Enhanced Hydrogen Storage Performance Research Articles

MOF-derived Ni3Fe/Ni/NiFe2O4@C for enhanced hydrogen storage performance of MgH2

Magnesium hydride (MgH2) is an important material for hydrogen (H2) storage and transportation owing to its high capacity and reversibility. However, its intrinsic properties have considerably limited its industrial application. In this study, the NiFe-800 catalyst as metal-organic framework (MOF) derivative was first utilized to promote the intrinsic properties of MgH2. Compared to pure MgH2, which releases 1.24 wt% H2 in 60 min at 275 °C, the MgH2-10 NiFe-800 composite releases 5.85 wt% H2 in the same time. Even at a lower temperature of 250 °C, the MgH2-10 NiFe-800 composite releases 3.57 wt% H2, surpassing the performance of pure MgH2 at 275 °C. Correspondingly, while pure MgH2 absorbs 2.08 wt% H2 in 60 min at 125 °C, the MgH2-10 NiFe-800 composite absorbs 5.35 wt% H2 in just 1 min. Remarkably, the MgH2-10 NiFe-800 composite absorbs 2.27 wt% H2 in 60 min at 50 °C and 4.64 wt% H2 at 75 °C. This indicates that MgH2-10 NiFe-800 exhibits optimum performance with excellent kinetics at low temperatures. Furthermore, the capacity of the MgH2-10 NiFe-800 composite remains largely stable after 10 cycles. Moreover, the Mg2Ni/Mg2NiH4 acts as a “hydrogen pump”, providing effective diffusion channels that enhance the kinetic process of the composite during cycling. Additionally, Fe0 facilitates electron transfer and creates hydrogen diffusion channels and catalytic sites. Finally, carbon (C) effectively prevents particle agglomeration and maintains the cyclic stability of the composites. Consequently, the synergistic effects of Mg2Ni/Mg2NiH4, Fe0, and C considerably improve the kinetic properties and cycling stability of MgH2. This work offers an effective and valuable approach to improving the hydrogen storage efficiency in the commercial application of MgH2.

Synergistic Effects of In‐Situ‐Formed Multivalent Titanium and Mg2Ni for Improving the Hydrogen‐Storage Properties of MgH2

AbstractMagnesium hydride (MgH2) has gained significant consideration as a cost‐effective solid‐state hydrogen‐storage material with a substantial hydrogen capacity. However, its practical applications are impeded by its poor kinetics and high thermal stability. In this study, we employed a hydrothermal method and high‐temperature calcination to prepare well‐dispersed NiTiO3 nanoparticles smaller than 20 nm. Next, we investigated the effect of the NiTiO3 nanoparticles for educating the hydrogen storage performance of MgH2. The synergistic catalytic effect of multivalent titanium and Mg2Ni/Mg2NiH4 enhanced hydrogen storage performance of the MgH2 system. The addition of 5 wt % NiTiO3 lowered the initial hydrogen evolution temperature of MgH2 to 194 °C. After 12 minutes at 275 °C, the 5 wt % NiTiO3‐MgH2 composites released 6.1 wt % of hydrogen. The dehydrogenation activation energy (Ea) of the 5 wt % NiTiO3‐MgH2 composites decreased significantly to 38.78±2.1 kJ/mol. Furthermore, hydrogen uptake of 5 wt % NiTiO3‐MgH2 at 125 °C reaches 5.1 wt % in 300 s under hydrogen pressure of 20 bar. These findings introduce an innovative concept for preparing high active catalysts for improving the dehydrogenation/hydrogenation kinetics of MgH2.

Experimental and Theoretical Investigation on the Enhanced Hydrogen Storage Performance of Ti–Cr–Mn–Fe-Based Alloys Modified by Nb Substitution

Experimental and Theoretical Investigation on the Enhanced Hydrogen Storage Performance of Ti–Cr–Mn–Fe-Based Alloys Modified by Nb Substitution

Production of Mg thin flakes with enhanced hydrogen storage performance

Flake-like particles are interesting materials for the preparation of alloys and homogeneous nanocomposites, they also have potential use as hydrogen storage materials. However, limited information is available regarding the synthesis of pure magnesium with flake-like morphology. In this study, the successful production of Mg flakes was conducted using a cost-effective and simple method, such as high energy ball milling. Various milling parameters, including different milling times and process control agents, were tested. Optimal conditions led to the formation of coarse flakes with ∼1.72 μm thickness, while a two-step milling process produced thinner flakes with submicron thickness (∼242 nm). Ductilization of the material and a significant reduction in crystal size during the milling process were observed via X-ray diffraction. Isothermal kinetic tests at 350 °C and 20 bar revealed improved hydrogen storage performance for both coarse and thin flakes compared to pristine Mg. Coarse flakes achieved capacities of 4.1 wt% in 60 min while thin flakes reached 4.6 wt% in 6 min, compared to 3.4 wt% achieved in 100 min by pristine Mg. The improved behavior of thin flake-shaped Mg was maintained at 300 °C and 20 bar, with 4.5 wt% of hydrogen absorbed in 6 min. Even at lower testing pressures (10 bar) higher capacities were achieved at the expense of slower kinetics. These findings suggest that thin flake-shaped Mg is a suitable material with enhanced performance for hydrogen storage applications.

Enhanced hydrogen storage performance of zinc and magnesium cobaltite nanocomposites

Renewable and sustainable energies are vital for the near future. Hydrogen, as a clean energy carrier, is a potential candidate for supplying energy in the foreseeable future. Nowadays, hydrogen storage technology has become a significant issue in the energy sector. In this study, ZnCo2O4/ZnO and MgCo2O4/MgO nanocomposites have been synthesized using the sol-gel method with stearic acid as a complexing agent. Different analyses were studied to examine the crystal structure, morphology, and physical properties of the as-prepared samples, including X-ray diffraction (XRD), Fourier transforms infrared (FT-IR), field emission scanning electron microscopy (FESEM), diffuse reflectance spectroscopy (DRS), and vibrating sample magnetometer (VSM). Various methods have been utilized for hydrogen storage technology. In a pioneering approach, the electrochemical hydrogen storage of samples was compared by the chronopotentiometry technique in KOH (4 M) electrolyte solution. The results reveal that ZnCo2O4/ZnO and MgCo2O4/MgO nanocomposites exhibit excellent discharge capacities of 4240 and 3529 mAh/g, respectively, after 11 cycles.

GdO@C composite catalyst for enhanced hydrogen storage performance of Mg–La–Ni alloy

GdO@C composite catalyst synthesis was achieved through a novel chemical blowing carbonization method. Nano-sized GdO uniformly distributed throughout a high-surface-area, defect-laden carbon matrix translates to catalytic performance. To elucidate the influence of GdO@C doping on hydrogen storage, Mg96La3Ni-GdO@C alloys were prepared by ball milling, and the hydrogen storage performance was evaluated. Adding GdO@C can refine the alloy particles, which boosts the surface area and the number of active sites available for the hydrogenation reaction. GdO@C greatly enhanced the de/hydriding kinetics of the alloys, with 1 wt% GdO@C exhibiting the optimal effect. At 360 °C, this material could quickly absorb a large amount of hydrogen (84.4 wt% of its maximum capacity) in just 2 min, but it only took 1.6 min to release a small amount (3 wt%). Doping the alloys with GdO@C reduced the activation energy barrier for dehydrogenation (to 106.3 kJ/mol) and shifted the endothermic peak to a lower temperature (334 °C). Nevertheless, there was no improvement observed in the thermodynamic properties of the composites, as the enthalpy change remained constant at 77.1 kJ/mol.

Enhanced hydrogen storage performance of g-C3N4/CoMn2O4 nanocomposites

Enhanced hydrogen storage performance of g-C3N4/CoMn2O4 nanocomposites

Synergetic effect of Ti3C2-X (X = Fe, Co, Ni) on enhanced hydrogen storage performance of MgH2-TiCrV composite

MgH2 has been attracted extensive attention because of its superior hydrogen storage performance and good reversibility. Further improvement of its kinetics and thermodynamic performances is needed to achieve widespread application. This article investigated the hydrogen storage properties of the thermodynamic optimized Mg-TiCrV hydrogen storage composite modified by layered Ti3C2 materials containing different 3d transition metal particles (Fe, Co, Ni). Mg-TiCrV/Ti3C2-X (X = Fe, Co, Ni) composites can absorb more than 5.30 wt% hydrogen within 1 min at 453 K under 3 MPa hydrogen pressure, and desorb more than 5.25 wt% hydrogen within 60 min at 543 K to 0.1 MPa. In particular, Mg-TiCrV/Ti3C2-Ni composite exhibited the best hydrogen storage properties, which can desorb 4.98 wt% hydrogen within 60 min at 523 K to 0.1 MPa hydrogen pressure and absorb 5.80 wt% hydrogen within 1 min at 453 K under 3 MPa hydrogen pressure. Structural analysis shows that the synergistic effect of layered material Ti3C2 and Ni particles promote the hydrogen release and uptake process.

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.

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.

Cheese-like Ti3C2 for enhanced hydrogen storage

MXenes are highly promising in efficient Mg-based hydrogen storage but their activity is insufficient due to the low efficiency of active sites. Here, for the first time, we propose a facile oxidation-etching-oxidation strategy to expose and optimize abundant internal active sites in a typical MXene (Ti3C2), avoiding additional introduction of active metal sites or complex structural optimization. The obtained cheese-like Ti3C2 with Ti/TiO2 activity sites enriched at the edge of through holes exhibits much better performance in terms of dehydrogenation temperature (from 190 °C) as well as rate in initial 10 min at 250 °C (0.37 wt%/min) than ordinary Ti3C2 when applied in Mg-based hydrogen storage. Compared to ordinary Ti3C2, the dehydrogenation temperature is 60 °C decreased and rate increases to 2-fold, respectively. This work elucidates that significantly enhanced hydrogen storage performance of MXenes can be realized by exposing abundant internal edge active sites via a facile oxidation-etching-oxidation strategy.

Interface and body engineering via aluminum hydride enabling Ti-V-Cr-Mn alloy with enhanced hydrogen storage performance

The theoretical hydrogen storage capacity of V-based solid solution materials can reach 3.8 wt%, but the hydrogen in VH hydride is difficult to release at ambient temperature and pressure, so addressing the issue of hydrogen release under mild conditions is essential. While AlH3 has high weight hydrogen storage density (10.1 wt%) and relatively mild hydrogen desorption temperature (≤150 °C). Therefore, using V-based solid solution as the main body, two kinds of hydrogen storage materials are synthesized into a new composite, which can obviously display enhanced hydrogen storage performance. In this work, the structural stability, kinetic and thermodynamic properties of TiV1.1Cr0.3Mn0.6 + x AlH3 (x = 0, 1, 3, 5, wt.%) composites are studied by means of density functional theory (DFT) calculation and experiment. The results show that the AlH3-doped composites have Al phase existed in the material via the way of embedding, which improves the hydrogen storage performance and activation property of V-base solid solution. With increasing AlH3 content, the activation energies (Ea) gradually decrease. The corresponding relationship between the theoreticalcalculation and the experimental results can provide reference for the subsequent screening of appropriate hydrogen storage materials with application prospect.

Synergistic enhancement of hydrogen storage properties in MgH2 using LiNbO3 catalyst

Extensive researches are being conducted to improve the high dehydrogenation temperature and sluggish hydrogen release rate of magnesium hydride (MgH2) for better industrial application. In this study, LiNbO3, a catalyst composed of alkali metal Li and transition metal Nb, was prepared through a direct one-step hydrothermal synthesis, which remarkably improved the hydrogen storage performance of MgH2. With the addition of 6 wt% LiNbO3 in MgH2, the initial dehydrogenation temperature decreases from 300 °C to 228 °C, representing a drop of almost 72 °C compared to milled MgH2. Additionally, the MgH2-6 wt.% LiNbO3 composite can quickly release 5.45 wt% of H2 within 13 min at 250 °C, and absorbed about 3.5 wt% of H2 within 30 min at 100 °C. It is also note that LiNbO3 shows better catalytic effect compared to solely adding Li2O or Nb2O5. Furthermore, the activation energy of MgH2-6 wt.% LiNbO3 decreased by 44.37% compared to milled MgH2. The enhanced hydrogen storage performance of MgH2 is attributed to the in situ formation of Nb-based oxides in the presence of LiNbO3, which creates a multielement and multivalent chemical environment.

Enhanced hydrogen storage performance of Li and Co functionalized h-GaN nanosheets: DFT study

Based on the density functional theory (DFT) computations, we investigated the hydrogen storage performances of alkali metal (Li) and transition metal (Co) decorated the defective GaN nanosheets. Fundamental aspects including the interaction properties, bonding characteristics, adsorption ability, frontier orbital, HOMO–LUMO energy gaps, natural bond orbital (NBO) analysis, projected densities of states (PDOS) and statistical thermodynamic stability have been demonstrated to analyze the interaction properties of H2 molecules. As a theoretical strategy, non-covalent interactions (NCI) and the atoms in molecules (QTAIM) descriptors were performed to depict weak interactions. The LiN-GaN and CoN-GaN systems and the H2 uptake capacity revealed to be 7.78% and 5.55%, respectively. Our results demonstrated that H2 molecules are introduced sequentially on the Li and Co that functionalized both sides of VN-GaN nanosheets yielded the gravimetric densities up to 8.158% (2Co-VN-GaN) that well above the gravimetric DOE achieve. The 2LiN-GaN and 2CoN-GaN are energetically more effective for the H2 adsorption, stable and preferred than pristine GaN nanosheet.Additionally, two binding mechanisms including polarization of the hydrogen molecules and σ orbitals hybridization of H2 molecules have been investigated to explain the interaction of H2 molecules. The hydrogen desorption enthalpy and desorption temperatures of hydrogen molecules, indicating the H2 molecules are easy to desorb from Li and Co decorated defective GaN nanosheets. These results suggest the possibility of an excellent and promising nanostructural material to improve the performance of hydrogen storage for in fuel cells application at ambient temperature.

Carbon coated La2Mg17 nanocrystalline for enhanced hydrogen storage performances

• Carbon coated nanoscale La-Mg alloy are constructed through a facile strategy; • The hydrogen ab/desorption kinetics were improved; • The dehydrogenation active energy was reduced significantly. Herein, carbon layer coated La-Mg intermetallic nanocrystallines were constructed via a facile process for an enhanced hydrogen storage performance. The hydrogen desorption capacity of carbon-covered sample after ten cycles was 3.5 wt.%, which was four times as high as that for the original. The coated sample presented the higher hydrogen storage capacity, lower dehydrogenation temperature and activity energy. Otherwise, the compositions and microstructures of the various samples were also investigated.

Room-temperature hydrogen storage performance of metal-organic framework/graphene oxide composites by molecular simulations

Metal-organic framework/graphene oxide (MOF/GO) composites have been regarded as potential room-temperature hydrogen storage materials recently. In this work, the influence of MOF structural properties, GO functional group contents and different amounts of doped lithium (Li+) on hydrogen storage performance of different MOF/GO composites were investigated by grand canonical Monte Carlo (GCMC) simulations. It is found that MOF/GO composites based on small-pore MOFs exhibit enhanced hydrogen storage capacity, whereas MOF/GO based on large-pore MOFs show decreased hydrogen storage capacity, which can be ascribed to the novel pores at MOF/GO interface that favors the enhanced hydrogen storage performance due to the increased pore volume/surface area. By integrating the small-pore MOF-1 with GO, the hydrogen storage capacity was enhanced from 9.88 mg/go up to 11.48 mg/g. However, the interfacial pores are smaller compared with those in large-pore MOFs, resulting in significantly reduced pore volume/surface area as well as hydrogen storage capacities of large-pore MOF/GO composite. Moreover, with the increased contents of hydroxyl, epoxy groups as well as carboxyl group modification, the pore volumes and specific surface areas of MOF/GO are decreased, resulting in reduced hydrogen storage performance. Furthermore, the room-temperature hydrogen storage capacities of Li+ doped MOF/GO was improved with increased Li+ at low loading and decrease with the increased Li+ amounts at high loading. This is due to that the introduced Li+ effectively increases the accessible hydrogen adsorption sites at low Li+ loading, which eventually favors the hydrogen adsorption capacity. However, high Li+ loading causes ion aggregation that reduces the accessible hydrogen adsorption sites, leading to decreased hydrogen storage capacities. MOF-5/GO composites with moderate Li+ doping achieved the optimum hydrogen storage capacities of approximately 29 mg/g.

Improving of hydrogen desorption kinetics of MgH2 by NaNH2 addition: Interplay between microstructure and chemical reaction

MgH2 based composites combined with NaNH2 were synthesized by mechanical milling for three different milling times ranging from 15 to 60 minutes. Microstructure and particle size of the samples were analyzed by SEM microscopy while desorption properties were followed by Thermal Desorption Spectroscopy (TDS). The kinetic properties of NaNH2-MgH2 composites were investigated by isoconversional kinetic method as implemented in code developed by our group. Composites show hydrogen desorption peaks shifted to lower temperatures in comparison to mechanically modified and as received MgH2. All NaNH2-MgH2 composites show enhanced kinetics with lowered apparent activation energy (Ea) in comparison to milled MgH2. The mechanism of desorption changes from Avrami–Erofeev n = 3 for as received MgH2 to Avrami–Erofeev n = 4 for composite materials. The change from 3 to 4 can be due to the modification of the nucleation process or a change in the dimensionality of the growth. Those high values of n disregard a diffusion control as a rate limiting step. It has been shown that there is a synergistic effect on the enhanced hydrogen storage performance of chemical reaction and structural changes caused by ball milling. This can be used as a starting point for synthesis of innovative hydrogen storage materials.

Enhanced hydrogen storage performance of magnesium hydride with incompletely etched Ti3C2Tx: The nonnegligible role of Al

The pronounced enhancement on the hydrogen storage performance of MgH2 has been achieved by completely etched MXenes. However, whether the completely removal of Al is necessary and what role the residual Al can play are still unresolved issues. Herein, for the first time, Ti3C2Tx MXenes with different residual Al are prepared to improve the hydrogen storage performance of MgH2. The result shows that the proper residual Al for incompletely etched Ti3C2Tx has a very important responsibility for the improvement of catalytic activity. Different with metallic Al and other Al-containing additives, the unique Ti-Al metallic bonds assisted by surface functional group (-O) can change the electronic structure of Al, which not only hinder the formation of Mg-Al alloys, but also assist the escape of H atoms from MgH2 and enhance the absorption of H atom on catalyst. Meanwhile, the de/hydrogenation process of MgH2 can further be enhanced by multivalent Ti. This report will arouse attention for incompletely etched MXenes and provide a new strategy to optimize properties of MXenes in various fields.

N-doped carbon coated Ti3C2 MXene as a high-efficiency catalyst for improving hydrogen storage kinetics and stability of NaAlH4

The synthesis of highly stable catalysts for the de/hydriding kinetics and cycle stability of NaAlH4 is crucial. Herein, N-doped carbon coated two-dimensional layered Ti3C2 (Ti3C2/NC) catalyst was synthesized by a self-polymerization and heat-treatment method. Impressively, the Ti3C2/NC catalyst remarkably improves the dehydrogenation properties of NaAlH4 with dramatically enhanced dehydrogenation kinetics and stability. In detail, after adding 10 wt% Ti3C2/NC, the initial dehydrogenation temperature is lowered to 85 °C, 3.0 wt% hydrogen is liberated within 4 min at 140 °C, the first step of hydrogen desorption is completed in 57 min at 100 °C, and its capacity retention after 15 cycle tests can remain up to 96.3%. It can be found that in-situ formed Ti-species (Ti0 and Ti3+) during ball milling and the interaction between pyridinic-N and Ti0 are responsible for the enhanced hydrogen storage performance of NaAlH4. Moreover, the carbon can efficiently stabilize Ti species and results in high stability. This finding provides a new understanding of Ti-based MXene to catalyze the hydrogen storage for NaAlH4.

Role of Mn-substitution towards the enhanced hydrogen storage performance in FeTi

The role of Mn substitution in FeTi towards the hydrogenation kinetics and hydrogen storage capacity was investigated using a combination of experimental and theoretical tools. Pristine and Mn-substituted FeTi was produced by electro-deoxidation of oxide precursors, such as natural ilmenite, titania and manganese dioxide. The produced materials were evaluated for hydrogen storage capacity. Ab-initio density functional theory (DFT) calculations were performed to understand the thermodynamics and kinetics of hydrogen absorption in pristine and doped FeTi. DFT calculations demonstrate that although thermodynamic and kinetic parameters of hydrogen absorption with Mn substitution is similar to those in the pristine FeTi, oxygen affinity of Mn at the surface is higher than Fe or Ti. We conclude that Mn acts as a sacrificial oxidizing element and oxidizes more readily at the surface over Fe or Ti, resulting in easy activation of the FeTi alloy. We show superior cyclic-hydrogen absorption behavior in bulk in FeTi with Mn substitution. After 20 charge-discharge cycles, the measured hydrogen storage capacity of FeTi with Mn substitution was steady ∼120 mA h/g (0.8 wt %), which is noticeably higher than that of pristine FeTi. The experimental and theoretical results shows that in case of a practical hydrogen storage scenario, Mn substitution will benefit in reducing absorption fatigue in FeTi. Further, most likely it may not be possible to use pristine FeTi phase.