MgH2 Hydride Research Articles

MXenes and MXene-Based Metal Hydrides for Solid-State Hydrogen Storage: A Review.

Hydrogen-driven energy is fascinating among the everlasting energy sources, particularly for stationary and onboard transportation applications. Efficient hydrogen storage presents a key challenge to accomplishing the sustainability goals of hydrogen economy. In this regard, solid-state hydrogen storage in nanomaterials, either physically or chemically adsorbed, has been considered a safe path to establishing sustainability goals. Though metal hydrides have been extensively explored, they fail to comply with the set targets for practical utilization. Recently, MXenes, both in bare form and hybrid state with metal hydrides, have proven their flair in ascertaining the hydrides' theoretical and experimental hydrogen storage capabilities far beyond the fancy materials and current state-of-the-art technologies. This review encompasses the significant accomplishments achieved by MXenes (primarily in 2019-2024) for enhancing the hydrogen storage performance of various metal hydride materials such as MgH2, AlH3, Mg(BH4)2, LiBH4, alanates, and composite hydrides. It also discusses the bottlenecks of metal hydrides for hydrogen storage, the potential use of MXenes hybrids, and their challenges, such as reversibility, H2 losses, slow kinetics, and thermodynamic barriers. Finally, it concludes with a detailed roadmap and recommendations for mechanistic-driven future studies propelling toward a breakthrough in solid material-driven hydrogen storage using cost-effective, efficient, and long-lasting solutions.

Structural, electronic, optical and elastic properties of Mg3TH7 (T=Mn, Tc and Re) complex hydrides: First-principles calculations

The structural, electronic, optical and elastic properties of Mg3TH7 (T=Mn, Tc, Re) complex hydrides have been investigated by using the density functional theory ‘DFT’ within the generalized gradient approximation ‘GGA’ parameterized by the Perdew, Burke and Ernzerhof ‘PBE’. The optimized lattice constants, atomic positions and interatomic distance are in good agreement with both theoretical results and experimental data available in the literature. Band structure, densities of states ‘DOS’, optical properties, and elastic constants have been calculated. The obtained results of elastic properties were compared with those of the simplest Mg-based hydride MgH2. More importantly, it is found that, the energy band gap is highly augmented when Mn atom is replaced by Re, but it is less pronounced when Re atom is replaced by Tc. From elastic constants calculations, it is noted that MgH2, Mg3MnH7, Mg3TcH7 and Mg3ReH7 compounds are mechanically stable and are brittle. In addition, the polycrystalline elastic properties such as bulk modulus, shear modulus, Young modulus and Poisson’s ratio were also determined by the Voigt-Reuss-Hill, ‘VRH’ approximation. It was found that the bulk modulus of complex hydrides Mg3TH7 (T=Mn, Tc and Re) are higher than that of MgH2 and increases with increasing atomic number of element (Mn, Tc, Re) in the sequence (B) Mg3MnH7 < (B) Mg3TcH7 < (B) Mg3ReH7. The shear anisotropy, linear bulk modulus and percentage anisotropy in compressibility and shear were also determined and discussed in details. Finally, Debye temperatures were calculated and discussed.

In-situ precipitation of ultrafine Mg2Ni particles in Mg-Ni-Ag metal fibers and their hydrogen storage properties

The intermetallic compound Mg2Ni shows improved hydrogen de-/absorption kinetics and a lower desorption temperature compared to pure Mg. However, the coarse Mg2Ni phase and its limited hydrogenation capacity restrict the application of the Mg2Ni alloy. In this study, an attempt was made to prepare Mg-Ni alloy fibers with a higher Mg content and a well-distributed Mg2Ni catalytic phase using the melt extraction (ME) method, and a unique metallic glass fiber was formed. With pre-annealing at 350 °C in a vacuum, uniformly dispersed Mg2Ni nanoparticles are in-situ formed, the phase transition is revealed to be metallic glass → Mg6Ni → Mg2Ni + Mg. About 1.5 wt% of hydrogen can be absorbed by the Mg-Ni fibers at 50 °C, and it is completely released in 8.8 min at 225 °C. Both the JMA and Kissinger models were utilized to accurately characterize the dehydrogenation activation energy, and the values of 90.4 and 95.8 kJ/mol were obtained, respectively. The hydrogen desorption process involves two distinct processes, the decomposition of Mg2NiH4 nanoparticles and MgH2 hydride in sequence, with dehydrogenation enthalpy changes of 64.5 and 78.2 kJ/mol, respectively. After hydrogen absorption and desorption cycles, a loose structure forms around the Mg2Ni nanoparticles. This structure serves as an efficient nucleation site for hydrides and provides diffusion paths for H atoms.

Density-functional quantum computations on bandgap engineering and tuning of optoelectronic properties of MgH2 via Mo doping: Prospects and potential for clean energy hydrogen-storage fuel and optoelectronic applications

With the increasing depletion of conventional energy sources and their detrimental environmental hazards, it is imperative to search for sustainable alternative clean energy sources. In the recent decades, hydrogen has emerged as potential source of clean energy. One of the potential alternatives to achieve the objective is the designing and characterization of materials for hydrogen-storage energy applications. In this regard, metal-bearing hydrides are the most promising candidates. For instance, magnesium-bearing hydrides are the focus of current research work owing to high hydrogen capacity of 7.6 wt%. In this paper, we first time report density functional-based quantum theoretical analysis to explore the potential of Mo-doped magnesium hydrides MgH2:Mo for optoelectronic and hydrogen-storage applications. For the quantum computations of the required optoelectronics and energy storage properties, we employed all-electron methods within generalized gradient approximation (GGA). Besides applying GGA approximation to account for the electronic correlated effects, we employed the Hubbard potential U (= 4 eV) for onsite repulsive Coulomb force. We predict that 10% doping by weight of Mo into MgH2 suppresses its insulating band gap of 4.9 eV to semiconducting band gap of order 3.15 eV for spin up and 0.15 eV for spin down. As such the doping of Mo can tune the the bandgap, structural, electronic and optoelectronic properties of MgH2 considerably for potential applications.

Hydrogen Diffusion on, into and in Magnesium Probed by DFT: A Review

Hydrogen is an energy carrier that can be a sustainable solution for alternative energy with zero greenhouse gas emissions. Hydrogen storage is a key point for hydrogen energy. Metals provide an access for safe, controlled and reversible hydrogen storage and release. Magnesium, due to its outstanding hydrogen storage capacity, high natural abundance, low cost and non-toxicity is one of the most attractive materials for hydrogen storage. The economic efficiency of Mg as a hydrogen accumulator is limited by its sluggish hydrogen sorption kinetics and high stability of its hydride MgH2. Many attempts have been made to overcome these shortcomings. On a microscopic level, hydrogen absorption by metal is a complex multistep process that is impossible to survey experimentally. Theoretical studies help to elucidate this process and focus experimental efforts on the design of new effective Mg-based materials for hydrogen storage. This review reports on the results obtained within a density functional theory approach to studying hydrogen interactions with magnesium surfaces, diffusion on Mg surfaces, into and in bulk Mg, as well as hydrogen induced phase transformations in MgHx and hydrogen desorption from MgH2 surfaces.

Effects of nanostructures on the hydrogen storage properties of MgH2 - A first principles study

Hydrogen storing properties of nanostructured MgH2 in two phases are investigated through first principles study using density functional theory. It is shown computationally that the hydrogen storage properties of MgH2 are significantly enhanced by proper engineering of the nanostructure. The nanoparticle clusters of MgH2 show linear behavior in adsorbing the hydrogen molecules and the binding energy values lie in the range −0.12eV to - 0.15eV. The MgH2 nanowires show non-linearity in hydrogen adsorption. For certain configuration, the hydrogen molecules binding energy values lie in the useful range (−0.15eV –> −0.27eV). Over all, the nanostructured MgH2 exhibits good hydrogenation and reduced desorption temperature. Selected configuration of the light metal free standing hydride MgH2 nanostructure, theoretically shows high hydrogen storage capacity which with suitable substrate is bound to reduce to the useful range of 6.4–8.8 wt%.

The Effect of High-Energy Ball Milling Conditions on Microstructure and Hydrogen Desorption Properties of Magnesium Hydride and Single-Walled Carbon Nanotubes

Magnesium hydride is considered to be one of the most promising hydrogen storage materials, although it nevertheless has some problems, such as the high value of the activation energy of hydrogen desorption. To solve this problem, some scientists have proposed adding nanocarbon materials, in particular carbon nanotubes, to magnesium hydride. Currently, a detailed understanding of the mechanisms of obtaining composites based on magnesium hydride and carbon nanotubes is lacking, as is our understanding of the effect of nanocarbon additives on the activation energy and temperature of hydrogen desorption depending on the parameters of the composite synthesis. In addition, the data obtained at various values of milling parameters are very different, and in some works the effect of carbon nanomaterials on the hydrogen properties of magnesium hydride was not confirmed at all. Thus, it is important to determine the effect of nanocarbon additives on the properties of hydrogen storage of magnesium hydride under various milling parameters. This work is devoted to the study of the effect of nanocarbon additives on magnesium hydride and the determination of the dependences of the hydrogen desorption temperature and activation energy on the synthesis parameters. Composite powders containing MgH2 with 5 wt.% single-walled carbon nanotubes (SWCNT) were prepared using a planetary ball mill. The milling was carried out at various milling speeds, namely 300, 660, and 900 rpm. Results suggested that the structure of the nanotubes is preserved with prolonged grinding of magnesium hydride and SWCNT in a ball mill for 180 min at a relatively low grinding speed of 300 rpm. The composite obtained with these parameters has the lowest temperature of hydrogen desorption and an activation energy of H2 desorption of 162 ± 1 kJ/mol H2, which is 15% lower than that of the magnesium hydride MgH2 (189 ± 1 kJ/mol H2).

Improving hydrogen storage performance of Mg-based alloy through microstructure optimization

Different fast forging processes are used for microstructure optimization in an attempt to improve hydrogen storage in Mg-based composites obtained from a mixture of Mg-22 wt% Ni powders. First, fast forging is employed at room temperature to change the amount of structural defects, produce fine grains and modify crystallographic textures. The effects of such microstructure modifications (including the exact nature of phases) on the H-storage behavior are investigated. A Mg {0001} basal fiber texture develops upon fast cold forging, which facilitates the initial activation of hydrogenation while, owing to the high stability of the MgH2 hydride, the kinetics of desorption remains rather slow. Second, to promote hydrogen desorption, forging is conducted at elevated temperature to form Mg2Ni phase. Interestingly, for this sample, faster desorption is recorded while slower absorption kinetics is obtained due to the occurrence of dynamic recrystallization inducing weaker texture and lower amount of structural defects. Third, annealing followed by cold forging is used to produce a microstructure consisting of fragmented Mg2Ni lamellae embedded in a textured Mg-matrix. Using this third approach, both hydrogen absorption and desorption kinetics are found to be markedly improved.

Enhancing (de)hydrogenation kinetics properties of the Mg/MgH2 system by adding ANi5 (A = Ce, Nd, Pr, Sm, and Y) alloys via ball milling

Magnesium (Mg)-based alloys have already been widely studied as the hydrogen storage materials because of their high reversible hydrogen storage capacity, low cost, light weight, etc. However, the poor de/hydrogenation kinetic properties dramatically hinder the practical applications. In this work, the MgH2-ANi5 (A = Ce, Nd, Pr, Sm, and Y) composites were prepared by a high-energy ball milling method, which can effectively refine the particle size thus improving the kinetic properties. Experimental results reveal that the MgH2-ANi5 composites mainly consist of Mg2NiH4, MgH2 and rare earth (RE) hydride, which will be dehydrogenated to form Mg2Ni, Mg and stable RE hydride reversibly. Accordingly, the as-milled MgH2-ANi5 (A = Ce, Nd, Pr, Sm, and Y) composites with various A-elements can respectively contribute to a reversible hydrogen storage capacity of 6.16 wt%, 5.7 wt%, 6.21 wt%, 6.38 wt%, and 6.5 wt% at a temperature of 300 °C, and show much better kinetic properties in comparison to the pure MgH2 without any additive. In-situ formed Mg2Ni and stable RE hydride (such as CeH2.73 and YH2) might act as effective catalysts to significantly improve the hydrogen storage properties of MgH2. The present work provides a guideline on improving the kinetic properties of the Mg-based hydrogen storage alloys.

Hydrogen Sorption Properties, Thermal Stability and Kinetics of Hydrogen Desorption From the Hydride Phase of The MgH2 of a Mechanical Alloys of Magnesium with Ti, Ni and Y

The mechanical alloys-composite MАs (Mg +10 % wt.Ti + 5 % wt.Y and Mg +10 % wt.Ni + 5 % wt.Y) were synthesized. The phase content, microstructure, the thermal stability, kinetics of hydrogen desorption from the MgH2 hydride phase of the obtained MAs were studiedby using XRD, SEM, TDS methods. It has been established that the addition of Ti + Y and Ni + Y to magnesium leads to significant improvement in the kinetics of hydrogen desorption from the MgH2 hydride phase, which is evidenced by a significant reduction (in 6 and 15 times)in the time of release of all hydrogen from MA1 and MA2, respectively. Due to, Ti, Ni,Y alloying, the decrease in the thermodynamic stability of MgH2 is not found.

A first-principles theoretical study on the potential thermoelectric properties of MgH2 and CaH2

First-principles calculations, Boltzmann transport equations, and a modified Slack’s model were used to investigate the Seebeck coefficient S, electrical conductivity σ, and thermal conductivity κ of hydrides MgH2 and CaH2. As a result, a largest zT value around 0.38 and 0.55 at 1000 K could be achieved when carrier concentration n ∼ 1.7 × 1021 cm−3 and n ∼ 7.4 × 1020 cm−3 in the p-type MgH2 and CaH2, respectively. Higher zT values (>1) could be achieved by reduction of the high thermal conductivity. The results of our study gave a support that hydrides MgH2 and CaH2 could be promising as thermoelectric materials.

An Analytical Bond Order Potential for Mg-H Systems.

Magnesium-based materials provide some of the highest capacities for solid-state hydrogen storage. However, efforts to improve their performance rely on a comprehensive understanding of thermodynamic and kinetic limitations at various stages of (de)hydrogenation. Part of the complexity arises from the fact that unlike interstitial metal hydrides that retain the same crystal structures of the underlying metals, MgH2 and other magnesium-based hydrides typically undergo dehydrogenation reactions that are coupled to a structural phase transformation. As a first step towards enabling molecular dynamics studies of thermodynamics, kinetics, and (de)hydrogenation mechanisms of Mg-based solid-state hydrogen storage materials with changing crystal structures, we have developed an analytical bond order potential for Mg-H systems. We demonstrate that our potential accurately reproduces property trends of a variety of elemental and compound configurations with different coordinations, including small clusters and bulk lattices. More importantly, we show that our potential captures the relevant (de)hydrogenation chemical reactions 2H (gas)→H2 (gas) and 2H (gas)+Mg (hcp)→MgH2 (rutile) within molecular dynamics simulations. This verifies that our potential correctly prescribes the lowest Gibbs free energies to the equilibrium H2 and MgH2 phases as compared to other configurations. It also indicates that our molecular dynamics methods can directly reveal atomic processes of (de)hydrogenation of the Mg-H systems.

Hydride Reduction of BaTiO3 - Oxyhydride Versus O Vacancy Formation.

We investigated the hydride reduction of tetragonal BaTiO3 using the metal hydrides CaH2, NaH, MgH2, NaBH4, and NaAlH4. The reactions employed molar BaTiO3/H ratios of up to 1.8 and temperatures near 600 °C. The air-stable reduced products were characterized by powder X-ray diffraction (PXRD), transmission electron microscopy, thermogravimetric analysis (TGA), and 1H magic angle spinning (MAS) NMR spectroscopy. PXRD showed the formation of cubic products—indicative of the formation of BaTiO3–xHx—except for NaH. Lattice parameters were in a range between 4.005 Å (for NaBH4-reduced samples) and 4.033 Å (for MgH2-reduced samples). With increasing H/BaTiO3 ratio, CaH2-, NaAlH4-, and MgH2-reduced samples were afforded as two-phase mixtures. TGA in air flow showed significant weight increases of up to 3.5% for reduced BaTiO3, suggesting that metal hydride reduction yielded oxyhydrides BaTiO3–xHx with x values larger than 0.5. 1H MAS NMR spectroscopy, however, revealed rather low concentrations of H and thus a simultaneous presence of O vacancies in reduced BaTiO3. It has to be concluded that hydride reduction of BaTiO3 yields complex disordered materials BaTiO3–xHy□(x–y) with x up to 0.6 and y in a range 0.04–0.25, rather than homogeneous solid solutions BaTiO3–xHx. Resonances of (hydridic) H substituting O in the cubic perovskite structure appear in the −2 to −60 ppm spectral region. The large range of negative chemical shifts and breadth of the signals signifies metallic conductivity and structural disorder in BaTiO3–xHy□(x–y). Sintering of BaTiO3–xHy□(x–y) in a gaseous H2 atmosphere resulted in more ordered materials, as indicated by considerably sharper 1H resonances.

Thin films as model system for understanding the electrochemical reaction mechanisms in conversion reaction of MgH2 with lithium

Metal hydrides are promising high-capacity anode materials for Li-ion batteries but their conversion reaction with lithium suffers from low reversibility at room temperature (RT). Irreversibility issues in magnesium hydride MgH2 thin films are investigated, as well-defined model system. Films are deposited over Cu current collectors by means of microwave plasma-assisted sputtering and coated with aluminum to minimize formation of passivating MgO native oxide. Structural and chemical properties of the electrodes have been analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and electrochemical impedance spectroscopy (EIS). Galvanostatic cycling reversibility at RT and C/50 regime is limited to 25% in the first cycle for 1 μm thick films. The lithiation of the thin film is complete and doubles its thickness. Despite drastic volume changes, neither cracks, voids, nor detachment of the thin film from the substrate are noticed. Moreover, electronic resistivity decreases upon lithiation due to the formation of metallic Mg. The origin of irreversibility phenomena in MgH2 films is attributed to sluggish mass transport of species within the electrode at RT.

Enhanced hydrogen sorption kinetics of co-doped MgH2 hydrides

Double substituted MgH2 sorption kinetic is studied by combining density functional theory (DFT) and Kinetic Monte Carlo (KMC) simulations. The DFT calculations were performed to compute the energy barriers of the relevant elementary processes, which will be used as a database for the KMC simulations. The study provides a discussion of the mechanism behind the hydrogen reaction path on magnesium hydride (adsorption, dissociation, surface migration, penetration, and diffusion) as we took into account the density distribution of hydrogen atoms as well as the filling ratios, the diffusion time and finally the temperature. Based on the obtained results, the double substitution not only improves MgH2 stability and desorption temperature but also its adsorption and desorption kinetics. Among the studied systems Mg14ZnLiH32 exhibits the best results with the fastest ab/desorption kinetic, in addition to its ideal heat of formation ΔH=-38.27 kJ/mol and high gravimetric capacity 7.25 wt%.

Hydrogen storage behavior of Mg@Mg2Si and Mg@Mg17Al12 alloys with additions of carbon allotropes and talc

Mg based hydrogen storage alloys containing catalyzing particles are frequently studied because the catalysis is one of possible ways how to speed-up effectively the hydrogen sorption kinetics. Ball milled alloys Mg@Mg2Si and Mg@Mg17Al12 are studied in the present paper. They consist of Mg grains, which hydrogen storage performance is catalyzed by the Mg2Si and Mg17Al12 particles. Graphite, amorphous carbon (carbon black) and magnesium silicate monohydrate (talc) were added to facilitate the fine ball milling. It was found that addition 0.14 wt% of amorphous carbon to Mg@Mg2Si shows the best hydrogen sorption kinetics and the highest sorption capacity of about 6 wt% H2. A weak destabilization of MgH2 hydride by Mg2Si and Mg17Al12 was observed. New technique of equilibrium hydrogen pressure estimation was proposed.

Catalytic effect of nickel phthalocyanine on hydrogen storage properties of magnesium hydride: Experimental and first-principles studies

The high dehydrogenation temperature of magnesium hydride MgH2 is still the main obstacle to its practical application as a solid-state hydrogen storage medium. Using experimental and first-principles calculations approaches, we, for the first time, investigate the catalytic effect and mechanism of nickel phthalocyanine on the dehydrogenation properties of MgH2. The results display that a small amount of nickel phthalocyanine can promote MgH2 dehydrogenation at significantly decreased temperatures by more than 90 °C relative to milled pristine or graphene-added MgH2 system. However, the agglomeration of MgH2 particles is not evidently alleviated through nickel phthalocyanine addition. When MgH2 is milled with graphene firstly and then the obtained mixture is further milled with nickel phthalocyanine, the dehydrogenation properties and agglomeration of MgH2 particles can be synergistically improved to some extent. The first-principles calculations of dehydrogenation enthalpy and binding energy account for the experimental differences in catalysis and aggregation-resistance abilities of nickel phthalocyanine and graphene on MgH2 particles. Notably, the NiN4-inserted graphene is predicted to be an ideal additive for MgH2, which combines the synergetic catalysis-confinement effect of nickel phthalocyanine and graphene on MgH2 particles. Analysis of electronic structures reveals that the excellent catalytic effect of nickel phthalocyanine on MgH2 can be ascribed to the more electron transfer between nickel phthalocyanine and MgH2, which induces the significantly weakened bond strength of MgH and decreased dehydrogenation enthalpy of MgH2.

Synergetic Effects toward Catalysis and Confinement of Magnesium Hydride on Modified Graphene: A First-Principles Study

Graphene nanosheet has recently demonstrated catalytic and agglomeration blocking effects toward MgH2 nanoparticles. Nevertheless, there is a very limited understanding of the relationship between the structural characteristics of graphene nanosheet and the hydrogen sorption properties of MgH2 nanoparticles. Using first-principles calculations, we investigate the structural, energetic, and electronic properties of MgH2 clusters supported on pristine and modified graphene with carbon vacancy or heteroatom (B, N, Si, P, S, Fe, Co, Ni, and Al) doping. The results show that the formation ability of vacancy and heteroatom defects in the graphene lattice is enhanced in the order of vacancy, Al, Ni, S, Co, Fe, Si, P, B, and N. Among them, the B- and P-doped graphene nanosheets, especially the B-doped one, exhibit remarkable synergetic effects toward enhancing the catalysis and confinement of MgH2 hydride. Analysis of electronic structures shows that the direct bonding between MgH2 clusters and B/P-doped graphene...

Electrochemical hydriding of nanocrystalline Mg-Ni-X (X = Co, Mn, Nd) alloys prepared by mechanical alloying and spark plasma sintering

In this work, MgNi26, MgNi26Mn10, MgNi26Co10 and MgNi26Nd10 alloys were prepared by mechanical alloying (MA) and subsequent spark plasma sintering (SPS). Mechanical alloying leads to a grain refinement and increases the concentration of lattice defects. SPS technology provides a compact material but with high porosity, consequently creating a high internal surface area within the volume of sample. The combination of the MA and SPS techniques produces a promising material in terms of fast hydriding kinetics and a high content of absorbed hydrogen. All samples were electrochemically hydrided in a 6 mol/L KOH solution at 80 °C for 480 min. The microstructures of the alloys were characterized by scanning electron microscopy and energy dispersive spectrometry. The phase compositions were characterized by X-ray diffraction, and the total hydrogen content in the hydrided pellets was measured using an inert gas fusion analyser. The dehydriding process was studied by thermogravimetry and mass spectrometry. The highest total amount of hydrogen was absorbed by the MgNi26Nd10 alloy, nearly 1.8 wt%. The main hydriding product was the binary hydride MgH2. The results of the mass spectrometry analysis reveal a significant reduction in the temperature of hydrogen evolution from magnesium hydride, probably due to the formation of fine microstructures of the hydrogenated alloys and catalytic effect of Ni. The decomposition temperature was reduced by more than 200 °C as compared to the commercial MgH2.

Isothermal activation, thermodynamic and hysteresis of MgH2 hydrides catalytically modified by high-energy ball milling with MWCNTs and TiF3

MgH2-M (M = MWCNTs or TiF3 or both of them) composites prepared by high-energy ball milling (HEBM) are used in this work to illustrate the effect of catalysts on isothermal activation, thermodynamic and hysteresis of MgH2 hydrides. The phase compositions, microstructures, particle morphologies and distributions of MgH2 with catalysts have been evaluated. The isothermal synergetic catalytic-activation and dehydrogenation effect of MWCNTs and TiF3 evaluated by P-C-T give the evidences that the addition of catalysts is an effective strategy to destabilize MgH2 and reduce the dehydrogenation temperatures. The isothermal activation process can be remarkly accelerated by adding MWCNTs or TiF3. It's worthnoting that fast initial absorption rate and high hydrogenation capacity are obtained for modified MgH2 when adding MWCNTs coupling with TiF3 and no special activation treatment is needed. The activation effect is mainly attributed to the large contraction/expansion stresses caused by accelerated catalytic desorption/absorption cycles. The catalytic effect on thermodynamic is mainly attributed to electronic exchange reactions with hydrogen molecules during the dissociation-absorption or recombination-desorption process. The thermodynamic hysteresis of catalyzed MgH2 is also investigated to evaluate the energy consumption and estimate the efficiency of the isothermal hydrogen absorption/desorption process. A probable synergetic catalytic-activation mechanism is probed.