Hydrogen Storage Properties Research Articles

Studies on hydrogen storage properties of TiVFeNi, (TiVFeNi)95Zr5 and (TiVFeNi)90Zr10 high entropy alloys

The major issues associated with High Entropy Alloys (HEAs) as hydrogen storage material are the activation of these alloys and low storage capacity. The aim of the present investigation is to reduce the activation process and increase the hydrogen storage capacity of TiVFeNi-based HEAs. We investigated the effect of different Zr content on the hydrogen storage properties of TiVFeNi-based HEAs. Four different Ti25V25Fe25Ni25, (TiVFeNi)95Zr5, (TiVFeNi)90Zr10, and (TiVFeNi)80Zr20 HEAs were synthesized through mechanical alloying. The as-synthesized Ti25V25Fe25Ni25 alloy possessed a mixture of bcc and fcc phases. However, the as-synthesized (TiVFeNi)95Zr5 and (TiVFeNi)90Zr10 HEAs possessed bcc and fcc phases with a ZrFe2 intermetallic phase. We found that as the Zr content increases, alloys' hydrogenation behavior, improves due to the better activation process. Among the studied HEAs, in present studies, the highest hydrogen storage capacity is found to be 2.86 wt% at RT with 10 atm of hydrogen pressure for (TiVFeNi)90Zr10 HEA after 15 activation cycles at different temperatures. The high absorption value was found due to the formation of intermetallic ZrFe2, which acts as a bridging entity on the surface of the synthesized bcc and fcc phases. The present study provides a detailed insight into how the presence of the ZrFe2 phase reduces the activation process as well as enhances the hydrogenation properties of TiVFeNi-based HEAs.

Advancing our understanding of the effect of Al/Mo substitution in the TiVNb alloy on the hydrogen storage properties

The refractory body-centered cubic (bcc) high entropy alloys (HEAs) have shown large hydrogen uptake around 2.0 H/M, but challenges remain, the most important being the high stability of the hydrides, which requires high desorption temperatures. In this work, we reported an efficient hydride destabilization with the addition Al/Mo as non-hydride forming elements in the ternary TiVNb alloy. The alloys in the Alx(TiVNb)1-x-yMoy (x = 0–0.20; y = 0–0.25) system were successfully synthesized with a single-phase bcc structure and decreasing lattice parameters as Al/Mo content increases. Pressure-composition isotherms curves reveals that the addition of Al/Mo destabilizes the hydride formation, and this could be attributed to multifactorial effects. The hydrogen uptake of the alloys is strongly associated with the amount of Al/Mo in the TiVNb, decreasing less drastically with Mo than with Al. The temperature of the phase transition during desorption strongly decreases with the Al/Mo content, in agreement with thermodynamic destabilization. Therefore, the present results demonstrate that the addition of Al/Mo to refractory HEAs can enhance the design of high-capacity alloys with tunable stability.

High entropy alloys for hydrogen storage applications: A machine learning-based approach

Hydrogen is a clean energy carrier and has potential applications in energy storage, power generation, and transportation. This study explores the efficient and safe storage of hydrogen, particularly through solid-state methods using high entropy alloys (HEAs). HEAs have garnered attention for their versatility in tailoring properties for hydrogen storage. The integration of Machine Learning (ML) in designing HEAs offers an expedited approach, analyzing datasets and predicting material properties to enhance storage capacity, kinetics, and stability. Despite significant progress, the study acknowledges certain research limitations, particularly its relatively narrow focus on applying ML to HEAs for hydrogen storage. One of the biggest challenges with HEAs is their complexity, which.necessitates larger datasets to develop accurate predictive models. Collecting and analyzing existing HEA data for hydrogen storage using ML techniques is the main objective. Using algorithms like support vector regression (SVR), K-nearest (KNN), and random forest (RF), hydrogen-to-metal ratio (H/M) and valence electron configuration (VEC) are accurately predicted. The study proposes alloys with potential for HEA formation, identifying 741 with quaternary and 631 with quinary HEAs. These compositions are newly proposed and do not yet exist. Out of these, 774 HEAs are identified as potential candidates for hydrogen storage applications. Applying ML techniques, the selection process is more efficient, reducing the dependency on time-consuming experiments and making it easier to discover promising candidates.

Unraveling the hydrogen storage features of A5B19-type La0.67R0.05Y0.13Mg0.15Ni3.70Al0.15 (R = La, Ce, Nd, Sm, Gd) alloys

In this work, we demonstrate the substitutional effect of typical A-side elements of Ce, Nd, Sm, and Gd on the crystal structure and hydrogen storage properties of an A5B19-type La0.72Y0.13Mg0.15Ni3.70Al0.15 alloy aiming to provide further design for enhancing the commercial application of RE–Mg–Ni-based alloys for nickel-metal hydride (Ni/MH) batteries. The results reveal that Ce substitution significantly improves discharge ability at higher rates, delivering 283.3 mAh g−1 at 5C and 183.7 mAh g−1 at 10C, which present increases of 16.7% and 44.0% over the unsubstituted alloy, respectively. Additionally, Sm substitution effectively extends the alloy's cycling life, retaining 66.2% capacity after 500 cycles, representing a 14.4% increase compared to the original alloy. Moreover, the substitution of Nd increases the hydrogen storage capacity from 1.23 wt% to 1.50 wt%, while Gd reduces plateau hysteresis and slope factor during (de)hydrogenation.

Density functional analysis of structural, mechanical, electronic, and hydrogen storage properties of thermodynamically stable lead-free hydrides [formula omitted](X = Cs, Fr): A perspective of clean energy and fuel

A density functional theory based calculations are performed to investigate structural, hydrogen storage, mechanical, electronic and thermodynamical properties of lead-free hydride perovskites XGeH3 (X=Cs, Fr). The optimized lattice constant and hence volume against the minimum energy is obtained and found to be 4.176 Å and 4.184 Å for CsGeH3 and FrGeH3 respectively. The gravimetric and volumetric hydrogen storage capacity of 1.43% and 1.00%, 72.81(g.H2/L) and 73.21(g.H2/L) for CsGeH3 and FrGeH3 respectively. The density of states and electronic band structure predicted the metallic nature of both hydrides which was affirmed by the Fermi Surfaces. The calculation of Poisson’s, Pugh’s ratio and Cauchy’s pressure suggested their brittle nature. The Debye temperature decreases with the increase of temperature while volume and entropy increase by increasing applied temperature. The present study shows the potential of lead-free hydride perovskites in hydrogen storage applications due to rather suitable gravimetric hydrogen capacity and high stability.

Experimental and Mathematical Investigation of Hydrogen Absorption in LaNi5 and La0.7Ce0.1Ga0.3Ni5 Compounds

In the present study, the hydrogen-absorption properties of the LaNi5 and the La0.7Ce0.1Ga0.3Ni5 compounds were determined and compared. This work is therefore divided into two parts: an experimental part that presents and discusses the kinetics and isotherms of hydrogen absorption in the two compounds at two different temperatures (298 K and 318 K). In addition, the temperature variations inside the hydride bed were determined. In the second section, the experimental isotherms were compared to a numerical model processed using statistical physics. Following that, thanks to the perfect agreement between the experimental data and the proposed model, the stereographic and energetic parameters associated with the hydrogen absorption reaction, such as the number of hydrogen atoms per receptor site (n1, n2), the densities of the sites (Nm1, Nm2), the half-saturation pressures (P1, P2) and the absorption energies (ΔE1, ΔE2) for each receptor site, were calculated. All of these parameters are acquired by making numerical adjustments to the experimental data. Thermodynamic functions, such as internal energy and Gibbs energy, which regulate the absorption process, were then identified using these parameters. For both compounds, all of the aforementioned were compared and discussed in relation to initial temperature and pressure. The results demonstrated that the hydrogen-storage properties in LaNi5 are enhanced by more than 30% of stored mass and kinetics when Ce and Ga are substituted at the La sites.

Regulation of nanoscale Mg/V incoherent interface interactions to enhance hydrogen storage properties in Mg/V multilayer films

Magnesium-based materials offer a promising, cost-effective, and high-capacity solution for hydrogen storage. However, their slow kinetics and elevated absorption/desorption temperatures limit their large-scale application. In this study, a series of Mg1-x/Vx (x = 0.05, 0.10, 0.15, 0.20) multilayer films were designed and fabricated using an ultra-high vacuum magnetron sputtering technique. Transmission electron microscopy (TEM) analysis revealed the presence of a discontinuous nanoscale V single-phase interlayer between the Mg layers, confirming the successful formation of Mg/V multilayer films. The surface of the deposited films predominantly consists of hexagonal particles of varying sizes stacked upon one another. Upon hydrogenation, tetragonal rutile structures of MgH2 and V2H were formed. The Mg0.95V0.05 film absorbed 6.40 wt% hydrogen within 15 min at 150 °C and desorbed 0.34 wt% hydrogen within 1.8 h at the same temperature, with an initial dehydrogenation temperature of 79 °C. The activation energies for hydrogen absorption and desorption were estimated to be 60 ± 7 and 140 ± 10 kJ/mol H2, respectively, significantly lower than the corresponding values of 100 and 160 kJ/mol H2 for conventional pure Mg/MgH2. The enhanced hydrogen absorption performance was attributed to the catalytic effect of nanocrystalline V at the Mg/V incoherent interface, while the improved desorption performance was due to the synergistic catalytic effect of nanocrystalline V2H at the MgH2/V2H incoherent interface. DFT calculations indicated that the interaction at the Mg/V incoherent interface promoted H atom adsorption and diffusion, significantly enhancing the hydrogenation and dehydrogenation performance of the multilayer films.

Facilitated hydrogen storage properties of MgH2 by Ni nanoparticles anchored on Mo2C@C nanosheets

Magnesium hydride (MgH2) holds promise as a hydrogen storage material, but its practical application is impeded by high desorption temperatures and slow kinetics, presenting substantial challenges. Herein, an efficient approach is proposed to synthesize Mo2C@C nanosheets-supported Ni nanoparticles (Ni/Mo2C@C-2) materials, which can operate as a highly efficient catalyst to enhance hydrogen desorption of MgH2. The ball-milled MgH2–7.5 wt% Ni/Mo2C@C-2 demonstrates prominent hydrogen desorption kinetics with an activation energy (Ea) of 97.22 kJ mol−1, alongside remarkable cycling stability, maintaining a capacity retention of 97.8% after 20 cycles. Consequently, the results reveal that the improvement of hydrogen storage properties for MgH2 can be attributed to the synergistic effect of the in-situ generated Mg2NiH4 with highly dispersion, the sustained Mo2C nanosheets, and highly graphitized carbon. This work provides a reliable strategy for constructing polyoxometalates derivatives to facilitate the hydrogen desorption and cycling of MgH2.

Microstructure, hydrogen storage properties, and thermodynamic characterization of ball-milled Mg90Ni5Y5 alloy

The hydrogen storage properties of the Mg90Ni5Y5 alloy were studied, which was prepared by vacuum electromagnetic induction melting and ball milling. The microstructure and phase evolution of the ball-milled alloys during the process of hydrogen absorption and desorption were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The alloys hydrogen storage properties were measured by semi-automatic Sievert instrument. Results show that the hydrogenated sample was composed of MgH2, Mg2NiH4 and YH3 phases. After dehydrogenation, Mg2NiH4 and MgH2 phases were completely decomposed, and YH3 could only be decomposed into YH2. After 2 cycles of adsorption dehydrogenation, the alloy was completely activated, and the maximum hydrogen desorption capacity was about 5.1 wt %. According to the Arrhenius equation, the ball-milled alloy activation energy of the dehydrogenation reaction of is only 75.7 kJ/mol.

Effects of amorphization and interlayer on the hydrogen storage properties of multi-component Ti-V-Zr-Nb-M (M = Mg, Al) alloy films

In this work, hydrogen storage properties of the multi-component amorphous Ti-V-Zr-Nb-M (M = Mg, Al) alloy films as prepared by a magnetron sputtering method are studied. In addition, the impact of different Pd layer numbers on the microstructure, morphology and hydrogen storage properties of the Ti-V-Zr-Nb alloy film is also investigated. The film retains an amorphous structure after hydrogen absorption and desorption, the hydrogenation capacity of the amorphous Ti-V-Zr-Nb alloy film reaches about 0.50 wt% at room temperature without activation and can release 0.18 wt% hydrogen at 250 ℃, the addition of lightweight elements Mg and Al improves the hydrogen absorption and release properties. Secondly, when the inserted Pd interlayers are increased from 2 to 10 layers, the dehydrogenation properties of Ti-V-Zr-Nb amorphous films are improved. The reduction in film thickness reduces the film sizes, and together with the Pd layers accelerates the dissociation and diffusion of hydrogen, both of these characteristics contribute to the improvement of dehydrogenation properties.

Effect and mechanism of graphite addition on microstructures and hydrogen storage properties of Mg–Y–Zn alloy

In this work, the Mg-9.1Y-1.0Zn alloy are prepared by semi-continuous casting, and then mechanical milled with graphite. The microstructures and hydrogen storage properties of milled composite are systematically studied. The results show that the as-cast Mg-9.1Y-1.0Zn alloy exhibits serious agglomeration after milling. The addition of graphite significantly restrains the agglomeration of alloy and further refines the particles. Compared with as-cast Mg-9.1Y-1.0Zn alloy, the hydrogen storage properties of Mg-9.1Y-1.0Zn alloy milled with graphite is greatly improved. It needs only three times activation to be fully activated and its maximum hydrogen storage capacity is about 6.7 wt%. Besides, its dehydrogenation activation energy is decreased by about 40 kJ mol−1 relative to as-cast Mg-9.1Y-1.0Zn alloy. During hydrogen absorption and desorption, the stable YH2 hydride is generated by the disproportionation decomposition of LPSO phase. The graphite and in-situ formed YH2 present the synergistic confinement and catalysis effects on the milled Mg–Y–Zn alloy particles, which is conductive to the enhancment of hydrogen storage properties.

Fluorinated carbon tubes as carriers for MgH2 with enhanced hydrogen storage performances

Heterogeneous elements doping in carbon materials has been an effective strategy to promote their chemical properties. In this work, fluorine atoms with strong electronegativity are doped on the surfaces of bamboo-shaped carbon nanotubes (FBCNTs) which serve as carriers for MgH2 nanoparticles (MgH2@FBCNTs) to improve the reversible hydrogen storage properties. Detailed experiments indicate that MgH2@FBCNTs begin to release hydrogen at 197.8 °C, and can release 5.36 wt% H2 at 275 °C within 30 min, and quickly absorb 3.48 wt% H2 at 100 °C under hydrogen pressure of 80 bar. In addition, cycling performance is significantly enhanced in the case of fluorinated Mg-based system. The mechanism of fluorine catalysis is mainly ascribed to the formation of C-F bonds, accelerating the dissociation or combination of hydrogen atoms, offering more active sites for the de/hydrogenation and preventing the growth and agglomeration during cycling. It is also important that fraction of F is consumed and form new phases MgF2/MgF2-xHx, which offers another pathway for H atoms.

Highly reversible Mg-containing multicomponent high-entropy alloys for electrochemical hydrogen storage applications

Magnesium containing high entropy alloys have gained attention recently as a potential material for hydrogen storage applications. In this work, five non-equiatomic compositions of MgTiZrNiAl HEAs were synthesized using a high-energy ball milling technique and electrochemically characterized for hydrogen storage performance. The concentrations of Mg and other constituent alloying elements are critical to achieving good storage capacity and other hydrogen storage properties. Interestingly, higher Mg atomic percent (40–50 at%) in the HEA matrix showed high gravimetric capacity, and increasing the constituent element like Ni has significantly enhanced the overall storage capacity, kinetics, and thermodynamic properties. Overall, 1 wt% of hydrogen was electrochemically stored with high reversibility, improved hydrogen diffusion coefficient, and anticorrosion ability.

Hydrogen Storage Properties of Metal-Modified Graphene Materials

The absence of adequate methods for hydrogen storage has prevented the implementation of hydrogen as a major source of energy. Graphene-based materials have been considered for use as solid hydrogen storage, because of graphene’s high specific surface area. However, these materials alone do not meet the hydrogen storage standard of 6.5 wt.% set by the United States Department of Energy (DOE). They can, however, be easily modified through either decoration or doping to alter their chemical properties and increase their hydrogen storage capacity. This review is a compilation of various published reports on this topic and summarizes results from theoretical and experimental studies that explore the hydrogen storage properties of metal-modified graphene materials. The efficacy of alkali, alkaline earth metal, and transition metal decoration is examined. In addition, metal doping to further increase storage capacity is considered. Methods for hydrogen storage capacity measurements are later explained and the properties of an effective hydrogen storage material are summarized.

Two-dimensional BC6Be: Reversible, high-capacity hydrogen molecule storage material predicted by first-principles calculations

The research was conducted to discover a material that can efficiently and effectively store hydrogen at appropriate conditions. Specifically, its focus was on examining the hydrogen storage properties of unaltered single-layer BC6Be using density functional theory techniques. The results revealed an intriguing phenomenon: H2 molecules spontaneously adhere to the BC6Be monolayer, exhibiting average adsorption energy spanning between −0.272 and −0.380 eV. Importantly, this adsorption is driven by physisorption, lacking any chemisorption bonding between the H2 molecule and the BC6Be surface, regardless of the interaction site. Noteworthy is the remarkable gravimetric and volumetric hydrogen storage capacities of the monolayer BC6Be, registering at 11.63 wt% and 108.5 g/L, respectively. Comparatively, the desorption temperature (TD) stands notably higher at around 247.15 K when juxtaposed with hydrogen's critical point (33.25 K). AIMD simulations were conducted to substantiate the results, confirming the adsorption of 12H2 molecules on BC6Be and verifying the system's stability. Overall, the findings of this work have shown the potential of the BC6Be monolayer as a highly promising material that offers efficient, reversible, and substantial hydrogen storage capabilities within real-world scenarios.

Lithium-modified B3C2P3 monolayer as a promising medium for reversible hydrogen storage

Although two-dimensional (2D) materials have been extensively studied as hydrogen storage media, the search for 2D materials with high hydrogen storage capacity and reversible hydrogen storage properties at room temperature remains challenging. In this context, B3C2P3 monolayer with Li modification is studied systematically by first-principles calculation. We find that Li-modified B3C2P3 monolayer can achieve a high hydrogen storage capacity of 8.99 wt% with an average adsorption energy of −0.23 eV/H2. Three of the H2 molecules are adsorbed around the Li atom, while the fourth H2 molecule is adsorbed above the buckled P atom due to the constricted space around the Li atom. Not only metal Li atoms but also the buckled substrate plays an important role in hydrogen adsorption, indicating that buckled 2D materials are more interesting and promising in hydrogen storage than flat 2D materials. The average desorption temperature (TD) calculated by van't Hoff formula is 293.84 K, which is very close to room temperature. In addition, at room temperature, the structure of hydrogen adsorption is stable at a low pressure of 3.21 MPa, suggesting a broad application prospect of in reversible hydrogen storage.

Synergistic integration of nickel, porous silicon, and thermally reduced graphene oxide for solid‐state hydrogen energy storage

AbstractSolid‐state hydrogen storage using metal hydrides offers the potential for high energy storage capacities. However, the requirement for high‐temperature operations (above 400°C) and challenges with heat exchange are significant drawbacks. From this perspective, adsorption on porous materials presents a viable solution to these challenges. Carbon nanostructures, such as graphene and graphene oxide (GO) derivatives, are well‐suited for hydrogen storage because of their lightweight nature, low density, and large surface area. However, the primary obstacle for practical applications is the poor storage capacity of carbon nanostructures under ambient conditions. Utilizing a cost‐effective transition element such as nickel as a catalyst offers significant potential for storing hydrogen in atomic and molecular forms by invoking the spillover mechanism. Thermally reduced graphene oxide (TrGO) modifies the surface, providing abundant active sites that attract hydrogen effectively. Porous silicon (PS) enhances the surface properties of graphene sheets, attracting hydrogen to the surface. The current study assesses a synthesized TrGO, PS, and Ni composition to leverage their individual properties for hydrogen storage. Field‐emission scanning electron microscopy examines the sheet structure of TrGO (used as the host material) and the incorporation of PS and Ni on its surface. The calculated specific surface area of TrGO is ~450 m2 g−1. X‐ray diffraction is used to identify the various phases in the composition, while Raman spectroscopy measures the degree of disorder within the composition. The pressure‐composition isotherms reveal hydrogen storage capacities of ~6.53 wt% for the TrGO + PS composition and ~2.43 wt% for the TrGO + PS + Ni composition. Despite the decrease in weight percentage of TrGO + PS + Ni due to the higher Ni content, dissociation enhances the adsorption rate from 0.35 to 0.53 wt% h−1.

Influence of doped ions on the electrochemical hydrogen storage properties of LaFeO3-based solid solutions

Perovskite oxides LaFeO3 has been considered as one of the most promising candidates as the negative electrode material of Ni/MH batteries, due to its advantages such as low cost, outstanding corrosion resistance and environmentally friendly. Nevertheless, the low electrical conductivities and poor specific capacities are the main obstacles of developing this material to practical application. Doping is an effective method to solve these problems. In this paper, nanosized LaFeO3-based solid solutions doped with Co3+, Mn3+, and Li+ ions were synthesized via sol-gel method, and the contents of the doped ions are set as 0.10. The substitution positions of the doped ions were discussed. The microstructure tests revealed that the doped samples were single phase structures, and the crystallite sizes of the doped samples were smaller than that of the undoped LaFeO3. The dispersion degrees of the doped samples were improved. The results of the spectra tests demonstrated that the doped ions decreased the band gap energies, the Co3+ and Mn3+ ions influenced the frequencies of Fe–O stretching vibrations, and partial replacement of La3+ ions by Li+ ions induced the shift of vibration modes of the La–O bond. Electrochemical hydrogen storage measurements showed that the doped samples possess significantly better properties than that of the undoped LaFeO3. Thereinto, the maximum discharge capacity of the Co3+ ion doped sample reached to 414 mAh/g at the 14th cycle and remained stable at around 400 mAh/g within the following cycles. Kinetic results further proved that the doped samples showed better performances. The hydrogen storage properties of doped LaFeO3 are closely associated with the contents of the oxygen vacancies and defects in the lattice of samples. In addition, the characteristics of the doped ions also play important roles in improving the hydrogen storage properties of the LaFeO3-based oxides.

Effects of Ti substitution by Zr, on the microstructure and hydrogen storage properties OF Ti2-xZrxCrV (x = 0.5, 1, 1.5, 2) alloys

The effect of the substitution of Ti by Zr on the crystal structure, microstructure, and first hydrogenation behavior of Ti2-xZrxCrV where X = 0.5, 1.0, 1.5, and 2.0 have been investigated. The samples were synthesized by arc-melting and characterized by X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The hydrogenation capacity was measured using a home-made Sieverts apparatus. Pure-Ti2CrV crystallizes in a body-centered cubic structure (BCC). Substitution of Ti by Zr leads to the appearance of a secondary phase, namely a C15 Laves phase for the Ti-containing samples, and C15 Laves phase plus a Zr-rich phase for the X = 2.0 sample. The substitution of Ti by Zr increased the lattice parameters in both phases for all samples. Increasing Zr content made the first hydrogenation faster but reduced the hydrogen capacity.

Modification of the hydrogen compression properties of Zr–Fe–Cr–V-based alloys through Ti doping

Hydrogen refueling stations typically rely on compressors to increase the pressure of hydrogen received from long-tube trailers, enabling efficient refill of hydrogen storage tanks. However, mechanical hydrogen compressors are unable to effectively harness residual hydrogen below 6 MPa in long-tube trailers. Herein, we developed a ZrFe2-based hydrogen compression alloy to enhance the hydrogen pressure that meets the input pressure requirement of mechanical hydrogen compressors. Specifically, the co-substitution of Cr and V for Fe was conducted to reduce the plateau slope and hysteresis, and Ti was introduced to partially substitute Zr to regulate the plateau pressure. The effects of Ti on the structure and hydrogen storage properties of Zr–Fe–Cr-based alloys have been investigated by first-principles calculations, wherein Zr1-xTixFe1.7Cr0.2V0.1 (x = 0, 0.1, 0.2, 0.3, 0.4) alloys were designed and synthesized. The optimized Zr0.8Ti0.2Fe1.7Cr0.2V0.1 alloy provided a hydrogen absorption capacity of 1.22 wt% under 3.88 MPa H2 pressure at 300 K and achieved an effective hydrogen compression capacity of 1.07 wt% at 355 K at an H2 desorption pressure of 6.36 MPa. This advancement holds great promise for the efficient utilization of residual hydrogen at approximately 6 MPa in long-tube trailers, thus leading to a significant improvement in hydrogen transportation efficiency.