Role of vacancy defects on the dehydrogenation properties of the ternary hydride ZrNiH3: Ab-initio insights

ZrNi is considered a promising candidate for hydrogen storage and nickel-metal hydride rechargeable batteries (Ni-MH). The effect of creating zirconium and nickel vacancy defects on the dehydrogenation properties of ZrNiH₃ is investigated by means of first-principles calculations. The results indicate that nickel vacancy is energetically more favorable to form in ZrNiH₃ than zirconium vacancy, because of the lesser formation energy of Ni-vacancy. For both Zr and Ni vacancy defects, the formation enthalpy decreases with increasing the concentration of vacancy and, vice versa. In particular, it is found that with ~2.4% of zirconium vacancy defects or with ~4.5% of nickel vacancy defects in ZrNiH₃, the formation enthalpy is around - 40 kJ/mol.H₂, which is recommended by the U.S. Department of Energy (DOE). It is worth noting also that with slightly higher vacancy defects ~2.8 of Zr-vacancy or ~5.3% of Ni-vacancy in ZrNiH₃, it becomes harder to store hydrogen in these systems without cooling. Moreover, the density of states (DOS) analysis indicates that the stability of ZrNiH₃ decreases with increasing Zr-vacancy and Ni-vacancy concentrations, through the shrinkage in the size of the total DOS and shifting in the valence bands near to Fermi level.     

Dual-tuning effect of In on the thermodynamic and kinetic properties of Mg2Ni dehydrogenation

Mg₂In_0.1Ni solid solution with an Mg₂Ni-type structure has been synthesized and its hydrogen storage properties have been investigated. The results showed that the introduction of In into Mg₂Ni not only significantly improved the dehydrogenation kinetics but also greatly lowered the thermodynamic stability. The dehydrogenation activation energy (E_a) and enthalpy change (ΔH) decreased from 80 kJ/mol and 64.5 kJ/mol H₂ to 28.9 kJ/mol and 38.4 kJ/mol H₂, respectively. The obtained results point to a method for improving not only the thermodynamic but also the kinetic properties of hydrogen storage materials.     

Interactions of Y and Cu on Mg2Ni type hydrogen storage alloys: A study based on experiments and density functional theory calculation

Evolution of microstructure and hydrogen storage performances were studied in a Y substituted Mg₂₄Ni₁₀Cu₂ hydrogen storage alloy. Interactions of Y and Cu on the phase structure and hydrogen storage properties were explore. Substitution by Y refined the microstructure and yield existence of YMgNi₄. Furthermore, Y addition promoted the replacement of Cu for Ni in the Mg₂Ni.The study of the alloy's dehydrogenation performance and mechanism showed that the addition of Y did not alter the mechanism of random nucleation and subsequent growth, but reduced the activation energy of the dehydrogenation of the alloy from 77.4 kJ/mol to 67.6 kJ/mol. The thermodynamic energy of the dehydrogenation was also improved, and the enthalpy change (ΔH) and entropy change (ΔS) of the Mg₂NiH₄ phase decreased from 67.1 J/K/mol H₂ and 123.1 J/K/mol H₂ to 61.1 J/K/mol H₂ and 115.4 J/K/mol H₂, respectively. Furthermore, the density functional theory calculation showed that the addition of Y promoted the substitution of Cu for Ni, further reduced the stability of the main hydride Mg₂NiH₄, facilitated the release of hydrogen, and reduced the ΔH and ΔS of the hydride dehydrogenation.     

Hydrogen solid storage: First-principles study of ZrNiH3

The ZrNiH₃ compound is a good candidate for hydrogen storage. In this work we used the first-principles calculation to study this compound. The crystal structures, the electronic properties and the optimization of the internal parameters are treated by the FP-LAPW method implanted in the WIEN2K code. The enthalpies of the dehydrogenation of the ZrNiH₃ compound are calculated. We found that the enthalpy is about −42.89 kJ/mol H, greater but similar to the experimental value of −34.3 kJ/mol H. Potential reasons for this discrepancy are discussed.     

Enhanced thermodynamic properties of ZrNiH3 by substitution with transition metals (V,Ti, Fe,Mn and Cr)

First-principles calculations based on Plane-Wave Self-Consistent Field (PWSCF) method, implemented in quantum espresso program, have been performed on ZrNiH₃ substituted with transition metals (V, Ti, Fe, Mn, and Cr). The study aims to investigate the heat of formation in terms of material stability and desorption temperature. It is found that the substitution by transition metals, results in a significant enhancement in the thermodynamic properties accompanied by an increase of the volumetric and gravimetric hydrogen storage capacities. In addition, the obtained values of heat of formation and desorption temperature corroborate with that required by the U.S. Department of Energy (DOE) for stability and volumetric capacity criteria. Moreover, Mn and Fe elements are found to present the lowest substituting content (34%) to obtain optimum hydrogen storage characteristics (enthalpy of formation of - 40 kJ/mol.H₂, decomposition temperature of 300 K and volumetric capacity of 134 g.H₂/l), without affecting the electronic structure and the metallic character of ZrNiH₃.     

Structure, morphology and hydrogen storage properties of a Ti0.97Zr0.019V0.439Fe0.097Cr0.045Al0.026Mn1.5 alloy

The Ti_0.97Zr_0.019V_0.439Fe_0.097Cr_0.045Al_0.026Mn_1.5 alloy is a hexagonal C14 Laves phase material that reversibly stores hydrogen under ambient temperatures. Structural changes are studied by XRD and SEM with regard to hydrogenation and dehydrogenation cycling at 25, 40 and 60 °C. The average particle size is reduced after hydrogenation and dehydrogenation cycling through decrepitation. The maximum hydrogen capacity at 25 °C is 1.71 ± 0.01 wt. % under 78 bar H₂, however the hydrogen sorption capacity decreases and the plateau pressure increases at higher temperatures. The enthalpy (ΔH) and entropy (ΔS) of hydrogen absorption and desorption have been calculated from a van’t Hoff plot as −21.7 ± 0.1 kJ/mol H₂ and −99.8 ± 0.2 J/mol H₂/K for absorption and 25.4 ± 0.1 kJ/mol H₂ and 108.5 ± 0.2 J/mol H₂/K for desorption, indicating the presence of a significant hysteresis effect.     

Thermodynamics of hydrogen production from urea by steam reforming with and without in situ carbon dioxide sorption

The thermodynamic effects of molar steam to carbon ratio (S:C), of pressure, and of having CaO present on the H₂ yield and enthalpy balance of urea steam reforming were investigated. At a S:C of 3 the presence of CaO increased the H₂ yield from 2.6 mol H₂/mol urea feed at 940 K to 2.9 at 890 K, and decreased the enthalpy of bringing the system to equilibrium. A minimum enthalpy of 180.4 kJ was required to produce 1 mol of H₂ at 880 K. This decreased to 94.0 kJ at 660 K with CaO-based CO₂ sorption and, when including a regeneration step of the CaCO₃ at 1170 K, to 173 kJ at 720 K. The presence of CaO allowed widening the range of viable operation at lower temperature and significantly inhibited carbon formation. The feasibility of producing H₂ from renewable urea in a low carbon future is discussed.     

Effect of Ni and SAPO-34 co-additive on enhancing hydrogen storage performance of MgH2

The hydrogen storage performances of MgH₂ improved by the addition of Ni and SAPO-34 were studied in detail. The mixture of MgH₂ with Ni and SAPO-34 was a physical reaction as shown by the X-ray diffraction (XRD) results. The SAPO-34 and Ni were uniformly distributed on the surface of MgH₂. The thermodynamic and kinetic properties of 90MgH₂/5Ni/5SAPO-34 were investigated by differential scanning calorimetry (DSC) and pressure-composition-isothermal (PCI) methods. The results showed that the dehydrogenation activation energy of 90MgH₂/5Ni/5SAPO-34 decreased by 64.3 kJ/mol compared with that of MgH₂. In addition, the relationship between the value of dehydrogenation heat and hydrogen content was also investigated by in-situ calorimetry. The enthalpy value of each sample in the dehydrogenation processes were calculated by in-situ calorimetry measurement. The dehydrogenation enthalpies of as-milled MgH₂ and 90MgH₂/5Ni/5SAPO-34 were 63.2 kJ/mol H₂ and 53.6 kJ/mol H₂, respectively. Thus, the co-doping of Ni and SAPO-34 contributed significantly to decrease the thermodynamic stability and improve the hydrogen sorption kinetic properties of MgH₂.     

Hydro-catalytic treatment of organoamine boranes for efficient thermal dehydrogenation for hydrogen production

This study aims to present the hydro-catalytic treatment of organoamine boranes for efficient thermal dehydrogenation for hydrogen production. Organoamine boranes, methylamine borane (MeAB), and ethane 1,2 diamine borane (EDAB), known as ammonia borane (AB) carbon derivatives, are synthesized to be used as a solid-state hydrogen storage medium. Thermal dehydrogenation of MeAB and EDAB is performed at 80 °C, 100 °C, and 120 °C under different conditions (self, catalytic, and hydro-catalytic) for hydrogen production and compared with AB. For this purpose, a cobalt-doped activated carbon (Co-AC) catalyst is fabricated. The physicochemical properties of Co-AC catalyst is investigated by well-known techniques such as ATR/FT-IR, XRD, XPS, ICP-MS, BET, and TEM. The synthesized Co-AC catalyst obtained in nano CoOOH structure (20 nm, 12% Co wt) is formed and well-dispersed on the activated carbon support. It has indicated that Co-AC exhibits efficient catalytic activity towards organoamine boranes thermal dehydrogenation. Hydrogen release tests show that hydro-catalytic treatment improves the thermal dehydrogenation kinetics of neat MeAB, EDAB, and AB. Co-AC catalyzed hydro-treatment for thermal dehydrogenation of MeAB and EDAB acceleras the hydrogen release from 0.13 mL H₂/min to 46.12 mL H₂/min, from 0.16 mL H₂/min to 38.06 mL H₂/min, respectively at 80 °C. Moreover, hydro-catalytic treatment significantly lowers the H₂ release barrier of organoamine boranes thermal dehydrogenation, from 110 kJ/mol to 19 kJ/mol for MeAB and 130 kJ/mol to 21 kJ/mol for EDAB. In conclusion, hydro and catalytic treatment presents remarkable synergistic effect in thermal dehydrogenation and improves the hydrogen release kinetics.     

Reversible hydrogen storage in a 3NaBH4/YF3 composite

A 3NaBH₄/YF₃ hydrogen storage composite was prepared through ball milling and its hydrogen sorption properties were investigated. It is shown that NaBH₄ does not react with YF₃ during ball milling. The dehydrogenation of the composite starts at 423 °C, which is about 100 °C lower than the dehydrogenation temperature of pure NaBH₄, with a mass loss of 4.12 wt%. Pressure–Composition–Temperature tests reveal that the composite has reversible hydrogen sorption performance in the temperature range from 350 °C to 413 °C and under quite low hydrogenation plateau pressures (<1 MPa). Its maximum hydrogen storage capacity can reach up to 3.52 wt%. The dehydrogenated composite can absorb 3.2 wt% of hydrogen within 5 min at 400 °C. Based on the Pressure–Composition–Temperature analyses, the hydrogenation enthalpy of the composite is determined to be −46.05 kJ/mol H₂, while the dehydrogenation enthalpy is 176.76 kJ/mol H₂. The mechanism of reversible hydrogen sorption in the composite involves the decomposition and regeneration of NaBH₄ through the reaction with YF₃. Therefore, the addition of the YF₃ to NaBH₄ as a reagent forms a reversible hydrogen storage composite.     

Effect of milling duration on hydrogen storage thermodynamics and kinetics of Mg-based alloy

Mechanical milling is widely recognized as the best method to prepare nano-structured magnesium based hydrogen storage materials. The composites La₇Sm₃Mg₈₀Ni₁₀ + 5 wt% TiO₂ (named La₇Sm₃Mg₈₀Ni₁₀–5TiO₂) whose structures are nano-crystal and amorphous accompanied by great hydrogen absorption and desorption properties were fabricated by mechanical milling. The research focuses on the effect of milling duration on the thermodynamics and dynamics. The instruments of researching the gaseous hydrogen storing performances include Sievert apparatus, DSC and TGA. The calculation of dehydrogenation activation energy was realized by applying Arrhenius and Kissinger formulas. The calculation results show the specimen milled for 10 h exhibits the optimal activation performance and hydrogenation and dehydrogenation kinetics. Extending or shrinking the milling duration will lead to the degradation of hydrogen storage performances. The as-milled (10 h) alloy at the full activated state can absorb 4 wt% hydrogen in 87 s at 473 K and 3 MPa and release 3 wt% H₂ in 288 s at 573 K and 1 × 10⁻⁴ MPa. The changed milling durations have little impact on the thermodynamic properties of experimental samples and the enthalpy change (ΔH) of the alloy milled for 10 h is 74.23 kJ/mol. Moreover, it is found that the as-milled (10 h) alloy displays the minimum apparent activation energy of dehydrogenation (59.1 kJ/mol), suggesting the optimal hydrogen storing property of the as-milled (10 h) alloy.     

Effects of REF3 (RE = Y,La, Ce) additives on dehydrogenation properties of LiAlH4

The catalytic effects of rare earth fluoride REF₃ (RE = Y, La, Ce) additives on the dehydrogenation properties of LiAlH₄ were carefully investigated in the present work. The results showed that the dehydrogenation behaviors of LiAlH₄ were significantly altered by the addition of 5 mol% REF₃ through ball milling. The destabilization ability of these catalysts on LiAlH₄ has the order: CeF₃>LaF₃>YF₃. For instance, the temperature programmed desorption (TPD) analyses showed that the onset dehydrogenation temperature of CeF₃ doped LiAlH₄ was sharply reduced by 90 °C compared to that of pristine LiAlH₄. Based on differential scanning calorimetry (DSC) analyses, the dehydriding activation energies of the CeF₃ doped LiAlH₄ sample were 40.9 kJ/mol H₂ and 77.2 kJ/mol H₂ for the first and second dehydrogenation stages, respectively, which decreased about 40.0 kJ/mol H₂ and 60.3 kJ/mol H₂ compared with those of pure LiAlH₄. In addition, the sample doped with CeF₃ showed the fastest dehydrogenation rate among the REF₃ doped LiAlH₄ samples at both 125 °C and 150 °C during the isothermal desorption. The phase changes in REF₃ doped LiAlH₄ samples during ball milling and dehydrogenation were examined using X-ray diffraction and the mechanisms related to the catalytic effects of REF₃ were proposed.     

Synthesis and hydrogen adsorption properties of a new iron based porous metal-organic framework

A new metal-organic framework [Fe₃O(OOC-C₆H₄-COO)₃(H₂O)₃]Cl·(H₂O)_x was synthesized with a specific surface area of 2823 m²/g and a lattice parameter of 88.61 Å. Isostructural with MIL-101, this compound exhibits similar hydrogen adsorption properties, with maximum adsorption capacity of 5.1wt.% H at 77 K. The adsorption enthalpy of hydrogen for MIL-101 and ITIM-1 (MIL-101Fe) at zero coverage was calculated for a wide temperature range of 77 K ÷ 324 K, considering corrections for the variation of hydrogen gas entropy with the temperature. The resulted adsorption enthalpy is 9.4 kJ/mol for MIL-101, in excellent agreement with the value reported in literature from microcalorimetric measurements, and a value of 10.4 kJ/mol at zero coverage was obtained for ITIM-1 (MIL-101Fe).     

Improved hydrogen storage properties of Mg/MgH2 thanks to the addition of nickel hydride complex precursors

In order to improve the hydrogenation/dehydrogenation properties of the Mg/MgH₂ system, the nickel hydride complex NiHCl(P(C₆H₁₁)₃)₂ has been added in different amounts to MgH₂ by planetary ball milling. The hydrogen storage properties of the formed composites were studied by different thermal analyses methods (temperature programmed desorption, calorimetric and pressure-composition-temperature analyses). The optimal amount of the nickel complex precursor was found to be of 20 wt%. It allows to homogeneously disperse 1.8 wt% of nickel active species at the surface of the Mg/MgH₂ particles. After the decomposition of the complex during MgH₂ dehydrogenation, the formed composite is stable upon cycling at low temperature. It can release hydrogen at 200 °C and absorb 6.3 wt% of H₂ at 100 °C in less than 1 h. The significantly enhanced H₂ storage properties are due to the impact of the highly dispersed nickel on both the kinetics and thermodynamics of the Mg/MgH₂ system. The hydrogenation and dehydrogenation enthalpies were found to be of −65 and 63 kJ/mol H₂ respectively (±75 kJ/mol H₂ for pure Mg/MgH₂) and the calculated apparent activation energies of the hydrogen uptake and release processes are of 22 and 127 kJ/mol H₂ respectively (88 and 176 kJ/mol H₂ for pure Mg/MgH₂). The change in the thermodynamics observed in the formed composite is likely to be due to the formation of a Mg_0.992Ni_0.008 phase during dehydrogenation/hydrogenation cycling. The impact of another hydride nickel precursor in which chloride has been replaced by a borohydride ligand, namely NiH(BH₄)(P(C₆H₁₁)₃)₂, is also reported.     

Microstructure and hydrogen storage properties of V48Fe12Ti15-xCr25Alx (x=0, 1) alloys

The microstructure and hydrogen storage characteristics of V₄₈Fe₁₂Ti_15-xCr₂₅Al_x (x = 0, 1) alloys prepared by vacuum arc melting were studied by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and pressure–composition isotherm measurements. It was confirmed that all of the alloys comprise a BCC phase, a Ti-rich phase, and a TiFe phase. Al as a substitute for part of the Ti content caused an increase of lattice parameters of the BCC phase and of the equilibrium pressures of hydrogen desorption, but decrease of the hydrogen storage capacities. The kinetic mechanism of the hydrogenation and dehydrogenation of the alloys was investigated by the classical Johnson–Mehl–Avrami equation. The reaction enthalpies (ΔH) for the dehydrogenation of alloys without and with Al were calculated by the Van't Hoff equation based on the PCI measurement data, which are 30.12 ± 0.14 kJ/mol and 28.02 ± 0.46 kJ/mol, respectively. The thermal stability of the metal hydride was measured by differential scanning calorimetry. The hydrogen desorption activation energies were calculated using the Kissinger method as 79.41 kJ/mol and 83.56 kJ/mol for x = 0 and 1, respectively. The results suggest that the substitution of titanium with aluminum improves the thermodynamic properties of hydrogen storage and reduces the kinetic performance of hydrogen desorption.     

Influence of adding graphene on the hydrogen storage thermodynamics and kinetics of as-milled CeMg12–Ni alloy

Graphene can been used to improve the hydrogen storage performance of magnesium based materials because of its outstanding electrical conductivity, high specific surface area, and good mechanical qualities. In this paper, mechanical ball milling method was utilized to prepare the CeMg₁₂/Ni alloy combined with graphene in order to investigate the impact of graphene on microstructure, kinetics, and thermodynamic properties of alloy. The results reveal that the addition of graphene can refine the grains of alloy, increase the surface defects of alloy particles and promote Ni to be dissolved in the main phase of the alloy. The absolute value of enthalpy drops from 65.27 kJ/mol to 60.3 kJ/mol when Graphene is added at a higher concentration. The addition of graphene improves the dehydrogenation performance of alloy hydride by lowering its thermal stability. Because of a minimum dehydrogenation activation energy of 85.23 kJ/mol and dehydrogenation characteristic time of 1090s, the alloy with 6 wt% Graphene exhibits the best dehydrogenation kinetic performances.     

Enhanced hydrogen properties of MgH2 by Fe nanoparticles loaded hollow carbon spheres

In the present investigation, we have reported the synergistic effect of Fe nanoparticles and hollow carbon spheres composite on the hydrogen storage properties of MgH₂. The onset desorption temperature for MgH₂ catalyzed with hollow carbon spheres and Fe nanoparticle (MgH₂-Fe-HCS) system has been observed to be 225.9 °C with a hydrogen storage capacity of 5.60 wt %. It could be able to absorb 5.60 wt % hydrogen within 55 s and desorb 5.50 wt % hydrogen within 12 min under 20 atm H₂ pressure at 300 °C. The desorption activation energy of MgH₂-Fe-HCS has been found to be 84.9 kJ/mol, whereas the desorption activation energies for as received MgH₂, Hollow carbon sphere catalyzed MgH₂ and Fe catalyzed MgH₂ are found to be 130 kJ/mol, 103 kJ/mol, and 94.2 kJ/mol respectively. MgH₂-Fe-HCS composite lowered the change in enthalpy of hydrogen desorption from MgH₂ by 20.02 kJ/mol as compared to pristine MgH₂. MgH₂-Fe-HCS shows better cyclability up to 24 cycles of hydrogenation and dehydrogenation of MgH₂. The mechanism for the better catalytic action of Fe and HCS on MgH₂ has also been discussed.     

Tuning the dehydrogenation performance of dibenzyl toluene as liquid organic hydrogen carriers

Strategies to decrease the dehydrogenation enthalpy (ΔH_d) of dibenzyl toluene (DBT) were examined by density functional theory (DFT) modeling. The stronger electron-donating substituent showed higher hydrogen-releasing properties. The sequences of the dehydrogenation process of perhydro-dibenzyl toluene (18H-DBT) and perhydro-lithium 3,5-dibenzyl phenolate (18H-DBT-OLi), which is the compound of modified DBT with the highest potential, were the same. The energy required to release hydrogen from 18H-DBT-OLi (11.514 kcal/mol) was smaller than that from 18H-DBT (12.574 kcal/mol). In the hydrogen-releasing process, the rate-determining steps for the dehydrogenation of 18H-DBT and 18H-DBT-OLi were the 12H-DBT → 10H-DBT + H₂ and 12H-DBT-OLi → 10H-DBT-OLi + H₂ steps, respectively. Furthermore, the charge distribution of 18H-DBT and 18H-DBT-OLi was also explored.     

The consequence of silicon additive in isothermal decomposition of hydrides LiH,NaH, CaH2 and TiH2

The study focuses on hydrogen desorption characteristics of lithium hydride (LiH), sodium hydride (NaH), calcium hydride (CaH₂), and titanium hydride (TiH₂) which permits a possible path regarding challenging goals of US DOE standards. This research reported the consequences of enrichment in hydrogen uptake 7.02 wt% in lithium hydride, 7.71 wt% in sodium hydride, 5.91 wt% in calcium hydride, and 5.00 wt% in titanium hydride using silicon as an additive when evaluated with the help of volumetric technique. The ball milling process with silicon additive for LiH, NaH, CaH₂, and TiH₂ shows depletion in dehydrogenation temperatures 523 K, 453 K, 488 K, and 463 K respectively. Similarly, the reduction in the activation energies reported due to ball milling process with silicon additive are 37 kJ/mol for lithium hydride, 42 kJ/mol for sodium hydride, 56 kJ/mol for calcium hydride and 45 kJ/mol for titanium hydride compared with crystalline powder samples of the respective materials. The outcome of Fourier-transform infrared spectroscopy of milled hydride samples after decomposition intimate rapid decrease in transmittance intensities due to hydrogen release because of the destabilization effect caused by silicon additive. The porosity and sponginess in high-resolution Transmission electron microscopy images after dehydrogenation reveals the hydrogen desorption from the sample materials.     

High‐pressure hydrogen storage properties of TixCr1 − yFeyMn1.0 alloys

Ti_xCr_{1 ? y}Fe_yMn_1.0 (x = 1.02, 1.05, 1.1, 0.05 ≤ y ≤ 0.25) alloys were prepared by plasma arc melting and annealing at 1273 K for 2 hours. The XRD results show that the main phase of all alloys is the C14 type Laves phase, and a little secondary phase exists in a mixture of the binary alloy phase. The lattice parameters increase with Ti super‐stoichiometry ratio increasing, whereas smaller lattice parameters emerge with increasing Fe stoichiometry content. Additionally, as the Ti super‐stoichiometry ratio decreases, the pressure‐composition‐temperature measurements indicated that hydrogen absorption and desorption plateau pressures of Ti_xCr_0.9Fe_0.1Mn_1.0 (x = 1.1, 1.05, 1.02) alloys increase from 3.15, 0.67, to 5.94, 1.13 MPa at 233 K, respectively. On the other hand, with the Fe content increasing in Ti_1.05Cr_{1 ? y}Fe_yMn_1.0 (0.1 ≤ y ≤ 0.25) alloys from 0.1 to 0.25, the hydrogen desorption plateau pressures increased from 1.41 to 2.46 MPa at 243 K. The hydrogen desorption plateau slopes reduce to 0.2 with Ti super‐stoichiometry ratio decreasing to 1.02, but the alloys are very difficult to activate for hydrogen absorption and cannot activate when the Fe substituting for Cr exceeds 0.2. The maximum hydrogen storage capacities were more than 1.85 wt% at 201 K. The reversible hydrogen storage capacities can remain more than 1.55 wt% at 271 K. The enthalpy and entropy for all hydride dehydrogenation are in the range of 21.0 to 25.5 kJ/mol H₂ and 116 to 122 J mol^?1 K^?1, respectively. Our results suggest that Ti_1.05Cr_0.75Fe_0.25Mn_1.0 alloy with low enthalpy holds great promise for a high hydrogen pressure hybrid tank in a hydrogen refueling station (45 MPa at 333 K), and the other alloys of low cost may be used for a potable hybrid tank due to high dissociation pressure at 243 K and high volumetric density exceeding 40 kg/m³.