Enhanced Hydrogen Storage Research Articles

Magnesium based multi-metallic hybrids with soot for hydrogen storage

Magnesium hydride is one of the most sought-after materials for solid state hydrogen storage due to its low cost and high gravimetric capacity (7.6 wt% hydrogen). However, high temperature of desorption (>350 °C) and slow kinetics limit its use for commercial on-board applications. In this work, accumulative roll bonding (ARB) technique has been utilized to synthesise Mg–LaNi5–Mg2Ni-soot hybrid with enhanced hydrogen storage properties. It is seen that the hybrid absorbs ∼6.2 wt% hydrogen at a plateau pressure of ∼2 bar at 300 °C and exhibits fast kinetics with ∼6.6 wt% hydrogen absorption within ∼30 min at 300 °C and 20 bar hydrogen pressure. The role of Mg2Ni as a catalyst as well as hydrogen absorbing medium provides an effect akin to ‘hydrogen pump’, thus enhancing the rate of hydrogen absorption. Presence of carbon in various forms such as aciniform, carbonaceous microgel and cenospheres (derived from soot) plays a vital role by providing channels for diffusion of hydrogen through the hybrid. The ARB technique provides an inexpensive and scalable method of synthesis of Mg based hybrids with large number of interfaces and high amount of strain leading to enhanced hydrogen storage properties.

Effect of Ti0.9Zr0.1Mn1.5V0.3 alloy catalyst on hydrogen storage kinetics and cycling stability of magnesium hydride

As a high-capacity hydrogen storage material, MgH2 still has the problem of high operating temperature and slow reaction kinetics. In this work, an TiMn2-based Laves phase alloy (Ti0.9Zr0.1Mn1.5V0.3, denoted as Ti–Mn) was first synthesized by arc melting and then employed to regulate the hydrogen storage properties of MgH2, with the carbon nanotubes (CNTs) as an aid agent to facilitate the hydrogen diffusion and heat transfer. It was shown that the introduction of Ti–Mn/CNTs can remarkably improve the hydrogen storage properties of MgH2. The MgH2 + 10 wt% Ti–Mn + 1 wt% CNTs composite has an initial dehydrogenation temperature of 195 °C and can absorb hydrogen at room temperature. As for the kinetics, it can release 6.1 wt% H2 in 5 min at 300 °C, and absorb 4.8 wt% H2 in 10 min at 150 °C. It still has a reversible capacity of 6.2 wt% after 100 cycles. Combination of Ti–Mn alloy and CNTs is more effective than Ti–Mn alloy or CNTs alone for regulating MgH2. Ti–Mn/CNTs does not alter the overall thermodynamics of MgH2. However, local destabilization of Mg–H bonds induced by the MgH2/Ti–Mn interfaces was observed experimentally and confirmed theoretically, which partially contributes to the enhanced hydrogen storage of MgH2. In addition, the active transition metals contained in the alloy was believed to accelerate the hydrogen dissociation and delivery during the hydrogen storage process. This work not only achieves the synergistic improvement of hydrogen storage of MgH2 by combination of Ti–Mn alloy and CNTs, but also presents the local destabilization mechanism to explain the improved hydrogen storage of MgH2 by Ti–Mn alloy experimentally and theoretically.

A DFT study on defects and N doping to enhance hydrogen storage in Mg-decorated graphene

In this study, first-principles calculations were used to conduct in-depth studies on multiple key aspects of N-doped defective graphene modified with Mg atoms, including structure, electronic property, thermal stability, as well as hydrogen storage performance and mechanism. The research results show that after the introduction of Mg, N atoms and vacancy defects, pristine graphene transforms from semi-metallic property to metallic property. And the AIMD results indicate excellent thermodynamic stability of the substrate. It can adsorb up to seven H2 molecules, and the adsorption energy values is between −0.15 and −0.21 eV, which is in the stable energy range (-0.15 to −0.60 eV). The hydrogen storage mechanism is mainly attributed to the van der Waals force caused by the polarization of H2 molecules and orbital hybridization between H atoms and the substrate. The calculation of the desorption temperature shows that this substrate can become a potential candidate for reversible hydrogen storage materials at temperatures above 206 K. Compared with graphene decorated with Mg atoms, the introduction of N atoms and vacancy defects significantly improved the hydrogen storage performance.

Improved hydrogen ab-/desorption performance of Ti–Cr based alloys via dual-effect of oxide reduction and element substitution by minor Al additive

Hysteresis of hydrogen storage alloys essentially hinders the compressibility and operation efficiency of metal hydride hydrogen compressors. In this work, minor Al additive was added into Ti–Cr based hydrogen compression alloys through induction levitation melting, and the apparent hysteresis was successfully ameliorated. The XRD and SEM results indicate homogeneous element distribution of a main C14 Laves phase of Ti0.96Zr0.06Cr1.0Mn0.6Fe0.4Alx (x = 0, 0.01, 0.02, 0.04, 0.08) alloys, and vanishing of a minor oxide phase in case the Al additive is introduced. As Al stoichiometry increases in the alloys, the hydrogenation plateau decreases obviously but the dehydrogenation plateau hardly changes. Meanwhile, the hydrogen capacity ascends initially but descends slightly. Additionally, no severe performance degradation is induced. The mechanism for overall performance improvement can be concluded as dual functions of Al additive: one can be oxide reduction of other elements during melting determined by XPS and ICP, and the other can be partial Al substitution for the B-side elements, leading to relieved deformation energy surrounding the vacant Al-containing interstitials. As to hydrogenation kinetics, the alloys exhibit accelerated hydrogenation rate with increased Al stoichiometry due to decreased activation energy and hydrogenation plateau. Furthermore, the first-principles calculation results indicate random Al substitution for the B-side atoms, and anisotropic expansion of the unit cell can be attributed to Al substitution at 6h sites. This work reveals a simple and effective way to enhance hydrogen storage performance of Ti–Cr based alloys.

Enhanced Hydrogen Storage Capacity in Two-Dimensional Fullerene Networks.

In contrast to isolated C60 molecular dispersion in solvents, the monolayer C60 networks synthesized by Hou et al. (Nature 2022, 606, 507-510) feature compact nanocages, serving as natural containers for hydrogen storage. The anisotropic lattice and intrinsic local strains induce delocalization of conjugated π orbitals within C60, enabling hydrogen chemisorption without an additional chemical modification. Through first-principles calculations and molecular dynamics simulations, we reveal the correspondence between chemisorption sites and orbital distributions, determining the orientation of polyhedrons formed by physiosorbed hydrogen molecules. The combination of chemisorption and physisorption processes significantly enhances hydrogen storage capacity in monolayer C60 networks while maintaining the thermodynamic stability of the nanocage structures. Numerical results indicate a maximum internal hydrogen pressure exceeding 116 GPa at room temperature and atmospheric pressure. These findings suggest that monolayer C60 networks are promising solid-state candidates for highly efficient hydrogen storage.

Layered double hydroxide-derived Mg2Ni/TiH1.5 composite catalysts for enhancing hydrogen storage performance of MgH2

Developing efficient catalysts is of great significance in improving the sluggish kinetics and high desorption temperature of MgH2 hydrogen storage material. Here, ultrathin NiTi-layered double hydroxide (NiTi-LDH) nanosheets are used as precursors to prepare Mg2Ni/TiH1.5 composite catalysts to improve the hydrogen storage properties of MgH2. The variation of Ni/Ti ratio in LDH plays an important role in regulating the composition, morphology and distribution of Mg2Ni/TiH1.5 catalysts, which significantly affect their synergistic catalytic effect. Mg2Ni/TiH1.5 composite catalyst exhibits significantly improved catalytic performance compared with conventional Ni-, Ti- and Ni/Ti-based catalysts. The optimal MgH2/Mg2Ni/TiH1.5 system shows a significantly reduced desorption temperature of 212 °C which is 133 °C lower than that of pure MgH2 (345 °C), and can release 5.97 wt% hydrogen within 300s at 300 °C. Further mechanism analysis reveals that the unique flaky morphology and suitable composition of Ni/Ti LDH can significantly enhance the synergistic effect of Mg2Ni and TiH1.5, which promotes the fracture of the HH and Mg-H bonds.

Enhancing Hydrogen Storage in AZ31 Alloy through Pd/G Composite

In this research, we investigated the catalytic effects of Palladium/Graphene(Pd/G) on AZ31 alloy for hydrogen storage. X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (SEM-EDS) were employed to confirm the homogeneous distribution of AZ31 and observe phase changes after mechanical alloying with the catalysts. The hydrogen storage properties of AZ31 with catalysts were systematically examined, and the time of maximum reaction rate for nucleation was determined using Avarami Plot. The results of the study show that the incorporation of 2% Pd/G resulted in the fastest hydrogen absorption and desorption time, taking 200 seconds to achieve 90% hydrogen storage with a maximum of 6.04 wt%. The corresponding maximum hydrogen desorption occurred in 694 seconds, reaching 6.03 wt%. Consequently, the introduction of 2% Pd/G catalyst proved to be effective in significantly enhancing the hydrogen ab/desorption rates of AZ31 alloy.

Synergistic enhancement of hydrogen storage performance of Mg-La-Ni alloy by CeO2@C composite catalyst

An enhanced chemical blowing carburation method was successfully employed to synthesize a CeO2@C composite catalyst. The catalyst comprises highly dispersed CeO2 nanoparticles within a porous carbon matrix, demonstrating a well-developed micropore structure, an ultrahigh specific surface area, and a high density of defects. Various amounts of CeO2@C were mechanically milled with an Mg96La3Ni alloy to investigate its hydrogen storage properties. The results demonstrated that incorporating CeO2@C significantly refined the Mg-based alloy, leading to an increase in both specific surface area and the number of active sites. The addition of CeO2@C greatly enhanced the hydrogen absorption and desorption kinetics of the alloy, with the optimal amount being 5 wt % CeO2@C. At 360 °C, the alloy could absorb 78.1% of its maximum hydrogen capacity within 2 min, and release an equal amount of hydrogen within 5 min, with the desorption activation energy decreasing to 107.33 kJ/mol H2. The incorporation of CeO2@C significantly reduced the desorption activation energy of the alloy while leaving its thermodynamic performance unaffected. The CeO2 nanoparticles and carbon matrix synergistically catalyze the reactions, with the former primarily facilitating nucleation and the latter facilitating hydrogen diffusion. This study offers novel insights into the design of magnesium-based hydrogen storage materials. The enhanced hydrogen storage performance demonstrated in this work shows the potential of CeO2@C modified Mg-based alloys for practical applications in hydrogen fuel cell vehicles, portable power sources, and other hydrogen energy storage systems.

Can endohedral transition metals enhance hydrogen storage in carbon nanotubes?

The safe and efficient use of hydrogen energy, which is in high demand worldwide today, requires efficient hydrogen storage. Despite significant advances in hydrogen storage using carbon-based nanomaterials, including carbon nanotubes (CNTs), efforts to substantially increase the storage capacity remain less effective. In this work, we demonstrate the effect of endohedral transition metal atoms on the hydrogen storage capacity of CNTs using reactive molecular dynamics simulations. We find that an increase in the volume fraction of endohedral nickel atoms leads to an increase in the concentration of physisorbed hydrogen molecules around single-walled CNTs (SWNTs) by approximately 1.6 times compared to pure SWNTs. The obtained results provide insight into the underlying mechanisms of how endohedral transition metal atoms enhance the hydrogen storage ability of SWNTs under nearly ambient conditions.

Tungsten clusters derived from phosphotungstic acid to enhance hydrogen storage efficiency in MgH2

MgH2 has a high hydrogen storage capacity but suffers from high operating temperature and slow dehydrogenation kinetics due to the strong Mg–H bond. Here, phosphotungstic acid are molecularly loaded on the surface of MgH2 submicron particles and then further reduced to tungsten clusters with size of ∼2 nm during hydrogen uptake/release operation. The tungsten clusters act as catalysts to reduce the dehydrogenation temperature and activation energy of MgH2 by 36 °C and 15 kJmol-1, respectively. W cluster-decorated MgH2 can release more than 6 wt% hydrogen in 30 min at 300 °C; even at 250 °C, the material can still absorb 6 wt% hydrogen in a few minutes and release 4 wt% hydrogen in 1 h, outperforming previously reported W-based catalysts (micro/submicron WO3 and WS2). In addition, this material also shows stable cycling performance. This study demonstrates promising prospects of polyoxometalates as efficient catalysts for hydrogen storage materials.

Utilizing Nanostructured Materials for Hydrogen Generation, Storage, and Diverse Applications.

The rapid advancement of refined nanostructures and nanotechnologies offers significant potential to boost research activities in hydrogen storage. Recent innovations in hydrogen storage have centered on nanostructured materials, highlighting their effectiveness in molecular hydrogen storage, chemical storage, and as nanoconfined hydride supports. Emphasizing the importance of exploring ultra-high-surface-area nanoporous materials and metals, we advocate for their mechanical stability, rigidity, and high hydride loading capacities to enhance hydrogen storage efficiency. Despite the evident benefits of nanostructured materials in hydrogen storage, we also address the existing challenges and future research directions in this domain. Recent progress in creating intricate nanostructures has had a notable positive impact on the field of hydrogen storage, particularly in the realm of storing molecular hydrogen, where these nanostructured materials are primarily utilized.

The role of transition metal doping in enhancing hydrogen storage capacity in porous carbon materials

Porous carbon materials with high specific surface area are potential hydrogen storage materials. However, due to the weak van der Waals forces between the material and H2, hydrogen can generally be stored only at a cryogenic temperature under high hydrogen pressure. To solve this problem, in this work, ZIF-8-derived porous carbon material (PCM) modified with transition metals (PCM-TMs, TM: Mn, Fe, Ni) was prepared to investigate the role of TM doping. The developed PCM-TMs have a high specific surface area (up to 1363 m2/g) and pore volume (up to 0.77 cm3/g). Experimental results show that PCM-TMs exhibit higher hydrogen storage capacity, usable capacity, and hydrogen uptake capacity per specific surface area compared to PCM. In addition, PCM-TMs have a higher isosteric heat of adsorption (Qst) than PCM, which suggests that TM doping enhances the interaction between H2 and carbon materials. Theoretical calculations further indicate that this interaction is a nearly weak chemisorption force (∼9.32 kJ/mol). Notably, Mn-doped porous carbon material (PCM-Mn) exhibits a hydrogen storage capacity of ∼3.45 wt% (20.44 g/L) at 77 K under 35 bar-H2. Even at 253 K under 50 bar-H2, the capacity can reach ∼1.41 wt% (8.34 g/L). The hydrogen uptake capacity per specific surface area for PCM-Mn reaches 1.03 × 10-3 wt% / m2·g-1 at 253 K under 50 bar-H2, which is 1.5 times larger than that of PCM. Under proper operating conditions, such as loading at 77 K and 35 bar-H2, and discharging at 253 K and 2 bar-H2, PCM-Mn can achieve a usable capacity of at least 19.30 g/L. The hydrogenation kinetics curves reveal that PCM-Mn can store 1.39 wt%-H2 (8.25 g/L) under 12 MPa H2 at 298 K, while it is only 0.88 wt% (5.53 g/L) for PCM at the same condition. This work provides valuable insight into improving the hydrogen storage performance of hydrogen storage materials of physisorption.

Enhanced hydrogen storage properties of Ti40-xV45Zr15Crx alloys by dual-phase nanostructures of eutectic and spinodal decomposition

Multi-principal elements alloys (MPEAs) with body center cubic (BCC) structure have shown great potential in hydrogen storage. However, the multi-cycle activation process and the high desorption temperature have inhibited their applications. In this study, the Ti40-xV45Zr15Crx (x = 1, 2, 3 at. %) alloys with three different BCC phases are synergized, and high hydrogenation capacities of over 2 wt% are achieved in the first hydrogen absorption. Owing to the formation of spinodal decomposition nanostructure in Ti38V45Zr15Cr2 alloy, 90 % of total hydrogen capacity is reached in 30s at 250 °C under 1 MPa H2, which indicates no incubation time is needed for activation. The Ti38V45Zr15Cr2 alloy also shows the highest reversible hydrogen storage capacity with fastest kinetics at 200 °C. The hydrogenation reaction is controlled by the 1D diffusion process of H atoms according to JMAK model. The spinodal decomposition structure can accelerate the decomposition of H2 molecules and the diffusion of H atoms by providing extra energy from large lattice distortion. The high-density interfaces in nano-eutectic structure can serve as active sites for the nucleation of hydrides and fast paths for the diffusion of H atoms.

Enhanced hydrogen storage in gold-doped carbon nanotubes: A first-principles study

Hydrogen as a clean energy source is receiving great attention, and over-ground storage using porous materials has been identified as a promising alternative to current solutions. The general disadvantage is the relatively weak solid–gas interaction and adsorption energy, providing low gravimetric and volumetric capacities and extreme operational conditions. Here we propose Au-doped carbon nanotubes (CNTs) as an efficient alternative for reversible hydrogen capture at high temperatures. This work investigates the properties of several modified CNTs using density functional theory. We analyze the binding and formation energies of the uniformed Au-doped CNTs and assess their adsorption capability. The hydrogen storage mechanisms of the nanostructures are studied in depth using partial density of states and charge transfer analysis showing that the increase of diameter has a positive effect on the outcome. Our findings show that the modified structures are able to capture from six to nine hydrogen molecules per gold atom, achieving volumetric capacities ranging from 154 to 330 g/l, surpassing the DOE target. In addition, the calculated desorption temperatures indicate high performance of Au-doped CNTs, obtaining hydrogen capture-release working conditions above 200 K.

High-capacity hydrogen storage through molecularly restructured and confined hydrogen hydrates

In the future landscape of sustainable energies and in combating global climate challenges, hydrogen plays a crucial role in both stationary and portable energy systems that currently supply 18 % of the total energy demand. High-capacity, safe, and cost-effective hydrogen storage is critical for advancing the hydrogen economy but remains a dauting challenge. A range of advanced material systems including metal hydrides, metal-organic frameworks, and 2D materials have been explored in efforts to achieve high storage capacity, but high operating pressures, low charging/discharging rates, and energy intensive discharging processes have hindered their development and deployment. Here, we report a green material paradigm for high storage capacity with fast charging/discharging and ambient temperature discharging. The material platform is a modified zeolite with rationally tuned pores and modified surface chemistry that exhibits long-term stability and stores hydrogen gas in the form of hydrogen hydrates. The selected pore dimensions enhance the hydrogen solubility through restructuring of water molecules, and the surface chemistry of the material leads to enhanced double donor-acceptor bonds with water molecules for enhanced hydrogen storage capacity. The material enables hydrogen storage in hydrogen hydrate form at 8–10 bar dropping the required storage pressure by two orders of magnitude lower compared to state-of-the-art materials and addresses long-standing hurdles of high operating pressure and slow formation kinetics of hydrogen hydrates providing a promising platform for hydrogen storage.

Enhanced hydrogen storage properties of MgH2 with the co-addition of LiBH4 and YNi5 alloy

MgH2, as one of the typical solid-state hydrogen storage materials, has attracted extensive attention. However, the slow kinetics and poor cycle stability limit its application. In this work, LiBH4 and YNi5 alloy were co-added as additives to MgH2 via ball milling, thereby realizing an excellent dehydrogenation performance and good cycle stability at 300 °C. The MgH2-0.04LiBH4-0.01YNi5 composite can release 7 wt.% of hydrogen in around 10 min at 300 °C and still have a reversible hydrogen storage capacity of 6.42 wt.% after 110 cycles, with a capacity retention rate as high as 90.3 % based on the second dehydrogenation capacity. The FTIR results show that LiBH4 can reversibly absorb and desorb hydrogen throughout the hydrogen ab/desorption process, which contributes a portion of the reversible hydrogen storage capacity to the MgH2-0.04LiBH4-0.01YNi5 composite. Due to the small amount of LiBH4 and YNi5, the dehydrogenation activation energy of MgH2 did not decrease significantly, nor did the dehydrogenation enthalpy (∆H) change. However, the MgNi3B2 and in-situ formed YH3 during the hydrogen absorption/desorption cycles is not only beneficial to the improvement of the kinetics performance for MgH2 but also improves its cycle stability. This work provides a straightforward method for developing high reversible hydrogen capacity on Mg-based hydrogen storage materials with moderate kinetic performance.

Enhanced hydrogen storage performance of magnesium hydride catalyzed by medium-entropy alloy CrCoNi nanosheets

The sluggish de/hydrogenation kinetics and stable thermodynamics of magnesium hydride (MgH2) are unfavorable for its large-scale application. Herein, the medium-entropy alloy CrCoNi nanosheets were synthesized and remarkably enhanced the low-temperature hydrogen storage performance of MgH2. Surprisingly, the initial dehydrogenation temperature of 9 wt% CrCoNi modified MgH2 was greatly reduced from 325 °C to 195 °C, a drop of 130 °C compared to non-additive MgH2. Also, the MgH2–CrCoNi composite released 4.84 wt% hydrogen at 300 °C even in 5 min and absorbed 3.19 wt% hydrogen at 100 °C within 30 min (3.2 MPa). The calculated de/rehydrogenation activation energy were reduced by 45 and 55 kJ mol−1, respectively. Further cyclic kinetics investigation indicates that the 9 wt%-CrCoNi doped MgH2 still presented good stability after 20 cycles, losing only 0.36 wt% hydrogen capacity. The XRD pattern validated that CrCoNi remained stable during the cyclic reaction process. Besides, the uniformly distributed CrCoNi nanosheets were in tight contact with the MgH2 surface, providing abundant catalytic active sites and low-energy barrier diffusion channels. Under synergistic catalysis, the H atoms are rapidly absorbed and released across the Mg/MgH2 interface, resulting in excellent kinetic properties. Briefly, this paper provides new references and inspirations to design efficient polymetallic catalysts for hydrogen storage materials.

Predictive Modeling of Molecular Mechanisms in Hydrogen Production and Storage Materials.

Hydrogen has been widely considered to hold promise for solving challenges associated with the increasing demand for green energy. While many chemical and biochemical processes produce molecular hydrogen as byproducts, electrochemical approaches using water electrolysis are considered to be a predominant method for clean and green hydrogen production. We discuss the current state-of-the-art in molecular hydrogen production and storage and, more significantly, the increasing role of computational modeling in predictively designing and deriving insights for enhancing hydrogen storage efficiency in current and future materials of interest. One of the key takeaways of this review lies in the continued development and implementation of large-scale atomistic simulations to enable the use of designer electrolyzer-electrocatalysts operating under targeted thermophysical conditions for increasing green hydrogen production and improving hydrogen storage in advanced materials, with limited tradeoffs for storage efficiency.

Enhanced hydrogen storage in Mg catalysed by Cu–Ni–Co–Fe quaternary multi-component alloy

Magnesium has been sought after material for hydrogen storage due to its high storage capacity (7.6 wt%) and low cost combined with easy availability. However, sluggish kinetics and high absorption temperature (>300 °C) make it inherently difficult to use in commercial applications such as automobile, which require hydrogen absorption/desorption near ambient temperature and pressure. In this work, Cu–Ni–Co–Fe multi-component transition metal alloy has been used as a catalyst for hydrogen sorption in magnesium. It is seen that the Mg–Cu0.15Ni0.35Co0.25Fe0.25 composite desorbs ∼6 wt% hydrogen at 250 °C at a plateau pressure of ∼0.4 bar and exhibits fast kinetics with ∼3.5 wt% hydrogen absorption in 3 min at 250 °C under 20 bar hydrogen. Synergistic effect of transition elements in a disordered solid solution act as pathway provider for hydrogen and therefore results in reduction in hydrogen desorption temperature, without compromising on the hydrogen storage capacity of the composite. Mg-based composites provide an economic and industrially scalable route for the commercial implementation of hydrogen-fuel cell combined system.

Solid-solution MAX phase TiVAlC assisted with impurity for enhancing hydrogen storage performance of magnesium hydride

Although MXene catalysts etched from precursor MAX have greatly improved the hydrogen storage performance of magnesium hydride (MgH2), the use of dangerous and polluting etchers (such as hydrofluoric acid) and the direct removal of potentially catalytically active A-layer substances (such as Al) present certain limitations. Here, solid-solution MAX phase TiVAlC catalyst without etching treatment has been directly introduced into MgH2 system to improve the hydrogen storage performance. The optimal MgH2-10 wt% TiVAlC can release about 6.00 wt% hydrogen at 300 °C within 378 s and absorb about 4.82 wt% hydrogen at 175 °C within 900 s. After 50 isothermal hydrogen ab/desorption cycles, the excellent cyclic stability and capacity retention (6.4 wt%, 99.6%) can be found for MgH2-10 wt% TiVAlC. The superb catalytic activity of TiVAlC catalyst can be explained by abundant electron transfer at external interfaces with MgH2/Mg, which can be further enhanced by impurity phase Ti3AlC2 due to strong H affinity brought from abundant electron transfer at internal interfaces (Ti3AlC2/TiVAlC). The influence of impurity phase which is common in MAX phase on the overall activity of catalysts has been firstly studied here, providing a unique method for designing composite catalyst to improve hydrogen storage performance of MgH2.