Hydrogen Storage Technologies Research Articles

The mechanochemistry of lanthanum dihydride (LaH\(_{2}\)) with hydrogen (H\(_{2}\)) using the ball-mill process and the effect of oxidation on the resulting products

The complex behavior of LaH2 during ball milling was investigated in this study, with its mechanical, chemical, and morphological changes explored. The relationship between milling time and hydrogen pressure reduction was uncovered through detailed experiments, reflecting the dynamic nature of the process. A transient yet significant event was observed upon unsealing the milling jar post-milling: the emergence of a minor fire ember, indicative of the interplay between mechanical forces and chemical reactivity within the LaH2 powder. Profound changes in the structure, composition, and shape were unraveled using advanced techniques such as X-ray diffraction (XRD), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM/EDX), and particle size distribution analysis. The resulting powder exhibited a dual-phase composition of lanthanum dihydride (LaH2, 68.1% to 71.5%) and lanthanum oxide (La2O3, 28.5% to 31.9%), reflecting a dynamic chemical equilibrium during milling. Particle size distribution analysis revealed a notable increase in average diameter to 6420 nm, accompanied by a polydispersity index (PDI) of 0.831, signifying a broadening compared to the initial LaH2 powder. The morphological evolution of the powder was elucidated through SEM imaging, showing predominantly spherical and rounded forms, indicating extensive particle agglomeration and plastic deformation during milling. Additionally, the formation of oxide layers on the powder surface, intertwined with pronounced particle agglomeration, was highlighted through EDX mapping, shedding light on the mechanical aspects of morphological evolution during milling. These findings contribute to our understanding of LaH2 behavior under extreme mechanical and chemical conditions and have implications for materials processing, hydrogen storage technologies, and broader applications in materials science and engineering.

Enhanced hydrogen storage performance of zinc and magnesium cobaltite nanocomposites

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

Recent Advances in the Preparation Methods of Magnesium-Based Hydrogen Storage Materials.

Magnesium-based hydrogen storage materials have garnered significant attention due to their high hydrogen storage capacity, abundance, and low cost. However, the slow kinetics and high desorption temperature of magnesium hydride hinder its practical application. Various preparation methods have been developed to improve the hydrogen storage properties of magnesium-based materials. This review comprehensively summarizes the recent advances in the preparation methods of magnesium-based hydrogen storage materials, including mechanical ball milling, methanol-wrapped chemical vapor deposition, plasma-assisted ball milling, organic ligand-assisted synthesis, and other emerging methods. The principles, processes, key parameters, and modification strategies of each method are discussed in detail, along with representative research cases. Furthermore, the advantages and disadvantages of different preparation methods are compared and evaluated, and their influence on hydrogen storage properties is analyzed. The practical application potential of these methods is also assessed, considering factors such as hydrogen storage performance, scalability, and cost-effectiveness. Finally, the existing challenges and future research directions in this field are outlined, emphasizing the need for further development of high-performance and cost-effective magnesium-based hydrogen storage materials for clean energy applications. This review provides valuable insights and references for researchers working on the development of advanced magnesium-based hydrogen storage technologies.

A feasibility study of Boree Salt body mapping in the Adavale Basin using passive seismic data

Hydrogen plays a pivotal role in the global energy transition and may require underground storage. So far salt cavern storage is the only proven technology for underground hydrogen storage. The Boree Salt in the Adavale Basin, mostly at depths from 1 to 2.5 km and up to 550 m thick, consists predominantly of halite and is deemed suitable for hydrogen storage. However, current maps are inadequate. Recently passive seismic data (ambient noise) have received much interest for subsurface imaging. The main signal from passive data is surface waves (usually below 2 Hz). The capability of surface waves for the Boree Salt body mapping is examined. Parameters of seismic sensor spacing, the dominant frequencies of the surface waves, and data noise levels are all considered. It is demonstrated that surface waves from ambient noise can map the Boree Salt bodies with a survey distance of ~40 km. Between frequencies of 0.12 and 0.25 Hz, results from the latter have better resolution because of a shorter wavelength. Moving to higher frequencies of 0.5 and 1 Hz, however, the resolution becomes worse, because the depth sensitivity of surface waves moves to the shallower part of the model with increasing frequencies, rendering them incapable of effectively probing the targeted depths. For signal/noise ratio above five, station spacing can be as large as 1 km without compromising quality. Therefore, cost-effective and environmentally friendly passive seismic data can be a good alternative to the traditional active-source data for deep salt body imaging.

Deep reinforcement learning-based optimal scheduling of integrated energy systems for electricity, heat, and hydrogen storage

The increasing load demands and the extensive usage of renewable energy in integrated energy systems pose a challenge to the most efficient scheduling of integrated energy systems (IES) because of the unpredictability and volatility of both the load side and renewable energy.Integrating heat storage and hydrogen storage technologies into integrated energy systems can effectively alleviate the phenomena of wind and solar power desertion caused by the instability of renewable energy sources. This study introduces a real-time optimal scheduling method based on the Soft Actor-Critic (SAC) algorithm, aimed at reducing system operating costs and enhancing the consumption rate of renewable energy. First, the established mathematical model is converted into a Markov Decision Process (MDP), the objective function is converted by designing the action state space and the reward function, and the deep reinforcement learning framework is established. Finally, the decision-making outcomes of intelligence in various energy storage scenarios of renewable energy consumption and extreme cases are analyzed and compared, and the results show that the heat storage and hydrogen storage system significantly improve the rate of renewable energy consumption and the economy of the system. This method is also shown to significantly improve the rate of renewable energy consumption.

Advancements in the modification of magnesium-based hydrogen storage materials

Magnesium-based hydrogen storage materials represent a hydrogen storage technology with broad application prospects. As the global energy crisis and environmental pollution issues become increasingly severe, hydrogen, as a clean and efficient energy source, has garnered growing attention. Magnesium-based hydrogen storage, serving as a crucial means for storing and transporting hydrogen, is gaining prominence due to its abundant resources, low cost, low density, and high hydrogen storage density. However, challenges in terms of absorption/desorption rates, temperature, activation energy, and enthalpy during hydrogen application impede its development. To address these challenges, this paper systematically reviews current research on magnesium-based hydrogen storage materials, encompasses their types, characteristics, and hydrogen absorption mechanisms. Furthermore, it delves into the impacts of nanoscale dimensions, alloying, doping, and catalysis on the performance of magnesium-based materials. The aim is to provide valuable insights for research in related fields.

Advancements in Solid-State Hydrogen Storage: A Review on the Glass Microspheres.

Glass microspheres, with their unique internal structure and chemical stability, offer a promising solution for the challenges of hydrogen storage and transmission, potentially advancing the utility of hydrogen as a safe and efficient energy source. In this review, we systematically evaluate various treatment and modification strategies, including fusion, sol-gel, and chemical vapor deposition (CVD), and compare the performance of different types of glass microspheres. Our synthesis of current research findings reveals that specific low-cost and environmentally friendly modification techniques can significantly enhance the hydrogen storage efficiency of glass microspheres, with some methods increasing storage capacity by up to 32% under certain conditions. Through a detailed life-cycle and cost-benefit assessment, our study highlights the economic and sustainability advantages of using modified glass microspheres. For example, selected alternative materials used in lightweight vehicles have been shown to reduce density by approximately 10% while reducing costs. This review not only underscores the contributions of modified glass microspheres to overcoming the limitations of current hydrogen storage technologies but also provides a systematic framework for improving their performance in hydrogen storage applications. Our research suggests that modified glass microspheres could help to make hydrogen energy more commercially viable and environmentally friendly.

Pumped-storage hydropower and hydrogen storage for meeting water and energy demand through a hybrid renewable energy system

AbstractThe majority of the Greek islands have autonomous energy stations, which use fossil fuels to produce electricity in order to meet electricity demand. Also, the water in the network is not fit for consumption. In this paper, the potential development of a hybrid renewable energy system is examined to address the issue of generating drinking water (desalination) and electricity while releasing zero pollutants into the atmosphere. Wind turbines supply wind energy, while an additional amount of energy is stored using pumped-storage hydropower and green hydrogen tanks. These two storage options are investigated for the purpose of storing and distributing clean wind energy in a controlled manner. Three scenarios are investigated. The first scenario only relies on the pumped-storage hydroelectricity technology (88% of the total annual power demand is covered), the second scenario investigates hydrogen storage technology (83% of the total annual electricity demand is covered), and the third scenario uses a hybrid storage solution consisting of pumped-storage hydropower and green hydrogen tanks (95% coverage).

Study on the impact of hydrogen storage temperature on iron-based thermochemical hydrogen storage technology

Thermochemical hydrogen storage technology based on iron-based materials has received significant attention owing to its low cost, safety features, and high volumetric hydrogen storage density. However, no consensus has been established on the optimal temperature range for hydrogen storage. This study investigated the impact of hydrogen storage temperature on hydrogen consumption capacity, hydrogen release capacity, and hydrogen storage energy consumption. The hydrogen storage temperature was optimized with the objectives of low energy consumption and high hydrogen storage density. The experiments were conducted using thermogravimetric analyzer and gram-scale packed-bed reactor setups, accompanied by thermodynamic and kinetic calculations. The research indicated that at 550 °C, the optimal hydrogen storage temperature, the lowest relative energy demand was 32.30 %, with the hydrogen consumption capacity reaching the theoretical maximum value of 4.8 %, and the hydrogen release capacity reaching 4.04 %. Furthermore, achieving the theoretical maximum value of hydrogen consumption capacity became exceedingly difficult when the hydrogen storage temperature exceeded 570 °C. Microstructural characterization and kinetic calculations revealed that this phenomenon was attributed to the formation of a dense iron layer on the particle surface, which impeded the solid-state diffusion of oxygen atoms. The formation of the intermediate phase wüstite was identified as the cause of the formation of the dense iron layer. Overall, this study provided theoretical support for iron-based thermochemical hydrogen storage processes and offered a perspective into the reaction behavior of the reduction of magnetite with hydrogen.

Significantly improved dehydrogenation of dodecyl-N-ethylcarbazole over supported PdFe bimetallic nanocatalysts via polydopamine surface modification of Al2O3

N-ethylcarbazole (NEC) has great application prospects in hydrogen storage due to its ability to dehydrogenate at lower energy and high hydrogen storage performance. Developing supported metal catalysts with high catalytic activity and stability is key to achieving large-scale application of LOHC hydrogen storage technology. In this paper, bimetallic FePd/Al2O3@PDA-GR catalysts used for the dehydrogenation process of 12H-NEC were prepared by stepwise reduction methods, including chemical reduction and galvanic replacement, using PDA-coated Al2O3 as the support. The characterization results showed that adding PDA could anchor the metal particles, improve the dispersion of metal particles on the support surface, and reduce the agglomeration phenomenon. The nanoparticles of bimetallic catalysts prepared by the galvanic replacement were small, with the particle size distribution of 0.86 nm-2.78 nm, and an average size of 1.52 nm. The large number of exposed active sites enabled the catalysts to reduce the dosage of Pd while still possessing excellent catalytic performance. And part of Pd was coated on Fe NPs in the Fe5Pd1/Al2O3@PDA-GR catalysts prepared by galvanic replacement, which improved the atom utilization of Pd. And there is an obvious electronic interaction between Fe and Pd. In the dehydrogenation process of 12H-NEC to NEC, The prepared FePd/Al2O3@PDA-GR catalyst exhibited excellent catalytic performance and had a significantly greater dehydrogenation efficiency than found in the literature, 95% for 1 h and 100% for 3 h at 180 °C. The temperature drop to 160 °C did not affect the dehydrogenation efficiency, which remained at 98.1% for 3 h. The prepared catalyst had good stability, and the dehydrogenation efficiency was 93.1% after five successive cycles.

Optimisation of design parameters for a novel two-piston ionic compressor applied in hydrogen storage

The ionic compressor is an advanced and prospective compression technology for hydrogen storage. However, a complex wave phenomenon was observed inside the compression chamber due to the fluid flow vortex. This complex gas-fluid interaction can be intervened by a new mechanical design of the motion piston. In this paper, the thermodynamic performance of a novel homocentric two-piston ionic compressor was carried out by mathematical modelling of one compression cycle. The optimisation of the design parameters of the compressor proposed was conducted by the Taguchi method. This study found that the piston diameter ratio was the dominating factor accounting for more than 80 % of the contribution to the mass delivered, power consumption and specific energy consumption. The optimal design parameters were obtained as 0.7 for the piston diameter ratio, 0.5 for the stroke diameter ratio of Piston A and 0.1 for the trajectory parameter. Under the optimal design parameters, the specific energy consumption was obtained as 1563.38 kJ/kg.

Assessing the Role of Hydrogen in Sustainable Energy Futures: A Comprehensive Bibliometric Analysis of Research and International Collaborations in Energy and Environmental Engineering

The main results highlighted in this article underline the critical significance of hydrogen technologies in the move towards carbon neutrality. This research focuses on several key areas including the production, storage, safety, and usage of hydrogen, alongside innovative approaches for assessing hydrogen purity and production-related technologies. This study emphasizes the vital role of hydrogen storage technology for the future utilization of hydrogen as an energy carrier and the advancement of technologies that facilitate effective, safe, and cost-efficient hydrogen storage. Furthermore, bibliometric analysis has been instrumental in identifying primary research fields such as hydrogen storage, hydrogen production, efficient electrocatalysts, rotary engines utilizing hydrogen as fuel, and underground hydrogen storage. Each domain is essential for realizing a sustainable hydrogen economy, reflecting the significant research and development efforts in hydrogen technologies. Recent trends have shown an increased interest in underground hydrogen storage as a method to enhance energy security and assist in the transition towards sustainable energy systems. This research delves into the technical, economic, and environmental facets of employing geological formations for large-scale, seasonal, and long-term hydrogen storage. Ultimately, the development of hydrogen technologies is deemed crucial for meeting sustainable development goals, particularly in terms of addressing climate change and reducing greenhouse gas emissions. Hydrogen serves as an energy carrier that could substantially lessen reliance on fossil fuels while encouraging the adoption of renewable energy sources, aiding in the decarbonization of transport, industry, and energy production sectors. This, in turn, supports worldwide efforts to curb global warming and achieve carbon neutrality.

Nix/TiO2 catalysts for enhancing the selectivity of methylcyclohexane dehydrogenation

The dehydrogenation of methylcyclohexane (MCH) is a widely used hydrogen storage technology, but nowadays, precious metal catalysts such Pt are used for this reaction and non-precious metal catalysts suffer from low selectivity and instability problems. Two catalysts, Ni20/TiO2 and Ni20/Al2O3, were prepared through the improved co-precipitation method and their dehydrogenation performance of MCH was compared. It was found that the application of TiO2 carrier could significantly reduce the acidity of the catalysts, and the nickel particles could be stably dispersed on the carriers, which could effectively improve the selectivity of the target product (toluene). In addition, the influences of different Ni contents, reaction temperatures, and weight hourly space velocity (WHSV) on the performance of the catalysts were also evaluated, and the results showed that the catalyst with 17.16 % Ni content exhibited high activity with up to 86.48 % conversion of MCH and 96.51 % selectivity of toluene, under atmospheric pressure condition with the reaction temperature of 375 °C and WHSV of 1.9 h−1, while 96.03 % and only 42.64 %, respectively, for the Ni20/Al2O3 catalyst. In addition, the catalyst exhibited excellent anti-coking ability, indicating that it has a promising future for industrial applications.

Research Progress and Application Prospects of Solid-State Hydrogen Storage Technology.

Solid-state hydrogen storage technology has emerged as a disruptive solution to the "last mile" challenge in large-scale hydrogen energy applications, garnering significant global research attention. This paper systematically reviews the Chinese research progress in solid-state hydrogen storage material systems, thermodynamic mechanisms, and system integration. It also quantitatively assesses the market potential of solid-state hydrogen storage across four major application scenarios: on-board hydrogen storage, hydrogen refueling stations, backup power supplies, and power grid peak shaving. Furthermore, it analyzes the bottlenecks and challenges in industrialization related to key materials, testing standards, and innovation platforms. While acknowledging that the cost and performance of solid-state hydrogen storage are not yet fully competitive, the paper highlights its unique advantages of high safety, energy density, and potentially lower costs, showing promise in new energy vehicles and distributed energy fields. Breakthroughs in new hydrogen storage materials like magnesium-based and vanadium-based materials, coupled with improved standards, specifications, and innovation mechanisms, are expected to propel solid-state hydrogen storage into a mainstream technology within 10-15 years, with a market scale exceeding USD 14.3 billion. To accelerate the leapfrog development of China's solid-state hydrogen storage industry, increased investment in basic research, focused efforts on key core technologies, and streamlining the industry chain from materials to systems are recommended. This includes addressing challenges in passenger vehicles, commercial vehicles, and hydrogen refueling stations, and building a collaborative innovation ecosystem involving government, industry, academia, research, finance, and intermediary entities to support the achievement of carbon peak and neutrality goals and foster a clean, low-carbon, safe, and efficient modern energy system.

Topology optimization of gyroid structure-based metal hydride reactor for high-performance hydrogen storage

Numerous engineering applications stand to gain substantial advantages by mitigating structural weight. While methods for optimizing continuous solids and discrete frame structures have long been available, the advent of additive manufacturing techniques has ushered in the potential for intricate geometries. In contrast, the hydrogen fuel sector confronts a pivotal challenge: the need to develop efficient hydrogen storage systems. Solid-state compounds like metal hydrides (MH) present a compelling solution among various hydrogen storage technologies thanks to their inherent safety attributes and superior hydrogen volumetric density. Nonetheless, the limitation of MH lies in its gravimetric density, impeding its application in mobility contexts. A transformative strategy addresses this limitation by seamlessly integrating the reactor tank into the vehicle's frame and chassis. This study introduces a pioneering concept—an optimally designed MH container incorporating a gyroid structure. Subsequently, this innovative design underwent rigorous analysis, employing finite element analysis (FEA) and computational fluid dynamics, assessing mechanical properties, heat transfer capabilities, and the efficiency of hydrogen charging into the MH within the structure. Using topology optimization of solid isotropic material with penalization method, a 17 % increase in the chamber volume and a concurrent reduction of the material by nearly 50 %. This profound transformation positively impacted the reactor's volumetric and gravimetric density. Despite a measurable reduction in strength, the optimized structure demonstrated resilience, successfully withstanding prescribed mechanical shear loads. Furthermore, the structure exhibited impressive rigidity, with displacement below 0.2 mm, rendering it suitable and highly competent for integration into assembly components like vehicle frames or chassis. Notably, the optimized structure exhibited a promising enhancement in hydrogen charging rate.

Boosting hydrogen storage capacity in modified-graphdiyne structures: A comprehensive density functional study

Graphdiyne (GDY) is a recently discovered two-dimensional carbon allotrope that holds significant promise for applications in hydrogen adsorption and storage technology. This study investigates the impact of nitrogen doping and sodium decoration on the hydrogen adsorption capacity of GDY nanosheets while examining their influence on electronic and structural properties. Various deliberate impurities are introduced to create modified-GDY structures. Nitrogen doping triggers a transition from a semiconductor to a semi-metallic state, driven by differences in electronegativity and adjustments in bond lengths. Cohesive energy (Ecoh) is found to be −7.231 eV for the most stable N-doped GDY. In contrast, sodium decoration enhances conduction by modifying charge distribution. The other most stable structures are Na-decorated GDY with Eads of −3.804 eV and N, Na-decorated GDY with −3.347 eV. Modified-GDY structures exhibit higher hydrogen adsorption energies compared to pristine GDY, with N-doped GDY displaying the highest energy levels (Eads = −0.455 eV). Maximum hydrogen adsorption capacities are assessed for each structure, and a notable improvement is observed in Na-decorated GDY (19 H2), significantly enhancing the storage capacity to 13.8 wt%, which shows a 10.21 wt% increase in H2 adsorption compared to pure GDY (3.59 wt%). These findings underscore the potential of modified-GDY for hydrogen storage applications, highlighting the effectiveness of structural carbon modification in enhancing hydrogen adsorption capacity.

Advances in hydrogen storage materials: harnessing innovative technology, from machine learning to computational chemistry, for energy storage solutions

The demand for clean and sustainable energy solutions is escalating as the global population grows and economies develop. Fossil fuels, which currently dominate the energy sector, contribute to greenhouse gas emissions and environmental degradation. In response to these challenges, hydrogen storage technologies have emerged as a promising avenue for achieving energy sustainability. This review provides an overview of recent advancements in hydrogen storage materials and technologies, emphasizing the importance of efficient storage for maximizing hydrogen's potential. The review highlights physical storage methods such as compressed hydrogen (reaching pressures of up to 70 MPa) and material-based approaches utilizing metal hydrides and carbon-containing substances. It also explores design considerations, computational chemistry, high-throughput screening, and machine-learning techniques employed in developing efficient hydrogen storage materials. This comprehensive analysis showcases the potential of hydrogen storage in addressing energy demands, reducing greenhouse gas emissions, and driving clean energy innovation.

Aboveground hydrogen storage – Assessment of the potential market relevance in a Carbon-Neutral European energy system

Hydrogen storage is expected to play a crucial role in the comprehensive defossilization of energy systems. In this context, the focus is typically on underground hydrogen storage (e.g., in salt caverns). However, aboveground storage, which is independent of geological conditions and might offer other technical advantages, could provide systemic benefits and, thereby, gain shares in the hydrogen storage market. Against this background, this paper examines the market relevance of aboveground compared to underground hydrogen storage. Using the open-source energy system model and optimization framework of Europe, PyPSA-Eur, the influence of geological independence, storage cost relations, and technical storage characteristics (i.e., efficiencies) on mentioned market relevance of aboveground hydrogen storage are investigated. Further, the expectable market relevance based on current cost projections for the future is assessed. The studies show that in terms of hydrogen capacities, aboveground hydrogen storage plays a considerably smaller role compared to underground hydrogen storage. Even when assuming comparatively low aboveground storage cost, it will not exceed 1.7% (1.9TWhH2,LHV) of total hydrogen storage capacities in a cost-optimal European energy system. Regarding the amounts of annually stored hydrogen, aboveground storage could play a larger role, reaching a maximum share of 32.5% (168TWhH2,LHVa-1) of total stored hydrogen throughout Europe. However, these shares are only achievable for low cost storage in particularly suited energy system supply configurations. For higher aboveground storage costs or lower efficiencies, shares drop below 10% sharply. The analysis identifies some especially influential factors for achieving higher market relevance. Besides storage costs, the demand-orientation of a particular aboveground storage system (e.g., hydrogen storage at demand pressure levels) plays an essential role in market relevance. Further, overall efficiency can be a beneficial factor. Still, current projections of future techno-economic characteristics show that aboveground hydrogen storage is too expensive or too inefficient compared to underground storage. Therefore, to achieve notable market relevance, rather drastic cost reductions beyond current expectations would be needed for all assessed aboveground hydrogen storage technologies.

Effect of different metal element substitution on microstructural and comprehensive hydrogen storage performance of Ti0·9Zr0·1Mn0·95Cr0·7V0.2M0.15 (M = Fe, Co, Ni, Cu, Mo) alloy

Hydrogen is now being used as a renewable clean energy carrier. One of the main issues with the application of hydrogen energy is a shortage of security and efficient hydrogen storage technology. TiMn-based alloys are considered promising hydrogen storage materials, but their comprehensive hydrogen storage properties and cyclic stable performance limit their further practical application. The hydrogen storage properties of alloys can be enhanced by substituting transition metal elements. Therefore, the comprehensive hydrogen storage performance of the Ti0·9Zr0·1Mn0·95Cr0·7V0.2M0.15 (M ​= ​Fe, Co, Ni, Cu, Mo) alloys was systematically investigated according to the Mn element on the B side is partially replaced by variety of transition metal elements. The M ​= ​Ni alloy, which showed the highest hydrogen storage capacity among the group of alloys, was used to explore cycle stability. The plateau pressures of the series alloys decreased in order, Fe ​> ​Co ​> ​Ni ​> ​Cu ​> ​Mo. Aspects of hydrogen absorption kinetics, all of the alloys can reach full hydrogen absorption saturation within 400 ​s at 303 ​K. The Ti0·9Zr0·1Mn0·95Cr0·7V0·2Mo0.15 alloy possessed the fastest hydrogen absorption kinetic rate (t0.9 ​= ​65 ​s) and the smallest hysteresis factor. This suggests that the substitution of Mo elements is effective in improving the hysteresis of the Laves phase alloys. Among the series of alloys, the M ​= ​Ni alloy exhibited the best overall hydrogen storage performance, which hydrogen storage capacity can reach 1.81 ​wt% and 97% of its capacity is kept after 100 cycles.

Single-Atom Ni Supported on TiO2 for Catalyzing Hydrogen Storage in MgH2.

As an efficient and clean energy carrier, hydrogen is expected to play a key role in future energy systems. However, hydrogen-storage technology must be safe with a high hydrogen-storage density, which is difficult to achieve. MgH2 is a promising solid-state hydrogen-storage material owing to its large hydrogen-storage capacity (7.6 wt %) and excellent reversibility, but its large-scale utilization is restricted by slow hydrogen-desorption kinetics. Although catalysts can improve the hydrogen-storage kinetics of MgH2, they reduce the hydrogen-storage capacity. Single-atom catalysts maximize the atom utilization ratio and the number of interfacial sites to boost the catalytic activity, while easy aggregation at high temperatures limits further application. Herein, we designed a single-atom Ni-loaded TiO2 catalyst with superior thermal stability and catalytic activity. The optimized 15wt%-Ni0.034@TiO2 catalyst reduced the onset dehydrogenation temperature of MgH2 to 200 °C. At 300 °C, the H2 released and absorbed 4.6 wt % within 5 min and 6.53 wt % within 10 s, respectively. The apparent activation energies of MgH2 dehydrogenation and hydrogenation were reduced to 64.35 and 35.17 kJ/mol of H2, respectively. Even after 100 cycles of hydrogenation and dehydrogenation, there was still a capacity retention rate of 97.26%. The superior catalytic effect is attributed to the highly synergistic catalytic activity of single-atom Ni, numerous oxygen vacancies, and multivalent Tix+ in the TiO2 support, in which the single-atom Ni plays the dominant role, accelerating electron transfer between Mg2+ and H- and weakening the Mg-H bonds. This work paves the way for superior hydrogen-storage materials for practical unitization and also extends the application of single-atom catalysis in high-temperature solid-state reactions.