Improved Hydrogen Storage Research Articles

Improved Hydrogen Storage Thermodynamics and Kinetics of As-Milled Ce-Mg-Ni-Based Alloys by Adding Ni

Improved Hydrogen Storage Thermodynamics and Kinetics of As-Milled Ce-Mg-Ni-Based Alloys by Adding Ni

Tuning Crystal Morphology in MOFs for Improved Hydrogen Storage

Tuning Crystal Morphology in MOFs for Improved Hydrogen Storage

Incorporation of TC4 (Ti-6Al-4V) to construct strong interfacial bonding with Mg matrix to achieve improved hydrogen storage kinetics

Effective contact between the catalyst and the Mg/MgH2 matrix is the key to efficiently enhancing the hydrogen storage kinetics. In this work, a Mg-10 wt% TC4 (Ti-6Al-4V) composite with strong interfacial bonding was prepared by vacuum hot pressing sintering, and the reinforcement mechanism of TC4 was investigated. The results indicated that TC4 has a significant improvement effect on the activation efficiency and hydrogen absorption/desorption kinetics. The hydrogen absorption and desorption activation energies of AZ91-TC4 (53.0/111.3 kJ/mol) are 19.6 and 37.2 kJ/mol lower than that of AZ91 without TC4, respectively. Moreover, TC4 can cause AZ91 to start dehydrogenation at 449 K, and the reduction is about 110 K. Except for the increase of grain boundaries and microcracks caused by TC4, the transition diffusion interface formed by TC4 and Mg matrix with a lower diffusion barrier can be used as a special fast diffusion channel to accelerate the hydrogenation process controlled by H atom diffusion. Meanwhile, the kinetic calculations indicate that the dehydrogenation process of AZ91 is controlled by the nucleation and growth step of Mg, and its nucleation activation energy is ca. 4 times the growth activation energy. TC4 and its induced precipitation of TiAl and Al8Mn5 can dramatically accelerate the nucleation process of Mg, resulting in the rate-determining step changing to the surface penetration of H atoms, and the desorption rate is significantly improved. These positive findings provide new tactics for designing excellent hydrogen storage catalysts.

FeNi3 alloy doped carbon spheres for improving hydrogen storage performance of MgH2

MgH2 is one of the ideal hydrogen storage materials because of its high hydrogen storage density, but the thermodynamic stability and slow kinetics of Mg/MgH2 system hinder its practical application. Transition metal catalyst doping has become an important strategy to improve the hydrogen storage kinetics of MgH2. In this work, FeNi3@CS was prepared by solvothermal method with carbon spheres (CS) as the support, and introduced into Mg/MgH2 system to prepare MgH2–FeNi3@CS composite. The initial dehydrogenation temperature of MgH2–FeNi3@CS composite is 565 K, which is 100 K lower than additive-free MgH2. At 423 K, MgH2–FeNi3@CS composite could absorb 4.5 wt% H2, while the hydrogen absorption capacity of MgH2 without additives is only 2.0 wt%. After 10 cycles, the hydrogenation and dehydrogenation capacity could be maintained at 5.6 wt% and 4.5 wt%, respectively. In addition, the activation energy of MgH2–FeNi3@CS composite decreased by 52 kJ/mol compared with MgH2. FeNi3 was in situ converted to Mg2NiH4 and Fe after hydrogenation-ball milling, which were considered as the catalytic active substances in Mg/MgH2 system. The synergistic catalysis of Mg2Ni/Mg2NiH4, Fe and carbon materials has a positive effect on improving the hydrogen storage performance of Mg/MgH2 system.

Physically activated resorcinol-formaldehyde derived carbon aerogels for enhanced hydrogen storage

Carbon aerogels have great potential as hydrogen storage materials owing to their exceptional specific surface area, low weight, and high porosity. These characteristics improve the ability to increase hydrogen adsorption capacity, making them promising candidates for hydrogen storage materials. Nevertheless, the implementation encounters obstacles such as limited storage capacity under ambient temperature and pressure. The present study reports the improved hydrogen storage capacity of carbon aerogels synthesized by Pekala's sol-gel method and optimized by physical activation. This study aims to optimize specific surface area and micropore volumes by physical activation to enhance hydrogen adsorption via the physisorption mechanism. The as-synthesized carbon aerogel has a specific surface area of 579.53 m2/g with a pore volume of 0.34 cm3/g whereas this surface area and pore volume have been tuned using its physical activation. The physically activated carbon aerogel shows a significantly higher specific surface area of 799.68 m2/g with a pore volume of 0.47 cm3/g as compared to the pristine carbon aerogel. This optimization in the specific surface area has enhanced the hydrogen storage capacity of carbon aerogel. The activated carbon aerogel exhibits a promising hydrogen storage capacity of 5.28 wt% at liquid nitrogen temperature under a hydrogen pressure of 22 atm whereas 3.39 wt% of hydrogen storage capacity has been seen in the unactivated carbon aerogel under the same conditions. In addition, activated carbon aerogel showed good hydrogen adsorption and desorption kinetics up to 30 cycles at room temperature (27 °C) under 22 atm hydrogen pressure. The reason behind enhanced hydrogen adsorption capacity in activated carbon aerogel has been put forward using various characterization techniques like XRD, TEM, SEM, and BET and discussed in the mechanism section.

Enhancing the dehydrogenation properties of LiAlH4 through the addition of ZrF4 for solid-state hydrogen storage

Hydrogen energy is emerging as an essential alternative to fossil fuels due to its clean energy profile, generating energy without greenhouse gas emissions. Solid-state hydrogen storage, particularly using complex hydrides like LiAlH4, holds promise due to high hydrogen capacities. However, practical applications of LiAlH4 face obstacles due to slow dehydrogenation kinetics and high decomposition temperatures. This study investigates the catalytic effect of ZrF4 on LiAlH4 to improve hydrogen storage properties. Incorporating 10wt.% ZrF4 has significantly lowered the onset desorption temperature from 160 °C to 80 °C. Desoption kinetic result showed that the addition of 10wt.% ZrF4 can enables the release of 5.6wt.% hydrogen in 120min at 100 °C, which is 50 times faster than in undoped samples. X-ray diffraction analysis indicated that ZrF4 facilitated the in-situ formation of Al3Zr and LiF phases during dehydrogenation, thereby enhancing catalytic efficiency. The desorption activation energies for first two reactions decreased significantly by ~ 16kJ/mol and ~24kJ/mol with ZrF4 doping. These findings suggest that ZrF4 effectively improves the hydrogen storage properties of LiAlH4, positioning it as a potential catalyst for solid-state hydrogen storage systems.

Etching physicochemical adsorption sites of biochar by steam for enhanced hydrogen storage

Enhancing the hydrogen storage capacity of carbon-based materials requires the precise synthesis of strong hydrogen adsorption sites. Consequently, this work suggests improving hydrogen storage capacity by employing H2O low-temperature etching technology. First, the simulation methods investigated the pore structure and oxygen-containing groups’ adsorption properties on hydrogen. The results showed that the oxygen-containing group could increase the adsorption energy of biochar on hydrogen, and the carboxyl group had the greatest effect. A suitable coupling of pores and oxygen-containing groups can improve the microporous region’s hydrogen storage capacity. Moreover, biochar may form a new ultra-microporous region (less than 0.5 nm) by etching it at 700 °C and 30 vol% H2O. After etching 90 min, the surface oxygen concentration remained stable at 14 at.%. In conjunction with results from mass spectrometry, we discovered that the process influencing pore growth was the heterogeneous interaction between CO and H2 to create CH4. At 25 ℃ and −196 ℃, the KSBC-30–60 showed superior hydrogen storage capacity compared to KSB. Its total adsorption capacity was 0.49 wt% and 5.28 wt%, respectively, and increased by 1.32 and 1.2 times. This study proposes a novel approach to improving hydrogen storage by etching porous carbon structures with H2O. The strategy has the potential for large-scale application and can be further utilized in the design and optimization of related carbon adsorbents.

Numerical studies of a new device for a cryo-adsorption hydrogen storage system

Cryo-adsorption is an attractive method for hydrogen storage. However, the non-uniformity of temperature during the charging process affects its performance. To improve the uniformity of the temperature field inside the hydrogen storage tank, and thus improve the hydrogen storage performance and hydrogen storage efficiency of the tank, this paper proposed a thermal management method that combines the central and spiral cooling tubes with vacuum adiabatic heat management. Accordingly, a numerical model was built to investigate the hydrogen adsorption performance of the installation. The results reveal that satisfactory temperature-uniformity was shown in charging and dormant stages. Suitable operating conditions also can improve hydrogen storage performance by reducing the impact of thermal effects. Moreover, the hydrogen storage capacity of activated-carbon cryo-adsorption is roughly 2.5 times that of cryo-compressed storage and 10 times that of ambient-compressed storage.

Vermiform Ni@CNT derived from one-pot calcination of Ni-MOF precursor for improving hydrogen storage of MgH2

The Ni-coated carbon nanotubes (Ni@CNT) composite was synthesized by the facile “filtration + calcination” of Ni-based metal−organic framework (MOF) precursor and the obtained composite was used as a catalyst for MgH2. MgH2 was mixed evenly with different amounts of Ni@CNT (2.5, 5.0 and 7.5, wt.%) through ball milling. The MgH2−5wt.%Ni@CNT can absorb 5.2 wt.% H2 at 423 K in 200 s and release about 3.75 wt.% H2 at 573 K in 1000 s. And its dehydrogenation and rehydrogenation activation energies are reduced to 87.63 and 45.28 kJ/mol (H2). The in-situ generated Mg2Ni/Mg2NiH4 exhibits a good catalytic effect due to the provided more diffusion channels that can be used as “hydrogen pump”. And the presence of carbon nanotubes improves the properties of MgH2 to some extent.

Sustainable fabrication of metal-organic frameworks for improved hydrogen storage

As greenhouse gas emissions become serious, the need for sustainable and efficient hydrogen storage solutions to replace traditional fuel energy becomes increasingly urgent. This study focuses on enhancing the hydrogen storage performance of CuBTC, a metal-organic framework (MOF) via green synthesis, aligning with the green circular economy principles of reducing energy consumption and chemical solvent waste. By applying the Design of Experiments methodology, we systematically explored the impact of different synthesis conditions on CuBTC properties, offering valuable insights for mechanochemical synthesis and hydrogen storage applications. Identified optimal conditions significantly increased CuBTC hydrogen uptake to 3.2 wt% at 20 bar, comparable to solvothermal CuBTC at 3.37 wt% and 10% higher than prior studies. This optimal CuBTC also possesses a comparable hydrogen adsorption rate to solvothermal CuBTC and an accelerated adsorption rate compared to smaller CuBTC crystal samples. A notable achievement of this work is the drastic reduction of the CuBTC synthesis time to just minutes while eliminating the need for chemical solvents. This breakthrough consumes less than 2% of the energy required for traditional solvothermal synthesis and completely avoids chemical solvent waste, marking a significant environmental and efficiency improvement. In addition, the CuBTC formation mechanism was explored in this research, shedding light on the intricate process of crystal structure development. Our findings demonstrate that the ball-milling technique can significantly enhance the hydrogen storage capabilities of CuBTC while reducing energy consumption and chemical solvent waste during the synthesis process.

Prediction of hydrogen storage in metal-organic frameworks using CatBoost-based approach

This study determined the machine-learning (ML) models for the discovery of efficient metal-organic framework (MOF) materials to improve hydrogen storage. We selected a sample of 5047 MOFs from the CoRE MOFs database and employed grand canonical Monte Carlo simulation results from the Hydrogen Materials Advanced Research Consortium (HyMARC) data center to evaluate the useable gravimetric (UG) capacities and useable volumetric (UV) capacities of these materials. ML models were employed to analyze the data. Seven key features were focused upon density, gravimetric surface area, volumetric surface area, void fraction (VF), pore volume (PV), largest cavity diameter, and pore-limiting diameter, and used to predict the UG and UV. The CatBoost model provided the most accurate predictions. In addition, SHapley Additive exPlanations analysis based on the CatBoost model revealed that the PV and VF significantly affected the hydrogen storage performance. A comprehensive analysis confirmed that the CatBoost model exhibited the highest prediction accuracy and identified specific combinations of structural features that significantly improved the hydrogen storage efficiency of the MOFs.

Effect of Ce0.6Zr0.4O2 nanocrystals on boosting hydrogen storage performance of MgH2

Magnesium hydride (MgH2) has been widely recognized as a highly promising solid-state media for hydrogen storage. However, the high operating temperature and the intrinsic sluggish kinetics hinder the practical application as a portable solid storage carrier. To address this issue, we have successfully fabricated a novel rare earth-containing bimetallic oxide additive, namely Ce0.6Zr0.4O2 nanocrystals, which exhibits a significant catalytic effect in enhancing the hydrogen storage properties of MgH2. By incorporating 7 wt% Ce0.6Zr0.4O2 into MgH2, the modified composite releases hydrogen as low as 201 °C. Furthermore, in an isothermal dehydrogenation test conducted at 270 °C for 8 min, approximately 6.15 wt% of H2 was desorbed. The composites can rapidly recharge hydrogen at a low temperature of 50 °C and 6.02 wt% H2 being absorbed within 3 min at 150 °C under 50.0 bar. Comparatively, the dehydrogenation activation energy of the Ce0.6Zr0.4O2-modified MgH2 significantly decreased compared to MgH2 by ball milling. In addition to its improved hydrogen storage properties, the composite also exhibits excellent cycling stability. Through cyclic de-/rehydrogenation experiments conducted at 270 °C, a capacity retention of 98.9 % was achieved over 20 cycles. This exceptional performance can be attributed to the in-situ formation of the CeH2.73/CeO2-x and ZrO2, which originated from the Ce0.6Zr0.4O2 additive following the first de-/rehydrogenation cycle. The uniform dispersion of the multiphase component nano-sized active species within the MgH2 matrix facilitates charge transfer and accelerates hydrogen diffusion. Density functional theory calculations revealed the dissociation energy barrier and dissociation energy of H2 were alleviated by integrating Zr into CeO2. This work provides valuable insights for further rational designs of novel catalysts by transition metals and rare earths in promoting the commercialization of MgH2.

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.

MOF-derived Cu based materials as highly active catalysts for improving hydrogen storage performance of Mg-Ni-La-Y alloys

Higher initial (de)hydrogenation temperature and sluggish kinetics are the main bottlenecks to develop Mg-based hydrogen storage alloys with high hydrogen capacity. One of the effective methods of solving these problems is introducing additives to enhance (de)hydrogenation kinetics and decrease particle sizes to lower (de)hydrogenation temperatures. In this work, Mg85-Ni10-La4.5-Y0.5 alloy doped with Cu@C nanoparticles is prepared, which could enhance (de)hydrogenation kinetics via introducing Cu nanoparticles as a catalyst and reduce the alloy particle sizes via acting as a grinding agent to lower (de)hydrogenation temperature. The results indicate the dehydrogenation temperature of the modified Mg85-Ni10-La4.5-Y0.5 composite could be decreased to 308.5 °C, absorb 4.73 wt% H2 at 220 °C within 1 min and release 5.01 wt% H2 within 4 min at 300 °C. Moreover, the capacity retention could be maintained around 98.8 % after 10 cycles at 300 °C, superior than those of Mg85-Ni10-La4.5-Y0.5 and milled-Mg85-Ni10-La4.5-Y0.5. DFT results and characterizations suggest that in-situ formed Mg2Cu could accelerate the dissociation of Mg-H bonds and the presence of amorphous carbon in Mg-Ni-La-Y-Cu system will further synergistically improve the (de)hydrogenation kinetics of Mg85-Ni10-La4.5-Y0.5. Reduced particle sizes under the aid of carbon frameworks also help introduce boundaries of the particles and shorten hydrogen diffusion pathways.

A2B7-type La–Mg–Ni alloys prepared by Mg thermal diffusion for improved hydrogen storage performance

A2B7-type La–Mg–Ni alloys prepared by Mg thermal diffusion for improved hydrogen storage performance

Microstructure and hydrogen storage properties of magnesium–gallium binary alloys

In this paper, gallium was used as alloying element to improve hydrogen storage properties of magnesium. Therefore, Mg–x wt% Ga (x = 5, 10, 25, 50) binary alloys were prepared by induction melting method. The microstructure and phase composition of Mg–Ga alloy were analyzed using X-ray diffractometer and scanning electron microscope. The results show that Mg–Ga binary alloys consist of Mg and Mg5Ga2 phases. The Mg and Mg5Ga2 react with H2 to form Mg2Ga and MgH2 during hydrogenation process. The hydrogen storage kinetics and thermodynamic properties of the alloys were tested using a Sieverts-type apparatus. It is found that the dehydrogenation rates of the samples increase with increasing gallium content, and they are all better than pure magnesium. Thermal analysis results indicate that increasing gallium content decreases dehydrogenation temperature of Mg–Ga alloy. The beneficial effects of adding gallium in magnesium is that interfaces and secondary phase resulted from alloying can promote the hydrogen desorption process of the alloy. The Mg–50 wt% Ga alloy has the lowest dehydrogenation activation energy. However, increasing gallium content inevitably reduces the hydrogen storage capacity of the Mg–Ga alloys. Furthermore, alloying with gallium does not change the thermomechanical properties of magnesium.

Benzyl-methylbenzyl-benzene: Improving hydrogen storage and release performance of dibenzyltoluene based liquid organic hydrogen carrier

Liquid organic hydrogen carrier (LOHC) technology enables the safe, easy, and cost-effective storage and transportation of large quantities of hydrogen using inexpensive and mass-produced compounds. The LOHC materials play a crucial role in hydrogen storage capacity, reaction kinetics, reaction temperature, and reversibility. However, the development and optimization of LOHC materials is limited due to using of mass-produced materials for bulk hydrogen logistics. Herein, we propose a molecular engineering approach to overcome the limitations of commercial dibenzyltoluene (DBT)-based LOHC systems, considered one of the most promising LOHC materials based on the heat transfer oil, Marlotherm SH (MSH), owing to its superior physical properties (wide liquid range, and non-flammable properties), low price, and low toxicity. We devised a new chemical structure, benzyl-methylbenzyl-benzene (BMB), with highly improved dehydrogenation/hydrogenation performance achieved by rearranging the methyl group of DBT to overcome the limitations of slow reaction kinetics in terms of its chemical structure. The BMB exhibits a 150 % faster hydrogenation than MSH at 150 °C, and it releases 170 % more hydrogen compared to DBT at 270 °C. In addition, we analyzed the dehydrogenation/hydrogenation pathways according to the structures of DBT and BMB. Furthermore, we found that BMB (27 %) is inevitably generated in the MSH synthesis process alongside DBT (73 %). Based on this, we propose a streamlined and sustainable engineered method for improved MSH material manufacturing with a high BMB ratio (∼70 %). The scientific findings provide a fundamental understanding of DBT-based LOHC systems and new insights into the design of novel LOHC candidates.

Lithium Borohydride Nanorods: Self-Assembling Growth and Remarkable Hydrogen Cycling Properties.

Nanostructured metal hydrides with unique morphology and improved hydrogen storage properties have attracted intense interests. However, the study of the growth process of highly active borohydrides remains challenging. Herein, for the first time the synthesis of LiBH4 nanorods through a hydrogen-assisted one-pot solvothermal reaction is reported. Reaction of n-butyl lithium with triethylamine borane in n-hexane under 50bar of H2 at 40-100°C gives rise to the formation of the [100]-oriented LiBH4 nanorods with 500-800nm in diameter, whose growth is driven by orientated attachment and ligand adsorption. The unique morphology enables the LiBH4 nanorods to release hydrogen from ≈184°C, 94°C lower than the commercial sample (≈278°C). Hydrogen release amounts to 13wt% within 40min at 450°C with a stable cyclability, remarkably superior to the commercial LiBH4 (≈9.1wt%). More importantly, up to 180°C reduction in the onset temperature of hydrogenation is successfully attained by the nanorod sample with respect to the commercial counterpart. The LiBH4 nanorods show no foaming during dehydrogenation, which improves the hydrogen cycling performance. The new approach will shed light on the preparation of nanostructured metal borohydrides as advanced functional materials.

Investigating the Catalytic Deactivation of a Pd Catalyst during the Continuous Hydrogenation of CO2 into Formate Using a Trickle-Bed Reactor

The practical application of formic acid production through the hydrogenation of CO2 has garnered significant attention in efforts to tackle the challenges associated with (1) achieving net-zero production of formic acid as a chemical feedstock and (2) improving hydrogen storage and transport. This study focuses on demonstrating the continuous operation of a trickle bed reactor for converting CO2 into formate using palladium on activated carbon (Pd/AC). Optimal temperature conditions were investigated through a dynamic operation for 24 h, achieving the maximum productivity of 2140 mmolFA·gPdsurf.−1·h−1 at 150 °C and 8 MPa, with an H2/CO2 ratio of 1:1; however, catalyst deactivation was observed in the process. Stability tests performed under continuous operation at 120 °C and 8 MPa with an H2/CO2 ratio of 1:1 indicated a gradual decline in productivity, culminating in a 20% reduction after 20 h. A comprehensive analysis comparing fresh and spent catalysts revealed that the diminished catalytic activity at elevated temperatures was attributed to the partial sintering and leaching of Pd nanoparticles during the hydrogenation process. These findings offer insights for the future development of novel Pd-based catalyst systems suitable for continuous hydrogenation processes.

Hybrid of bulk NbC and layered Nb4C3 MXene for tailoring the hydrogen storage kinetics and reversibility of Li–Mg–B–H composite: An experimental and theoretical study

The Li-Mg-B-H composite (2LiBH4 + MgH2) is acknowledged as a promising material for hydrogen storage due to its large hydrogen capacity (11.4 wt.%). However, the sluggish kinetics and poor reversibility make it difficult to be practically used. In this work, the hydrogen storage performances of 2LiBH4 + MgH2 have been significantly improved by a hybrid of bulk NbC and layered Nb4C3 MXene (denoted as “Nb–C”). The 2LiBH4 + MgH2 + 6 wt.% Nb–C can release 8.5 wt.% H2 within 30 min at 400 °C and the dehydrogenated composite can absorb 9.3 wt.% H2 within 30 min at 350 °C and 7.5 MPa H2. The reversible dehydrogenation capacity maintains at 8.4 wt.% after 24 cycles, with a capacity retention ratio of 95.4 %. By contrast, the undoped 2LiBH4 + MgH2 suffers from serious capacity degradation, with the capacity decreased dramatically to 3.5 wt.% after 3 cycles. Microstructural studies revealed that the doped composite has uniform particle and elemental distributions and possesses various multiphase interfaces of LiH/MgB2/NbC/Nb4C3, which is beneficial to hydrogen diffusion during the hydrogen uptake and release process. Theoretical studies by first principle calculation presented an extended bond length of the Mg–H and B–H bonds in the 2LiBH4 + MgH2 + NbC system, which may also explain the improved hydrogen storage properties of 2LiBH4 + MgH2 by addition of Nb-C. This work provides new insights into the role of transition metal carbides in regulating the Li–Mg–B–H hydrogen storage materials both experimentally and theoretically.