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In the pursuit of sustainable energy solutions, the development of materials with efficient hydrogen and methane storage capacities is imperative, particularly for advancing hydrogen-powered vehicles. Metal–organic frameworks (MOFs) have emerged as promising candidates to meet the stringent targets set by the Department of Energy for both hydrogen and methane storage. This study employs Grand Canonical Monte Carlo simulations to investigate the usable hydrogen and methane gravimetric and volumetric storage capacities of the recently synthesized SIGSUA. A comparative analysis encompasses the selected MOFs with similar metal compositions, those with comparable density and average pore radius, and classical benchmarks, such as IRMOF-15 and IRMOF-20, all evaluated at room temperature and moderate pressures ranging from 25 to 35 MPa. The results reveal that SIGSUA demonstrates noteworthy gravimetric and volumetric storage capacities for both hydrogen and methane, rivaling or surpassing those of the selected MOFs for analysis. These findings underscore the potential of SIGSUA in advancing clean energy storage technologies. [ABSTRACT FROM AUTHOR]

The reversible hydrogenation/dehydrogenation of aromatic molecules, known as liquid organic hydrogen carriers (LOHCs), is considered an attractive option for the safe storage and release of elemental hydrogen. The LOHC systems based on the alkoxy-naphthalene/alkoxy-decalin studied in this work can become potentially attractive from the point of view of the thermodynamic conditions of the reversible hydrogenation/dehydrogenation processes. This work reports the results of a complex experimental investigation of the thermochemical properties of the reactants of the LOHC systems. The enthalpies of formation were measured using high-precision combustion calorimetry, the enthalpies of vaporization and sublimation were derived from the vapor pressure–temperature dependencies measured using the transpiration method, and the melting temperatures and enthalpies of fusion were measured using the differential scanning calorimetry method. The liquid-phase enthalpies of formation of methoxy- and ethoxy-substituted naphthalenes and methoxy- and ethoxy-substituted decalins were derived and used for the thermodynamic analysis of hydrogenation/dehydrogenation reactions and transferhydrogenation reactions. [ABSTRACT FROM AUTHOR]

There is growing interest in the use of hydrogen as a transportation fuel but the environmental benefits of using hydrogen depend critically on how it is produced and distributed. Leading alternatives to using fossil natural gas to make hydrogen through the conventional method of steam methane reforming include using electrolyzers to split water into hydrogen and oxygen, and the use of biogas as an alternative feedstock to fossil natural gas. This report examines the latest carbon intensity (CI) estimates for these and various other hydrogen production processes, adding important nuances to the general “colors of hydrogen” scheme that has been used in recent years. CI values for hydrogen production can vary widely both within and across hydrogen production pathways. The lowest CI pathways use biomass or biogas as a feedstock, and solar or wind power. The report also analyses jobs creation from new hydrogen production facilities and shows that these benefits can be significant for large-scale facilities based on either future biomass/biogas-to-hydrogen or solar-hydrogen production technologies. Recommendations include setting stricter goals for the state’s Low Carbon Fuel Standard (LCFS) program to continue to reduce the carbon footprint of California’s transportation fuels.

Nanoscale magnesium clusters are important potential hydrogen storage materials, and density functional theory (DFT) is mainly used for their theoretical investigation. The results of the coupled-cluster theory at the singles and doubles level with a perturbative treatment of triples [CCSD(T)] were employed previously to choose proper exchange–correlation (XC) functionals in DFT calculations for magnesium clusters, but it is too expensive to be applied to Mgn with n > 7. The diffusion Monte Carlo (DMC) method is employed in this work to study magnesium clusters up to nanosize. The error of atomization energies with DMC using single-determinant-Jastrow (SDJ) trial wavefunctions has been shown to be somewhat larger than that of CCSD(T) for many molecules. However, cohesive energies with DMC using SDJ for Mgn with n ≤ 7 are in excellent agreement with those of CCSD(T) using the aug-cc-pVQZ basis set, with a difference of less than 1 kcal/mol. DMC results are employed to investigate the performance of different XC functionals on magnesium clusters. Our results indicate that the PBE0 functional is the best XC functional for determining the lowest-energy isomer when compared with DMC results, while the RPBE functional is the best XC functional for calculating cohesive energies per atom of these magnesium clusters with a mean absolute error of 0.5 kcal/mol. These XC functionals are expected to provide reasonable results for even larger magnesium clusters. [ABSTRACT FROM AUTHOR]

Hydrogen (H2) combustion and solid oxide fuel cells (SOFCs) can potentially reduce aviation-produced greenhouse gas emissions compared to kerosene propulsion. This paper outlines a methodology for evaluating performance and emission tradeoffs when retrofitting conventional kerosene-powered aircraft with lower-emissionH2 combustion and SOFC hybrid alternatives. The proposed framework presents a constant-range approach for designing liquid hydrogen fuel tanks, considering insulation, sizing, center of gravity, and power constraints. A lifecycle assessment evaluates greenhouse gas emissions and contrail formation effects for carbon footprint mitigation, while a cost analysis examines retrofit implementation consequences. A Cessna Citation 560XLS+ case study shows a 5% mass decrease for H2 combustion and a 0.4% mass decrease for the SOFC hybrid, at the tradeoff of removing three passengers. The lifecycle analysis of green hydrogen in aviation reveals a significant reduction in CO2 emissions for H2 combustion and SOFC systems, except for natural-gas-produced H2 combustion, when compared to Jet-A fuel. However, this environmental benefit is contrasted by an increase in fuel cost per passenger-km for green H2 combustion and a rise for natural-gas-produced H2 SOFC compared to kerosene. The results suggest that retrofitting aircraft with alternative fuels could lower carbon emissions, noting the economic and passenger capacity tradeoffs.

Motivated by the recent experimental study on hydrogen storage in MXene multilayers [Liu et al., Nat. Nanotechnol. 16, 331 (2021)], for the first time we propose a workflow to computationally screen 23 857 compounds of MXene to explore the general relation between the activated H2 bond length and adsorption distance. By using density functional theory we generate a dataset to investigate the adsorption geometries of hydrogen on MXenes, based on which we train physics-informed atomistic line graph neural networks (ALIGNNs) to predict adsorption parameters. To fit the results, we further derived a formula that quantitatively reproduces the dependence of H2 bond length on the adsorption distance from MXenes within the framework of Pauling's resonating valence bond theory, revealing the impact of transition metal's ligancy and valence on activating dihydrogen in H2 storage. [ABSTRACT FROM AUTHOR]

One of the important tasks of improving the properties of metal hydride reactors is the design of system with optimized heat and mass transfer. Many works are devoted to the selection of the optimal heat exchanger for metal hydride hydrogen storage systems. At the same time, it is necessary to consider the composition of the metal hydride bed, which affects thermal conductivity as well. Little attention has been paid to the study of heat transfer properties in hydrogen storage systems with a heat exchanger and a metal hydride bed based on magnesium hydride and carbon nanotubes. In this work we used numerical simulation to determine the effectiveness of carbon nanotubes addition and heat exchangers with different fin number and geometries on high-temperature magnesium-based hydrogen storage tanks performance. It was found, that increasing the number of fins from three to five makes a smaller contribution in the temperature increasing as compared to the addition of three fins to the heater. The three solid, radial and complex fins have a similar effect on the average Mg/MgH 2 bed temperature at 60 min. The most optimal fin number and geometry is three radial fins in terms of the efficiency and the volume it occupies. The addition of carbon nanotubes increases the average temperature of the Mg/MgH 2 bed by 67 K for a reactor equipped with a heater without fins. Hydrogen storage system with three radial fins and Mg/MgH 2 bed enhanced with carbon nanotubes provides an increase in the average bed temperature of about 180 K as compared to system without fins and nanotubes. This leads to a reduction in the hydrogen absorption time to reach 90% saturation by almost 63% for the three radial fins reactor with carbon nanotubes addition to the metal hydride bed. It has been confirmed that the addition of carbon nanotubes to Mg/MgH 2 makes a significant contribution to the heat transfer in the metal hydride bed. In addition, it is shown that both an increase in the heat transfer area and the thermal conductivity coefficient leads to a significant improvement in the efficiency of the metal hydride reactor. In the future, the obtained results can be taken into account when designing hydrogen storage systems based on these materials. • The different geometries of fins for heat exchanger in MHB are reviewed. • MHB with different numbers and geometries of fins were simulated and tested. • The influence of CNT on the rate of hydrogen saturation by the MHB was studied. • The thermal conductivity of MgH 2 +CNT was 2–4 times higher than that of Mg/MgH 2. [ABSTRACT FROM AUTHOR]

Hydrogen storage materials are crucial for the development of clean energy technologies, as they offer a sustainable solution for energy storage. Among various materials, magnesium hydride (MgH 2) offers excellent storage capacity and cost performance. However, its practical application is limited by slow dehydrogenation kinetics and high operating temperatures. To overcome these challenges, novel methods with improved properties are needed. This study aims to explore a two-dimensional (2D) MgH 2 structure and its modifications using density functional theory (DFT) and ab initio molecular dynamics (AIMD) calculations. We investigate the thermodynamic stability and dehydrogenation properties of pure 2D MgH 2 , as well as 2D MgH 2 doped with transition metals (Al, Cr, and Nb) and Mg-defects. Additionally, the effects of biaxial strain on pure 2D MgH 2 are explored. The results indicate that the decomposition temperature and stability can be reduced by introducing transition metals, applying biaxial strain, and creating defects. Furthermore, the Cr-doped 2D MgH 2 system exhibits excellent hydrogen storage performance and dehydrogenation kinetics under ambient conditions. It has a formation enthalpy of −39.68 kJ/mol.H 2 , a desorption temperature of 292.53 K, and an hydrogen storage capacity of 7.368 wt%. We also calculated the activation energy for hydrogen diffusion, showing that the lowest value, 0.089 eV, is observed in the Al-doped structure, indicating the fastest hydrogen diffusion among the modifications. These results are helpful for the understanding of absorption/desorption of the 2D MgH 2 system and could ultimately improve the design of Mg-based H 2 -storage materials. [Display omitted] • Stability and dehydrogenation properties of 2D MgH 2 are explored through DFT and AIMD simulations. • Thermodynamic properties were improved by applying compressive/tensile stress, metal doping, and vacancy-like defects. • Cr-doped 2D MgH 2 reaches up to 7.368 wt% with an dehydrogenation temperature of 292.53 K. • The diffusion of hydrogen atom is easier within Al-doped 2D MgH 2 than in other systems. [ABSTRACT FROM AUTHOR]

In this study, sustainable nanoporous carbon materials that are efficient, renewable, cost-effective and adaptable were developed. These microporous feature carbon adsorbents were synthesized utilizing a straightforward and efficient method. Plum stones are residual fruit materials that offer a financially feasible and sustainable carbon source with exceptional porosity and desirable elemental composition. The plum stones underwent carbonization and were subsequently chemically modified with polyaniline nanofibers and then subjected to chemical activation using different activating agents. This yielded sustainable nanoporous carbon with a high degree of porosity, in conjunction with doping with precious high electron density elements such as O, N and S. The sustainable nanoporous carbons that have been developed exhibits exceptional microporosity, with BET-SSA of 1705 m2 g−1 and a pore volume of 0.726 cm3 g−1, besides, the dominance of ultramicropores of 0.6 nm size. This in addition to convenient doping of oxygen, nitrogen and sulfur elements which are crucial for H 2 uptake. The developed nanoporous carbon demonstrated highly promising capabilities for storing H 2 molecules at cryogenic and ambient temperatures. The sustainable adsorbent achieved hydrogen storage capacities of 4.63 and 0.45 wt% at 77, 296 K, and a pressure of 40 and 80 bar, respectively. This H 2 storage capacity at RT is often regarded as one of the highest reported in the literature for nanoporous adsorbents. Moreover, study investigated the separation selectivity of developed adsorbents for CO 2 /H 2 based on uptake ratio at 30 bar and RT. The results demonstrated a significant separation selectivity reaching a value of 382.5 for the CO 2 /H 2 , which is regarded as one of the most elevated values documented in the existing literature for nanoporous carbon materials. Thus, the presented sustainable nanoporous materials have shown great promise for hydrogen storage, pre-combustion CO 2 capture and H 2 purification applications at ambient temperature. • Sustainable and cost-effective microporous carbons were developed. • Plum stones and their composites with nanofibers were used as renewable carbon precursor. • Efficient nanoporous carbon with high SSA and doped with precious heteroatoms were developed. • Ultra-micropores doped with O and N were engineered for high H 2 uptake at RT. • Outstanding H 2 uptake values of 4.63 and 0.45 wt% at 77, 296 K, were achieved. [ABSTRACT FROM AUTHOR]

Using first-principles calculations, we explore the potentials of boron hydride (BH) for hydrogen (H 2) storage. Lithium (Li) and potassium (K) dopants enhance the H 2 storage capabilities of BH. The binding energies of Li, and K are found as −2.65 and −1.69 eV, respectively, indicating a strong binding. Ab initio molecular dynamic (AIMD) simulations at 400 K provide insights into the thermal stability of Li-, and K-doped BH. Notably, H 2 molecule adsorptions on metal-decorated BH result in substantial binding energies of −0.45 and −0.29 eV/H 2 for Li, and K, respectively. Under layered adsorption, the BH–4Li (BH–4K) accommodates up to 38H 2 (34H 2) molecules, boasting an impressive gravimetric density of 26.46 (16.57) wt.%. Even a single layer of H 2 over BH–4Li, and BH–4K corresponds to 11.70 wt% and 7.56 wt%, respectively. Adsorption mechanism of H 2 could be tuned under the influence of stress and strain. Additionally, thermodynamic analysis based on Langmuir model is employed to elucidate the H 2 storage capabilities under practical conditions of temperature and pressure. [Display omitted] • Boron Hydride Monolayer (BH-ML) has been investigated as H 2 storage materials •Selected light metals (Li, and K) were used to decorate the BH-ML •Stabilities of dopants on BH-ML were confirmed •Li, and K-doped BH-ML resulted into tremendously high H 2 storage •Thermodynamic analysis further verified the practical H 2 storage applications [ABSTRACT FROM AUTHOR]

This paper employs first-principles calculations to comprehensively investigate the structural, dynamic, electronic, mechanical, and optical properties of A 2 BH 6 (A = K, Rb; B Ge, Sn) perovskite hydrides. Mechanical, thermodynamic, and dynamic stabilities are confirmed through calculations of elastic constants, formation energies, and phonon dispersion. The B/G ratio, below 1.75, indicates a brittle nature and a preference for covalent bonding. Electronic property analysis reveals that these hydrides are indirect band gap semiconductors with band gap values of 1.897 eV, 2.468 eV, 2.129 eV, and 2.657 eV, respectively. Optical property studies demonstrate high ultraviolet absorption. A key focus of this study is the gravimetric hydrogen storage capacities, which are found to be 3.84 wt% for K 2 GeH 6 , 2.97 wt% for K 2 SnH 6 , 2.48 wt% for Rb 2 GeH 6 , and 2.09 wt% for Rb 2 SnH 6. These findings not only enrich the research on the physical properties of perovskite hydrides but also provide an important theoretical basis and new options for the development of efficient hydrogen storage materials. The crystal structure, hydrogen storage capacity and band gap value of A 2 BH 6 (A = K, Rb; B Ge, Sn). [Display omitted] • A 2 BH 6 (A = K,Rb; B Ge,Sn) perovskite has been investigated using first-principles. • A 2 BH 6 (A = K, Rb; B Ge, Sn) exhibits thermodynamic, mechanical and dynamical stability. • A 2 BH 6 (A = K, Rb; B Ge, Sn) is a medium width indirect band gap semiconductor. • A 2 BH 6 (A = K, Rb; B Ge, Sn) has a hydrogen storage capacity of 2.09 W% to 3.84 W%. • The desorption temperature is found to be 221.1 K for K 2 SnH 6. [ABSTRACT FROM AUTHOR]

The practical application of hydrogen in daily life as a daily energy source, in competition with fossil fuels, is dependent upon the overcoming of the technical challenges associated with the storage of this energy. Although a considerable number of studies have been conducted on the storage of hydrogen in porous synthetic materials, including MOFs and carbon-based structures, there are fewer studies utilizing natural zeolites for the same purpose. In this study, the usability of natural chabazite (Raw-CHA) from Bala (Türkiye) for hydrogen storage was investigated. Firstly, the H+ form of Raw-CHA was obtained by modification with 1.0 M NH 4 NO 3 solutions at 80 °C for 4 h, followed by calcination at 400 °C for 5 h. Secondly, the H+ form was treated with different concentrations (0.05, 0.15, 0.25 and 0.50 M) of AgNO 3 , Ca(NO 3) 2.4H 2 O and Ni(NO 3) 2.6H 2 O solutions at 80 °C for 4 h to evaluate the effect of ion exchange with different cations on hydrogen adsorption. The samples were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), energy dispersive X-ray spectroscopy (EDS) and nitrogen adsorption methods. The hydrogen adsorption capacities of all the samples at 77 K exhibited a range of 0.818–1.080 wt%. [Display omitted] • Pretreatment with NH 4 NO 3 and calcination improved the hydrogen adsorption capacity. • Cation exchange after the pretreatment further enhanced hydrogen adsorption. • The highest hydrogen uptake was obtained after treatment with 0.05 M nickel nitrate. [ABSTRACT FROM AUTHOR]

Metal hydride is a type of solid hydrogen storage material that offers excellent hydrogen absorption and desorption reaction properties. However, there is a strong thermal effect during the reaction process when the materials are applied in reactors. Thus, effective thermal management techniques are crucial for promoting efficient reactions. Prior studies on the subject have shown that phase change materials can be coupled with metal hydride reactors to transfer the reaction heat. To further enhance the transfer of heat and reaction efficiency of the metal hydride reactors based on phase change materials, this study explored heat transfer enhancement methods on the phase change materials side, including adding heat transfer fins and discussing the fin parameters and composite foam metal. The findings of the study showed that in comparison to the reactor without fins, the absorption rate of adding 10 sets of fins can increase by 28%, and as the number of fins increased to 14, this value could increase to 39.4%. The use of Y-shaped fins did not substantially improve the reaction rate, mainly due to the sufficient number of straight fins, and the heat transfer area reaching the limit of the fin enhanced the process of heat transport. Thus, the improved method of using copper foam is further considered. Compared with the reactor with and without fins, the absorption rate of the copper foam coupled reactor is increased by 23.4% and 61.3%, respectively. • The fins on the PCM side can enhance the performance of MH reactors. • The shape and quantity of fins have limited performance enhancement effect. • Foam metal can significantly break the upper performance limit of fins. • MH reactor based on PCM composite copper foam shows excellent performance. [ABSTRACT FROM AUTHOR]

This study investigates strain engineering to optimize hydrogen storage in Mg₂NiH₄, with a focus on enhancing ionic conductivity and approaching room-temperature desorption. Using density functional theory (DFT), we analysed the effects of uniaxial and biaxial tensile and compressive strains on the structural, mechanical, diffusion kinetics, and electronic properties of Mg₂NiH₄. The activation energy for hydrogen diffusion was found to range from 0.38 to 0.45 eV under different strain conditions. The application of strain significantly influences ionic conductivity, with uniaxial strain resulting in values between 1.18 and 25.5 S/m, and biaxial strain yielding values from 12.3 to 18.3 S/m. Mechanical analysis shows that Mg₂NiH₄ exhibits brittle behaviour across all strain conditions. Additionally, electronic structure analysis indicates that the material maintains its metallic properties under both uniaxial and biaxial strain. Although the study did not achieve room-temperature desorption, it demonstrated significant progress, with desorption occurring at approximately 500 K. These results demonstrate that strain engineering can significantly improve ionic conductivity and facilitate hydrogen desorption closer to practical room temperature, providing valuable insights for optimizing Mg₂NiH₄ for practical hydrogen storage applications. • Strain Engineering can make Mg ₂ NiH ₄ more competitive for hydrogen storage. • Both uniaxial and biaxial tensile strains significantly improve hydrogenation and dehydrogenation kinetics in Mg ₂ NiH ₄. • Ionic conductivity improves notably under both compressive and tensile strain conditions. • The results meet DOE standards, Improving hydrogen storage potential in Mg 2 NiH 4. • Improvement in the thermodynamic properties of Mg ₂ NiH ₄ under uniaxial and biaxial strains. [ABSTRACT FROM AUTHOR]

Understanding the effects of Scandium (Sc) on the hydrogen absorption and desorption capabilities and the underlying mechanisms within Ti–Sc alloys is crucial for their applications as hydrogen storage materials. In this study, we explore the influence of Sc on deuterium (D) behavior in Titanium (Ti) films through a combination of experimental characterization and theoretical simulations. The Sc-doped Ti films with different Sc ratio were prepared using magnetron sputtering. Our findings indicate that Sc doping raises the D absorption temperature from 350 °C to 500 °C, and the Sc-doped Ti deuteride films exhibit higher apparent activation energies and temperatures for D desorption. Results from both experiments and DFT calculations indicate that these phenomena are attributed to the atomic size effect, in which the larger Sc atoms reduce the Ti–H spacing, thereby strengthening the interaction between the adjacent Ti atoms and H atoms. The enhanced interaction presents a greater challenge for H atom diffusion within α-Ti and complicates the dissociation of TiH 2. This study provides a vital theoretical and experimental basis for understanding the effects of Sc doping on the hydrogen absorption and desorption properties in titanium alloys. • Ti–Sc films possess higher hydrogen storage ability at high temperatures. • Sc increases the apparent activation energies for D desorption. • Sc doping strengthens the Ti–H bonds and enhances the hydride stability. • The rate-determining step of D absorption in Ti–Sc films changes with temperature. [ABSTRACT FROM AUTHOR]

The underground hydrogen storage represents a promising long-term, large-volume solution for hydrogen and hydrogen-methane blends, which is crucial for the anticipated "hydrogen economy" in South Asia. The suitability of any storage location hinges on its capacity and the associated costs of storage. This study provides a comparative analysis of the storage capacities for green hydrogen across fifty-nine porous geological reservoirs in India, Bangladesh, Pakistan, and Sri Lanka— the four major South Asian economies. The levelized cost of hydrogen storage (LCHS) was calculated for pure hydrogen storage in these basins. Additionally, the storage capacities of the five largest basins from India, Bangladesh, and Pakistan were evaluated for hydrogen-methane blends at 25%, 50%, and 75% concentrations. The findings indicate that South Asia's total pure hydrogen storage capacity is 29,799.43 TWh, with India contributing over 75%. Furthermore, hydrogen-methane blends were found to store more energy than pure hydrogen, with a 75% hydrogen blend storing over 65% more energy in the same basin. The primary cost factors for hydrogen storage in South Asia are compressor costs, followed by the costs of working gas and well construction. Under the parameters considered, the LCHS in India, Bangladesh, Pakistan, and Sri Lanka are $2.01, $1.28, $1.2, and $2 per kilogram of injected hydrogen. • 59 porous reservoirs of South Asian countries were evaluated for hydrogen storage. • Pure hydrogen storage capacity of South Asia is 29,799.43 TWh. • Hydrogen-methane blends store more energy than pure hydrogen in the same volume. • In South Asia, compressors have the highest capital cost, and working gas the lowest. • The LCHS: India $2.75/kg, Bangladesh $2.03/kg, Pakistan $1.95/kg, Sri Lanka $2.74/kg. [ABSTRACT FROM AUTHOR]

Efficient hydrogen storage is essential for its use as an energy source. Considering the various methods, hydrogen storage in solid materials shows great promise but requires further research. This study employs density functional theory using the Wien2k, with the LSDA method to determine the stability of this storage mode, and LSDA + mBJ to calculate the electronic, optical, and thermoelectric properties of AcH 3 and LaH 3. The electronic properties reveal that XH 3 (X = Ac, La) exhibits a semiconducting nature with indirect energy gaps in both cases. The analysis of hydrogen storage properties determined the gravimetric hydrogen storage capacities for AcH 3 and LaH 3 to be 1.297 and 2.086 wt%, respectively. Calculations of the elastic constants validated the mechanical stability of these compounds. Thermoelectric characteristics, including electrical and thermal conductivity, Seebeck coefficient, electronic specific heat capacity, and Pauli magnetic susceptibility, have been evaluated, highlighting their p-type characteristics. The figure of merit indicates their potential for thermoelectric devices. Gravimetric ratios suggest significant hydrogen storage capacity, which could contribute to various transportation and energy applications. [Display omitted] • Identified XH 3 (X = Ac, La) as promising materials for sustainable hydrogen storage solutions. • Optimized structural and elastic properties for efficient green energy storage. • Advanced first-principles approach enhances understanding of hydrogen storage materials. • Enhanced thermoelectric efficiency of XH 3 (X = Ac, La), crucial for renewable energy technologies. • Unveiled electronic and optical properties supporting advanced green hydrogen applications. [ABSTRACT FROM AUTHOR]

Hydrogen storage has garnered significant interest in recent years due to hydrogen's potential as an energy source. Research in this area focuses on exploring the hydrogen storage capabilities of newly identified compounds. This study presents a characterization of CsXH 3 (X = Ca, Sr, Ba) perovskite-type hydride compounds for the first time to assess their potential for hydrogen storage applications. The structural, mechanical, electronic, optical, and thermoelectric responses of studied hydrides are examined utilizing WIEN2k software. The calculated formation energy (ΔH F) values for CsCaH 3 , CsSrH 3, and CsBaH 3 are noticed as −3.20, −2.80, and −2.65 eV, respectively, ensuring their thermodynamic stability of these hydrides. The studied compositions exhibit their direct band gap of 3.21, 2.75, and 2.25 eV, which align well with other theoretical studies. Analysis of optical behavior exhibits that absorption of electromagnetic radiation starts in visible spectra and becomes maximum in the UV range. Furthermore, temperature-dependent transport characteristics including σ, κ e , S, PF, C v, and ZT are evaluated utilizing the BoltzTraP code. The large value of ZT suggests their suitability for thermoelectric application. For CsCaH 3 , CsSrH 3, and CsBaH 3 , the gravimetric ratios for hydrogen storage are 1.75, 1.34, and 1.10 wt %, respectively. This computational analysis marks a significant advancement in understanding different physical properties and possible implications of these hydrides in the fields of thermoelectric and hydrogen storage. [Display omitted] • The perovskites hydrides are emergent materials for hydrogen storage. • Structural, thermodynamic and thermally stable. • Thermodynamic, structural, and mechanical stability. • The absorption bands of light energy exist in the ultraviolet to the visible region. • The Large Debye and melting temperatures make them suitable for industrial applications. [ABSTRACT FROM AUTHOR]

Hydrogen energy represents a vital solution to the challenges posed by global warming and the advancement of a new energy paradigm. Underground salt caverns are considered optimal sites for large-scale hydrogen storage due to their cost-effectiveness, heightened safety measures, minimal hydrogen loss rates, flexible and swift injection-production conversion capacity, and pure hydrogen storage capability. Additionally, converting hydrogen to electricity can help alleviate the intermittency of renewable energy sources. However, due to the unique properties of hydrogen, further research is needed to ensure its safety. In this study, a three-dimensional full-scale model of an aboveground injection-production station for hydrogen storage in underground salt caverns is established to analyze the safety of the hydrogen explosion accident. Various equivalence ratio concentrations and ignition positions of the explosion development process and corresponding explosion characteristic parameters are compared to explore the hydrogen explosion accident evolution law and influence mechanism. Simultaneously, the hazardous area of high-temperature and high-pressure of the explosion and the safety distance are determined. The results reveal that overpressure and high-temperature flames from the compressor room severely affected the metering station in the -Y direction, forming a large area of high temperature and pressure damage on the ±Y side of the metering station. The temperature in the compressor room can reach up to 2400 K, with local pressure exceeding 6 bar, posing a severe risk of fatalities for personnel within the room. The hydrogen concentration affects the number of overpressure peaks in the explosion process. The occurrence, location, and quantity of venting external unburned hydrogen determine both the number and intensity of overpressure peaks. The minimum safety distances in the ± Y direction are 47.6 m and 43.9 m, respectively. [Display omitted] • The ground building model of UHS in salt caverns for hydrogen explosion is established. • Safe distance of the compressor room in UHS system is obtained. • Influence mechanism of various factors on explosion behavior is analyzed. • Spatial-temporal evolution process of hydrogen explosion accidents consists of four stages. • Damage effect of explosion accident consequence is quantitatively assessed. [ABSTRACT FROM AUTHOR]

An efficient energy carrier has become crucial as the globe shifts towards renewable energy. Many individuals regard hydrogen as the fuel of the future and a universal clean energy source. Unsurprisingly, the lack of advantages and technological challenges associated with hydrogen storage have resulted in a tardy mainstream adoption of the hydrogen economy. Due to the present commercial technology, which involves keeping H 2 in a pressurized and liquified state that demands extremely high pressure and extremely low temperature, storing H 2 under safe and operational circumstances continues to be a difficult process. Research on solid-state H 2 storage materials is underway to address this issue. Due to its high gravimetric capacity (the mass of borohydride materials release over 10% of H 2), borohydride is one of the solid-state H 2 storage materials that could be used. Mg(BH 4) 2 , a member of the borohydride family, has a high gravimetric capacity (14.9 wt%), which makes it a promising material for storing hydrogen. Nevertheless, slow sorption kinetics, poor reversibility, and a high thermal breakdown temperature (over 300 °C) prevent its practical utilization. Various approaches have been established so far to enhance the performance of Mg(BH 4) 2 , the primary focus of this review is on the current advancements (for the years 2018–2023). With this objective in mind, we discussed about its synthesis, structure, and additive use to alter Mg(BH 4) 2 property. Our main focus was on the methodologies that were modified to add an additive to Mg(BH 4) 2 , and we concluded by analysing the approaches in light of the US DOE's ultimate target for hydrogen storage. [Display omitted] • Synthesis of Mg(BH4)2 using ball milling is more effective compared to other methods. • Temperature and pressure play an import role in polymorphism of Mg(BH 4) 2. • Additive methodologies have been studied under the framework of DOE from 2018 to 2023. • Ball milling has proven to be the most effective method for incorporating additives into Mg(BH 4) 2. • RHC has significant potential as future materials for onboard hydrogen storage. [ABSTRACT FROM AUTHOR]

Liquid organic hydrogen carrier (LOHC) systems offer a promising way to store hydrogen using the existing infrastructure for liquid fuels. While LOHC hydrogenation and dehydrogenation processes have so far mainly been investigated using thermocatalytic processes, this work explores the concept of a low‐temperature (<80 °C) electrochemical acetone/isopropanol LOHC cycle and indicates its potential benefits for a future hydrogen economy. This electrochemical liquid organic hydrogen carrier (EC‐LOHC) system builds on low‐cost chemicals with low ecotoxicology. In this study, the influence of temperature and fuel concentrations on the polarization curves of the electrochemical hydrogenation and dehydrogenation units in a small, single‐cell set‐up is investigated using proton exchange membrane fuel cell components. Based on the experimental results, efficiencies are determined for a power‐to‐power cycle that can be competitive to mature hydrogen storage technologies, such as liquid and compressed hydrogen storage. Finally, material‐related challenges are discussed, encouraging future research in this new field of hydrogen storage. [ABSTRACT FROM AUTHOR]

Underground hydrogen storage (UHS) critically relies on cushion gas to maintain pressure balance during injection and withdrawal cycles, prevent excessive water inflow, and expand storage capacity. Interfacial tension (IFT) between brine and hydrogen/cushion gas mixtures is a key factor affecting fluid dynamics in porous media. This study develops four machine learning models— Decision Trees (DT), Random Forests (RF), Support Vector Machines (SVM), and Multi-Layer Perceptrons (MLP)—to predict IFT under geo-storage conditions. These models incorporate variables such as pressure, temperature, molality, overall gas density, and gas composition to evaluate the impact of different cushion gases. A group-based data splitting method enhances the realism of our tests by preventing information leakage between training and testing datasets. Shapley Additive Explanations (SHAP) reveal that while the MLP model prioritizes gas composition, the RF model focuses more on operational parameters like pressure and temperature, showing distinct predictive dynamics. The MLP model excels, achieving coefficients of determination (R2) of 0.96, root mean square error (RMSE) of 2.10 mN/m, and average absolute relative deviation (AARD) of 3.25%. This robustness positions the MLP model as a reliable tool for predicting IFT values between brine and hydrogen/cushion gas (es) mixtures beyond the confines of the studied dataset. The findings of this study present a promising approach to optimizing hydrogen geo-storage through accurate predictions of IFTs, offering significant implications for the advancement of energy storage technologies. • ML techniques were used to estimate IFT in H 2 /cushion gas (es)-brine systems. • A novel data splitting method focused on gas composition over sample quantity. • Inputs were pressure, temperature, molality, overall gas density, and gas composition. • The MLP model outperformed other models. • Shapley Additive Explanations (SHAP) approach was used to interpret the results. [ABSTRACT FROM AUTHOR]

The location of the H atoms in Ti, Zr, and Hf is crucial to the formation of the hydrides in these metals as it influences the crystal lattice transformation and the hydrogen diffusion involved in the hydride formation process. Although Ti, Zr, and Hf are all of hexagonal close-packed structure with similar lattice parameters, the solute H atom occupies the octahedral interstice in Ti but the tetragonal interstice in Zr and Hf, of which the origin is still mysterious. In the present work, the origin of the distinct site occupation behavior of H atom in Ti and Zr/Hf is investigated through first principles calculations. The calculated solution energies confirm that H prefers the octahedral interstice in Ti but the tetrahedral interstice in Zr and Hf. We ascribe the distinct site occupations of H in Ti and Zr/Hf to the varying Coulomb repulsion between the H (as a screened proton in the metals) and the matrix atoms against the interstitial size. The competition between the H-induced electron accumulation effect and the matrix atom debonding effect might matter as well. We propose that, as a general rule, a H atom prefers the site with a trade-off between a large space and a high electron density in metals. • Hydrogen occupies octahedral interstice in Ti but tetrahedral interstice in Zr/Hf. • H-metal atom Coulomb repulsion is responsible for the distinct site occupation of H. • H-induced electron redistribution might matter to the distinct site occupation of H. • H prefers the site with a trade-off between large space and high electron density. [ABSTRACT FROM AUTHOR]

The transition to a hydrogen future in the US will be driven by the demand for low-carbon energy carriers and enabled by the development of a robust hydrogen supply chain. Storing large quantities of hydrogen in the subsurface will likely be vital to this process. Two potential options to develop underground hydrogen storage (UHS) facilities are to repurpose existing subsurface gas storage facilities or to build new facilities. Regardless of the option chosen, the technoeconomics of UHS are not yet well understood. In this paper, we developed a technoeconomic analysis approach and applied it to a dataset of the technical characteristics of the existing underground natural gas storage facilities in the Commonwealth of Pennsylvania. The estimated levelized cost of hydrogen storage calculated for developing a new depleted hydrocarbon site ranged from $0.73 to $1.29/kg, while the cost to convert an existing site within PA's size range was 67%–99% of a new facility and ranged from $0.72 to $0.88/kg H 2. The highest LCHSs are for the Pennsylvania UHS facilities with the smallest capacities, but costs decrease as storage capacity increases only up to 1 Bcf. If cushion gas could be procured from a cheaper source, the median LCHS could be reduced by 36%. If an onsite electricity generation source, like solar or wind, is available to supplement electricity required and the overall price of electricity could be reduced by 50%, the LCHS could be reduced by 11% for a newly constructed storage site and 29% at a repurposed underground gas storage (UGS) site. Our results suggest that if existing UGS facilities in Pennsylvania were converted to store pure H 2 rather than natural gas, approximately 88% of the state's need for annual H 2 demand buffering in 2050 might be satisfied given that those facilities operate like current UGS facilities. • The costs of hydrogen storage were found to vary by size and depth of reservoirs. • The major costs drivers included the costs of surface equipment and electricity. • Hydrogen stored in existing UGS sites in PA can cover its 88% of demand in 2050. [ABSTRACT FROM AUTHOR]

Electrode materials based on zinc molybdenum oxides were designed by the saccharide-assisted sol-gel procedure for electrochemical hydrogen storage (EHS). By using different characterization methods to observe the formation of nanostructures, it was possible to determine that carbon texture was present on the nanostructured surfaces of zinc molybdenum oxides. The effects of employing various saccharides (mono, di, and poly saccharides) as carbon sources and fuel on the microstructure, electrochemical behaviors, and purity of synthesized samples were compared. The growth of nanocomposites including Zn 2 Mo 3 O 8 , ZnMo 8 O 10 , and Mo 8 O 23 phases was facilitated by the saccharide. A charge-discharge method was used to build three-electrode cells and expose them to galvanostatic cycling. To ascertain the stability of electrode architectures, cycling performance at various rates was carried out. The samples' hydrogen storage capabilities were examined, and the sample generated with glucose showed an optimum capacity about 1017 mAhg−1 after 15th cycle. • Saccharide assisted sol-gel synthesis of carbonous zinc molybdate nanocomposites as electrode materials. • Investigation of crystallinity, microstrain and structural parameters. • The assessment of hydrogen storage activity using comparative chronopotentiometry study. • Understanding of redox and physisorption-based efficient storage mechanisms. [ABSTRACT FROM AUTHOR]

Using density functional theory (DFT) and ab-initio molecular dynamics (AIMD) simulations, this paper thoroughly studied H 2 storage properties on Ca-decorated two dimensional (2D) Irida-graphene. The results manifest the pure Irida-graphene is not suitable for hydrogen storage due to the feeble adsorption ability for H 2 molecule, while the H 2 adsorption performance can be significantly strengthened through calcium (Ca) decoration. Charges transfer causes Ca atoms to firmly adsorb onto the octagonal carbon ring based on the largest binding energy, avoiding the formation of metal clusters. Moreover, the total number of 32H 2 molecules can be stably adsorbed by the both sides of Ca-decorated Irida-graphene with an ideal H 2 adsorption energy of −0.177 eV/H 2. Meanwhile, the estimated hydrogen storage weight density reaches up to 8.0 wt%, exceeding the target of 5.5 wt% reported from the U.S. Department of Energy (DOE) at 2025 year. In addition, the desorption temperature (T d) and AIMD simulations confirm that H 2 molecules can be quickly desorbed under the operated temperature at ambient conditions. These phenomenal findings demonstrate that Ca-decorated Irida-graphene can be expected to be an excellent material for storing hydrogen. [Display omitted] • H 2 adsorption properties of Ca-decorated 2D Irida-graphene were comprehensively investigated using DFT and AIMD simulation. • Ca-decorated 2D Irida-graphene is proven to be stable enough for hydrogen storage. • Maximum hydrogen storage weight density of Ca-decorated 2D Irida-graphene reaches 8.0 wt%, surpassing the objective specified by U.S. DOE. • Desorption temperature and AIMD simulation verify that the reversibility of H 2 storage at ambient conditions. [ABSTRACT FROM AUTHOR]

It has always been a difficult problem to design Kubas-type hydrogen storage materials that make hydrogen molecules activate but do not dissociate. Density functional theory calculations confirm that Ti decorated B-doped biphenylene is the first two-dimensional room-temperature hydrogen storage sponge reported so far. The hydrogen adsorption energy of Ti-decorated B-doped biphenylene is in the range of −0.29 ∼ −0.51 eV with hydrogen storage capacity is 6.58–9.13 wt%. What's very interesting and exciting is that the Kubas interaction between Ti sites and H 2 can be regulated by changing the electron occupation state of the d x2-y2 orbitals of Ti, and this regulation can be realized through the uniaxial lattice strain in the XOY plane. The average hydrogen adsorption energy of tensile Ti-decorated B-doped biphenylene ranges between −0.34 ∼ −0.66 eV, while −0.22 ∼ −0.48 eV for compressed one. This process makes the reversible hydrogen storage as simple and feasible as a sponge absorbing water. This study provides clear structural for the transformation mechanism to form a folded structure and also provides an important precedent model. Ti decorated B-doped biphenylene makes the room-temperature reversible hydrogen storage as simple and feasible as a sponge absorbing water. [Display omitted] • Ti-decorated BPN with different proportions of B were systematically constructed. • B doping enhances binding energy and ionization characteristics of Ti sites. • The hydrogen capacity of Ti-decorated BBPN reached 6.58–9.13 wt%. • Kubas interaction is regulated by occupation state of the Ti-d x2-y2 orbital. • E a is −0.34∼-0.66 eV for tensile Ti-BBPN, while −0.22∼-0.48 eV for compressed one. [ABSTRACT FROM AUTHOR]

This work investigated the influence of Ti and Nb interchangeability on the hydrogen sorption properties of the Ti x Nb 80-x Al 10 Cr 10 (x = 30, 40, and 50) multicomponent system. The CALPHAD method was successfully employed to design body-centered cubic (BCC) solid solutions. These alloys absorb hydrogen at room temperature, achieving a hydrogen-to-metal ratio of about 1.7. Pressure-Composition-Temperature diagram measurements demonstrated that increasing Ti content at the expense of Nb led to increased stability of the metal hydrides. DFT calculations of the pure elements and binary hydrides of the Ti–Nb–Al–Cr system were carried out, and the lattice parameters of the BCC alloy and FCC hydride and the enthalpy of hydride formation were estimated by applying an ideal mixing rule. The calculated and experimental results showed satisfactory agreement, indicating that the theoretical approach can be used to estimate the structural and thermodynamic parameters of alloys and hydrides of the Ti x Nb 80-x Al 10 Cr 10 system. [Display omitted] • The single-phase BCC Ti x Nb 80-x Al 10 Cr 10 (x = 30, 40, and 50) alloys were designed. • Increasing Ti content at the expense of Nb increases the stability of the hydrides. • The hydride stability is not directly correlated with the lattice volume of the host metal. • DFT and the mixture rule were employed to predict structural and thermodynamic parameters. [ABSTRACT FROM AUTHOR]

Scientists devote their time and energy to studying and developing hydrogen storage devices to address the energy crisis and climate change. Because of this, investigations are conducted to reveal the optoelectronic, structural, bader charge, electronic charge density, and hydrogen storage properties of X 2 LiAlH 6 (X = K, Mn) within the framework of density functional theory, and calculations of the structural characteristics were carried out utilizing local and nonlocal, and hybrid functionals. An additional onsite Coulomb parameter (GGA + U), which includes the Hubbard parameter, was used to apply the potential. Calculations based on the Kramer-Kroning principle were used to determine the dielectric function, refractive index, extinction coefficient, and energy loss function. The results indicate that K 2 LiAlH 6 and Mn 2 LiAlH 6 are highly suitable for hydrogen storage applications. The gravimetric ratios of hydrogen storage capacities for both investigated materials are 5.2 wt %, and 7.5 wt %, respectively. The interaction of the Mn-d, Li-s, K-s, and H-s/p orbitals was the cause of hybridization, according to the optoelectronic characteristics. Compound stability is indicated by the negative computed formation energy of the materials under investigation. The electronic charge density analysis showed a mixed-bond semiconductor with low ionicity and high covalence. In addition, the radiation shielding properties of Mn 2 LiAlH 6 and K 2 LiAlH 6 were investigated using Phy-X software, showing promising results in linear attenuation, half-value layer, and mean free path, particularly for Mn 2 LiAlH 6 due to its higher atomic number. This groundbreaking study represents a pioneering computational exploration of X 2 LiAlH 6 , offering promising advancements for future research in hydrogen storage applications. • The structural properties of X 2 LiAlH 6 were analyzed using DFT, revealing promising stability metrics. • Mn 2 LiAlH 6 shows enhanced radiation shielding due to its higher atomic number and interaction effects. • Hydrogen storage capacity for K 2 LiAlH 6 and Mn2LiAlH6 was calculated to be 5.2 wt % and 4.7 wt %, respectively. • Phy-X software simulations revealed Mn 2 LiAlH 6 's superior shielding performance against gamma rays. • Optical properties demonstrated high absorption coefficients, indicating potential for energy applications. [ABSTRACT FROM AUTHOR]

In the field of hydrogen storage and transportation, the development of hydrogen barrier coatings with excellent hydrogen permeation resistance is crucial for reducing hydrogen-induced damage caused by hydrogen leakage and hydrogen embrittlement. In recent years, benefiting from its excellent hydrogen barrier performance and wide application range, polymer-based hydrogen barrier composite coatings, membrane and films are expected to become an essential technology in promoting efficient hydrogen storage and transportation in the future. Primarily, starting from the material design of the composite systems, commonly applied gas barrier polymers and two-dimensional nanofillers are explicitly outlined. The detailed data of hydrogen barrier performance as well as advantages and disadvantages of their applications in this field are analysed and highlighted, and strategies are conceived and proposed to optimize their hydrogen barrier performance. Then, the major factors influencing the performance of hydrogen barrier composite system are put forward, providing ideas for strengthening the performance of hydrogen barrier composite from diverse perspectives and exploring failure mechanisms. Finally, a systematic classification overview of the currently researched hydrogen barrier composite system has been provided, and based on their different categories, the development trend of how to achieve large-scale applications of these coatings in the future is discussed. The H 2 barrier composite membrane, coating & film exhibit tremendous application prospects in abundant hydrogen-related fields. [Display omitted] • The H 2 barrier composites for efficient H 2 transportation and storage are discussed. • Major gas barrier polymers are explicitly summarized. • Common two-dimensional gas barrier fillers are outlined and compared. • Future development and optimization of H 2 barrier composites are envisioned. [ABSTRACT FROM AUTHOR]

Hydrogen storage in porous geological formations can potentially provide large-scale, seasonal storage of energy. This study investigates the effect of relative permeability hysteresis on the storage processes, particularly addressing the effects on the dynamics of the hydrogen plume, on the two-phase flow regime in the wellbore, and on the storage operations. Numerical simulations of the underground hydrogen storage processes are conducted for scenarios which account for and which ignore hysteresis. The hysteretic constitutive relationships used are based on two independent, experimentally derived datasets from literature. In scenarios that account for hysteresis, the hydrogen plume is less mobile and the hydrogen mass is more dispersed than in scenarios without hysteresis. In addition, hysteresis leads to increased brine upconing and influx into the production borehole. A simple analysis of the two-phase flow regime in the borehole provides an estimate of the required minimum flow rate to ensure annular flow. Though different, both hysteretic constitutive relationships used in this study yield the same trend. All the effects of hysteresis mentioned above are detrimental for hydrogen recovery and tend to be more significant in the first few storage cycles. Operationally, these problems could be addressed by providing for a rest period between injection and production that is long enough to let the hydrogen plume accumulate near the well and potentially by the use of a cushion gas. • Analysed effects of relative permeability hysteresis in underground hydrogen storage. • Hysteresis reduces hydrogen recovery especially in initial storage cycles. • Hysteresis reduces mobility of the hydrogen plume and increases its spread and extent. • Hysteresis increases brine upconing and affects the wellbore flow regime. [ABSTRACT FROM AUTHOR]

A typical feature that the LOHC technology shares with other types of chemical hydrogen storage is that the release of hydrogen from the carrier requires an input of heat. In many use cases where waste heat from external sources is not available (e.g. in heavy-duty mobility), this is seen as a major drawback. In this paper, we show that autothermal LOHC dehydrogenation offers a very attractive way to overcome this drawback. In detail, we demonstrate autothermal hydrogen release from dicyclohexylmethane using diphenylmethane oxidation to benzophenone as source of heat. The full storage cycle involves benzophenone hydrodeoxygenation to dicyclohexylmethane, dicyclohexylmethane dehydrogenation to diphenylmethane, and diphenylmethane oxidation to benzophenone. We studied both the individual reaction steps using pure feedstocks and the integral cycle in which the intermediates and by-products of each reaction remain in the system for the subsequent reaction step. Although no efforts have yet been made to develop special catalyst materials for this purpose, the results with the applied commercial hydrodeoxygenation (Pd/C), dehydrogenation (Pt on alumina) and partial oxidation (VO x /TiO 2) catalysts are already very promising. The storage cycle can be closed with high selectivity and with only minor total oxidation losses. The proposed concept of autothermal LOHC dehydrogenation offers the potential to increase the amount of useable hydrogen from a given amount of charged hydrogen carrier by up to 30%. • Autothermal dehydrogenation enables chemical hydrogen storage without external heat. • Dehydrogenation heat is provided through partial oxidation of the hydrogen carrier. • Regeneration takes place through hydrodeoxygenation at energy-rich locations. • Individual reaction steps and influencing parameters have been studied. • Full autothermal hydrogen storage cycle demonstrated for model system. [ABSTRACT FROM AUTHOR]

The potential solution to hydrogen storage and transportation challenges is provided by liquid fuel-based on-line hydrogen production. An online hydrogen production device has been constructed and the stable output of hydrogen at 6.8 bar under dynamic conditions of 6–13 Nm3/h has been achieved. To achieve optimal economic and thermodynamic performances, the mathematical models for mass, energy, and techno-economics are constructed based on field test data. The Non-Dominated Sorting Genetic Algorithm is employed to update temperature splitting points between multi-stage heat exchangers, targeting multi-objective optimization of heat exchange area, system energy efficiency, and annual average cost. Pareto optimal solutions indicate that such optimization can improve system energy efficiency by 0.03%–3.76% and decrease the hydrogen production cost from 0.004 $/kg to 0.599 $/kg. This work demonstrates the feasibility and effectiveness of multi-objective optimization for online hydrogen production system design and offers important guidance for decision-making in heat exchange network schemes. [Display omitted] • An on-line hydrogen production device based on MSR was established. • The device achieved a stable hydrogen output at 6.8 bar under dynamic conditions. • Mathematical model & multi-objective optimization is investigated for the device. • Solutions with favorable economic and thermodynamic performances were obtained. [ABSTRACT FROM AUTHOR]

Underground hydrogen storage (UHS) addresses the volume issue in hydrogen storage but the storage sites are prone to leakage. Currently, modeling-based approaches that utilize the reservoir's history for leakage detection are critically lacking for UHS. These methods offer a cheap and reliable approach to complement monitoring efforts of a UHS process. In this research, a semi-analytical modeling approach using pressure transient analysis is presented to detect leakage, estimate the leakage rate, and identify the most influential factors affecting the magnitude of the leakage rate in a multi-layered reservoir, in which hydrogen migrates from a target to a non-target layer. Multi-parameter sensitivity analysis using factorial design reveals hydraulic conductivity and layer flow capacity as key factors affecting leakage rate. A double evaluation algorithm with the capability of estimating the hydraulic conductivity is introduced that offers its highest accuracy (90%) when the first layer's flow capacity is lower than the second layer's. • Pressure transient approach for leakage detection in underground hydrogen storage. • Hydraulic conductivity and layer flow capacity parameters affect leakage the most. • Algorithm for hydraulic conductivity estimation using target layer's pressure data. [ABSTRACT FROM AUTHOR]

The testing of relay protection devices is an extremely important task on which the stable and safe operation of the power systems depends. One of the most complex and responsible kinds of protection in networks with rotating generation, which includes hydrogen fuel generation, is protection against loss-of-synchronism. Integration of heterogeneous generating electrical devices based on renewable energy sources and based on a hydrogen fuel cell is associated with the need for reliable relay protection. It disconnects tie-lines between the systems in out-of-step conditions. And it is a challenging task to simulate input signals corresponding to the exact settings of the out-of-step protection to make sure it operates correctly. This is because one has to simulate exact parameters of impedance locus (its radius, coordinates of the center in the impedance plane, spin direction, speed, etc.) while available tools embedded in testing devices often don't support such parameters directly. To deal with the problem, the authors present the approach to simulate instantaneous values of line currents and phase-to-ground voltages during the out-of-step operation. These electrical signals form the locus of the impedance vector with the desired parameters to test the operation of the out-of-step protection devices. The software based on the proposed algorithm also provides a graphical representation of the simulation results. All the proposed solutions proved to reduce the time required for commissioning of out-of-step protection and thereby increase tests quality and speed. (provided to the authors on 29.08.2024 for printing in IJHE from the archive of Fermaltech Montenegro Limited, made by A.L. Gusev using Designer. On the DALL E 3 platform.). [Display omitted] [ABSTRACT FROM AUTHOR]

Creating the porous Zinc-Zeolitic Imidazolate Framework (Zn-ZIF) using a solvothermal technique addresses the need for advanced materials with distinctive properties and cost-effectiveness in modern applications. The PXRD, SEM, UV-DRS, TEM, and TGA/DTG are used to characterize different concentrations of Zn-ZIF. Zn-ZIF's crystalline structure and phase purity have been verified by PXRD. Using diffuse reflectance spectra, the Kubelka-Monk function determined the band gaps of the Zn-ZIF samples, and scanning electron microscopy revealed a more porous structure. At 77 K and 1 bar, the Zn-ZIF solution with a 2:1 ratio had the highest hydrogen storage capacity (1.71 wt%). The electrochemical behavior of several Zn-ZIF electrodes in a 6 M KOH electrolyte was evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) experiments. The Zn-ZIF electrode with a 2:1 ratio exhibits a low charge transfer resistance and a high proton diffusion coefficient (D) of 1.687 × 10−4 cm2 s−1. The characteristics of the 2:1 synthesized Zn-ZIF electrode as a supercapacitor were investigated. Our analysis of the generated Zn-ZIF material's specific capacitance values after 2000 cycles revealed an impressive retention rate of nearly 89 %, with values of 296.6 Fg-1. In addition, we examined the photocatalytic activities of the as-synthesized material by exposing it to ultraviolet light and seeing how it degraded organic dyes such as Cango-Red (CR) dye. With a photocatalytic efficacy of 95.06 % for CR dye, Zn-ZIF (2:1 ratio) is the most effective. These findings should provide new knowledge for researchers interested in developing novel Zn-ZIF materials for photocatalytic, energy storage, and hydrogen storage applications. [ABSTRACT FROM AUTHOR]

Exploring high‐performance catalysts for hydrogen storage in magnesium hydride (MgH2) is crucial but still a challenge. Herein, Nb2CTx with controllable surface termination groups is developed as an efficient catalyst and the bifunctional modulation (adsorption energy and work function) of different surface termination groups (F, O, OH, or defects) is explored. First, compared to F and O, the introduction of OH on the surface or the direct removal of functional groups both leads to a significant increase in the adsorption of H by Nb2CTx. Second, compared to the surface bare, OH‐rich Nb2CTx has a lower work function, making it easier for hydrogen to enter Mg/MgH2 from the Nb2CTx surface or escape from the Mg/MgH2 surface into the Nb2CTx, thus facilitating the hydrogen ad/desorption properties of MgH2, i.e., the rate‐determining step (RDS) shifts from penetration to diffusion. The Nb2CTx‐KOH‐catalyzed MgH2 with optimal surface termination groups, therefore exhibits a release of 6.56 wt.% H2 in 5 min at 250 °C, and 6.46 wt.% H2 uptake within 5 min at 150 °C. The dehydrogenation and hydrogen uptake activation energies show 49.5% and 60.1% enhancements over pristine MgH2. In addition, a storage capacity of 5.51 wt.% is maintained after 50 dehydrogenation/hydrogenation cycles. [ABSTRACT FROM AUTHOR]

Eight scenarios where high efficiency reversible solid oxide cells (rSOC) are combined with an offshore wind farm are identified. Thanks to the PyPSA power system modelling tool combined with a sensitivity study, optimized rSOC system capacities, hydrogen storage capacities, and subsea cable connection capacities are investigated under various combinations of rSOC system capital cost, prices paid for hydrogen, and electricity prices, which give indications on the most profitable scenario for offshore hydrogen production from a 600 MW wind farm situated 60 km from shore. Low electricity prices (yearly average 45 £/MWh) combined with mild fluctuations (standard deviation 6 or 13 £/MWh) call for dedicated hydrogen production when the hydrogen price exceeds 4 £/kg. High electricity prices (yearly average 118 or 204 £/MWh), combined with extreme fluctuations (standard deviation between 73 and 110 £/MWh), make a reversible system economically profitable. The amount of hydrogen which is recommended to be reconverted into electricity depends on the price paid for hydrogen. Comparison of the optimized cases to the default case of a wind farm without hydrogen production improved profit by at least 3% and up to 908%. Comparison to the default case of dedicated hydrogen production, showed that in the case of low hydrogen prices, an unprofitable scenario can be made profitable, and improvement of profit in the case of a profitable default case starts at 4% and reaches numbers as high as 324%. [ABSTRACT FROM AUTHOR]

Highlights This study investigates the relationship between microstructure and mechanical properties of carbon fiber reinforced epoxy composites, specifically in the context of lightweight hydrogen storage pressure vessels manufactured by the filament winding process. The filament winding technique often introduces variability in fiber orientation and porosity which can lead to inconsistencies in mechanical properties. By investigating the influence of dynamic loading over a range of strain rates, from quasi‐static to 100 s−1, this research aims to understand the effects of different fiber orientations (±15° and ±30°) and multilayer structures on the performance of these composites. Using a custom‐designed Interrupted Dynamic Tensile Test (IDTT) apparatus, we investigated how damage mechanisms evolve during rapid tensile deformation. The results showed that porosity has a significant impact on mechanical performance, particularly at high strain rates, where cracks initiate at pores and propagate via fiber/matrix decohesion and fiber breakage. These microstructural defects contribute to mesoscopic failure mechanisms such as transverse cracking and micro‐delamination between composite layers. The mechanical properties were found to be strain rate sensitive, with visco‐damage phenomena playing a critical role in determining the damage evolution under dynamic loading. These findings provide important insights into the design and optimization of hydrogen storage vessels, highlighting the importance of controlling porosity and understanding the response of the composite to varying strain rates for improved durability and performance. Comprehensive analysis of dynamic loading. Influence of fiber orientation and porosity on mechanical integrity. Visco‐damage and failure mechanisms under high strain rates. [ABSTRACT FROM AUTHOR]

The hydrogen storage capabilities of the metal–organic framework (MOF) CALF-20 are examined experimentally with both cryogenic and near-ambient temperatures. This framework has a pore size that is nearly ideal for cryogenic hydrogen storage. Density functional theory (DFT) studies provide insights into the hydrogen binding sites within CALF-20. [ABSTRACT FROM AUTHOR]

A series of microporous defective HKUST-1 materials (DMT-HK-nF) are synthesized employing varying amounts (n = 10, 30, and 50 wt%) of 3,5-dinitrobenzoic acid (DNBA) and 1,3,5-benzene tricarboxylic acid as linkers. Subsequently, stepwise washing and solvent exchanges are conducted to enhance the density of Cu(I) sites and increases the surface area. DMT-HK-30F exhibits superior H 2 storage capacity (2.55 wt% at 77 K, 100 kPa and 0.93 wt% at 298 K, 7 MPa), approximately 41% and 48% higher compared to pristine HKUST-1 (1.82 wt% at 77 K, 100 kPa, and 0.63 wt% at 298 K, 7 MPa), respectively. This improvement is attributed to an increase in Cu(I) sites and the introduction of linker defects. However, further addition of DNBA decreases the H 2 storage capacity due to a reduction in Cu(I) sites and surface area caused by the formation of "missing metal cluster" defects. This study demonstrates that the simultaneous introduction of appropriate defects and high-density Cu(I) sites into the microporous structure is an effective strategy for enhancing the hydrogen storage performance of metal-organic frameworks. [Display omitted] • Defective HKUST-1-based MOFs were prepared by adding DNBA, a fragment linker. • StepWise washing and solvent exchanges increased the density of Cu(I) sites and the surface area. • Adding 30 wt% DNBA (DMT-HK-30 F) significantly enhanced H 2 uptake. • Missing-linker defects and high-density Cu(I) sites greatly enhanced H 2 uptake. • Excessive DNBA addition reduced H 2 uptake due to the formation of missing-metal-cluster defects. [ABSTRACT FROM AUTHOR]

Practical applications of magnesium hydride are hampered by high thermodynamic stability and slow kinetics. The design of highly active catalysts is essential to improve the kinetics of MgH 2. Although studies concerned with the interaction between MgH 2 and catalyst have remained quite active, detailed investigation of the beneficial effect from the phase transformation is lacking. Herein, a high-activity VS 2 was designed and introduced to catalyze MgH 2 , and the MgH 2 -VS 2 system exhibited superior hydrogen desorption capabilities at comparatively low temperatures (3.5 wt% H 2 , 1800 s, 225 °C). This enhancement in the hydrogen storage performance of MgH 2 was attributed to the in-situ phase transformation of the catalytic species during hydrogen cycling. DFT calculations demonstrated the catalytic effect of VS 2 and in-situ formation of new species relative to MgH 2. Our results provide a deeper insight into enhancing dehydrogenation mechanism on metal hydrides of the high-activity catalyst. • MgH 2 -VS 2 showed superior dehydrogenation kinetics (3.5 wt% H 2 in 1800 s at 225 °C). • The dehydrogenation activation energy was reduced from 154 kJ/mol to 89.09 kJ/mol. • Unique catalytic effect of highly reactive VS 2 was revealed. [ABSTRACT FROM AUTHOR]

Hydrogen energy plays a growing role in the present energy market and attracts more attention in scientific researches and commercial application. Hydrogen energy has an increasing attractive in energy market due to its high energy density, pollution-free utilization usage and wide availability. Current challenge which obstructs large-scale application is safe and reliable hydrogen storage, which requires finding promising materials to promote hydrogen energy. Therefore, we have predicted three potential lithium-transition metal-based hydrides LiTM 3 LiH 8 (TM = Sc, Ti V) for hydrogen storage based on first principles calculation. The stability analysis based on formation energy, elastic constants and phonon spectra confirms all hydrides are stable and feasible in practical application. Besides, they have a increasing ductility in the order of Sc, Ti and V. Among all studied materials, LiV 3 LiH 8 has the best mechanical characteristics due to its excellent ductility and high Young's modulus (123.19 GPa), which are beneficial for resistance to adverse external surroundings. The electronic properties suggest that all hydrides metallic in band structures. Meanwhile, we analyzed how hydrogen was storage and the binding information from multiple perspectives, including the charge analysis, DOS, ELF and COHP. From multiple analyses of bond strengths, except the strong binding from transition metal, the centered Li atom is verified to possess greater influence than corner Li atom, which makes a viable regulation of hydrogen properties by substituting centered alkali metal atom in future. As concluded in this study, LiTi 3 LiH 8 has a high storage capacity of 4.83 wt% along with a desorption temperature of 305.5 K, which is considered as a promising hydrogen storage material. • Novel cubic hydrides LiTM 3 LiH 8 (TM = Sc, Ti, V) are studied by first-principles for hydrogen storage. • All hydrides are metallic in band structures and LiV 3 LiH 8 is ductile in elastic properties. • The multiple bond analyses indicate centered-Li atom has a greater effect on hydrogen binding. • LiTi 3 LiH 8 has a high storage capacity of 4.83 wt% along with a desorption temperature of 305.5 K. [ABSTRACT FROM AUTHOR]

Researchers are investigating the integration of metal hydride reactors (MHR) with phase change materials (PCMs) to enhance hydrogen storage and thermal energy management. This approach, first proposed in 2013, combines two technologies for improved thermal management and energy efficiency. Despite numerous numerical studies, experimental investigations on MHR-PCM integration remain limited. This study experimentally evaluates an MHR filled with TiMn2-type hydride and coconut oil PCM, achieving a maximum hydrogen storage efficiency of 40% at specific ab/desorption pressures of 16/0.05 bar. Adding 1 wt% of additives like graphite, Al 2 O 3 and MgO, significantly reduces absorption time and boosts hydrogen storage capacity by 11%. Additionally, two-dimensional numerical modeling was developed, validating experimental results with less than ±8% error, thus demonstrating the effectiveness of MHR-PCM systems in hydrogen storage applications. [Display omitted] • Experimental study of H 2 storage performance of an MH reactor equipped with PCM. • The hydrogen storage efficiency is limited to 40 % during H 2 ab/desorption cycle. • The insertion of 1 wt% additives into PCM reduced the H 2 absorption time by 50 %. • Gaussian and sigmoid functions fit well the experimental PCM melting fraction. [ABSTRACT FROM AUTHOR]

In this paper, a novel methodology to improve the structural behaviour and durability of bedded salt caverns for hydrogen storage is proposed. The suggested technology consists in applying a gunite lining over the whole cavern surface by means of a pneumatic air blowing. This continuous flow projected at high speed onto the cavern surface produces a self-compacted gunite facing. The effect of adding a gunite lining on the structural performance of a bedded salt cavern is analysed. The nonlinear finite element method is then applied to solve the inherent nonlinear solid mechanics problem. It is shown that reinforcing salt caverns with a gunite lining improves the cavern behaviour, specially in the case of caverns located within a horizontal salt stratum confined between other strata. When dealing with these salt formations, the stratum geometry limits the cavern height. In general, wider caverns that exhibit larger displacements are required to achieve a huge storage capacity. Moreover, these caverns can be located at a considerable depth, where the temperature has an important role on the creep deformation process. Therefore, the proposition of stabilization techniques is required to ensure both their structural integrity and the ground subsidence. This technology allows the safe exploitation of salt caverns located at bedded-type stratified horizontal salt formations. [Display omitted] • Gunite lining of salt caverns. • Green Hydrogen storage. • Underground Hydrogen Storage. • Underground storage in salt bedded formations. • Geomechanics and Solid Mechanics with numerical modelling. [ABSTRACT FROM AUTHOR]

Aqueous ammonium ion batteries (AIBs) pose the advantages of high safety, low cost, and high efficiency, capturing substantial research interest. The intrinsic chemical properties of NH4+ promote the formation of hydrogen bonds with other constituents in AIBs, critically influencing the processes of NH4+ transfer, storage, and diffusion. This review delves into the pivotal role of hydrogen bonding chemistry in AIBs. Firstly, the principles of hydrogen bond are elucidated as the dominant chemical interaction governing NH4+ dynamics in AIBs. Subsequently, a detailed analysis is conducted on the impacts of hydrogen bonds in both electrolytes and electrode materials. Furthermore, the practical applications of hydrogen bonding chemistry within the context of AIBs are assessed. Finally, strategic insights and future research directions are proposed to harness hydrogen bonding effects for optimizing AIB performance. This review aims to define the mechanisms and impacts of hydrogen bonds in AIBs, providing robust strategies to enhance electrochemical performance, deepen the understanding of energy storage mechanisms, and guide the future advancement of AIBs technology. [ABSTRACT FROM AUTHOR]

Fluctuations in the production of renewable-based electricity have to be compensated by converting and storing the energy for later use. Underground methanation reactors (UMR) are a promising technology to address this issue. The idea is to create a controlled bio-reactor system in a porous underground formation, where hydrogen obtained from renewable energy sources by electrolysis and carbon dioxide from industrial sources are fed into the reactor and converted into methane. Microorganisms, known as methanogenic archaea, catalyze the chemical reaction by using the two non-organic substrates as nutrients for their growth and for their respiratory metabolism. The generated synthetic methane is renewable and capable to compete with the fossil methane. Mathematical models play an important role in the design and planning of such systems. Usually, a numerical solution of the model is required since complex initial-boundary problems cannot be solved analytically. In this paper, an existing bio-reactive transport model for UMR is simplified to such an extent that an analytical solution of the advection-dispersion-reaction equation can be applied. A second analytical solution is used for the case without dispersion. The analytical solutions are shown for both the educt (hydrogen) and the reaction product (methane). In order to examine the applicability of the analytical models, they are compared with the significantly more complex numerical model for a 1D case and a 3D case. It was shown that there is an acceptable agreement between the two analytical solutions and the numerical solution in different spatial plots of hydrogen and methane concentration and in the methane concentration in the withdrawn gas. The mean absolute error in the mole fraction is well below 0.015 in most cases. The spatial distribution of the hydrogen concentration in the comparison to the 3D case shows a higher deviation with a mean absolute error of approx. 0.023. As expected, the model with dispersion shows a slightly lower error in all cases, as only here the gas mixing resulting in smeared displacement fronts can be represented. It is shown that analytical modeling is a good tool to get a first estimation of the behavior of an UMR. It allows to help in the design of well spacing in combination with the injection rate and injected gas composition. Nevertheless, it is recommended to use more complex models for the later detailed analysis, which require a numerical solution. [ABSTRACT FROM AUTHOR]

In this paper, compositions within the TiZrAlCrMn, TiZrAlCrFe, and TiZrAlMnFe alloy systems that form the C14 Laves phase are investigated. The design, synthesis, structural, and hydrogen storage characterizations for an equiatomic and a non‐equiatomic composition for each alloy system are presented. Additionally, the further development of a thermodynamic method for the calculation of pressure‐composition‐isotherms (PCIs) is presented of C14 Laves phase alloys that absorb hydrogen by solid solution. Overall, the results shown in this paper indicate that Al‐containing multicomponent alloys can present promising hydrogen storage performance under high pressures. Nonetheless, high concentrations of aluminum in highly concentrated (equiatomic) alloys can have a negative impact on the hydrogenation properties. The Ti0.29Zr0.05Al0.05Cr0.26Mn0.35 composition showed promising hydrogenation/dehydrogenation properties. The gravimetric capacity of this alloy is ≈1.76 wt.% H2 and the PCIs measured indicate that this material has potential for high‐pressure hydrogen storage and compression applications. The use of the presented thermodynamic model for the design of multicomponent alloys is suggested. [ABSTRACT FROM AUTHOR]

In this study, under the conformity of engineering reality, considering the influence of slip coefficient on the variation range of winding angle, 15 composite lay‐up schemes of hydrogen storage vessels were designed using grid theory, and the hydrogen storage vessels's structural strength was analyzed. The distribution of non‐geodesic fiber windings on the outer surface of the inner layer was solved using differential theory and the winding principle, and ABAQUS established the finite element model. The maximum stress value and stress distribution of the composite layer of the hydrogen storage vessel along the fiber direction were studied, the damage of the composite layer was analyzed, and the pressure and mode of the bursting were predicted. Results show that the structural strength of the hydrogen storage vessel designed by this method can be effectively guaranteed. The hoop winding layer bears the majority of the stress on the hydrogen storage vessel, while the helical winding layer's fiber strength is not entirely utilized. The hydrogen storage vessel gains greater structural strength when the circumferential winding layer is concentrated and situated at the outermost portion of the composite layer. The layup scheme has an impact of approximately 17.21% on burst pressure. Highlights: Effect of slip coefficient on the change of winding angle.Different forms of composite lay‐up schemes were designed.The stress distribution in the composite layer was studied.Analyzed structural strength and damage of the composite layer.Predicted the pressure and mode of bursting. [ABSTRACT FROM AUTHOR]

In order to cope with the increasing energy demand and achieve the "double carbon "goal of China's 14th Five-Year Plan," combined with hydrogen energy storage technology, it has the characteristics of zero pollution, high efficiency and rich source. In the context of reducing energy consumption and the vigorous development of hydrogen energy storage technology, a multi-objective optimization configuration model with economy, energy consumption index and carbon emission index is proposed, which takes into account the working characteristics of the hydrogen energy storage system, and the exothermic heat release from the electrolysis tanks and fuel cells when they are working to provide the loads with an additional heat source of the Combined Cooling, Heating and Power (CCHP) system, to reduce energy consumption and carbon emission. Finally, taking a region as an example, a multi-objective optimization algorithm based on decomposition is used to solve the model, so as to obtain a series of alternatives with better optimization effect. At the same time, the two-way projection method based on interval intuitionistic fuzzy information is used to make decisions, and the scheme that optimizes the economy, energy consumption index and carbon emission index is obtained, which verifies the feasibility of the system proposed in this paper. [ABSTRACT FROM AUTHOR]