition from the aspect of establishing universally accepted criteria for the characterization and classification of eco-friendly polymers, which is essential to ensuring transparency and trust among consumers. Additionally, the recycling infrastructure needs substantial improvement to manage the end-of-life stage of polymer products effectively. Moreover, the lack of standardized regulations and certifications for sustainable polymers adds to the complexity of this problem. In this paper we propose solutions from the aspect of standardization protocols for the characterization of polymers foreseen as materials that should be used in Zero Energy Innovations in Hydrogen Storage. The role model standards originate from eco-labeling procedures for materials that come into direct or prolonged contact with human skin, and that are monitored by different methods and testing procedures. In conclusion, the challenges of transitioning to green practices in polymer production and processing demands a concerted effort from experts in the field which need to emphasize the problems of the analysis of toxic ultra trace and trace impurities in samples that will be used in hydrogen storage, as trace impurities may cause terrific obstacles due to their decreasing the safety of materials. Overcoming these obstacles requires the development and application of current state-of-the-art methodologies for monitoring the quality of polymers during their recycling, processing, and using, as well as the development of other technological innovations, financial initiatives, and a collective commitment to fostering a sustainable and environmentally responsible future for the polymer industry and innovations in the field of zero energy applications.

Exploring Nanomaterials for Hydrogen Storage: Advances, Challenges, and Perspectives.

Hydrogen energy heralded for its environmentally friendly, renewable, efficient, and cost-effective attributes, stands poised as the primary alternative to fossil fuels in the future. Despite its great potential, the low volumetric density presents a formidable challenge in hydrogen storage. Addressing this challenge necessitates exploring effective storage techniques for a sustainable hydrogen economy. Solid-state hydrogen storage in nanomaterials (physically or chemically) holds promise for achieving large-scale hydrogen storage applications. Such approaches offer benefits, including safety, compactness, lightness, reversibility, and efficient generation of pure hydrogen fuel under mild conditions. This article presents solid-state nanomaterials, specifically nanoporous carbons (activated carbon, carbon fibers), metal-organic frameworks, covalently connected frameworks, nanoporous organic polymers, and nanoscale metal hydrides. Furthermore, new developments in hydrogen fuel cell technology for stationary and mobile applications have been demonstrated. The review outlines significant advancements thus far, identifies key barriers to practical implementation, and presents a perspective for future sustainable energy research. It concludes with recommendations to enhance hydrogen storage performance for cost-effective and long-lasting utilization.

Physical properties of the XScH3 (X: Ca, and Mg) perovskite hydrides and their hydrogen storage applications

We conducted a comprehensive investigation into the structural, mechanical, electronic, magnetic, thermodynamic, optical, and hydrogen storage properties of the novel XScH3 (X: Ca and Mg) perovskite hydrides by using density functional theory (DFT). Our calculations of the cohesive energy and elastic constants demonstrated that XScH3 compounds exhibit both thermal and mechanical stability. The metallic nature of current materials is based on the investigation of the electronic band structure and total density states. The analysis of Pugh’s ratio (B/G) indicated that these hydrides were ductile materials. Furthermore, it was found that their bonding type was primarily ionic. These substances have been classified as conductors with antiferromagnetic qualities in terms of their magnetic properties. Furthermore, these materials exhibited promising effects on optical properties such as conductivity, absorption, dielectric function, and refractive index. Our predictions revealed that CaScH3 was found to be optically superior hydride. The dynamic stability of these crystals was assessed by analyzing their phonon dispersion curves and by molecular dynamics simulations. Additionally, we studied their thermal properties, including heat capacity, entropy, energy, and free energy, as functions of temperature. Furthermore, our study investigated the hydrogen storage capacity of XScH3 compounds, with CaScH3 and MgScH3, demonstrating hydrogen storage capacities of 3.43 wt.% and 4.18 wt.%, respectively. This study marks the first exploration of XScH3 perovskite hydrides and offers new options for hydrogen storage materials.

Evaluating hydrogen storage potential of NaNbO3-xHx: DFT-based approach

Alternative energy carrier materials are needed since non-renewable energy resources are diminishing at a fast rate. Increasingly, hydrogen storage has gained popularity as a clean energy source. For the first time, NaNbO3-xHx has been explored computationally as a potential material for hydrogen storage using the GGA-PBE approach as implemented in the CASTEP code. Structural, elastic, mechanical, electronic, and optical characteristics have been investigated to evaluate the suitability of the proposed material for hydrogen storage applications. All H-incorporated concentrations are thermodynamical and energetically stable and can be synthesized. Structural parameters vary with varying hydrogen concentrations; however, against each hydrogen concentration, the material maintains cubical geometry. The NaNbO2.7H0.3 show the highest (742.92 GPa) bulk modulus, while NaNbH3 stands with the lowest (52.48 GPa) among all. Standardizing the Poisson ratio reveals a brittle nature except for the X=0.3 composition. With increasing H-incorporation in the structure, the band gap increases (1.624 eV » 2.505 eV) and also causes electronic nature shifting (p-type → n-type); however, the band gap remains indirect over different symmetry points in BZ. Hence, have the potential for numerous optoelectronic applications. Furthermore, optical parameters, dielectric constant, refractive index, extinction coefficient, reflectivity, absorption coefficients, and loss functions are analyzed, which reveal the potential for numerous optoelectronic applications. Hydrogen storage capacity achieved up to 2.48 %, allowing this material to be utilized in energy storage systems.

First principles study of chromium-based hydrides for optoelectronics and hydrogen storage applications

The first-principles study employed on chromium-based hydride XCrH3 (X: Na, K) is the first time studied and investigated different physical properties incorporated for optoelectronics and hydrogen storage applications. The structural properties results revealed that these materials have cubic phases, with lattice constants are 3.54 Å (NaCrH3), and 3.74 Å (KCrH3), which was also confirmed by the XRD analysis. The XRD results revealed that the intensity of KCrH3 is shifted towards to lower angle (2θ) degree due to high lattice constants and inter-planner distance. Moreover, both materials exhibited thermodynamically and mechanically stable due to negative formation energy, and elastic constants, and obeyed the Born approximation criteria. The phonons dispersion curve shows that XCrH3 is dynamically stable due to no imaginary frequency presence. Electronic properties found that current materials have metallic characteristics, due to zero band-gap energy, which plays a vital role in hydrogen storage applications. Magnetic properties exhibited paramagnetic behavior of current materials highly contributed to hydrogen storage application due to unpaired electrons and studied materials have spin-polarized magnetic nature. However, elastic properties confirmed that these materials are found hard, and brittle, with an ionic bonding nature between the atoms, and an anisotropic character. Besides this, different optical parameters have studied like as conductivity, absorption coefficient, refractive index, reflectance, and loss function and the results revealed that the examined materials dominated the role in LED, sensors, solar cells, and optoelectronics applications. Thermal analysis revealed that increasing temperature increases energy and entropy but decreases free energy. Among the studied materials, NaCrH3 has a high gravimetric ratio of 3.87 wt%, and KCrH3 is 3.21 wt%. These materials provided new potential for hydrogen storage applications.

A Case Study of Maritime Hydrogen Energy Development in Jiangsu Province in China

This study aims to develop a systematic review of hydrogen energy storage technologies and maritime applications, intending to present an international perspective on the matter. This study analyses the role of advanced storage methods in enabling renewable energy systems integration in coastal regions, using Jiangsu Province of China as an example. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) was used as the research method. Data was obtained from research studies over the period 2015–2023. The analysis included a total of 96 papers from Web of Science, Scopus, IEEE Xplore, and ScienceDirect databases. Results show that Europe and East Asia led publications at the intersection of hydrogen storage and marine applications over the past decade. One of the main issues associated with maritime hydrogen adoption found in the dissertation is related to the mismatch between technological readiness levels and commercial maturity. Findings indicate promise for fuel cell integration with ships, ports, offshore wind farms, and other coastal transport sectors. However, the realization of the project depends on infrastructure development, policy support, and viable business models tailored to the marine environment. Focused demonstration projects and public-private collaboration can further progress towards robust hydrogen-based energy storage ecosystems in suitable regions like Jiangsu and beyond.

Atomistic-scale insights into hydrogen diffusion barrier in nickel hydride: Complex interplay between short- and long-range hydrogen arrangement and hydrogen concentration

Metal hydrides, such as those containing Pd, Ni and Mg, are being considered as potential candidates for hydrogen storage applications. The sluggish hydrogen uptake/release in such materials at ambient conditions presents a major issue. The timescales are dictated mainly by diffusion, as it is usually the rate-controlling step. In order to identify practical strategies for improving the kinetics, one must therefore gain an atomistic-scale understanding of the hydrogen diffusion, which is generally lacking from experiments. We address this gap by analyzing the hydrogen hopping mechanism and the associated barriers in two million different hydrogen configurations in NiHx (x = 0–1) using computational techniques. A distribution of hopping barriers is observed. The barriers lie between 0.3–0.7 eV. Three factors, namely, the short- and long-range hydrogen arrangement and the hydrogen concentration influence the barrier. We also show that depending on these factors, two different H hopping mechanisms may prevail. At higher H concentration, the lattice expands by as much as 19 % by volume, making it easier for the hydrogen atom to hop. Therefore, hydrogen diffusion is sluggish in the initial α phase, which may explain the experimentally-observed induction behavior. This study highlights the complexity associated with the metal hydride systems and provides the basis for further molecular scale kinetic studies of metal hydride systems.

Dipole-induced hydrogen bonds enhanced P/O co-doped Lyocell-based porous carbon fiber cloth for hydrogen storage under ambient pressure

Currently, the hydrogen storage application of carbon-based adsorbent materials is mostly implemented under the pressure conditions of 30–300 bar, while there is few targeted studies conducted on the unsaturated adsorption under ambient pressure conditions. Therefore, based on industrialized Lyocell biopolymer fiber precursors and the enhancement effects of dipole-induced hydrogen bonds (DIHB), this work presents a facile construction strategy for P/O co-doped Lyocell-based porous carbon fiber cloth (Ly-ACF-F40). By the technical route of thermal stabilization---sonication assisted phosphoric acid activation---hydrogen bonds introduced by interfacial fluorination, the constructed Ly-ACF-F40 acquires a high specific surface area (1870 m2/g) and total pore volume (1.277 cm3/g), and an excellent hydrogen storage capacity of 3.22 wt% under ambient pressure conditions (77 K, 1 bar). The study directly demonstrated in the experiment that dipole induced hydrogen bonding H(I)-H(II)···F can effectively enhance the atmospheric hydrogen storage density on the basis of other eliminating influencing factors of specific surface area. The simple construction strategy of porous carbon-based materials can provide reference for the research of unsaturated adsorption hydrogen storage materials under ambient pressure conditions, also assist in the application and promotion of low-cost solid hydrogen storage materials.

Feeling the strain: Enhancing the thermodynamics characteristics of magnesium nickel hydride Mg2NiH4 for hydrogen storage applications through strain engineering

This work is based on density functional theory (DFT) and studies the structural, electronic, thermodynamic properties and dehydrogenation kinetics of the hydride Mg2NiH4 under different uniaxial and biaxial strain applied to Mg2Ni or Mg2NiH4. structural properties are first studied based on generalized gradient (GGA) and local density (LDA). Thermodynamic and electronic properties and dehydrogenation kinetics are then studied using the GGA method based on the Perdew-Burke-Ernzerhor (PPE) approximation. The results obtained show that uniaxial/biaxial tensile and compressive strains are capable of inducing structural deformation by increasing the value of the strain step on both Mg2Ni and Mg2NiH4, and that these strains applied to Mg2NiH4 are capable of reducing the stability of the system more than strains applied to Mg2Ni, due to the contribution of strain energy. More specifically, it lowers the enthalpy of formation to −40 kJ/mol.H2 under compressive strain ε = −7.5% or biaxial tensile strain ε = +7.8%, which corresponds exactly to the ideal value suggested by the US Department of Energy (DOE) for materials suitable for hydrogen storage. And the decomposition temperature fell within the fuel cell operating range (PEM) of 289–393 K. On the other hand, under uniaxial and biaxial strains, the activation energy of hydrogen atom diffusion in Mg2NiH4 varied between 0.40 eV and 0.22 eV, resulting in a remarkable improvement in dehydrogenation properties. Analysis of the total (TDOS) and partial (PDOS) density curves shows that the Mg2NiH4 system has a metallic characteristic, and that this characteristic is maintained by increasing the strain pitch, with a variation in the energy width of the valence band.

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.

Fine-tuned MOF-74 type variants with open metal sites for high volumetric hydrogen storage at near-ambient temperature

Adsorbent-based hydrogen storage systems offer a potential solution to current challenges in hydrogen storage, particularly those requiring high pressures or cryogenic temperatures. Specifically, the use of metal–organic frameworks (MOFs) featuring open metal sites that strongly adsorb hydrogen represents a promising strategy for near-ambient-temperature hydrogen storage. This study investigates the hydrogen storage properties of M2(dondc) (M = Mg2+, Co2+, and Ni2+), an extended version of MOF-74. Among this series, Ni2(dondc) exhibits the second-highest volumetric hydrogen capacity of 10.74 g L−1 at 298 K under pressure swing adsorption conditions (100 to 5 bar) at ambient temperatures. The superior hydrogen storage performance of Ni2(dondc) is attributed to its highly polarizable Ni open metal sites and a significant heat of adsorption of 12.2 kJ mol−1. These findings are corroborated by temperature-programmed desorption spectroscopy and van der Waals-corrected density functional theory calculations. In addition to its exceptional hydrogen capacity, Ni2(dondc) exhibits robust structural stability and long-term durability, positioning it as a promising candidate for near-ambient-temperature hydrogen storage applications.

Zirconium-Modified Medium-Entropy Alloy (TiVNb)85Cr15 for Hydrogen Storage.

In this study, we investigate the effect of small amounts of zirconium alloying the medium-entropy alloy (TiVNb)85Cr15, a promising material for hydrogen storage. Alloys with 1, 4, and 7 at.% of Zr were prepared by arc melting and found to be multiphase, comprising at least three phases, indicating that Zr addition does not stabilize a single-phase solid solution. The dominant BCC phase (HEA1) is the primary hydrogen absorber, while the minor phases HEA2 and HEA3 play a crucial role in hydrogen absorption/desorption. Among the studied alloys, Zr4 (TiVNb)81Cr15Zr4 shows the highest hydrogen storage capacity, ease of activation, and reversibly retrievable hydrogen. This alloy can absorb hydrogen at room temperature without additional processing, with a reversible capacity of up to 0.74 wt.%, corresponding to hydrogen-to-metal ratio H/M = 0.46. The study emphasizes the significant role of minor elemental additions in alloy properties, stressing the importance of tailored compositions for hydrogen storage applications. It suggests a direction for further research in metal hydride alloys for effective and safe hydrogen storage.

High-temperature all-solid-state batteries with LiBH4 as electrolyte – a case study exploring the performance of TiO2 nanorods, Li4Ti5O12 and graphite as active materials

Abstract The hexagonal high-temperature form of LiBH4 is known as a fast ion conductor. Here, we investigated its suitability as a solid electrolyte in high-temperature all-solid-state cells when combined with the following active materials: Li metal, graphite, lithium titanium oxide (Li4Ti5O12, LTO), and nanocrystalline rutile (TiO2). First results using lithium anodes and rutile nanorods as cathode material show that a cell constructed by simple cold-pressing operates at reversible discharge capacities in the order of 125 mA h g−1 at a C-rate of C/5 and at temperatures as high as 393 K. Besides TiO2, the compatibility of the LiBH4 with other active materials such as graphite and LTO was tested. We found evidence of possible interface instabilities that manifest through rare, yet still detrimental, self-charge processes that may be relevant for hydrogen storage applications. Moreover, we investigated the long-term cycling behavior of the cells assembled and demonstrate the successful employment of LiBH4 as an easily processable model solid electrolyte in practical test cells.

A comprehensive approach for doping selection and assessment in porous materials for hydrogen storage: CNTs study case

Identifying a nanostructure suitable for hydrogen storage presents a promising avenue for the secure and cost-effective utilization of hydrogen as a green energy source. This study introduces a systematic approach for selecting optimal doping on porous materials, emphasizing the intricate interplay between doping with the material's structure and the interaction between doping and hydrogen. Our proposed approach serves as a framework for evaluating and predicting the performance of doped materials. To validate the efficacy of our strategy, we conduct a comprehensive investigation in carbon nanotubes (CNTs). Applying our criteria, we systematically screen several dopants in CNTs. The results highlight Cu-doped CNTs as promising candidates for hydrogen storage applications. Focusing on Cu-doped CNTs, we analyze binding energy, charge transfer, partial density of states (PDOS), and desorption temperature to assess the performance of modified CNTs. Additionally, we explore the feasibility of doped CNTs featuring various sizes of copper clusters and the effect on the release temperature, i.e., complete regeneration. The findings indicate that incorporating 5 to 6% copper impurity onto CNT surfaces renders these nanostructures highly applicable for reversible hydrogen storage near ambient conditions.

Boosting hydrogen storage capacity in modified-graphdiyne structures: A comprehensive density functional study

Graphdiyne (GDY) is a recently discovered two-dimensional carbon allotrope that holds significant promise for applications in hydrogen adsorption and storage technology. This study investigates the impact of nitrogen doping and sodium decoration on the hydrogen adsorption capacity of GDY nanosheets while examining their influence on electronic and structural properties. Various deliberate impurities are introduced to create modified-GDY structures. Nitrogen doping triggers a transition from a semiconductor to a semi-metallic state, driven by differences in electronegativity and adjustments in bond lengths. Cohesive energy (Ecoh) is found to be −7.231 eV for the most stable N-doped GDY. In contrast, sodium decoration enhances conduction by modifying charge distribution. The other most stable structures are Na-decorated GDY with Eads of −3.804 eV and N, Na-decorated GDY with −3.347 eV. Modified-GDY structures exhibit higher hydrogen adsorption energies compared to pristine GDY, with N-doped GDY displaying the highest energy levels (Eads = −0.455 eV). Maximum hydrogen adsorption capacities are assessed for each structure, and a notable improvement is observed in Na-decorated GDY (19 H2), significantly enhancing the storage capacity to 13.8 wt%, which shows a 10.21 wt% increase in H2 adsorption compared to pure GDY (3.59 wt%). These findings underscore the potential of modified-GDY for hydrogen storage applications, highlighting the effectiveness of structural carbon modification in enhancing hydrogen adsorption capacity.

Effective hydrogen storage in Na2(Be/Mg)H4 hydrides: Perspective from density functional theory

The utilization of hydrogen energy has garnered significant attention as a viable and environmentally friendly energy alternative. However, there exist some technological challenges pertaining to the storage of hydrogen. In this context, the present study utilizes first-principles calculations to examine the physical characteristics of Na2(Be/Mg)H4 hydrides to better understand their potential for use in hydrogen storage applications. The structure stability of Na2BeH4 and Na2MgH4 hydrides is assessed by formation enthalpy and phonon dispersion calculations. Elastic constants have been utilized to determine the elastic and mechanical stabilities of the studied hydrides. Both hydrides satisfy the established Born stability criteria, suggesting that both Na2BeH4 and Na2MgH4 are mechanically stable compounds. The assessment of electronic properties reveals that Na2BeH4 and Na2MgH4 have semiconducting characteristics with direct and indirect band gaps of 2.22 and 3.10 eV, respectively. Furthermore, various optical characteristics have been evaluated and compared. The computed values of gravimetric and volumetric hydrogen storage capacities for Na2BeH4 (Na2MgH4) hydrides are 6.78 (5.38) wt% and 85.11 (62.78) gH2l−1, respectively, fulfilling the standard set by US-DOE for 2025. This study suggests that both Na2BeH4 and Na2MgH4 hydrides have the potential to be an incredibly efficient choice for solid-state hydrogen storage.

Theoretical investigation of XSnH3 (X: Rb, Cs, and Fr) perovskite hydrides for hydrogen storage application

The current study investigated the structural, mechanical, electronic, and optical properties of new perovskite hydrides XSnH3 (X = Rb, Cs, and Fr) for hydrogen storage applications using a first-principles study with the GGA-PBE approach. The calculated lattice constants form optimized cubic crystal have 4.40 Å, 4.49 Å and 4.53 Å for RbSnH3, CsSnH3, and FrSnH3 hydrides, respectively. These materials were found to be thermodynamically and mechanically stable structures owing to their negative cohesive energy and elastic constants. Additionally, molecular dynamics (MD) calculations were performed to study the thermal stability of the current materials. These results indicate that the considered materials were stable and exhibited no structural deformation. The electronic band structure and density of states confirmed that the current materials exhibit metallic behavior via overlapping of the valence and conduction bands with a zero-energy band gap. It was found these compounds have anisotropic and rigid in nature. The Poisson's ratio, Pugh's ratio (B/G), and Cauchy pressure (CP) values indicate that the current compounds have ionic bonding and brittle behavior. Different optical parameters were calculated for these materials, such as the conductivity, dielectric function, loss energy, refractive index, and adsorption. Interestingly, these optical parameters indicate that XSnH3 is promising for optoelectronic, photonic, and energy storage applications. Finally, the calculated hydrogen storage capacities for RbSnH3, CsSnH3, and FrSnH3 are 1.45 wt%, 1.18 wt %, and 0.87 wt %respectively. These results show that current materials have the potential and promise for hydrogen storage applications, and devices.

Developing the insight for systematic exploration of hydrogen storage in RbMgF3

In the present work, the density functional theory calculation has been performed for RbMgF3-xHx with GGA-PBE approximation implemented in CASTEP code. First time the structural, mechanical, electronic and optical properties of perovskite RbMgF3-xHx (x = 0, 0.3, 0.6, 0.9, 1.2, 1.5, 1.65, 1.80, 1.95, 2.25, 2.55, 2.85 and 3.0) has been investigated in details along with hydrogen storage applications. The results of formation enthalpy and elastic constants indicate that the materials are synthesizable. It has been found that the concentration of hydrogen storage decreases the elastic moduli and anisotropy whereas the bandgap becomes narrow because of the shifting of conduction band toward the fermi level. This indicates that hydrogen inclusion altered the electronic properties of the material and material can also be used in various optoelectronic devices alongwith hydrogen storage application. The crystal structure shifted from cubic to tetragonal during the hydrogen storage. The optical properties were thoroughly investigated between 0 and 10 eV. It has been found optical properties are enhanced with the doping concentration of hydrogen, which makes them good candidates for optoelectronic devices. The gravimetric ratio of hydrogen increased up to 2.61% with hydrogen incorporation. The presented material is an efficient material not only for opto-electronic applications but also for hydrogen storage as well.

The first principles insights of aluminum-based hydrides for hydrogen storage application

Hydrogen storage is an urgent issue for mobile applications, to overcome this issue solid materials have a potential role for hydrogen storage applications. Moreover, the perovskite hydride materials have been extensively investigated for improvement in the field of hydrogen storage. However, this work is focused on the computational study of XAlH3 (X: Na, Mg) perovskite-type hydrides for different physical properties and hydrogen storage applications. Both materials were found thermodynamically, and mechanically stable from the negative formation energy and elastic properties. They exhibited cubic phases with computed lattice constants are 3.827 Å and 3.752 Å, respectively. The electronic properties indicated that both compounds have a metallic nature, and found the high contribution of Al-p state, and H-1s state near the Fermi level. However, the Hirshfeld net charge analysis detected, that charge transfer from Al and X (Na, Mg) atoms to H atoms. Furthermore, the metallic hydrides have promised candidates for hydrogen storage applications. Both compounds have observed non-magnetic behavior with zero magnetic moments. Elastic constants were calculated to determine the mechanical stability of the compounds, it was found that MgAlH3 is harder than NaAlH3, and it exhibited that higher Bulk, Shear, and Young's modulus. The Poisson's, and Pugh's (G/B) ratios suggested that ionic boning of the atoms, additionally, Pugh's ratio (B/G) and Cauchy pressure (Cp) confirmed that NaAlH3 ductile and MgAlH3 is brittle behavior. Besides this, Optical properties were determined for both compounds including the dielectric function, conductivity, refractive index, absorption, and loss function. It is found that the MgAlH3 compound optical more suitable than NaAlH3 due to calculated optical factors promised and both compounds are undertaken for solar cells, optoelectronics, and energy storage applications. Finally, the computed hydrogen storage capacity for NaAlH3 and MgAlH3 compounds are 6.01 wt%, and 5.56 wt% respectively. These results revealed that both have the potential materials for hydrogen storage, but NaAlH3 unique material to fulfill the US-DOE criteria of 2020.