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The development of the first microfluidic paper-based analytical device (µPAD) for the speciation of inorganic arsenic in environmental aqueous samples as arsenite (As(III)) and arsenate (As(V)) which implements hydride generation on a paper platform is described. The newly developed µPAD has a 3D configuration and uses Au(III) chloride as the detection reagent. Sodium borohydride is used to generate arsine in the device's sample zone by reducing As(III) in the presence of hydrochloric acid or both As(III) and As(V) (total inorganic As) in the presence of sulfuric acid. Arsine then diffuses across a hydrophobic porous polytetrafluoroethylene membrane into the device's detection zone where it reduces Au(III) to Au nanoparticles. This results in a color change which can be related to the concentration of As(III) or total inorganic As (i.e., As(III) and As(V)) concentration. Under optimal conditions, the µPAD is characterized by a limit of detection of 0.43 mg L−1 for total inorganic As (As(III) + As(V)) and 0.41 mg L−1 for As(III) and a linear calibration range in both cases of 1.2–8.0 mg As L−1. The newly developed µPAD-based method was validated by applying it to groundwater and freshwater samples and comparing the results with those obtained by conventional atomic spectrometric techniques. [ABSTRACT FROM AUTHOR]

A novel visual detection method was developed for the determination of zinc (Zn) in whole blood and cells using gold nanoclusters (AuNCs) immobilized paper. The detection of Zn was based on a headspace-solid phase extraction (HS-SPE), visible fluorescence from the AuNCs coated paper was quenched by ZnH 2 generated from hydride generation (HG). The potential mechanism was investigated by using X-ray photoelectron spectroscopy (XPS) and Density Functional Theory (DFT). The selectivity was significantly increased because the zinc hydride was effectively separated from sample matrices by hydride generation. A limit of detection (LOD) of 3 μg L −1 Zn 2+ and a relative standard deviation (RSD, n = 7) of 2% at a concentration of 50 μg L −1 of Zn 2+ were obtained when using a commercial fluorescence spectrophotometer as the detector. In visual detection, as low as 20 μg L −1 of Zn 2+ in biological samples can be easily discriminated from the blank with the naked eye. The proposed method retains several unique advantages, including straightforward, rapid, affordable and equipment-free for visual detection. [ABSTRACT FROM AUTHOR]

This paper provides an in-depth examination of critical and strategic raw materials (CRMs) and their crucial role in the development of electrolyzer and fuel cell technologies within the hydrogen economy. It methodically analyses a range of electrolyzer technologies, including alkaline, proton-exchange membrane, solid-oxide, anion-exchange membrane, and proton-conducting ceramic systems. Each technology is examined for its specific CRM dependencies, operational characteristics, and the challenges associated with CRM availability and sustainability. The study further extends to hydrogen storage and separation technologies, focusing on the materials employed in high-pressure cylinders, metal hydrides, and hydrogen separation processes, and their CRM implications. A key aspect of this paper is its exploration of the supply and demand dynamics of CRMs, offering a comprehensive view that encompasses both the present sttate and future projections. The aim is to uncover potential supply risks, understand strategies, and identify potential bottlenecks for materials involved in electrolyzer and fuel cell technologies, addressing both current needs and future demands as well as supply. This approach is essential for the strategic planning and sustainable development of the hydrogen sector, emphasizing the importance of CRMs in achieving expanded electrolyzer capacity leading up to 2050. • Analyzes CRMs in hydrogen tech, focusing on electrolyzers and fuel cells. • Explores CRM implications in hydrogen storage and separation. • Investigates CRM supply and demand, identifying risks and strategies. • Highlights the role of CRMs in sustainable hydrogen sector development. [ABSTRACT FROM AUTHOR]

Using the WIEN2k code, first-principles simulations of ZrXH 3 (X = Zn, Cd) hydride perovskites are performed to determine their hydrogen storage properties. The purpose of this study is to investigate their structural, optoelectronic, hydrogen storage, mechanical and thermoelectric properties. The structural analysis demonstrates their stability through the heat of formation along with desorption temperature and shows that these compositions belong to the orthorhombic space group Cmcm (no.63). The band structure and density of states are estimated for electronic characteristics, indicating the metallic nature of both compositions. Analysis of elastic properties such as elastic constants, Pugh's ratio, bulk modulus, Poisson's ratio, and anisotropy factor are explored to determine the mechanical stability of these compositions and demonstrate their suitability as a transport medium in hydrogen storage systems even at higher pressure. To study the optical behavior of the perovskites under consideration for hydrogen storage applications, the dielectric parameters, dielectric constants, refractive index, optical conductivity, absorptivity, and energy loss function are studied. The present paper represents the initial theoretical effort toward future exploration of these materials for hydrogen storage applications. [Display omitted] Using the WIEN2k code, first-principles simulations of ZrXH 3 (X = Zn, Cd) hydride perovskites are performed to determine their hydrogen storage properties. The purpose of this study is to investigate their structural, optoelectronic, hydrogen storage, mechanical and thermoelectric properties. The structural analysis demonstrates their stability through the heat of formation along with desorption temperature and shows that these compositions belong to the orthorhombic space group Cmcm (no.63). The band structure and density of states are estimated for electronic characteristics, indicating the metallic nature of both compositions. Analysis of elastic properties such as elastic constants, Pugh's ratio, bulk modulus, Poisson's ratio, and anisotropy factor are explored to determine the mechanical stability of these compositions and demonstrate their suitability as a transport medium in hydrogen storage systems even at higher pressure. To study the optical behavior of the perovskites under consideration for hydrogen storage applications, the dielectric parameters, dielectric constants, refractive index, optical conductivity, absorptivity, and energy loss function are studied. The present paper represents the initial theoretical effort toward future exploration of these materials for hydrogen storage applications. • Stability of ZrXH 3 (X = Zn, Cd) hydride perovskites is confirmed by Enthalpy of formation. • ZrXH 3 (X = Zn, Cd) hydride perovskites have high value of decomposition temperature. • The gravimetric hydrogen storage capacities comes out to be 1.89 % and 1.46 % respectively. • Metallic behavior is reveled by electronic structure of these hydrides. [ABSTRACT FROM AUTHOR]

Hydrogen is an attractive automotive fuel because it is carbon-free, abundantly available from water, and has an exceptional mass-energy density. Hydrogen storage has become a trendy topic in recent years with its ability to design low-cost, lightweight materials that can reversibly and rapidly store hydrogen near ambient conditions. Various materials-based systems, such as metal hydrides and metal-organic frameworks (MOFs), have been introduced. This paper discusses and compares each material in terms of hydrogen storage capacity, kinetics, and viability. Different types of metal hydrides, such as magnesium hydrides, complex hydrides, and intermetallic-compounds hydrides, are considered. Furthermore, promising MOFs materials such as zinc- and copper-based MOFs are mentioned. The paper also compares the materials in terms of storage cost, which is rarely discussed in the literature. Results show that metal hydrides require severe pressures and temperatures to achieve optimum storage capacity, which is difficult to obtain and maintain. On the other hand, MOFs have some advantages, such as high surface area, high pore volume, as well as rich open metal sites. However, these properties being offered via MOFs have a limitation of low hydrogen uptake at ambient temperatures for hydrogen storage. This limitation is overcome by designing MOFs with unsaturated open metal sites. Future research is needed to optimize metal hydrides and MOFs to perform better under normal operating conditions to meet the recommendations of the United States Department of Energy. [ABSTRACT FROM AUTHOR]

Three kinds of structured carbon-nanofibers/carbon-paper (CNFs/CP) composites were synthesized through in-situ growth of CNFs on the surface of CP by catalytic chemical vapor deposition, and directly employed as the catalytic supports to disperse active Pt nano-particles for decalin dehydrogenation to produce CO x -free hydrogen. The CNFs/CP composites combined the unique physico-chemical properties of CNFs and the excellent thermal conductivity and the large geometric surface area of CP, making them favorable for heat transfer to the strongly endothermic dehydrogenation reaction. The reaction and composite variables such as the feed volume and the CNF yield were optimized for pursuing the maximum amount of hydrogen evolution in a definite reaction time. The effects of morphology, texture property and microstructure as well as surface chemistry of CNFs of different CNFs/CP composites on the catalytic performance were investigated. The results show that the largest accumulative hydrogen amount (4.32 mol/g Pt ) in 2 h was generated from a proper volume of decalin over a novel structured Pt/CNFs/CP catalyst, which was fabricated with an appropriate growth of CNFs yielding 2.7 (wt./wt.) on CP via catalytic decomposition of CO gas over Fe particles. [ABSTRACT FROM AUTHOR]

Hydrides enable handling hydrogen at low pressure and near room temperature, offering higher volumetric densities than compressed or liquid hydrogen and enhancing safety. The CALPHAD method, rooted in the principles of thermodynamics, offers a systematic approach for predicting phase equilibria and thermodynamic properties in multicomponent materials. This comprehensive review paper aims to provide a detailed overview of the application of the CALPHAD method in the realm of metallic and complex hydrides. After an introduction to the fundamental thermodynamic aspects of hydrides, key elements of applying the CALPHAD method to model metal-hydrogen systems and complex hydrides are discussed. Subsequently, recent publications are reviewed, highlighting key findings and recent progresses in the field. Finally, the challenges that must be overcome to achieve further progress in this area are explored. [ABSTRACT FROM AUTHOR]

Among the global carbon emissions in different fields, the carbon emissions in the transportation sector account for more than 1/4. Only the development of passenger car technology makes it difficult to achieve the climate goals. E-bike is considered to be one of the effective solutions. Hydrogen energy, as one of the representatives of new energy, has the advantages of cleanliness, high efficiency, and high energy density. Therefore, in this paper, a long-range hydrogen-electric hybrid bike and its energy management strategy are designed to achieve optimal performance. Herein, two energy management strategies, including the threshold-based and fuzzy logic optimized threshold-based strategy, are designed and compared by evaluating the parameters of equivalent hydrogen consumption, state of charge fluctuation, and the final state of the control system. The results show that with an initial SOC of 50% for Li-ion battery, the fuzzy logic optimized threshold-based strategy reduces equivalent hydrogen consumption by up to 16% compared to the threshold-based strategy. Besides, the fluctuation of the Li-ion battery's state of charge could be reduced by up to 54.7%, indicating that the fuzzy logic optimized threshold-based strategy is a promising energy management strategy for fuel cell hybrid E-bike. [Display omitted] • A long-range hydrogen-electric hybrid E-bike with metal hydride hydrogen storage is designed. • A fuzzy logic optimized threshold-based energy management strategy (EMS) is proposed. • Li-ion battery SOC fluctuations could be reduced by up to 54.7% via fuzzy logic optimized EMS. • Fuzzy logic optimized EMS shows self-adaptability and economic H 2 consumption for hybrid E-bike. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this work was to determine the hydrogen production from paper mill wastes using microbial consortia of solid substrate anaerobic digesters. Inocula from mesophilic, continuous solid substrate anaerobic digestion (SSAD) reactors were transferred to small lab scale, batch reactors. Milled paper (used as a surrogate paper waste) was added as substrate and acetylene or 2-bromoethanesulfonate (BES) was spiked for methanogenesis inhibition. In the first phase of experiments it was found that acetylene at 1% v/v in the headspace was as effective as BES in inhibiting methanogenic activity. Hydrogen gas accumulated in the headspace of the bottles, reaching a plateau. Similar final hydrogen concentrations were obtained for reactors spiked with acetylene and BES. In the second phase of tests the headspace of the batch reactors was flushed with nitrogen gas after the first plateau of hydrogen was reached, and subsequently incubated, with no further addition of inhibitor nor substrate. It was found that hydrogen production resumed and reached a second plateau, although somewhat lower than the first one. This procedure was repeated a third time and an additional amount of hydrogen was obtained. The plateaux and initial rates of hydrogen accumulation decreased in each subsequent incubation cycle. The total cumulative hydrogen harvested in the three cycles was much higher (approx. double) than in the first cycle alone. We coined this procedure as IV-SSAH (intermittently vented solid substrate anaerobic hydrogen generation). Our results point out to a feasible strategy for obtaining higher hydrogen yields from the fermentation of industrial solid wastes, and a possible combination of waste treatment processes consisting of a first stage IV-SSAH followed by a second SSAD stage. Useful products of this approach would be hydrogen, organic acids or methane, and anaerobic digestates that could be used as soil amenders after post-treatment. [Copyright &y& Elsevier]

Abstract: Paraformaldehyde was employed as a hydride source in the palladium-catalyzed hydrodehalogenation of aryl iodides and bromides. High throughput screening using a paper-based colorimetric iodide sensor (PBCIS) showed that Pd(OAc)2 and Cs2CO3 were the best catalyst and base, respectively. Aryl iodides and bromides were hydrodehalogenated to produce the reduced arenes using Pd(OAc)2 and Pd(PPh3)4 catalyst. This catalytic system showed good functional group tolerance. In addition, it was found that paraformaldehyde is the hydride source and the reducing agent for the formation of palladium nanoparticles. [Copyright &y& Elsevier]

Treatment of 1,2-di(pyrrol-1-yl)ethane 4with oxalyl chloride gave a low yield of 5,6-dihydrodipyrrolo[1,2-d;2′,1′-g][1,4]diazepin-11-one 2, by an unexpected electrophilic substitution–decarbonylation process. The diazepinone 2is unreactive to electrophiles, but can be deoxygenated to 5,6-dihydro-11H-dipyrrolo[1,2-d;2′,1′-g][1,4]diazepine 9with lithium aluminium hydride. Reaction of 1,1-di(pyrrol-1-yl)methane 5with triphosgene gives the related dipyrrolo[1,2-c;2′,1′-f]pyrimidin-10-one 3. NMR spectroscopic and X-ray crystal structure comparisons of 2and 3show that there is unexpectedly greater conjugation in the compound with the core seven-membered ring, 2, even though the molecule as a whole is less planar than 3. The corresponding reactions of 4or 5with thiophosgene did not give cyclisation products but the O-methyl thioesters 7and 8were obtained (89 and 27%, respectively). [ABSTRACT FROM AUTHOR]

Direct ethanol fuel cells (DEFCs) provide a portable and environmentally friendly power source with high energy density. However, the slow kinetic of the ethanol oxidation reaction (EOR) has hindered the commercialization of DEFCs. Palladium (Pd)-based nanomaterials are the best promising catalysts for EOR due to the high catalytic activities and relatively abundant reserves. In this paper, we developed a simple and green way for the preparation of palladium hydride (PdH 0.43) and Au/PdH 0.43 heterostructures. Ethylene glycol (EG) provided the source of H atoms for the formation of PdH 0.43 in synthesis process. The as-synthesized PdH 0.43 and Au/PdH 0.43 nanocrystals were extremely stable under ambient conditions and annealing at 300 °C under Ar. Compared with PdH 0.43 and commercial Pd/C, Au/PdH 0.43 presented a higher mass activity of 2659 mA mg−1, a lower oxidation peak potential, and a higher catalytic stability for oxidizing ethanol. Remarkably, the improved catalytic performance might arise from the synergistically modulation of electronic structure, the enhanced resistance to poisoning products and the acceleration of electron transfer by the formation of palladium hydrides and abundant heterostructures of Au/PdH 0.43. This work provides a promising reference for the development of metal-hydride nanomaterials and heterostructures as efficient catalysts. • The PdH 0.43 and Au/PdH 0.43 were prepared with ethylene glycol as the H source. • The PdH 0.43 and Au/PdH 0.43 were extremely stable in the air over six months. • Au/PdH 0.43 can maintain the stability of structure even annealing at 300 °C in Ar. • Au/PdH 0.43 exhibited a higher performance toward EOR than PdH 0.43 and Pd/C. • The improved activities might arise from the doping of H and heterostructures. [ABSTRACT FROM AUTHOR]

The low thermal conductivity of hydrogen storage materials significantly limits the reaction rate of hydrogen storage and release in metal hydrides reactors. In present paper, a heat transfer fluid channel was designed by topology optimization method to enhance the heat transfer performance and increase the hydrogen storage and release rates. Firstly, a series of channel structures were obtained through two-dimensional topology optimization, then they were embedded into metal hydride reaction beds by three-dimensional reconstruction. The hydrogen storage and release performance of different reaction beds were analyzed, the most effective bed structure was derived and compared with the finned bed. The results show that the hydrogen storage and release time of the designed fluid channel reaction bed is 31.5% and 24.4% less than the finned bed. Lastly, the hydrogen storage and release performance of the designed reaction bed under different operating conditions were examined. The appropriate operation conditions were derived: for hydrogen storage, hydrogen pressure of 1.0 MPa, HTF inlet velocity of 0.25 m s−1 and inlet temperature of 293 K; for hydrogen release, hydrogen pressure of 0.1 MPa, HTF inlet velocity of 0.25 m s−1 and inlet temperature of 363 K. Moreover, the reaction bed designed by topology optimization has obvious advantages and shows better hydrogen storage and release performance compared to finned reactors under various operating conditions. • A reactor structure for hydrogen storage is obtained by topology optimization. • The absorption and desorption time of optimized reactor is 31.5% and 24.4% less than the finned reactor. • The appropriate operation conditions for hydrogen storage and release are obtained. • The optimized reactor has better performance than finned reactors under various conditions. [ABSTRACT FROM AUTHOR]

This paper presents a review of recent research and development progress on green hydrogen energy systems and associated thermal management and waste heat recovery technologies. First, hydrogen production methods are briefed. Second, various electrolysis systems used for carbon free hydrogen production from renewable and nuclear resources are discussed. Then, hydrogen utilization using proton-exchange fuel cells is scrutinized. Next, hydrogen energy systems integrated with metal hydride energy storage are elaborated. A focus of this review is on thermal management and process intensification technologies for hydrogen energy systems and integrated metal hydride hydrogen storage technologies. Various process and heat transfer enhancement techniques for heat removal and utilization are presented. Advanced cooling technologies for hydrogen energy systems such as two-phase and boiling for cooling, microchannels for heat removal, CO2 air conditioner and using nanofluids for heat removal are discussed. Finally, heat recovery technologies in green hydrogen energy systems are summarized. This review has also identified future research and technology development needs for green hydrogen energy utilization, thermal management, and heat recovery systems. [ABSTRACT FROM AUTHOR]

The first principle of calculation is a computational technique based on quantum mechanics that may precisely determine the ground-state electronic structure and associated mechanical and thermodynamic characteristics of solid materials. This study explains the history of first-principles development, calculation techniques, and the use of ultra-soft pseudopotential in hydrogen storage materials based on an inquiry and analysis of the findings of previous research. This paper primarily reviews the research progress of first principles in improving two-dimensional hydrogen storage materials, metal-organic framework materials, alkali metal-base composite hydrides, and metal-base hydrogen storage materials in order to speculate on the hydrogen storage mechanisms of materials. It is possible to estimate the location of hydrogen adsorption in a material by computing its electronic structure, band structure, electron density, and lattice vibration. This information is then used to compute the hypothetical new hydrogen storage material. Finally, the direction of first-principles computing in hydrogen storage materials is anticipated. • The research progress of DFT in predicting and simulating new hydrogen storage materials is introduced. • The merits and demerits of the application of DFT in solid hydrogen storage and its future development direction are pointed out. [ABSTRACT FROM AUTHOR]

This paper investigates an innovative study on the performance of a hybrid condensing boiler-fuel cell micro-cogeneration system for single residential applications. It combines experimental and dynamic numerical investigations including renewable energy for green hydrogen production and solid storage. Basing on the hourly measurements for a typical winter day, a dynamic model was developed and validated against different home heating need. Highlighting the influence home energy needs on fuel cell operating mode, it shows that single homes with low energy demand led to reduce the fuel cell's yearly operation below 50 %. In low-energy homes, a reduction in fuel cell size led to an increase in yearly operation to 60-70 % and achieved a 55 % electrical coverage rate. The integration of metal hydride hydrogen solid storage, powered by renewable sources, is emphasized. This setup increases heat demand, influencing fuel cell operation. In winter season, fuel cell operated for an average of 611 h, compared to 61 h in summer. System efficiency averaged 91 % annually, peaked at 95 % in summer, and sustained 93 % when both FC and condensing boiler were switched on. [Display omitted] • Modeling of a hybrid Boiler-Fuel Cell MCHP system for residential energy management. • Calibration of the FC-MCHP model using experimental data from a real MCHP unit. • Electrical and thermal coverage of the FC-MCHP unit with green hydrogen production and storage under different scenarios. • Strategies for optimal hydrogen consumption in in residential application. • Impact of solid-state hydrogen storage on FC-MCHP consumption and thermal management. [ABSTRACT FROM AUTHOR]

Hydrogen, known for its renewable nature, high energy utilization efficiency, and clean combustion, holds significant importance as a component in future energy systems. However, the development of an economical, safe, and efficient method for hydrogen storage remains a formidable challenge. In recent decades, researchers have made significant progress in achieving reversible hydrogen absorption and release using various metal hydrides. Among them, magnesium hydride (MgH 2) has attracted considerable attention for its high energy density, low cost, and good reversibility. Nevertheless, the high hydrogen absorption and desorption temperature, sluggish kinetic properties, and poor cycling performance of MgH 2 remain as the bottlenecks for its practical application. To mitigate these deficiencies, significant research efforts have been focused on the development of carbon-based materials as a means of preparing multifunctional materials. Carbon-based materials have demonstrated great potential in facilitating synergistic modification strategies, such as nanosizing, catalytic effects, and spatial confinement, which have been proven effective in enhancing the hydrogen storage performance of MgH 2. In this paper, we present a comprehensive overview of various carbon-based materials, highlighting their unique properties and their contribution to improving hydrogen storage within MgH 2 matrices. To be specific, we have been systematically reviewed the synergistic impacts of carbon materials, metal-organic frameworks, transition metal carbides (MXenes), and their respective composites on enhancing the hydrogen storage performance of MgH 2. Additionally, this study underscores the benefits of utilizing multifunctional carbon-based materials as modifiers for MgH 2 and proposes potential avenues for academic research. [Display omitted] • The properties and benefits of various carbon-based materials has been comprehensively reviewed. • Carbon-based materials and their roles in improving the hydrogen storage of MgH 2 have been thoroughly investigated. • The promise of multifunctional carbon-based materials as modifiers for MgH 2 is highlighted. • The future directions of carbon-based materials in hydrogen storage are discussed. [ABSTRACT FROM AUTHOR]

Aluminum hydride (AlH 3) dust is a high-capacity hydrogen storage material but is prone to explosion. In this paper, explosion characteristics and flame propagation behavior of AlH 3 dust are investigated. The results indicate that the exposure of bare aluminum and the increase of specific surface area lead to the maximum explosion pressure of AlH 3 dust being 4 times higher than that of Al dust. The enhancement of heat transfer by hydrogen combustion causes a higher combustion rate, leading to a higher maximum explosion pressure rise rate and flame propagation velocity of AlH 3 dust. The thermo-diffusive instabilities and the evolution of hydrogen result in a pulsation flame propagation velocity of AlH 3 dust. Combining the explosion temperature calculated by NASA CEA with the explosion residues analysis, the explosion mechanism of AlH 3 dust is further revealed. The break of the oxide film and the combustion of hydrogen result in a different explosion mechanism. • The explosion characteristics and flame propagation behavior of AlH 3 dust are investigated. • The hydrogen evolution characteristic is studied by the comparison of Al dust. • The explosion mechanism of AlH 3 dust is revealed. [ABSTRACT FROM AUTHOR]

The safety and stability of metal hydride reactor (MHR) structure are significantly important for normal operations of hydrogen isotope storage and supply system. Moreover, considering that the experiments of studying the fatigue and creep properties of MHR structure are always time, money, difficulty and energy consuming. To further improve the service life of MHR as well as lower the failure risk, this paper proposes a system integration method based on ASME code validation, which combines genetic algorithm (GA) and back propagation neural network (BPNN) for rapid assessment of creep-fatigue life (CFL) and optimal design of structural parameters. First, numerical simulation is applied to perform thermal-mechanical coupled finite element analysis and verified by ASME code. Then, parametric sensitivity analysis and experimental design of parameter-based training set based on Taguchi method were performed, and response values are obtained from physical models combined with numerical simulations. Finally, a parametric optimization procedure combining BPNN and GA is developed based on the training data. In the workflow, parametric data flow is passed through the experimental design, numerical simulation, prediction and optimization processes. The results show that the proposed BPNN proxy model based on ASME code validation has good performance in predicting the life of MHR. Based on this, the life of the MHR is improved by 8% compared to the reference sample. • The correlation between creep-fatigue life (CFL) of metal hydride reactor (MHR) and design parameters is established. • Numerical models combining BPNN with ASME Code are available for assessment of CFL of MHR. • The sensitivity analysis is applied to measure the effect of design parameters on CFL of MHR. • Optimal design scheme of MHR is performed through an integrated design optimization method. [ABSTRACT FROM AUTHOR]

The cost of hydrogen production from environmentally friendly energy resources is a primary barrier to fully realizing a hydrogen economy. Therefore, a detailed analysis of hydrogen production costs from various sustainable routes is required. This paper presents a comparative economic study of hydrogen production using several nuclear reactors integrated with electrolysis hydrogen production methods. The Hydrogen Economic Evaluation Program (HEEP) software is used for comparing hydrogen production using different technologies. The HEEP tool was developed by International Atomic Energy Agency (IAEA) and offers comprehensive data for the different nuclear power plants, hydrogen production processes, and various storage and transportation options. The current study utilizes HEEP capabilities to evaluate the cost of nuclear hydrogen production and compare it with non-nuclear sources. Furthermore, it considers the cost of hydrogen storage and transportation options. The reactors considered are Advanced Pressurized Water Reactor (APWR) and High Temperature Gas-cooled Reactor (HTGR) to power low- and high-temperature electrolyzers. In addition, the costs of hydrogen produced using electricity from grid, solar, and wind are evaluated and compared with that of nuclear plants. It is found that the cost of hydrogen production and storage using Compressed Gas (CG) from an APWR plant is 8.2 $/kg for a plant capacity of 360 MWe; the cost is reduced to 6.06 $/kg when the capacity increased to 1117 MWe. It is also found that HTGR integrated with HTSE can produce hydrogen at 3.51 $/kg, which is slightly lower than the case of using the grid electricity, which costs 3.55 $/kg. • Studied costs of electrolysis hydrogen production using APWR and HTGR at different scales. • Compared costs of hydrogen production using nuclear, solar, wind, and grid electricity. • Considered additional costs for compression, liquefaction, and metal hydride storage options. • Evaluated and compared vehicle and pipeline transportation costs for 500 km. [ABSTRACT FROM AUTHOR]

Aluminum hydride (AlH3), as a potential new metal fuel, has attracted extensive attention in the field of hydrogen storage materials, propellants and energetic materials due to its excellent properties. In this paper, a new organic liquid phase reduction method was used to prepare AlH3, and the microstructure and composition of the prepared samples were characterized by SEM–EDS, XRD, FT-IR, XPS, etc. The main crystal phase of the prepared AlH3 was α-AlH3, with high quality and no other impurities. The thermal decomposition behavior and non-isothermal reaction kinetics of AlH3 were investigated by TG-DSC. The results show that there are three exothermic stages in the heating process of AlH3: dehydrogenation of AlH3, first oxidation of Al, and second oxidation of Al. The activation energy of the dehydrogenation of AlH3 is 77.8675 kJ/mol (Kissinger method) and 81.4862 kJ/mol (Ozawa method), respectively. The morphology evolution of AlH3 particles during the heating process (300–3000 K) was simulated using a reaction kinetics method based on the ReaxFF force field. The response behavior of AlH3 in the instantaneous high-temperature detonation environment was investigated using the high-energy laser-induced shock wave technique. Under the impact of a high-energy laser (1006 mJ), the AlH3 sample undergoes an ultra-fast reaction and generates a large amount of plasma. The expansion of the plasma pushes the surrounding air to form a supersonic shock wave and propagates forward. The shock wave propagation velocity of AlH3 is 690.99 m/s in the range of 2.1–12.35 μs, and the higher the laser energy, the faster the shock wave propagation velocity. This study provides the basis for the application of AlH3. [ABSTRACT FROM AUTHOR]

The world is still largely dependent on oil and natural gas for its energy requirements which are harmful to the environment; therefore, it is high time that we look for alternative technologies for our growing energy needs. One such emerging area is fuel cell technology which produces clean energy in the form of electrical power. Integrating a Metal Hydride Hydrogen Storage (MHHS) system with a fuel cell can help increase energy efficiency. The heat dissipated during hydrogen absorption in MHHS can be used in other applications. In this paper, energy and exergy analysis of a fuel cell-based integrated system is performed. The system presents a Reversible Proton Exchange Membrane Fuel Cell capable of working in dual modes, i.e., as an Electrolyser as well as a fuel cell. The MHHS and Vapour Absorption Refrigeration System (VARS) are coupled with a reversible fuel cell for hydrogen storage and cooling applications, respectively. While working in the fuel cell mode, maximum efficiency of 47.84% is evaluated at 80 °C. The system efficiency with and without the VARS system at 80 °C was 73.29% and 47.84%, respectively. On the contrary, in the electrolyzer mode, the maximum efficiency comes out to be 85.65%. The use of the MHHS system for hydrogen storage results in excess heat release, and as a result, the overall efficiency of the electrolyzer was increased to 94.05%. • Thermodynamic integration of PEMFC with MHHS and VARS is performed. • Effect of key parameters on fuel cell system performance is investigated. • System energy and exergy efficiency of 73.3% and 59.5% respectively are reported. • The proposed system can achieve maximum electrolyzer efficiency of 85.65%. • Maximum cooling output from vapour absorption system is found to be 60.56 kW. [ABSTRACT FROM AUTHOR]

To design and optimize the thermal management of metal hydride (MH) tank, high-fidelity model (HFM) composed of numerous partial differential equations, is often adopted to capture the spatial evolution of key parameters accurately. However, computational difficulties raise in dealing with such nonlinear interconnections for system-level simulation. Therefore, the model reduction of MH system has drawn much attention aiming at the trade-off between accuracy and computational cost. In this paper, a hybrid modeling method which integrates advantages of the state-space model (SSM) and HFM, is proposed and applied for the model reduction of MH tank. In particular, four data-driven matrices are introduced to improve the model accuracy. The results show that the root mean square errors of the average temperature between hybrid reduced model (HRM) and HFM are 0.0399 K and 0.1989 K respectively for the cases without and with thermal management. In addition, the HRM is able to capture dynamic characteristic under perturbed input variables with a relative error of temperature within 0.4%, indicating great potential for system-level simulation. What's more, the analysis of predominant pole derived from the state matrices of different thermal managements, reveals that the expanded graphite has superior effect on the adjustment time extension compared with fins, while the fins have distinct advantages in heat transfer enhancement at the cost of volumetric hydrogen storage density. • A hybrid modeling method combining state-space model and data-driven correction is proposed. • The reduced model of MH tank shows great agreement with HFM under various operation parameters. • The accuracy of reduced model has also been verified for the MH tank with thermal management and perturbed variables. • The effect of thermal management on the dynamic characteristic of MH tank is summarized. [ABSTRACT FROM AUTHOR]

In this paper, three optimisation methods are used to determine the parameters of a commercial metal hydride hydrogen tank, considered as a grey box in which the thermophysical parameters are unknown. These parameters are essential for the development of energy management strategies and the study of tank ageing. A model of the hydride tank containing an AB 5 intermetallic was developed and experimentally validated. An absorption test campaign of the studied tank was carried out to collect data necessary for the optimisation algorithms. A comparative study was carried out in accordance with the speed of convergence and precision between the three stochastic optimisation methods: Particle Swarm Optimisation (PSO), Genetic Algorithm (GA) and Differential Evolution (DE). The results of the simulation of the storage system using the parameters determined by the algorithms show a remarkably close agreement with the experimental data, with a maximum error of 2.1%. • Innovative proposal for the determination of parameters of a metal hydride hydrogen tank. • Experimental test for the static characterization of a metal hydride tank for hydrogen storage. • An experimentally verified mathematical model for the hydrogen storage system is put forth. • Validation with experimental data and three stochastic optimisation methods: PSO, GA and DE. [ABSTRACT FROM AUTHOR]

The perovskite-type hydride compounds are potential candidate materials in the field of hydrogen storage. This paper presents a systematical study of XTiH 3 (X = K, Rb, Cs) using density functional theory. The analysis of formation energy, elastic properties and phonon dispersion curves indicate that all the studied materials are thermodynamically, mechanically and dynamically stable. By analyzing the B/G ratio, it is determined that these compounds are brittle materials. The electronic properties reveal that the XTiH 3 compounds exhibit semi-metallic characteristics. The charge transfer characteristics of these compounds were analyzed using Bader partial charges. Moreover, the thermodynamic characteristics of these compounds were investigated and the dependence of their free energy, entropy and heat capacity on the temperature were analyzed. Finally, the gravimetric hydrogen storage capacities of KTiH 3 , RbTiH 3 and CsTiH 3 were calculated to be 3.36, 2.22 and 1.65 wt%, respectively. The hydrogen desorption temperatures of KTiH 3 , RbTiH 3 and CsTiH 3 were found to be 209 K, 161 K and 107 K, respectively. To our knowledge, this study represents the very first investigation of XTiH 3 compounds and offers valuable references to this hydrogen storage material. [Display omitted] • XTiH 3 (X = K, Rb, Cs) perovskite have been investigated using first-principles. • XTiH 3 perovskite exhibit thermodynamic, mechanical and dynamical stability. • The gravimetric hydrogen storage capacity is found to be 3.36 wt% for KTiH 3. [ABSTRACT FROM AUTHOR]

This paper reports a summary of the studies on the mechanisms that govern the generation of hydrides and other volatile species through reaction with aqueous boranes (CVG). This derivatization reaction has been used since the early 1970s for elemental determination and speciation from the trace level down to the ultratrace level and below. An IUPAC project, concluded in 2011, reported on the mechanisms of hydrogen transfer from borane to the analytical substrate and served to remove erroneous concepts that had dominated CVG until the early 2000s. Following the conclusion of the IUPAC project, many studies have been published on the mechanisms of CVG under conditions approaching those of analyzes of real samples. These studies included the definition of more general reaction models, which valid under non-analytical conditions, the mechanism of action of additives and interferences in CVG of volatile hydrides. In addition to the analytical utility for CVG, the results represent a contribution to the knowledge of the chemistry of aqueous boranes. Other studies will be necessary to clarify still unknown aspects, among them the identity of volatile transition metal species formed by reaction of metal ions with aqueous boranes. [ABSTRACT FROM AUTHOR]

The superconducting state in a carbonaceous sulfur hydride (C–S–H) system is probably characterized by the record-high critical temperature of 288 K (p ≈ 267 GPa). We determined the properties of the C–S–H superconducting phase within the scope of both classical Eliashberg equations and the Eliashberg equations with vertex corrections. We took into account the scenarios pertinent to either the intermediate or the high value of an electron–phonon coupling constant (λ ≈ 0.75 or λ ≈ 3.3 , respectively). The scenario for the intermediate value, however, cannot be actually realized due to the anomalously high value of the logarithmic phonon frequency (ω ln / k B = 7150 K) it would require. On the other hand, we found it possible to reproduce correctly the value of T C and other thermodynamic quantities in the case of strong coupling, with all the reservations discussed in the presented paper. The vertex corrections lower the order parameter values within the range from ≈ 50 K to ≈ 275 K. For the upper critical field H C 2 ≈ 27 T, the Ginzburg–Landau parameter κ is of the order of 1.7. The strong-coupling scenario for the C–S–H system is also suggested by the high values of λ estimated for H 3 S (λ ≈ 2.1 , κ ≈ 1.5), La H 10 (λ ≈ 2.8 – 3.9 , κ ≈ 1.6), and Y H 6 (λ ≈ 1.7 , κ ≈ 1.3) compounds. In the case of the C–S–H system, we also anticipate the presence of the antiferromagnetic state above the superconducting state like in the dense C S 2 superconductor. For p ≈ 174 GPa and T C ≈ 180 K, the magnetic ordering transition occurs at T N ≈ 213 K. [ABSTRACT FROM AUTHOR]

The structural and magnetic properties of the multicomponent R–Fe–H compounds with a high content of Fe and H are reported. The process of synthesis of the hydrides (R,R′)2Fe14BH5.5 [where R and R′ are light (Nd) and heavy (Dy, Ho, Er, Tm) rare earth metals, respectively] with a maximum hydrogen content is described in detail. The paper also provides insights into the synthesis of single-crystalline hydrides using the example of the R2(Fe,Co)14BH3 series. The hydrides (R,Nd)2Fe14BH5.5, R2(Fe,Co)14BH3, R2(Fe,Al)17H3 have a significantly increased volume as compared to the parent materials. High-field magnetization results of both parent and hydrogenated compounds at low temperatures are presented. Spin–reorientation phase transitions induced by an external magnetic field are observed. The parameter of the intersublattice exchange interaction and the influence of hydrogen on it are estimated within the framework of the mean field theory. The magnetocaloric effect of the compounds with a magnetic compensation point is studied with a special emphasis placed on the change of the sign of the effect. [ABSTRACT FROM AUTHOR]

The storage of hydrogen in metal hydride reactors is examined experimentally and numerically in this paper. In this respect, as-received LaNi 5 powders are coated with different amounts of copper by using copper sulphate solution to accelerate the hydrogen charging processes. The thermal conductivity of the copper-coated storage material is found to reach up to 8 times of the uncoated powders. A two-dimensional axisymmetric model regarding complex heat and mass transfer occurring during hydrogen charging process in metal hydride reactors is numerically solved at macro level. The developed model is validated by using experimental data related to the amount of hydrogen stored and the reactor temperatures. In accordance with the experimental results, the simulation results show that more homogenous temperature distribution in the reactor can be obtained with the copper coating due to improved thermal properties. Moreover, charging time is also improved by the copper coating. However, since the reactor is loaded with coated/uncoated LaNi 5 powders at the same weight of 65 g, the total amount of hydrogen stored decreases with the copper coating due to reduced amount of LaNi 5. • LaNi 5 powders are coated with copper to improve hydrogen storage performance. • Thermal conductivity is notably improved with copper additive. • Hydrogen charging time is significantly shortened with copper additive. • A 2D axisymmetrical model is developed to simulate the hydrogen storage. • The experimental and numerical results are in good agreement. [ABSTRACT FROM AUTHOR]

With hydrogen contents 6.69 and 7.49 wt%, Sn(AlH 4) 4 and Zr(AlH 4) 4 were experimentally synthesized, but their structures, bonding natures and hydrogen storage properties were not further investigated. This paper determines the low energy structures of Sn(AlH 4) 4 and Zr(AlH 4) 4 crystals by using global optimization algorithm combined with density functional theories, and analyze their electronic structures and bonding properties. The most stable structures of Sn(AlH 4) 4 and Zr(AlH 4) 4 contain isolated H 2 molecules. The formation enthalpies of Zr(AlH 4) 4 reaches 1.0 eV and the value of Sn(AlH 4) 4 is a little smaller. In Zr(AlH 4) 4 , the AlH 5 , AlH 6 and Al 2 H 6 units are connected tightly by Zr atoms through H bridges. In Sn(AlH 4) 4 , the AlH 6 units form a net structure, and the Sn atom exists in SnH 3 with one shared H atom. The bonding characteristics are analyzed by calculating charge populations and crystal orbital hamilton population (COHP). The metal components (Al, Sn, Zr) and H atoms form polarized covalent bonds. The covalent contributions are close for Sn–H and Al–H bonds but the charge values on the Sn atoms are much smaller. For the Zr–H bonds, both the charges on the Zr atoms and the covalent contributions are smaller than the values of the Al–H bonds. Combining the bonding natures and the structure features, it suggests that proper electronegativity of the metal atoms (Sn and Zr here) is the key factor for the stabilities and reversible hydrogen storage properties of metal aluminum hydrides. • The crystal phases of Sn(AlH 4) 4 and Zr(AlH 4) 4 are predicted. • The metal components (Al, Sn, Zr) and H atoms form polarized covalent bonds. • In Zr(AlH 4) 4 , Polarized covalent Zr–H bond is weaker than Al–H bond. • Hydrogen storage capacity in Sn(AlH 4) 4 and Zr(AlH 4) 4 reaches 6.69 and 7.49 wt%,respectively. • The electronegativity of metal atoms in aluminum hydrides is related to structural stability and reversible hydrogen storage. [ABSTRACT FROM AUTHOR]

In this paper, we report the preparation of high-purity 28Si silicon and 72Ge germanium isotopes and their volatile hydrides with controlled concentrations of the 29Si and 73Ge nonzero nuclear spin isotopes for producing Si/SiGe heterostructures for quantum computers employing the nuclear spin state as a qubit. We have prepared 28SiH4 and 28Si samples containing about 99.9, 99.99, and 99.999% 28Si as a major isotope and 340 ± 8, 41.1 ± 4.3, and 11.4 ± 0.1 ppm of the 29Si isotope. In addition, we obtained high-purity 72GeH4 and 72Ge samples containing about 99.9% 72Ge as a major isotope and 109.9 ± 9.6 ppm of the 73Ge isotope. [ABSTRACT FROM AUTHOR]

In this paper, based on the study of hydrogen accumulation in the electrodes of nickel–cadmium batteries, a high-capacity hydrogen storage system (HSS) is proposed. It has been experimentally proven that hydrogen accumulates in the electrodes of nickel–cadmium batteries in large quantities over the course of their operation. It has been shown that hydrogen accumulates in metal–ceramic matrices of sintered oxide–nickel electrodes in the form of metal hydrides. The gravimetric capacity of the nickel matrix is 20.3 wt% and the volumetric capacity is 406 kg m−3. The obtained gravimetric capacities for metal–ceramic matrices exceed almost four times the criteria for onboard hydrogen storage systems established by the US Department of Energy (DOE), as well as previously obtained results for any reversible hydrogen accumulation materials. In addition, in our previous papers, it was proved that if we use thermal runaway for the desorption of hydrogen from metal hydrides then the kinetic and thermodynamic criteria established by the US DOE may be significantly exceeded. Thus, within the framework of the proposed HSS, using the electrochemical method of hydrogen accumulation and the thermal runaway process, one can not only achieve all of the criteria established by the US DOE for HSS but also significantly exceed them. [ABSTRACT FROM AUTHOR]

Nowadays, due to the increasing use of electric vehicles, manufacturers are making more and more innovations in the batteries used in electromobility, in order to make these vehicles more efficient and provide them with greater autonomy. This has led to the need to evaluate and compare the efficiency of different batteries used in electric vehicles to determine which one is the best to be implemented. This paper characterises, models and compares three batteries used in electromobility: lithium-ion, lead-acid, and nickel metal hydride, and determines which of these three is the most efficient based on their state of charge. The main drawback to determine the state of charge is that there are a great variety of methods and models used for this purpose; in this article, the Thévenin model and the Coulomb Count method are used to determine the state of charge of the battery. When obtaining the electrical parameters, the simulation of the same is carried out, which indicates that the most efficient battery is the Lithium-ion battery presenting the best performance of state of charge, reaching 99.05% in the charging scenario, while, in the discharge scenario, it reaches a minimum value of 40.68%; in contrast, the least efficient battery is the lead acid battery, presenting in the charging scenario a maximum value of 98.42%, and in the discharge scenario a minimum value of 10.35%, presenting a deep discharge. This indicates that the lithium-ion battery is the most efficient in both the charge and discharge scenarios, and is the best option for use in electric vehicles. In this paper, it was decided to use the Coulomb ampere counting method together with the Thévenin equivalent circuit model because it was determined that the combination of these two methods to estimate the SOC can be applied to any battery, not only applicable to electric vehicle batteries, but to battery banks, BESS systems, or any system or equipment that has batteries for its operation, while the models based on Kalman, or models based on fuzzy mathematics and neural networks, as they are often used and are applicable only to a specific battery system. [ABSTRACT FROM AUTHOR]

This paper is a synthesis of the methods used for hydrogen production and the storage of hydrogen in the form of metal hydrides and different methods of hydrogen storage in various materials are presented. It also presents the Romanian vision in relation to the existing and future projects that include the production of hydrogen and its use in energy. [ABSTRACT FROM AUTHOR]

Metal-hydrides offer a potentially competitive method for compressing hydrogen, particularly where waste heat is available. Metal hydrides are metal alloys or intermetallic compounds that react reversibly with H 2. They readily absorb low-pressure H 2 at low temperature, and then release H 2 at a higher pressure when the temperature is raised. The high pressure H 2 is released at a pressure above that expected from standard press-temperature relations. The absorption and desorption pressures of the hydrides are determined by their thermodynamic properties (enthalpy and entropy). To achieve compression ratios above about 10, more than one stage of compression is typically required. The challenge is to find alloy pairs that can work together effectively to achieve the desired compression from the heating/cooling available. Previously, a thermodynamic model has been proposed for identifying suitable metal hydrides that can be paired together to achieve a desired compression. This paper describes methods used previously in the literature to select alloy pairs, and applies the current method to an example selection of 33 hydrides with potential for hydrogen compression. The example application aims to find pairs that can compress a H 2 stream from 10 to 350 bar using a temperature range of 30–150 °C, however the theory could readily be adapted to different compression ratios and temperature ranges. For the specific example evaluated none of the potential pairs were able to meet the compression target, however, modification of the parameters (heating/cooling availability) or alloy properties could resolve this issue. • Review of methods used to select alloys for metal hydride hydrogen compressors. • Worked example of thermodynamic model developed by [ 6 ] for the selection of alloy pairs for a dual stage compressor. • Application of model to real alloys highlighted in [ 2 ] incorporating effect of hysteresis and plateau slope. [ABSTRACT FROM AUTHOR]

This work highlights the recent advancements in the hydrogen value chain for the Middle East region by evaluating the feedstock, production technologies, storage options, delivery routes, and end-user applications. It discusses the national strategies for implementing the hydrogen value chain in the Middle East from 2020 to 2050. The challenges in the hydrogen value chain from techno-economic, safety, and social perspectives are also discussed in this study. Hydrogen production technologies are analyzed and compared. Steam-methane reforming has a high efficiency of 74% and a low hydrogen cost of $2.27/kg-H 2 , making it the most dominant technology for hydrogen production. Electrolysis has a lower efficiency of 60% and a higher hydrogen cost of $10.30/kg-H 2, with more potential for further improvments. Furthermore, hydrogen storage options are compared. Compressed gas and cryogenic liquid options have the highest storage capacities of 39.2 and 70.9 kg/m3, respectively. However, they are not entirely safe due to the high flammability of hydrogen. Two hydrogen explosion incidents are also reported, the first explosion at the Fukushima nuclear power plant in 2011 and the second in the Hindenburg fire in 1937. Metal hydrides propose a safer and more effective option, but they are still under research and development. For H 2 transportation options, pipelines and cryogenic tankers are the most conventional and efficient options (above 99%). Ships have the largest capacity of 10,000 tons per shipment and the maximum investment costs of 465M - 620M$ per barge, but they are not feasible. This review paper will help researchers and practitioners analyze the hydrogen value chain in a more systematic way for further improvements toward more practical applications. • Several Middle East countries have developed national strategies for the hydrogen economy. • Steam-Methane Reforming is the most widely used method for hydrogen production. • Electrolysis and photolysis need major technical advances to be commercialized. • Hydrogen delivery infrastructure requires further development for a future hydrogen economy. • Hydrogen Value Chain implementation has some techno-economic and safety and social challenges. [Display omitted] [ABSTRACT FROM AUTHOR]

Novel metal hydride (MH) hydrogen storage tanks for fuel cell electric forklifts have been presented in this paper. The tanks comprise a shell side equipped with 6 baffles and a tube side filled with 120 kg AB 5 alloy and 10 copper fins. The alloy manufactured by vacuum induction melting has good hydrogen storage performance, with high storage capacity of 1.6 wt% and low equilibrium pressure of 4 MPa at ambient temperature. Two types of copper fins, including disk fins and corrugated fins, and three kinds of baffles, including segmental baffles, diagonal baffles and hole baffles, were applied to enhance the heat transfer in metal hydride tanks. We used the finite element method to simulate the hydrogen refueling process in MH tanks. It was found that the optimized tank with corrugated fins only took 630 s to reach 1.5 wt% saturation level. The intensification on the tube side of tanks is an effective method to improve hydrogen storage performance. Moreover, the shell side flow field and hydrogen refueling time in MH tanks with different baffles were compared, and the simulated refueling time is in good agreement with the experimental data. The metal hydride tank with diagonal baffles shows the shortest hydrogen refueling time because of the highest velocity of cooling water. Finally, correlations regarding the effect of cooling water flow rate on the refueling time in metal hydride tanks were proposed for future industrial design. • Novel MH hydrogen storage tanks for fuel cell electric forklift were simulated. • Simulations were validated by the experimental data on refueling time. • Optimized MH tank only took 630 s to reach 1.5 wt% saturation level. • Dimensionless correlations were proposed to estimate the hydrogen refueling time. [ABSTRACT FROM AUTHOR]

The efficient operation of a metal hydride reactor depends on the hydrogen sorption and desorption reaction rate. In this regard, special attention is paid to heat management solutions when designing metal hydride hydrogen storage systems. One of the effective solutions for improving the heat and mass transfer effect in metal hydride beds is the use of heat exchangers. The design of modern cylindrical-shaped reactors makes it possible to optimize the number of heat exchange elements, design of fins and cooling tubes, filter arrangement and geometrical distribution of metal hydride bed elements. Thus, the development of a metal hydride reactor design with optimal weight and size characteristics, taking into account the efficiency of heat transfer and metal hydride bed design, is the relevant task. This paper discusses the influence of different configurations of heat exchangers and metal hydride bed for modern solid-state hydrogen storage systems. The main advantages and disadvantages of various configurations are considered in terms of heat transfer as well as weight and size characteristics. A comparative analysis of the heat exchangers, fins and other solutions efficiency has been performed, which makes it possible to summarize and facilitate the choice of the reactor configuration in the future. [ABSTRACT FROM AUTHOR]

This paper presents a comparative study of two cases of metal hydride hydrogen storage units working on (i) LaNi 5 (ii) Compacts of LaNi 5 incorporated with expanded natural graphite (ENG). It has been observed from the previous studies that the hydriding/dehydriding reactions eventually causes large strain changes, due to which the hydride forming metal alloys disintegrate and form a powder bed. Such reactor beds usually have a low thermal conductivity which minimizes the heat transfer phenomenon occurring during the absorption of hydrogen gas. Therefore, there is a need to implement heat augmentation methods to significantly enhance the thermal conductivity. The objective of this research is to present a 2-D numerical model using Finite Volume Method (FVM) and estimate the hydrogen storage performance of a cylindrical metal hydride bed for both the cases, i.e. powdered metal hydride bed and ENG compacts-based reactor bed at different values of inlet pressure and heat transfer fluid temperature. In this study, a detailed investigation on the absorption process reveals that reactor beds with compacted disks of LaNi 5 and ENG demonstrate an enhanced effective thermal conductivity and efficient mass transfer. The simulation results show that a remarkable improvement in the heat transfer and hydrogen storage capacity with reduced absorption time can be achieved by using LaNi 5 and ENG compacts. It was observed that the average reactor bed temperature dropped from 345.13 K to 337.37 K when the ENG based compacted disks was introduced into the reactor bed. Moreover, for supply pressure of 24 bar and fluid temperature of 293 K, the time taken to absorb hydrogen into the rector to achieve stabilized hydrogen storage capacity was estimated to be 446s and 232 s for the case of metal hydride and ENG compacts-based bed, respectively. • A 2-D numerical model was developed to estimate the hydrogen system performance. • Comparative performance analysis is carried out for two different cases. • The absorption time of hydrogen is 446s and 232s for cases (i) and (ii). • Maximum average bed temperature is reduced by 7.76 K. [ABSTRACT FROM AUTHOR]

The most critical development in conventional underwater applications in recent years is to use hydrogen energy systems, including Air Independent Propulsion (AIP) systems. Proton Exchange Membrane (PEM) fuel cell-powered AIP systems increase interest worldwide. They offer many advantages such as longer endurance time without going to the surface for 2–3 weeks or without snorkeling with an average speed, perfectly silent operation, environmentally friendly process, high efficiency, and low thermal dissipation underwater. PEM fuel cells require a continuous source of hydrogen and oxygen as reactants to sustain a chemical reaction to produce electrical energy. Hydrogen storage is the critical challenge regarding the quality of supplied hydrogen, system weight, and volume. This paper reviewed hydrogen/oxygen storage preferences coupled with PEM Fuel Cell applications in the literature for unmanned underwater vehicles. Since underwater vehicles have different volume and weight requirements, no single hydrogen storage technique is the best for all underwater applications. • Hydrogen is the preferred fuel for underwater vehicles. • Underwater vehicles use hydrogen energy systems having Air Independent Propulsion (AIP) systems. • This paper review H 2 /O 2 storage preferences coupled with PEM Fuel Cell applications for unmanned underwater vehicles. • Compressed, and metal hydride-based H 2 storages are suitable for small to medium submarines. [ABSTRACT FROM AUTHOR]

Hydrogen storage and release process of metal hydride (MH) accompany with large amount of reaction heat. The thermal management is very important to improve the comprehensive performance of hydrogen storage unit. In present paper, thermochemical material (TCM) is used to storage and release the reaction heat, and a new sandwich configuration reaction bed of MH-TCM system was proposed and its superior hydrogen and thermal storage performance were numerically validated. Firstly, the optimum TCM distribution with a volume ratio (TCM in inner layer to total) of 0.4 was derived for the sandwich bed. Then, comparisons between the sandwich reaction bed and the traditional reaction bed were performed. The results show that the sandwich MH-TCM system has faster heat transfer and reaction rate due to its larger heat transfer area and smaller thermal resistance, which results in the hydrogen storage time is shortened by 61.1%. The heat transfer in the reaction beds have significant effects on performance of MH-TCM systems. Increasing the thermal conductivity of the reaction beds can further reduce the hydrogen storage time. Moreover, improving the hydrogen inflation pressure can result in higher equilibrium temperature, which is beneficial for the enhancing heat transfer and hydrogen absorption rates. •Integrating TCM in MH hydrogen storage reactor can recycle the reaction heat. •A new sandwich configuration reaction bed of MH-TCM system was proposed. •The new reaction bed can shorten hydrogen storage time by 61.1%. •Improving TCM thermal conductivity or H 2 pressure are efficient ways to accelerate hydrogen storage rate. [ABSTRACT FROM AUTHOR]

This research paper describes a simplified and quick method for determining the exchange current densities of the H 2 O/H 2 system on powder composite electrodes made of hydrogen storage intermetallics. The method is based on the hydrogen storage electrode potential jump upon its galvanostatic overswitching from the cathodic to the anodic direction for low- and high charge/discharge rates. Indeed, research findings indicate that the discharge rate/exchange current density quotient depends either linearly or exponentially on the potential jump for low- and high-charge/discharge rates. This study also defines the applicability ranges for both types of dependencies with the best accuracy for calculating exchange currents (relative experimental error ≤5%) corresponding to potential jumps of up to 0.037 V (discharge rates of up to 0.2C) and 0.08–0.20 V (discharge rates over 0.3C). Furthermore, this study presents other instances of determining exchange currents versus cycling determination for different intermetallics and discusses the effect of the hydride material surface modification and charge/discharge rate conditions on the exchange current density. [Display omitted] • The exchange current density of the H 2 O/H 2 system, i H 2 O / H 2 0 , will be determined from the overswitch potential jump, Δ E (j) . • At low charge/discharge rate (up to 0.2C), the i H 2 O / H 2 0 increase linearly with a decrease in the Δ E (j) . • At high charge/discharge rate (above 0.3C), the i H 2 O / H 2 0 increase exponentially with a decrease in the Δ E (j) . [ABSTRACT FROM AUTHOR]

This paper presents results on the kinetics of the synthesis of the Cr2Ta intermetallic compound via calcium hydride reduction and the influence of various technological parameters on this process. We have observed anomalous Cr2Ta formation kinetics, in particular, an explosive increase in the amount of this phase as a certain synthesis temperature is reached. The apparent activation energy for the calcium hydride synthesis of the Cr2Ta intermetallic compound has been determined to be ~291 kJ/mol, approaching the activation energy for heterodiffusion in various Laves phases (Cr2Ti, Cr2Nb, Co2Nb, and Fe2Ti). The results obtained in this study are used to gain insight into the mechanism of the calcium hydride synthesis of Cr2Ta. Calcium hydride reduction has been shown to be potentially attractive for the preparation of refractory intermetallics. Further work in this direction will make it possible to obtain high-quality powder and compact articles from it. [ABSTRACT FROM AUTHOR]

Metal alloys and intermetallic compounds offer an attractive method for safely storing hydrogen (H2). The metal alloys absorb H2 into their structure, often swelling and fracturing as a result of phase transformation during hydride formation/decomposition cycles. The absorption of H2 is an exothermic process, requiring the effective and efficient removal of heat. This can be challenging as heat transfer to/from powdered beds is notoriously difficult, and often limited by poor thermal conductivity. Hence, the observed reaction kinetics for absorption and desorption of H2 is dominated by heat flow. The most common method for improving the thermal conductivity of the alloy powders is to prepare them into composite structures with other high thermal conductivity materials, such as carbons and expanded natural graphite. Such composite structures, some also combined with polymers/resins, can also mitigate safety issues related to swelling and improve cyclic durability. This paper reviews the methods that have been used to prepare such composite structures and evaluates the observed impact on thermal conductivity. [ABSTRACT FROM AUTHOR]

This paper reports on an energy/exergy analysis of a standalone solar-hydrogen system with a metal hydride (MH) system thermally managed using a phase change material (PCM). This is a self-contained thermal management arrangement that stores the heat released from the MH unit, when it is being charged and transfers it back to the MH while discharging hydrogen. The first and second laws of thermodynamics were used to develop a mathematical model in MATLAB to simulate this system and quality its performance from the energy and exergy viewpoints. The model was then applied on a passive standalone house, with ∼3.8 MWh/year electricity demand, located in southeast Australia. The exergy efficiencies of the solar PV, electrolyser, fuel cell and the whole solar hydrogen system were found to be 6.5%, 88%, 50.6%, and 3.74%, respectively. The paper also provides the detailed entropy generation and exergy analysis on the MH hydrogen storage unit together with its PCM-based thermal management arrangement. The results show that the annual entropy generation, exergy destruction and exergy efficiency of the MH hydrogen storage unit were 173 Wh/K, 51.5 kWh, and 98.8%, respectively. • Exergy analysis of phase change material used for metal hydride thermal management in solar hydrogen system. • The energy and exergy efficiencies of the solar PV are around 6.1% and 6.5%, respectively. • Energy and exergy of solar-hydrogen system were 3.48% and 3.74%, respectively. • Exergy efficiency of the MH thermal management using PCM was 98.8%. [ABSTRACT FROM AUTHOR]

TiFe is one of the most promising hydrogen storage materials owing to its high volumetric hydrogen capacity, moderate operating temperature, and low cost. Oxygen is an inevitable impurity that affects the hydrogen storage properties of TiFe alloys. In this paper, the effect of oxygen addition on the phase composition and hydrogen storage properties of TiFe alloys is systematically investigated. We found that a high oxygen addition improves the initial hydrogen sorption of TiFe. The TiFe-O 3.78 alloy achieves full activation after two ab/desorption cycles at room temperature. The high oxygen content facilitates the formation of Ti 4 Fe 2 O oxide in TiFe alloy, leading to improved activation kinetics. Moreover, due to the oxygen addition, the amount of TiFe primary phase reduces, and the corresponding hydrogen capacity degrades. Increasing oxygen content also leads to a slight increase in the hydrogenation equilibrium pressure, but almost no impact on the thermodynamics of TiFe alloy. • Oxygen addition decreased the TiFe phase fraction and reduced hydrogen storage capacity. • High oxygen content addition facilitates room temperature activation of TiFe alloy. • The TiFe-O 3.78 alloy can be easily fully activated within 2 hydrogen cycles at room temperature. • Oxygen addition resulted in a slight increase in equilibrium pressures of TiFe-alloys. [ABSTRACT FROM AUTHOR]

The recycling of REEs from the end of life (EoL) products, such as nickel metal hydride batteries (NiMH), offers great opportunities for their supply in Europe. In the presented paper, the application of 'green' extractants such as citric (CA), metatartaric (TA), and ethylenediaminedisuccinic acid (EDDS) (also with H2O2 addition) for the recovery of REEs was studied. The studies were conducted considering the effects of the phase contact time, the initial concentration of CA, TA, and EDDS, as well as H2O2, pH, and temperature. It was found that the addition of TA to the CA solution meant that higher rates of metal ion binding and, thus, leaching was observed. The optimal conditions were obtained in the system: CA-TA and H2O2 for the concentration 0.6M-0.3 M-2%. [ABSTRACT FROM AUTHOR]

Ab initio calculation and data mining are very useful methods to predict the interrelationships among structure properties. In this paper, the first-principles modelling based on the density functional theory (DFT) was used to explore the structural, mechanical, and electronic properties of ten hydrides REH 2 (RE = La, Ce, Pr, Nd, Sm, Tb, Dy, Ho, Er, Tm). From the present work, it can be noted that LaH 2 , CeH 2 , NdH 2, and PrH 2 compounds crystallizing in the hydrogen-rich cubic phase present good mechanical properties which could be of use to future applications in hydrogen storage. Furthermore, the electronic structures were also evaluated to provide a deep insight regarding their trends and confirm the metallic character of these systems. While, HoH 2 , DyH 2 , ErH 2 , TbH 2 , TmH 2 , SmH 2 hydrides are mainly hard and rigid systems with high values of the bulk modulus (B), shear modulus (G), Young's modulus (E), micro-hardness (H), and low values of B / G ratio. More significantly, the adopted principal component analysis (PCA) provided an advantageous technique in selecting and identifying the minimum of inputs variables necessary to capture all information of the systems. • A DFT investigation of mechanical and electronic properties for ten rare-earth hydrides has been performed. • Elastic and mechanical properties for some dihydrides are studied. • The paper explores results connected with a new approach based on data mining. • LaH 2 , CeH 2 , NdH 2 and PrH 2 are very promising compounds for possible applications in hydrogen storage. [ABSTRACT FROM AUTHOR]

Thermal management of metal hydride (MH) hydrogen storage systems is critically important to maintain the hydrogen absorption and release rates at desired levels. Implementing thermal management arrangements introduces challenges at system level mostly related to system's overall mass, volume, energy efficiency, complexity and maintenance, long-term durability, and cost. Low effective thermal conductivity (ETC) of the MH bed (~0.1–0.3 W/mK) is a well-known challenge for effective implementation of different thermal management techniques. This paper comprehensively reviews thermal management solutions for the MH hydrogen storage used in fuel cell systems by also focusing on heat transfer enhancement techniques and assessment of heat sources used for this purpose. The literature recommended that the ETC of the MH bed should be greater than 2 W/mK, and heat transfer coefficient with heating/cooling media should be in the range of 1000–1200 W/m2K to achieve desired MH's performance. Furthermore, alternative heat sources such as fuel cell heat recovery or capturing MH heat during charging and releasing it back during discharging have also been thoroughly reviewed here. Finally, this review paper highlights the gaps and suggests directions accordingly for future research on thermal management for MH systems. • Heat transfer challenges and enhancement techniques of MH are discussed. • Thermal management arrangements of MH hydrogen storage are reviewed. • Research gaps and directions for future studies are provided. [ABSTRACT FROM AUTHOR]

Applied to a hydrogen absorption-desorption cycle, the hydrogen storage bed will experience higher exchange temperatures and variety of mechanical load. Due to the complex structure of the double-layered annulus metal hydride bed and the importance of thermal stress on the failure of a metal hydride bed, the numerical modeling of its hot spot stress was carefully carried out. Moreover, in this paper, an analysis method considering the limit failure mode condition is proposed to deal with the stress analysis in the process of hydrogen absorption and desorption. According to the proposed analysis method, the maximum stress of thermal-structural coupling in the process of hydrogen absorption occurs at about 1/3 along the diameter direction and at the geometric mutation of the connection between the cooling pipe and the main body of the hydrogen storage bed in the process of hydrogen desorption. Apart from that, the hydrogen storage bed is also subjected to thermal-mechanical fatigue by the iterative process of absorption and desorption, and its operating temperature range is in the thermal creep temperature region. Based on the distribution of the stress and temperature, evaluation hot sites were selected and the ASME-NB and ASME-NH codes were used to evaluate fatigue and fatigue creep, respectively. The evaluation showed that the fatigue damage generated during its service life is small, while the creep damage is relatively large and the total damage generated during the service life of the hydrogen storage bed is within the safe range. Aiming at the structure and complex process of a double-layer hydrogen storage bed, creep and fatigue evaluation methods are proposed, various failure modes of hydrogen storage bed are highlighted, and the relationship between process parameters and life is established. [ABSTRACT FROM AUTHOR]