Hydrogen Release Research Articles

Light-Enabled Reversible Hydrogen Storage of Borohydrides Activated by Photogenerated Vacancies.

Borohydrides, known for ultrahigh hydrogen density, are promising hydrogen storage materials but typically require high operating temperatures due to their strong thermodynamic stability. Here we introduce a novel light-induced destabilization mechanism for hydrogen storage reaction of borohydrides under ambient conditions via photogenerated vacancies in LiH. These vacancies thermodynamically destabilize B-H bonds through the spontaneous "strong adsorption" of BH4 groups, which trigger an asymmetric redistribution of electrons, enabling hydrogen release at near room temperature, approximately 300 °C lower than the corresponding thermal process. By utilizing specially designed "nano-photothermal reactors", which optimize thermodynamic destabilization effect with nanoscale dispersed LiH and create space-confined "hotspots" to enhance hydrogen storage kinetics, we achieve an ultrahigh hydrogen storage capacity of 11.02 wt % H2 in LiBH4 using only light irradiation. This light-induced destabilization mechanism can also be extended to other alkali metal borohydrides, offering insights for developing solid-state hydrogen storage materials under mild conditions.

Photothermally-activated suspended aerogel triggers a biphasic interface reaction for high-efficiency and additive-free hydrogen generation.

The need for a sustainable hydrogen supply has sparked significant efforts to develop effective liquid hydrogen carriers with high hydrogen content that can be safely stored and undergo controlled hydrogen release. However, a major challenge lies in the ultralow hydrogen evolution rate caused by the direct dehydrogenation of liquid hydrogen carriers. Conventionally, accelerant additives are employed to improve the dehydrogenation rate, but this strategy inevitably sacrifices the hydrogen storage density. Therefore, achieving high-efficiency hydrogen release and high storage density remains a daunting task. Herein, we develop an innovative photothermally-activated suspended biphasic reaction strategy, which absorbs solar radiation and re-radiates infrared photons to induce photothermal evaporation and in situ dehydrogenation of liquid hydrogen carriers, fundamentally circumventing the employment of additives. Furthermore, by leveraging this phase transition-induced biphasic reaction design, the strategy improves the required reaction temperature and drastically lowers hydrogen transport resistance. Therefore, an impressive hydrogen evolution rate of 386 mmol g-1 h-1 is achieved from pure formic acid with an ultrahigh hydrogen storage density of 53 g L-1, representing a threefold improvement in rate compared to state-of-the-art strategies. Our approach introduces a fresh perspective for the dehydrogenation of liquid hydrogen carriers, encompassing formic acid, hydrazine hydrate, and so on, and concurrently guarantees exceptional hydrogen release capabilities and excellent hydrogen storage density.

Electrocatalytic performance of transition metal mono-carbides (TM: CrC, FeC, MnC, TiC, VC) decorated on palladium-encapsulated fullerenes (TM-Pd@C60) for hydrogen evolution reaction (HER): A DFT perspective

The search for efficient and cost-effective electrocatalysts for the hydrogen evolution reaction (HER) is critical for advancing renewable energy technologies. This study employs density functional theory (DFT) at the MN12-SX/GenECP/Def2svp/LanL2DZ computational method to investigate the electronic, structural, and catalytic properties of modified fullerene (C60) systems encapsulated with palladium (Pd) and doped with transition metal carbides: CrC, FeC, MnC, TiC, and VC. Frontier molecular orbital (FMO) analysis reveals significant changes in the HOMO-LUMO gap upon doping, indicating enhanced electronic conductivity essential for catalytic activity. The lowest energy gaps 0.081 eV for MnC–Pd@C60 and 0.096 eV for VC-Pd@C60 were observed thus showing their readiness in terms of electron transfer. HER activity was assessed through the calculation of Gibbs free energy changes (ΔGH) for hydrogen adsorption. The results highlight TiC–Pd@C60, FeC–Pd@C60, and CrC–Pd@C60 as having optimal ΔGH values close to zero, suggesting their superior catalytic performance. Structural analysis confirms the stability of these doped systems, with minimal distortions observed in the fullerene framework upon metal encapsulation and doping. Vibrational analysis revealed that Pd@C₆₀ complexes show reduced M − C vibrations and the formation of M − H bonds, indicating efficient hydrogen adsorption, especially in MnC–Pd@C₆₀ and VC-Pd@C₆₀. Thermodynamics investigation show MnC–Pd@C₆₀ and VC-Pd@C₆₀ to exhibit highly exothermic and spontaneous hydrogen adsorption. Overall, Ti, Fe, and Cr-based catalysts show weaker interactions, which might favor the desorption step in HER. On the other hand, catalysts with V and Mn show strong hydrogen interactions via the Tafel step, which might benefit initial hydrogen adsorption but could require optimization to ensure efficient hydrogen release.

Enhancing the power density of hydrogen release from LOHC systems by high Pt loadings on hierarchical alumina support structures

Enhancing the power density of hydrogen release from LOHC systems by high Pt loadings on hierarchical alumina support structures

Effect of cylinder to nozzle distance on the concentration profile induced by impingement of unignited hydrogen release at different pressures

Effect of cylinder to nozzle distance on the concentration profile induced by impingement of unignited hydrogen release at different pressures

Rapid Hydrolysis of Submicron Magnesium Catalyzed by In Situ-Generated Multi-Nickel Alloys.

The hydrolysis of lightweight metal-based materials is a promising technology for supplying hydrogen to portable fuel cells. Various additives for the catalytic modification of Mg hydrolysis have been investigated. Efficient catalysts and small magnesium particle sizes are key to enhancing the rate of hydrogen production. In this study, submicron Mg and in situ-generated multi-Ni alloy catalysts (NiM@Gn) are prepared and composited for the first time. Among the composites prepared, Mg-5wt.%NiM@Gn exhibits the best hydrolysis performance. This composite can release 804.4mL g-1 hydrogen within 30 s (98.32% of the total yield), and its initial hydrogen release rate is as high as 5480mL g-1 min-1, with a low apparent activation energy of hydrolysis of 10.85kJ mol-1. Submicron Mg greatly improves the rate of the hydrolysis reaction, and graphene facilitates the exfoliation of agglomerated Mg particles in water. Mg2Ni and (Fe, Ni) alloys generate microgalvanic cells with Mg in situ, significantly enhancing the electrochemical corrosion efficiency of Mg. Theoretical calculations show that these alloys accelerate electron transfer and coupling on the Mg surface. This study guides for the design and preparation of multi-catalysts and establishes the feasibility of submicron Mg for hydrogen generation through hydrolysis.

Development of a Hydrogen Fuel Cell Hybrid Urban Air Mobility System Model Using a Hydrogen Metal Hydride Tank

Hydrogen fuel cell-based UAM (urban air mobility) systems are gaining significant attention due to their advantages of higher energy density and longer flight durations compared to conventional battery-based UAM systems. To further improve the flight times of current UAM systems, various hydrogen storage methods, such as liquid hydrogen and hydrogen metal hydrides, are being utilized. Among these, hydrogen metal hydrides offer the advantage of high safety, as they do not require the additional technologies needed for high-pressure gaseous hydrogen storage or the maintenance of cryogenic temperatures for liquid hydrogen. Furthermore, because of the relatively slower dynamic response of hydrogen fuel cell systems compared to batteries, they are often integrated into hybrid configurations with batteries, necessitating an efficient power management system. In this study, a UAM system was developed by integrating a hydrogen fuel cell system with hydrogen metal hydrides and batteries in a hybrid configuration. Additionally, a state machine control approach was applied to a distribution valve for the endothermic reaction required for hydrogen desorption from the hydrogen metal hydrides. This design utilized waste heat generated by the fuel cell stack to facilitate hydrogen release. Furthermore, a fuzzy logic control-based power management system was implemented to ensure efficient power distribution during flight. The results show that approximately 43% of the waste heat generated by the stack was recovered through the tank system.

Beyond Hydrolysis: Scalable, On-Demand Dihydrogen Release from NaBH4 enables Circular and Sustainable Process Design

Hydrogen storage in its elemental form poses significant safety and economic challenges. Metal hydrides, particularly sodium borohydride, offer a promising alternative because of their superior safety profiles and enhanced transportability. This study presents a scalable hydrogen release system based on sodium borohydride and commercially available alcohols and acids. The system enables rapid, controlled hydrogen generation achieving quantitative yields. Quantum chemical calculations were performed to propose a mechanism for the alcoholysis of NaBH4 with isopropyl alcohol (IPA) and acid present. It was demonstrated that the reaction proceeds via isopropoxy substituted borane derivatives BH(3-n)OiPrn (for n = 0, 1, 2, 3), which can form Lewis acid-base adducts with IPA. These Lewis acid-base adducts serve as reaction complexes for -bond metathesis, upon which an equivalent of hydrogen gas is released. Notably, the spent fuel can be regenerated to sodium borohydride using established chemical reactions, ensuring the system's sustainability and applicability for larger-scale hydrogen production

Passivation of acceptors in GaN by hydrogen and their activation

Abstract GaN is an important semiconductor for energy-efficient light-emitting devices. Hydrogen plays a crucial role in gallium nitride (GaN) growth and processing. It can form electrically neutral complexes with acceptors during growth, which significantly increases the acceptor incorporation. Post-growth annealing dissociates these complexes and is widely utilized for activating Mg acceptors and achieving conductive p-type GaN. In this work, we demonstrate that other acceptors, such as C and Be, also form complexes with hydrogen similar to Mg. The effect of thermal annealing of GaN on photoluminescence (PL) was investigated. In samples moderately doped with Be, the BeGa-related yellow luminescence (YLBe) band intensity decreased by up to an order of magnitude after annealing in N2 ambient at temperatures Tann = 400900 °C. This was explained by the release of hydrogen from unknown traps and the passivation of the BeGa acceptors. A similar drop of PL intensity at Tann = 350900 °C was observed for the CN-related YL1 band in unintentionally C-doped GaN and also attributed to passivation of the CN acceptors by hydrogen released from unknown defects. In this case, the formation of the CNHi complexes was confirmed by the observation of the rising BL2 band associated with these complexes. At Tann > 900 °C, both the YLBe and YL1 intensities were restored, which was explained by the removal of hydrogen from the samples. Experimental results were compared to the first principles calculations of complex dissociation and hydrogen diffusion paths in GaN.

Transformation of Sugar Cane Lignin into Renewable Fuel-Range Cyclo-Alkanes: In-Situ Hydrogen Release Using Earth-Abundant AlCl3 and Biobased Mannose Triflate Support

Transformation of Sugar Cane Lignin into Renewable Fuel-Range Cyclo-Alkanes: In-Situ Hydrogen Release Using Earth-Abundant AlCl₃ and Biobased Mannose Triflate Support

Exploring hydrogen adsorption and release in 2D M2C-MXenes: structural and functional insights.

Two-dimensional M2C-MXenes, characterized by their lightweight nature, tunable surface structures, and strong affinity for hydrogen, hold significant promise for addressing various challenges in hydrogen energy utilization. This study focuses on investigating the hydrogen adsorption and desorption properties, as well as the stability of hydrogenated compounds in 19 pure M2C-MXenes nanosheets. The results indicate that hydrogen adsorption on M2C primarily occurs through weak physisorption, with Mn2C and Fe2C from the fourth period, and Ag2C and Cd2C from the fifth period exhibiting the lowest adsorption energies. In contrast, hydrogen atoms are adsorbed on M2C primarily through chemisorption, leading to the potential dissociation of H2molecules into two hydrogen atoms. Among the M2C-MXenes, Ti2C, and Zr2C in thed4andd5, respectively, demonstrate the most stable hydrogen atom binding. Hydrogen evolution is most facile on Cu2C and Ag2C surfaces. Two types of stacking configurations, face-centered cubic and hexagonal close-packed, are observed for hydrogenated M2C surfaces (e.g. Co2C and Zr2C), showing excellent thermodynamic stability. This work elucidates the hydrogen utilization performance of pure M2C-MXenes nanosheets and guides future research aimed at achieving high hydrogen storage capacities through the functional tuning of MXenes.

Investigation of Solid-State Thermal Decomposition of Ammonia Borane Mix with Sulphonated Poly(Ellagic Acid) for Hydrogen Release

Investigation of Solid-State Thermal Decomposition of Ammonia Borane Mix with Sulphonated Poly(Ellagic Acid) for Hydrogen Release

Stabilisation of a Strontium Hydride with a Monodentate Carbazolyl Ligand and its Reactivity.

The molecular strontium hydride 2 [(dtbpCbz)SrH(L)]2 (L=benzene, toluene) was isolated and stabilized by employing a sterically demanding carbazole ligand (dtbpCbz=1,8-bis(3,5-ditertbutylphenyl)-3,6-ditertbutylcarbazolyl). Compound 2 was synthesized via phenylsilane metathesis with the corresponding amide (dtbpCbz)SrN(SiMe3)2 and characterized by 1H NMR, XRD and vibrational spectroscopy methods. We further investigated the stoichiometric reactivity of 2 towards carbon monoxide, azobenzene and trimethylsilylacetylene, showing three distinct reactivity pathways: addition, reduction and deprotonation. The reaction of 2 with carbon monoxide yields the ethenediolate complex 4 via addition, while with azobenzene reduction of the N-N double bond and release of hydrogen were observed, affording a heteroleptic strontium complex with a radical azobenzenyl ligand (5). The terminal alkyne is deprotonated by the hydride moiety to give the acetylide complex 6.

CO-Tolerant Heterogeneous Ruthenium Catalysts for Efficient Formic Acid Dehydrogenation.

The development of improved and less costly catalysts for dehydrogenation of formic acid (HCOOH) is of general interest for renewable energy technologies involving hydrogen storage and release. Theoretical calculations reveal that ruthenium (Ru) nanoparticles supported on nitrogen-doped carbon should be appropriate catalysts for such transformations. It is predicted that nitrogen doping significantly decreases the formation of CO, but at the same time increases CO tolerance of the catalysts. To prove these hypotheses heterogeneous ruthenium catalysts supported on porous nitrogen-doped carbon (Rux/CN) with hierarchical structure were synthesized using carbon nitride (C3N4) as template and phenanthroline (Phen) as ligand. Experimental tests in HCOOH dehydrogenation revealed that the optimal catalyst Ru7/CN exhibited good thermal stability at 140 °C and a high turnover frequency (TOF >1300 h-1), which is more than one order of magnitude higher than that of the commercial Ru5/C catalyst.

H Induced Metal-Insulation Transition Boosts the Stability of High Temperature Polymer Electrolyte Membrane Fuel Cells.

High temperature polymer electrolyte membrane fuel cells (HT-PEMFCs) have garnered significant attention due to their expanded range of hydrogen sources and simplified management systems. However, the frequent start-up and shut-down (SU/SD) caused fuel starvation operation condition seriously deteriorates the performance and lifetime of the fuel cell. In this manuscript, VO2 was incorporated in the anode to restrain fuel starvation of the electrode. Under the operation condition, the insulative VO2 would reversibly transform into metallic HxVO2 by intercalating hydrogen, and HxVO2 can automatically release hydrogen, which could act as the hydrogen buffer and suppress reverse-current degradation. After the hydrogen release, the generated insulating VO2 would prevent the side reactions during fuel starvation. Compared to the traditional Pt anode, the electrode with VO2 showed much higher output power and greatly improved durability after fuel starvation. This work demonstrates the in situ reversible hydrogen storage/release-controlled metal-insulator phase transition strategy to enhance the durability of fuel cells.

H Induced Metal‐Insulation Transition Boosts the Stability of High Temperature Polymer Electrolyte Membrane Fuel Cells

AbstractHigh temperature polymer electrolyte membrane fuel cells (HT‐PEMFCs) have garnered significant attention due to their expanded range of hydrogen sources and simplified management systems. However, the frequent start‐up and shut‐down (SU/SD) caused fuel starvation operation condition seriously deteriorates the performance and lifetime of the fuel cell. In this manuscript, VO2 was incorporated in the anode to restrain fuel starvation of the electrode. Under the operation condition, the insulative VO2 would reversibly transform into metallic HxVO2 by intercalating hydrogen, and HxVO2 can automatically release hydrogen, which could act as the hydrogen buffer and suppress reverse‐current degradation. After the hydrogen release, the generated insulating VO2 would prevent the side reactions during fuel starvation. Compared to the traditional Pt anode, the electrode with VO2 showed much higher output power and greatly improved durability after fuel starvation. This work demonstrates the in situ reversible hydrogen storage/release‐controlled metal‐insulator phase transition strategy to enhance the durability of fuel cells.

Unveiling the Potential of Heterogeneous Systems for Reversible Hydrogen Storage in Liquid Organic Hydrogen Carriers.

Transitioning towards a carbon-free economy is the current global need of the hour. The transportation sector is one of the major contributors of CO2 emissions in the atmosphere disturbing the delicate balance on the Earth, leading to global warming. Hydrogen has emerged as a promising alternative energy carrier capable of replacing fossil fuels, with advancements in systems facilitating its storage and long-distance transport. In this context, the concept of liquid organic hydrogen carriers (LOHCs) is taking the lead, offering a plausible solution because of its compatibility with the existing gasoline infrastructure, while eliminating the challenges associated with the conventional hydrogen storage methods. Key LOHC systems, such as methylcyclohexane/toluene and H-18-dibenzyltoluene/dibenzyltoluene (H-18-DBT/DBT), have been extensively researched for large-scale applications. However, challenges persist, particularly concerning the endothermic nature of the reactions involved. In this regard, of particular interest are the multifunctional heterogeneous catalysts supported on a single support, offering cost-effective and energy-efficient solutions to circumvent issues related to the endothermicity of the reactions. In this review, solid heterogeneous catalysts that have been developed and investigated for reversible dehydrogenation and hydrogenation reactions have been presented. These catalysts include monometallic, bimetallic, and pincer complexes supported on materials designed for efficient hydrogen uptake and release.

Effect of Al3V alloy on the hydrogen storage properties of MgH2

Al–V alloy was firstly prepared by arc melting followed by grinding using a stainless steel mortar. The alloy is mainly made up of Al3V, together with a little amount of Al8V5 and Al, and the particles in range of 1–30 μm. Among the MgH2–Al3V composites with Al3V concentrations of 1, 5 and 7 wt%, the MgH2-5 wt% Al3V composite exhibits the best hydrogen absorption and release kinetic performance. The MgH2-5 wt% Al3V composite can absorb 5.9 wt% of hydrogen within 3600 s at a temperature of 523 K. Despite the lower temperature of 423 K, it can also uptake hydrogen 1.71 wt% in 3600s. During dehydrogenation, MgH2-5 wt% Al3V releases 6.52 wt% of hydrogen in 350s at 673 K. The initial dehydrogenation temperature was lowered to 564 K. The activation energies of hydrogenation and dehydrogenation for MgH2-5 wt% Al3V composite are 87.98 kJ/mol and 85.57 kJ/mol, respectively. And the Al3V remains unchangeable in the hydrogen absorption/desorption cycle. After 20 cycles, the retention of hydrogenation and dehydrogenation capacity was 97% and 99%, respectively. The presence of Al3V and oxygen vacancies plays an important role in the improvement of hydrogen storage properties of MgH2. This study provides new ideas for the designing Al–V alloy catalyst for enhancing hydrogen storage performances of MgH2.

CO‐tolerant heterogeneous ruthenium catalysts for efficient formic acid dehydrogenation

The development of improved and less costly catalysts for dehydrogenation of formic acid (HCOOH) is of general interest for renewable energy technologies involving hydrogen storage and release. Theoretical calculations reveal that ruthenium (Ru) nanoparticles supported on nitrogen‐doped carbon should be appropriate catalysts for such transformations. It is predicted that nitrogen doping significantly decreases the formation of CO, but at the same time increases CO tolerance of the catalysts. To prove these hypotheses heterogeneous ruthenium catalysts supported on porous nitrogen‐doped carbon (Rux/CN) with hierarchical structure were synthesized using carbon nitride (C3N4) as template and phenanthroline (Phen) as ligand. Experimental tests in HCOOH dehydrogenation revealed the optimal catalyst Ru7/CN exhibiting good thermal stability and a high turnover frequency (TOF > 1300 h‐1), which is more than one order of magnitude higher than that of the commercial Ru5/C catalyst.

The Integration of Thermal Energy Storage Within Metal Hydride Systems: A Comprehensive Review

Hydrogen storage technologies are key enablers for the development of low-emission, sustainable energy supply chains, primarily due to the versatility of hydrogen as a clean energy carrier. Hydrogen can be utilized in both stationary and mobile power applications, and as a low-environmental-impact energy source for various industrial sectors, provided it is produced from renewable resources. However, efficient hydrogen storage remains a significant technical challenge. Conventional storage methods, such as compressed and liquefied hydrogen, suffer from energy losses and limited gravimetric and volumetric energy densities, highlighting the need for innovative storage solutions. One promising approach is hydrogen storage in metal hydrides, which offers advantages such as high storage capacities and flexibility in the temperature and pressure conditions required for hydrogen uptake and release, depending on the chosen material. However, these systems necessitate the careful management of the heat generated and absorbed during hydrogen absorption and desorption processes. Thermal energy storage (TES) systems provide a means to enhance the energy efficiency and cost-effectiveness of metal hydride-based storage by effectively coupling thermal management with hydrogen storage processes. This review introduces metal hydride materials for hydrogen storage, focusing on their thermophysical, thermodynamic, and kinetic properties. Additionally, it explores TES materials, including sensible, latent, and thermochemical energy storage options, with emphasis on those that operate at temperatures compatible with widely studied hydride systems. A detailed analysis of notable metal hydride–TES coupled systems from the literature is provided. Finally, the review assesses potential future developments in the field, offering guidance for researchers and engineers in advancing innovative and efficient hydrogen energy systems.