High-density Hydrogen Research Articles

2D Metal/Graphene and 2D Metal/Graphene/Metal Systems for Electrocatalytic Conversion of CO2 to Formic Acid.

Efficiently transforming CO2 into renewable energy sources is crucial for decarbonization efforts. Formic acid (HCOOH) holds great promise as a hydrogen storage compound due to its high hydrogen density, non-toxicity, and stability under ambient conditions. However, the electrochemical reduction of CO2 (CO2 RR) on conventional carbon black-supported metal catalysts faces challenges such as low stability through dissolution and agglomeration, as well as suffering from high overpotentials and the necessity to overcome the competitive hydrogen evolution reaction (HER). In this study, we modify the physical/chemical properties of metal surfaces by depositing metal monolayers on graphene (M/G) to create highly active and stable electrocatalysts. Strong covalent bonding between graphene and metal is induced by the hybridization of sp and d orbitals, especially the sharp , , and orbitals of metals near the Fermi level, playing a decisive role. Moreover, charge polarization on graphene in M/G enables the deposition of another thin metallic film, forming metal/graphene/metal (M/G/M) structures. Finally, evaluating overpotentials required for CO2 reduction to HCOOH, CO, and HER, we find that Pd/G, Pt/G/Ag, and Pt/G/Au exhibit excellent activity and selectivity toward HCOOH production. Our novel 2D hybrid catalyst design methodology may offer insights into enhanced electrochemical reactions through the electronic mixing of metal and other p-block elements.

Phase Diagram Analysis of High-Pressure/High-Temperature Polymorphs of Ammonia Borane.

Ammonia borane (NH3BH3) is a promising hydrogen-storage material because of its high hydrogen density. It is employed as a hydrogen source when synthesizing superconducting polyhydrides under high pressure. Additionally, NH3BH3 is a crystallographically interesting compound that features protonic hydrogen (Hδ+) and hydridic hydrogen (Hδ-), and it forms a dihydrogen bond, which explains its stable existence as a solid. Herein, X-ray diffraction experiments were performed at high pressures (HPs) and high temperatures (HTs) of up to 30 GPa and 300 °C, respectively, to investigate the HP/HT phase diagram of NH3BH3. A new HP/HT phase (HPHT2) was identified above 9 GPa and 150 °C. Crystal-structure analysis using the Rietveld method and stability verification using density functional theory calculations revealed that HPHT2 has a P21/n (Z = 4) structure, similar to that of a previously reported HP/HT phase (HPHT) that appears at a lower pressure. HPHT2 is denser than the HP phases that appear at room temperature (HP1 and HP2) at the same pressure (up to ∼17 GPa). In the phase diagram, the phase-boundary line between HPHT and HP1 is a downward convex curve. These unconventional phenomena in the density and phase boundary can be attributed to the influence of dihydrogen bonding on the crystal structure and phase diagram.

A benchmark for extreme conditions of the multiphase interstellar medium in the most luminous hot dust-obscured galaxy at z = 4.6

WISE J224607.6–052634.9 (W2246–0526) is a hot dust-obscured galaxy at z = 4.601, and the most luminous obscured quasar known to date. W2246–0526 harbors a heavily obscured supermassive black hole that is most likely accreting above the Eddington limit. We present observations with the Atacama Large Millimeter/submillimeter Array (ALMA) in seven bands, including band 10, of the brightest far-infrared (FIR) fine-structure emission lines of this galaxy: [OI]63 μm, [OIII]88 μm, [NII]122 μm, [OI]145 μm, [CII]158 μm, [NII]205 μm, [CI]370 μm, and [CI]609 μm. A comparison of the data to a large grid of CLOUDY radiative transfer models reveals that a high hydrogen density (nH ∼ 3 × 103 cm−3) and extinction (AV ∼ 300 mag), together with extreme ionization (log(U) = − 0.5) and a high X-ray to UV ratio (αox ≥ −0.8) are required to reproduce the observed nuclear line ratios. The values of αox and U are among the largest found in the literature and imply the existence of an X-ray-dominated region (XDR). In fact, this component explains the a priori very surprising non-detection of the [OIII]88 μm emission line, which is actually suppressed, instead of boosted, in XDR environments. Interestingly, the best-fitted model implies higher X-ray emission and lower CO content than what is detected observationally, suggesting the presence of a molecular gas component that should be further obscuring the X-ray emission over larger spatial scales than the central region that is being modeled. These results highlight the need for multiline infrared observations to characterize the multiphase gas in high redshift quasars and, in particular, W2246–0526 serves as an extreme benchmark for comparisons of interstellar medium conditions with other quasar populations at cosmic noon and beyond.

Open circuit potential decay transients quantify interfacial pH swings during high current density hydrogen electrocatalysis

Open circuit potential decay transients quantify interfacial pH swings during high current density hydrogen electrocatalysis

Hydrogen production by NH3 decomposition at low temperatures assisted by surface protonics.

Ammonia, which can be decomposed on-site to produce CO2-free H2, is regarded as a promising hydrogen carrier because of its high hydrogen density, wide availability, and ease of transport. Unfortunately, ammonia decomposition requires high temperatures (>773 K) to achieve complete conversion, thereby hindering its practical applicability. Here, we demonstrate that high conversion can be achieved at markedly lower temperatures using an applied electric field along with a highly active and readily producible Ru/CeO2 catalyst. Applying an electric field lowers the apparent activation energies, promotes low-temperature conversion, and even surpasses equilibrium conversion at 398 K, thereby providing a feasible route to economically attractive hydrogen production. Experimentally obtained results and neural network potential studies revealed that this reaction proceeds via HN-NH intermediate formation by virtue of surface protonics.

Ammonia blends for gas-turbines: Preliminary test and CFD-CRN modelling

Ammonia, with its high hydrogen density, cost effectiveness and ease of storage, is emerging as a potential fuel to meet decarbonisation targets in various sectors. However, the combustion of pure ammonia poses challenges due to its low calorific value and reactivity. Existing gas turbine combustion systems, refined over decades with conventional fuels, struggle to maintain comparable flue gas emission concentrations when burning ammonia.Overcoming this challenge requires a paradigm shift in gas turbine combustion, with implications for chemistry and combustor design methodology. Research into the chemical kinetic mechanism for ammonia combustion worldwide reveals differences in flame radical pools compared to methane combustion. The dominant NOx formation mechanism shifts to a "fuel-bound nitrogen" type, which differs from the "thermal" mechanism in hydrocarbon and hydrogen combustion.The integration of chemical reaction rates into Computational Fluid Dynamics (CFD) models with transport equations results in impractical computational times for industrial applications. Therefore, streamlined approaches such as chemical reaction reduction methods are being developed. This involves the construction of lumped parameter models (Chemical Reactor Network - CRN) to identify key parameters that affect species production. A reliable CRN implementation involves the identification of critical volumes using a preliminary CFD approach (CFD-CRN).This paper analyses preliminary experimental tests by Baker Hughes on an industrial burner using different ammonia, hydrogen, and methane fuel mixtures. The NOx results show a different behavior between methane and hydrogen. While the detailed mechanisms behind these results remain open questions, the CFD-CRN modelling approach is adopted. A proposed CRN is investigated for methane, hydrogen, and ammonia blends, providing insight into key parameters and a reasonable physical explanation for the different NOx results. A single calibration parameter (ϕpilot/ϕref) is used to predict accurately NOx emissions using experimental data available from experimental campaign.

Simulating Hydrogen Diffusion in ZrH Moderator and its Impact on Coupled Neutronic-Thermal Simulation of a Heat Pipe Microreactor

Metal hydride moderators are a common material choice for moderating compact reactor designs, as their high thermal limits and high density of hydrogen make them favorable for operation. One additional attribute of metal hydrides, zirconium hydride in particular, is the relatively large mobility of hydrogen within the metal lattice, especially at high temperatures and under large thermal gradients. As hydrogen’s spatial distribution directly impacts neutron thermalization in the system, and therefore power shape, changes in hydrogen concentration of the moderator may be important to analyze. This work couples OpenMC and MOOSE in order to solve the feedback loop of the coupled power distribution-thermal distribution-hydrogen migration without relying on mesh discretization. Functional expansions are used extensively as a method of transferring spatial information, and continuously varying material tracking is used in the neutronic solver to represent the change in hydrogen concentrations. The resulting hydrogen redistribution is highlighted, as well as the resulting neutronic and thermal impact of this redistribution.

A computational analysis of cryogenic hydrogen release under various conditions

Cryogenic liquid hydrogen offers a promising solution for achieving high-density hydrogen storage and efficient on-site distribution. However, the potential hazards associated with hydrogen leakages necessitate thorough investigations. This research aims to model cryogenic hydrogen release from circular and high aspect ratio (HAR) nozzles tested by Sandia. The test conditions cover reservoir pressures and temperatures corresponding to cryogenic hydrogen storage. The study conducts computational simulations using OpenFOAM to examine hydrogen concentration, temperature fields, mass fraction, and temperature distributions, achieving good agreement with the experimental data. To further explore, the study of velocity variations shows a consistent decay rate with room-temperature jets. The numerical data reveals comparable inverse centreline hydrogen mass fractions (0.254 for HAR and 0.26 for circular) and normalised centreline temperature decay rates (0.031 for HAR and 0.032 for circular). The present computational model holds the potential for further analysis of cryogenic hydrogen in large-scale facilities.

Present State and Future Outlook of Ammonia Production through Photocatalytic Nitrate Reduction

Ammonia (NH3) production has gained increasing attention owing to its versatility in both industrial and agricultural applications, as well as its potential as a next‐generation energy carrier with a high hydrogen density. Given the energy‐intensive and environmentally impactful nature of the Haber–Bosch process, there is a pressing need for a sustainable NH3 synthesis method under ambient conditions. Nitrate (NO3−) emerges as a compelling nitrogen source due to its numerous advantages over inert nitrogen (N2) gas, such as its relatively low dissociation energy and high aqueous solubility. Moreover, NO3− is a common contaminant found in wastewater, posing a threat to aquatic ecosystems. The photocatalytic NO3− reduction to NH3, which utilizes sunlight to convert contaminants into value‐added chemicals, aligns perfectly with the need for sustainable solutions. This perspective reviews the latest advancements in the field of photocatalytic NO3− to NH3 conversion. The mechanism behind the conversion of NO3− to NH3 is briefly explained, and photocatalysts exhibiting high selectivity and activity in NH3 production, along with other influential factors, are summarized. Additionally, current challenges and future prospects within this field are discussed.This perspective will provide a valuable guidance for future research in the realm of photocatalytic NH3 production via NO3− reduction.

Design and optimization of high-density cryogenic supercritical hydrogen storage systems integrating with dual mixed refrigerant cycles

To address the low density of high-pressure gaseous hydrogen and evaporation issues associated with liquid hydrogen storage, cryogenic supercritical hydrogen storage method is presented in this paper. Based on a dual parallel mixed refrigerant cycle (DPMR) and a dual cascade mixed refrigerant cycle (DCMR), the density of supercritical hydrogen product is 70.74 kg/m3, closely approaching liquid hydrogen. The processes are simulated in Aspen HYSYS, optimized by genetic algorithm for lower specific energy consumption (SEC). Thermodynamic analysis is conducted to compare with hydrogen liquefaction processes, demonstrating the feasibility and superiority of proposed process. The results show that the DPMR process has an SEC of 6.422 kWh/kgH2 and exergy efficiency of 52.66%, while DCMR is 6.872 kWh/kgH2 and 49.24%. Additionally, the inclusion of ortho-para convertors in DPMR process is investigated to further analyze the impact of heat release for ortho-para conversion. Furthermore, a techno-economic analysis is conducted on three processes, validating the economic feasibility. The study indicates that cryogenic supercritical hydrogen storage system is of great significance to the development of high-density hydrogen storage technology. The DPMR and DCMR presented in this paper can significantly improve the energy efficiency and provide valuable information for the design of high-density hydrogen storage system.

1D Spatially Resolved Model of Alloyed Catalyst Degradation in LT-PEMFC

Low-temperature fuel cells with proton exchange membrane (LT-PEMFC) are among the most promising energy devices for future decarbonizaion of heavy-duty long-distance transport. Fuel cells use hydrogen as the energy source and air as oxidizer to produce electricity in catalyzed electrochemical process, with only side-products being heat and water. Despite some clear advantages over other energy sources, i.e. batteries, their adoption is still somewhat limited by some prominent factors such as high price and limited durability. Both of these factors are closely related to the use of specific catalyst materials needed to ensure high efficiency and power density of hydrogen fuel cells. Due to its high catalytic activity, Pt is traditionally used as a catalyst material, dispersed in form of nanoparticles on a highly porous carbon matrix ensuring good accessibility of hydrogen and air to the catalyst surface and efficient removal of water.Due to harsh local conditions in the catalyst layer, i.e. high temperatures of up to 80° C, high humidity and high electric potentials, catalyst nanoparticles are exposed to various degradation processes. Electrochemical corrosion of carbon support can result in detachment of particles and their consequent agglomeration, which results in a decrease of specific area suitable for electrochemical reactions. Despite high redox potential of Pt (1.115 V vs. SHE), high electric potential in fuel cell cathode can also lead to electrochemical dissolution of catalyst particles, which is additionally accelerated by their small size. Dissolved catalyst can either redeposit to larger particles, resulting in net growth of catalyst particles (so-called Ostwald ripening), or diffuse in proton exchange membrane, where it is reduced by crossover hydrogen. Both processes result in a loss of electrochemically active surface area in the catalyst layer.To reduce the amount of Pt used and thus lower the price, new types of catalyst materials are being developed, using alloys of Pt with other metals, such as Co, Cu or Ni, which also increases the specific electrochemical activity of the material. [1] Since alloying metals have lower redox potential compared to Pt, alloyed catalyst are more susceptible to dissolution, which represents a significant challenge in their wider adoption. Degradation is somewhat mitigated by preconditioning of catalyst nanoparticles during which Pt shell is formed around alloy particle core, resulting in higher stability of core-shell catalysts. Despite clear advantages, the use of alloyed catalyst might introduce some new risks in terms of fuel cell durability. Dissolution of alloying metal introduces ions of transition metals into the membrane, where they could serve as a catalyst in chemical reactions leading to the chemical degradation of the membrane [2]. Metal ions can also block the active sites in proton exchange membrane and thus reduce its proton conductivity, while diffusion from cathode to anode catalyst layer and deposition on catalyst surface can present a risk of anode catalyst surface passivization [3].To improve the understanding of aforementioned processes, we propose a 1-dimensional spatially and temporally resolved degradation model of alloyed catalyst degradation in the membrane-electrode assembly (MEA). The model describes the changes of cathode core-shell catalyst structure as a redistribution of particle core sizes and shell thicknesses due to electrochemical surface oxidation, dissolution and redeposition. To provide realistic internal states of the fuel cell during operation, the degradation model is coupled with advanced spatially and temporally resolved model of the fuel cell operation [4]. Dissolution model represents a source of Pt and alloying ions in the catalyst layer, which is coupled to 1D model of ion diffusion in the catalyst layer and the membrane, taking into account the specifics of transport in different MEA components. The transport model is further coupled with potential ion sinks, such as reduction in the presence of hydrogen, interaction with the proton exchange membrane and redeposition on the anode.Preliminary results indicate that Pt ions diffusion results in spatial inhomogeneities of catalyst layer degradation. The location and mechanism of metal ion deposition depends on the redox potential of metal and can occur in either membrane or anode catalyst layer. The model shows great promise in developing a better understanding of degradation processes of alloyed catalyst materials and could in future guide a development of better operation strategies for fuel cell use, mitigating their degradation and improving their lifetime.[1] E. Antolini et al., J. Power Sources. 160 (2006) 957–968.[2] M. Strlič et al., Acta Chim. Slov. 50 (2003) 619–632.[3] A. Han et al., Int. J. Hydrogen Energy. 45 (2020) 25276–25285.[4] A. Kregar et al., Appl. Energy. 263 (2020) 114547

Visualization of Hydrogen Bubbles Using Synchrotron X-Ray CT inside Porous Transport Layer of Direct Toluene Electro-Hydrogenation Electrolyzers

Toluene is a highly versatile solvent commonly used in many industries due to its high energy density and effective hydrogen carrier properties. It can store a considerable amount of hydrogen in a relatively small volume, making it a promising hydrogen carrier for various applications. Toluene's high volumetric energy density also makes it one of the best hydrogen carriers available. Additionally, toluene is easy to handle and transport as it is a liquid at room temperature, and it can be stored and transported like any other liquid fuel. Furthermore, toluene is a safer alternative for hydrogen storage compared to other hydrocarbons due to its low toxicity.Direct toluene-electro hydrogenation electrolyzer is a promising method that enables the simultaneous performance of water electrolysis and toluene hydrogenation in a single system. However, during the toluene direct electrolytic hydrogenation process, the formation of hydrogen bubbles from the electrolysis of water hinders the toluene hydrogenation reaction, leading to a reduced conversion rate of methylcyclohexane (MCH) and Faraday efficiency.In this study, we aimed to understand the conditions for hydrogen bubble generation and transport. We quantitatively evaluated the generation amount and distribution of hydrogen bubbles by visualizing them in an operating electrochemical cell using Synchrotron X-ray CT. Figure 1 displays the distribution of hydrogen bubbles along the porous transport layer (PTL) of the electrochemical cell. These bubbles were visualized using the raw images obtained from Spring-8 and subsequently reconstructed. The cell was operating at a current density of 200 mA/cm2 for a period of 30 minutes with pure water supplied to the anode side. Darker areas in the images indicate regions with hydrogen bubbles, which have a lower density and atomic weight than other substances in the PTL. Therefore, they are more transparent to X-rays and appear darker in the image. Higher current values and longer operation times led to increased hydrogen bubble generation, with a significant increase observed at 30 minutes. By visualizing these hydrogen bubbles, we were able to evaluate the generation distribution, amount, and transport of hydrogen, which can help improve the direct toluene-electro hydrogenation electrolyzer system. Acknowledgement This study was based on results obtained from the Development of Fundamental Technology for Advancement of Water Electrolysis Hydrogen Production in Advancement of Hydrogen Technologies and Utilization Project (P14021) commissioned by the New Energy and Industrial Technology Development Organization (NEDO). References Nagasawa K, Sugita Y, Atienza-Márquez A, Kuroda Y, Mitsushima S. Effect of the cathode catalyst loading on mass transfer in toluene direct electrohydrogenation. Journal of Electroanalytical Chemistry 2023:117431. https://doi.org/10.1016/J.JELECHEM.2023.117431.Shigemasa, A. Atienza-Márquez, K. Inoue, S. Jang, F. Reyna-Peña, T. Araki, “Visualization of dragged water and generated hydrogen bubbles in a direct toluene electro-hydrogenation electrolyzer,” J. Power Sources 2023; 554:232304. https://doi.org/10.1016/j.jpowsour.2022.232304.Nagasawa, A. Kato, Y. Nishiki, Y. Matsumura, M. Atobe, S. Mitsushima, “The effect of flow-field structure in toluene hydrogenation electrolyzer for energy carrier synthesis system. Electrochemical Acta 2017; 246:459-65. https://doi.org/10.1016/j.electacta.2017.06.081. Nagasawa, K. Tanimoto, J. Koike, K. Ikegami, S. Mitushima, “Toluene permeation through solid polymer electrolyte during toluene direct electro-hydrogenation for energy carrier synthesis”, Journal of Power Sources, Vol.439, (2019) 22707. https://doi.org/10.1016/j.jpowsour.2019.227070. Figure 1 SPring-8 CT Visualization Reconstructed image after 30 minutes of operation at 200 mA/cm². Figure 1

A flexible adhesive hydrogel dressing of embedded structure with pro-angiogenesis activity for wound repair at moving parts inspired by commercial adhesive bandages

Compared with the wound in the flat part of human body, the repair of the wound in the joint, armpit and other frequently moving parts is still a complex problem. Although many flexible and adhesive hydrogel dressings for the repair of wounds at moving parts have been developed, in order to improve their flexibility and adhesion, most hydrogel dressings use synthetic polymers and natural polymers to form composite hydrogels, which greatly reduces their biocompatibility and bioactivity compared with a single natural polymer hydrogel. They can only passively provide a barrier to the wound and the process of wound repair is slow, which seriously hinders their further application. Inspired by commercial adhesive bandages, we have successfully constructed a flexible adhesive hydrogel dressing of embedded structure with pro-angiogenesis activity. The hydrogel was prepared by the adhesive and non-adhesive parts by topological adhesion and molecular entanglement. Due to the high-density hydrogen bonding, hydrogels possessed good adhesion and flexibility, which allowed them to repair wounds of moving parts successfully. In addition, the non-adhesive part loaded with exosomes was directly in contact with the wound, minimizing the stimulation of the wound tissue by cytotoxic materials, and continuously releasing active substances to promote vascular regeneration. This biocompatible flexible and adhesive hydrogel dressing with pro-angiogenesis activity shows strong potential in wound tissue remodeling, providing a new strategy for the treatment of moving parts or sensitive wound parts.

Potentially reversible hydrogen storage medium: Calcium-decorated boron-doped blue phosphorene

Developing novel hydrogen storage materials with high capacity and efficient reversibility at ambient conditions is crucial to the extensive use of hydrogen energy. In this study, we have systematically investigated the hydrogen storage performances of Ca-decorated boron-doped blue phosphorene (B@BlueP) monolayers by using first-principles calculations. The results show that substitutional boron doping can enhance the interaction between the Ca atom and BlueP and effectively hinder the formation of Ca clusters on the surface of BlueP. The Ca-decorated B@BlueP can store six hydrogen molecules per Ca atom with average adsorption energies of around 0.17–0.24 eV/H2. Electronic structure analysis confirms that both the polarization of hydrogen molecules under the local electrostatic field and the hybridization of Ca-s/d orbitals with H2-σ orbitals contribute to the adsorption of hydrogen molecules in the surrounding of the Ca atom. The decoration of double-sided Ca atoms can lead to a high theoretical gravimetric hydrogen density of 7.29–7.76 wt%, exceeding the storage goal of 5.50 wt% proposed by US-DOE for applications. Furthermore, the practical hydrogen storage capacity at different pressures and temperatures was also studied through thermodynamic analysis, and the storage capacity is calculated to be around 5.50 wt% in practical circumstances (298 K/30 atm and 358 K/5 atm are used as adsorption and desorption conditions, respectively). Hence, the Ca-decorated B@BlueP monolayers have promising potential as reversible hydrogen storage materials under ambient conditions.

Preliminary analysis of refilling cold-adsorbed hydrogen tanks

The effective storage of hydrogen is a critical challenge that needs to be overcome for it to become a widely used and clean energy source. Various methods exist for storing hydrogen, including compression at high pressures, liquefaction through extreme cooling (i.e. -253 °C), and storage with chemical compounds. Each method has its own advantages and disadvantages. MAST3RBoost (Maturing the Production Standards of Ultraporous Structures for High Density Hydrogen Storage Bank Operating on Swinging Temperatures and Low Compression) is a European funded Project aiming to establish a reliable benchmark for cold-adsorbed H2 storage (CAH2) at low compression levels (100 bar or below). This is achieved through the development of advanced ultraporous materials suitable for mobility applications, such as hydrogen-powered vehicles used in road, railway, air, and water transportation. The MAST3RBoost Project utilizes cutting-edge materials, including Activated Carbons (ACs) and high-density MOFs (Metal-organic Frameworks), which are enhanced by Machine Learning techniques. By harnessing these materials, the project seeks to create a groundbreaking path towards meeting industry goals. The project aims to develop the world’s first adsorption-based demonstrator at a significant kg-scale. To support the design of the storage tank, the project employs Computational Fluid Dynamics (CFD) software, which allows for numerical investigations. In this paper, a preliminary analysis of the tank refilling process is presented, with a focus on the impact of the effect of the tank and hydrogen temperatures on quantity of hydrogen adsorbed.

Ni-based catalyst assisted by MnO to boost the hydrogen storage performance of magnesium hydride

Magnesium hydride (MgH2) stands out as a promising solid-state material for high-density hydrogen storage, offering enormous potential for applications in hydrogen transportation and storage. However, the stable thermodynamics and sluggish kinetics of dehydrogenation/hydrogenation of MgH2 impede its practical use in on-board hydrogen storage. In this study, the nanocomposite of nickel/manganese oxide (Ni/MnO) was successfully synthesized through the hydrogenation of nickel-manganese two-dimensional layered double hydroxide (NiMn-LDH) and then introduced into MgH2 by ball milling to form BM-MgH2-Ni/MnO composite. Notably, BM-MgH2-Ni/MnO-10 displayed excellent hydrogen absorption/dehydrogenation properties. For example, its onset hydrogen release temperature was remarkably reduced to 175.6 °C, 84 °C lower than that of BM-MgH2. At a temperature of 250 °C, it could desorb about 6.2 wt% of H2 within 60 min. The fully dehydrogenated product could absorb 5.5 wt% of H2 within 10 min at 150 °C. Moreover, BM-MgH2-Ni/MnO-10 exhibited excellent cycling performance. Throughout the cycling process, the in-situ formation of Mg2Ni/Mg2NiH4 and metal Mn was detected, leading to a synergistic effect that significantly enhanced the hydrogen storage capability of MgH2. This study presents innovative concepts for designing active catalysts to enhance the kinetics of de-/hydrogenation reactions of MgH2.

Methods for Estimating Hydrogen Fuel Tank Characteristics

Abstract The pressure vessels needed to store hydrogen for next-generation hydrogen fuel cell vehicles are expected to be a substantial portion of the total system mass, volume, and cost. Gravimetric capacity, volumetric capacity, and cost per kilogram of usable hydrogen are key performance metrics that the U.S. Department of Energy (DOE) uses to determine the viability of hydrogen fuel cell systems. Research and development related to hydrogen storage systems covers a wide range of potential operating conditions, from cryogenic temperatures to high temperatures (above ambient) and low pressure to high pressure. Researchers at PNNL have developed methods for estimating these key pressure vessel characteristics to support on-board hydrogen storage system design and performance evaluation and to support decision-making about DOE hydrogen storage system research investments. This article describes the pressure tank estimation methodology that has been used as a stand-alone calculation and has been incorporated into larger system evaluation tools. The methodology estimates the geometry, mass, and material cost of type I, type III, and type IV pressure vessels based on operating pressure and material strength at the system's operating temperature, using classical thin-wall and thick-wall pressure vessel stress calculations. The geometry, mass, and material cost requirements of the pressure vessel have significant impacts on the total system performance. For example, hydrogen storage materials that can separately achieve a very high hydrogen density can be deemed impractical for use in fuel cell vehicle hydrogen storage systems because the pressure tank containing them is too large, heavy, or expensive. This article describes the design philosophy and analytical process of the tank characteristic estimation methodology, which has been implemented in spreadsheet calculation tools and system-level analysis tools used by DOE researchers. Each of the three tank types (type I, type III, and type IV) uses a different analysis methodology with some common elements. This article also provides examples of implementing the methodology to perform parametric studies of all three pressure vessel types. The goal of this article is to present the methodology in sufficient detail so it can be implemented in other hydrogen fuel cell vehicle design and analysis tools.

High solid content waterborne polyurethane and the coatings with double crosslinking structure and multiple hydrogen bonds

The development of coating and emulsion with excellent scratch resistance, friction resistance, high transparency, and yellowing resistance is of great significance for protecting the substrate, reducing the wear of the material, and improving the curing and. drying speed of the coating. Therefore, a double-crosslinked waterborne polyurethane (DCWPU) was prepared in this paper to make up for the shortcomings of slow drying speed and poor toughness of the coating film in a single cross-linked system. Meanwhile, DCWPU utilizes chemical bonding crosslinking network and high-density hydrogen bonding array to cooperate with each other, which is beneficial to improve the mechanical properties of the double-crosslinking system. Herein, 3 (2-hydroxyethyl) isocyanurate (THEIC) was introduced as the intramolecular crosslinking agent, and isophorone isocyanate trimer (IPDI-3), which has the same keto azocyclic structure as THEIC, was added as the post crosslinking agent to further increase the crosslinking degree of the system. The effects of cross-linked monomer content in waterborne polyurethane on scratch resistance, friction resistance, and corresponding emulsion solid content of the coating were studied in the work. It was found that with the increase of double cross-linked monomer content, the hydrogen bond force could be effectively improved, and the mechanical properties, wear resistance and solid content of the emulsion could be significantly improved. It is worth mentioning that DCWPU-3 showed the best comprehensive properties. The emulsion solid content was 48.9%, the tensile strength of the film was increased to 21.8 MPa, the elongation at break was 627.2%, the hardness was 4 H, and the wear amount was 1.2 mg.

2D transition metal carbides trigger enhanced dehydrogenation and reversibility properties in Mg(BH4)2

Although Mg(BH4)2 has been widely studied in the hydrogen storage field for its high hydrogen density, its terrible dehydriding kinetics and cycling features remain impediments to practical applications. Herein, introducing different MXenes (Ti3C2, Ti2C, Nb2C) with novel two-dimensional structures as catalysts into Mg(BH4)2 has been demonstrated to be an efficient approach to boosting the hydrogen storage properties. 30 wt% MXenes in Mg(BH4)2 causes a considerable reduction in its hydrogen release temperature, remarkable increases in its dehydrogenation rate and capacity, and an enhancement to its reversibility. The Mg(BH4)2-30Ti2C as the most excellent composite starts to liberate hydrogen from 132 °C, 143 °C lower than that of Mg(BH4)2. Furthermore, at 260 °C, the Mg(BH4)2-30Ti2C composite desorbs 10.2 wt% H2, which is much higher than that of Mg(BH4)2 (1.5 wt%). Theoretical calculations elucidate the weakening of B-H bonds caused by the electron transfer at the Mg(BH4)2/MXenes interfaces, and the dehybridization effect between the B and H orbits. X-ray photoelectron spectroscopy (XPS) analyses prove the in-situ formation of multiphase interfaces resulting from the interaction of Mg(BH4)2 and MXenes during milling and dehydrogenation processes, which could increase electron conduction and facilitate hydrogen diffusion. These factors contribute to the outstanding dehydrogenation properties of Mg(BH4)2.

Ultrasonic gas flow metering in hydrogen-mixed natural gas using Lamb waves

Hydrogen mixing in existing natural gas pipelines efficiently achieves large-scale, long-distance, and low-cost hydrogen delivery. The physical properties of hydrogen and natural gas differ significantly. Hydrogen-mixed natural gas modifies the flow state and thermodynamic properties of the original natural gas in the pipeline. Hydrogen-mixed natural gas can lead to increased errors in ultrasonic flow metering because of the high sound speed and low density of hydrogen. Ultrasonic flowmeter installation distances need to be re-determined. In this study, a Lamb wave non-contact ultrasonic gas flow meter is used to measure the flow of hydrogen-mixed natural gas in a T-type pipeline. The greater the hydrogen mixing ratio, the higher the flow rate of the branch pipeline, and the shorter the installation distance of the ultrasonic flow meter, for example, 10% at 150D, 20% at 110D, and 30% at 20D. The time-difference method with high accuracy and broad applicability is used to calculate the flow rates of COMSOL simulated values. The errors between COMSOL simulation and theoretical flow rates at the shortest installation distance downstream do not exceed 3%. The errors at the position where the mixing uniformity is 80% are significantly higher than those at the shortest installation distance, and the maximum error is about 7.7%. The COMSOL simulation results show the feasibility and accuracy of ultrasonic gas flow metering of hydrogen-mixed natural gas.