Molecular Hydrogen Research Articles

Heterogeneously Catalyzed Reductive Depolymerization of Lignin to Value-Added Chemicals.

Lignin is an abundant renewable source of aromatics, but its complex heterogeneous structure poses challenges for its depolymerization and valorization. Heterogeneously catalyzed reductive depolymerization (HCRD) has emerged as a promising approach, utilizing heterogeneous catalysts to facilitate selective bond cleavage in lignin and hydrogen transfer to stabilize the products under mild conditions. This review provides a comprehensive understanding of the hydrogen transfer mechanisms in HCRD, involving different hydrogen sources, including molecular hydrogen, alcohols, formic acid, etc., and the native hydrogen donor groups in lignin. The interaction between hydrogen sources and catalyst design is explored, emphasizing how catalyst characteristics must align with specific hydrogen transfer pathways to optimize efficiency and selectivity. Precious metal-based and non-precious metal-based catalysts are examined, highlighting advances that enhance hydrogen activation and transfer. Comparative analyses of hydrogen sources reveal distinct advantages and limitations. The significance of HCRD in lignin valorization and the development of integrated biorefineries is underscored, emphasizing its potential to contribute to a sustainable bioeconomy through improved process integration and economic viability.

Non-Adiabatic Excited-State Time-Dependent GW (TDGW) Molecular Dynamics Simulation of Nickel-Atom Aided Photolysis of Methane to Produce a Hydrogen Molecule

Methane photolysis is a very important initiation reaction from the perspective of hydrogen production for alternative energy applications. In our recent work, we demonstrated using our recently developed novel method, non-adiabatic excited-state time-dependent GW (TDGW) molecular dynamics (MD), how the decomposition reaction of methane into a methyl radical and a hydrogen atom was captured accurately via the time-tracing of all quasiparticle levels. However, this process requires a large amount of photoabsorption energy (PAE ∼10.2 eV). Moreover, only one hydrogen atom is produced via a single photon absorption. Transition metal atoms can be used as agents for photochemical reactions, to reduce this optical gap and facilitate an easier pathway for hydrogen production. Here, we explore the photolysis of methane in the presence of a Ni atom by employing TDGW-MD. We show two possibilities for hydrogen-atom ejection with respect to the location of the Ni atom, towards the Ni side or away from it. We demonstrate that only the H ejection away from the Ni side facilitates the formation of a hydrogen molecule with the quasiparticle level corresponding to it having an energy close to the negative ionization potential of an isolated H2 molecule. This is achieved at a PAE of 8.4 eV which is lower compared to that of pristine methane. The results obtained in this work are an encouraging step towards transition metal-mediated hydrogen production via photolysis of hydrocarbons.

Emission of high rovibrational hydrogen molecules under detached plasma conditions by recycling on the tungsten wall

Abstract It is well known that the rate coefficient of molecular-assisted recombination (MAR) varies by several orders of magnitude depending on the rovibrational states of the hydrogen molecules. A molecular dynamics simulation is performed to estimate the rovibrational states of recycled hydrogen molecules at the divertor in the JA-DEMO reactor under detached plasma conditions. The simulation results reveal that molecules in high rovibrational states are released even with low incident energy, which will be the dominant condition under detached plasma conditions. Molecules generated in this way can strongly affect the formation of the detached plasma via a molecular assisted-process such as MAR.

Non-classical effective methods for reduction of heteroaromatic compounds

The review summarizes the known data on various methods for saturation and dearomatization of heterocyclic moieties, forming diverse aromatic compounds. Since the classical hydrogenation of substrates with molecular hydrogen has a number of fundamental drawbacks that hinder both its use at the laboratory level and its widespread implementation in industrial production, the main attention is paid to non-classical methods described in the literature over the last 20-25 years. The methods of ammonia-free Birch reduction, transfer hydrogenation, reduction by Hantzsch esters and some other reactions involving heterocyclic compounds are summarized and systematized. It is shown that such methods of reduction or dearomatization of heterocycles can in some cases be more efficient than classical procedures.<br> The bibliography includes 173 references.

Au/Ag@ZnS yolk-shell photocatalysts enhanced with noble metals and hyaluronic acid for efficient hydrogen production in rheumatoid arthritis therapy

Rheumatoid arthritis, characterized by the abnormal proliferation of synovial cells and extensive macrophage infiltration, is a chronic inflammatory disease. Molecular hydrogen, known for its antioxidant properties, has shown promise in eliminating reactive oxygen species. However, the low solubility and bioavailability of hydrogen limit the effectiveness of this therapy. To overcome these issues, we developed a novel yolk-shell heterostructure, H-AAZS (Au/Ag@ZnS modified hyaluronic acid), utilizing a hydrothermal cation exchange process. Through ion doping, semiconductor hybridization, and Schottky barriers in H-AAZS, photocatalysis for hydrogen generation has been successfully implemented using 660 nm laser irradiation. Additionally, the H-AAZS demonstrate the capacity for mild photothermal therapy, inducing apoptosis in synovial cells with Au's hot electrons with 660 nm laser irradiation. This strategy not only improves the abnormal proliferation of synovial cells but also avoids the exacerbation of inflammation caused by thermal stimulation. Both in vitro and in vivo experiments validate the synergistic effects of hydrogen production mediated anti-inflammatory responses, macrophage polarization and photothermal therapy. Therefore, this work represents a significant advancement as it ingeniously harnesses photocatalysis to modulate the synovial microenvironment while mitigating the side effects associated with photothermal therapy. This nanocrystal provides new and valuable insights into the potential treatment of Rheumatoid arthritis.

The Molecular Cloud Life Cycle. II. Formation and Destruction of Molecular Clouds Diagnosed via H2 Fluorescent Emission

Molecular hydrogen (H2) formation and dissociation are key processes that drive the gas life cycle in galaxies. Using the SImulating the LifeCycle of Molecular Clouds zoom-in simulation suite, we explore the utility of future observations of H2 dissociation and formation for tracking the life cycle of molecular clouds. The simulations used in this work include nonequilibrium H2 formation, stellar radiation, sink particles, and turbulence. We find that at early times in the cloud evolution H2 formation rapidly outpaces dissociation and molecular clouds build their mass from the atomic reservoir in their environment. Rapid H2 formation is also associated with a higher early star formation rate. For the clouds studied here, H2 is strongly out of chemical equilibrium during the early stages of cloud formation but settles into a bursty chemical steady state about 2 Myr after the first stars form. At the latest stage of cloud evolution, dissociation outweighs formation and the clouds enter a dispersal phase. We discuss how theories of the molecular cloud life cycle and star formation efficiency may be distinguished with observational measurements of H2 fluorescence with a space-based high-resolution far-UV spectrometer, such as the proposed Hyperion and Eos NASA Explorer missions. Such missions would enable measurements of the H2 dissociation and formation rates, which we demonstrate can be connected to different phases in a molecular cloud’s star-forming life, including cloud building, rapidly star forming, H2 chemical equilibrium, and cloud destruction.

Effect of limited hydrolysis on the structure and gel properties of soybean isolate proteins: A comparative study of papain or/and trypsin

Plant protein's gelation is crucial in various food applications, and hydrolysis may enhance their gelation properties. In this study, we prepared soybean protein isolate hydrolysates (SPIH) using trypsin and/or papain, and found significant improvement in the solubility and gelling properties. These proteases broken down the peptide bonds and caused the exposure of hydrophobic groups as well as the unfolding of protein. Low molecular weight (<35 kDa) SPIHs were generated by the two-step enzymatic hydrolysis, showing significant improvements in storage modulus (G′), loss modulus (G″), viscosity, strength, and water-holding capacity (WHC). Among, PT-10 exhibited the highest WHC (61.72 ± 0.36 %), gel strength (4.67 ± 0.12 g), and network cross-linking density (0.33 ± 0.01 mol/m3), while its solubility was also significantly increased up to 254 %. According to the results of gel molecular force interactions, disulfide bonds, hydrophobic interactions and hydrogen bonds involved in the gel network formation. These findings reveal that the appropriate hydrolysis modification may improve SPI gel's properties and expand its application in gel foods.

Cobalt-based Molecular Electrocatalyst-Mediated Green Hydrogen Generation: A Potential Pathway for Decarbonising Steel Industry

Cobalt-based Molecular Electrocatalyst-Mediated Green Hydrogen Generation: A Potential Pathway for Decarbonising Steel Industry

Thermophysical Properties of the Hydrogen Carrier System Based on Aqueous Solutions of Isopropanol or Acetone

One concept for the safe storage and transport of molecular hydrogen (H2) is the use of hydrogen carrier systems which can bind and release hydrogen in repeating cycles. In this context, the liquid system based on isopropanol and its dehydrogenated counterpart acetone is particularly interesting for applications in direct isopropanol fuel cells that are operated with an excess of water. For a comprehensive characterization of diluted aqueous solutions of isopropanol or acetone with technically relevant solute amount fractions between 0.02 and 0.08, their liquid density, liquid viscosity, and interfacial tension were investigated using various light scattering and conventional techniques as well as equilibrium molecular dynamics (EMD) simulations between (283 and 403) K. Polarization-difference Raman spectroscopy (PDRS) was used to monitor the liquid-phase composition during surface light scattering (SLS) experiments on viscosity and interfacial tension. For comparison purposes and to expand the database, capillary viscometry and dynamic light scattering (DLS) from bulk fluids with dispersed particles were also applied to determine the viscosity while the pendant-drop (PD) method allowed access to the interfacial tension. By adding isopropanol or acetone to water, density and, in particular, interfacial tension decrease significantly, while viscosity shows a pronounced increase. The behavior of viscosity and interfacial tension is closely related to the strong hydrogen bonding between the unlike mixture components and the pronounced enrichment of both solutes at the vapor–liquid interface, as revealed by EMD simulations. For an aqueous solution with an isopropanol amount fraction of 0.04, minor variations in interfacial tension and viscosity were found in the presence of pressurized H2 up to 7.5 MPa. Overall, the results from this study contribute to an extended database for diluted aqueous solutions of isopropanol or acetone, especially at temperatures above 323 K.

Precise synthesis of cyclopropyl methyl ketone via proton transfer of 5-chloro-2-pentanone driven by hydrogen bonds

The traditional synthesis methods of cyclopropyl methyl ketone (CPMK) have some disadvantages such as low yield, slow reaction rate and unclear catalytic mechanism. To solve these problems, a new strategy is developed to synthesize CPMK from 5-chloro-2-pentanone (CPE) using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). Experiment results show that the yield of CPMK reached a maximum of 96.5% in DBU at 40°C for 30min. The mechanism study shows that the hydrogen bond between DBU and CPE is the key to drive the deprotonation and cyclization of CPE. The hydrogen bond is formed between the N atom on C=N of DBU and the α-H on the methylene group associated with the carbonyl group on CPE. The catalyst DBU is converted into [DBUH]+Cl−, which can be reclaimed and recycled completely. The density functional theory (DFT) calculation confirmed the existence of molecular hydrogen bonds and proved that the hydrogen bond driving force is the key to the reaction. The hydrogen bond driven mechanism provides a new idea for the basic research of cyclization reaction.

Super-hybrid transition metal sulfide nanoarrays of NiS nanoparticle/WS2 nanosheet/Ni3S4 nanoparticle with abundant plane- and edge-type active interfaces for robust all-pH hydrogen evolution

Transition metal sulfides (TMSs) are primitive composition of biocatalysts that are active for molecular hydrogen production. The development of non-precious TMSs with appropriate spatial ordering has great potentials to contribute high-level hydrogen generation. Herein, super-hybrid transition metal sulfide nanoarrays of NiS nanoparticle/WS2 nanosheet/Ni3S4 nanoparticle (Super-NiS/WS2/Ni3S4) with high spatial ordering and abundant plane- and edge-type WS2-NiS and WS2-Ni3S4 heterointerfaces were elaborately constructed though manipulating the sequential dissociation of phosphotungstic acid (PW12) as W precursor and nickel foam as Ni precursor in one pot. When evaluated for the electrocatalytic hydrogen evolution reaction (HER), the Super-NiS/WS2/Ni3S4 only required overpotentials of 57, 95, and 151 mV to drive HER in alkaline, acid, and neutral media, respectively, and presented favorable reaction kinetics and test stability. The theoretical and experimental results verify the adsorption and dissociation of water molecules are preferential on WS2-plane-related heterointerfaces. The Gibbs free energy (ΔGH*) analysis indicated the WS2-plane-NiS interface is thermodynamically optimal for HER. Moreover, the collaborations of the abundant plane- and edge-type active interfaces, the open nanosheet-based vertical array, and the phosphorus doping in Super-NiS/WS2/Ni3S4 strengthen mass transport and electron transfer in electrocatalysis. The polyoxometalates-based synthetic strategy will inspire the new vision for the rational design and construction of advanced functional materials.

Molecular hydrogen inhibits neuroinflammation and ameliorates depressive-like behaviors and short-term cognitive impairment in senescence-accelerated mouse prone 8 mice

Molecular hydrogen inhibits neuroinflammation and ameliorates depressive-like behaviors and short-term cognitive impairment in senescence-accelerated mouse prone 8 mice

Formation of molecular hydrogen in diamond-like carbon films during deposition: Molecular dynamics simulations

The existence states of the H atoms in hydrogenated diamond-like carbon (a-C:H) films were simulated using a modified REBO II potential function-based large-scale atomic/molecular parallel simulator (LAMMPS) and neutral C and H atom beam impingement. The fraction of the H atoms in the incident source (H-flux fraction) in the source must be considered when investigating the effects of the incident energy combination on the H content and mass density of the films. In simulations a-C:H film deposition using a 15 % H-flux fraction, films with densities of 2.6–2.8 g/cm3 could be obtained, and their H content varied with the incident energy. However, the H contents of films simulated using a 70 % H-flux fraction could be kept in the range of 40–50 at.%. The H atoms in the films preferentially reacted with the C atoms to form CH bonds. Regardless of the incident energy combination used, the total sp3C fraction in the film increased with the H-flux fraction of the source. An incident energy of >36 eV for the H atoms was necessary to form H2 during the film deposition. Instead of being formed in the surface growth zone, H2 molecules were synthesized in the stabilized zone, where a high density of sp3C—Hn was favorable.

Mitigating environmental toxicity with hydrogen nanobubbles: A mitochondrial function-based approach to ecological restoration

In biological systems, nanobubbles (NBs) effectively enhance hydrogen molecule retention and scavenging reactive oxygen species (ROS), but the underlying mechanisms remain elusive. To investigate this, we prepared hydrogen NB water samples with consistent dissolved hydrogen levels but varying NB densities to explore their physicochemical properties and effects on green algae (Chlorella vulgaris) under oxidative stress induced by copper ions (Cu2+) and cadmium ions (Cd2+). The results indicated a strong correlation between the hydrogen NB number density and the 25 % inhibitory concentration of Cu2+ over 24 h, with ROS removal efficiency increased with the NB number density. Gas chromatography showed that the hydrogen NBs in the solution had a high gas density that enhanced hydrogen transport into C. vulgaris. With regard to mitochondrial activity, hydrogen NBs were observed to enhance the function of mitochondrial complexes I and V and increase the mitochondrial membrane potential. Experiments with C. vulgaris mitochondrial electrodes showed that the electron transfer rates increased significantly in the presence of hydrogen NBs. We concluded that the high gas density of hydrogen NBs augments intracellular hydrogen delivery and strengthens mitochondrial functions.

Elucidating the isotope effect in the Morse approximation of the ground state electronic term of hydrogen molecules nH2, n = 1 ÷ 7. Showcasing the Herzberg anomaly and anharmonicity

The Morse function is the simplest anharmonic approximation of the potential of a diatomic molecule, for which the vibrational Schrödinger equation could be solved almost precisely. Despite its crudeness, the Morse function has been widely used in solving various problems in molecular spectroscopy. In recent years, special attention was paid to the existence of two Morse approximations for the electronic terms U(r) of diatomic molecules, M1(r) and M2(r), which differ by the selection of primary fitting parameters and satisfactorily reproduce different parts of U(r). Some fine features of simple terms U(r), whose form does not differ much from the Morse function, could be highlighted by considering difference functions U(r) − M(r). The set of vibrational levels G(υ), predicted by Morse approximation, can be conveniently characterized by the difference functions Δ1G(υ) and Δ2G(υ), which are, respectively, the energies of vibrational quanta and the rates of their change. The function Δ2G(υ) can be considered as a generalization of the anharmonicity constant, determined experimentally by the position of levels υ = 0,1,2. Finally, analysing the anharmonicity, it is useful to compare the results obtained for various isotopologues, for which U(r) is the same, but the density of vibrational levels is different. The maximal range of isotope effects is expected for hydrogen, which has seven known isotopes, including extremely short-lived ones. In this work, the influence of the reduced mass on the results of the approximation of the electronic ground state potential U(r) by the Morse function is studied for seven isotopologues of hydrogen molecule nH2 (n = 1–7). For each isotopologue, alternative approximations M1(r) and M2(r) are considered. The systematic deviation of M1(r) from U(r) increases with r, reaching 1700–2770 cm−1 (for 7H2–1H2) in the region of the asymptote. The systematic deviation of M2(r) from U(r) decreases at larger distances: it is dome-shaped with a maximum of ca. 1500 cm−1 at r ∼ 2 Å, after which it falls to zero. The M2(r) curves for different isotopologues diverge by less than 20 cm−1. The U(r) − M(r) functions are used to analyse the so-called “Herzberg anomaly” in the region where M1(r) and M2(r) intersect U(r). For example, at around r = 1.08 Å the U(r) − M2(r) function shows anomalous negative values ranging from −125 cm−1 (for 1H2) to −142 cm−1 (for 7H2).

Diffusion and Spectroscopy of H2 in Myoglobin

The diffusional dynamics and vibrational spectroscopy of molecular hydrogen (H2) in myoglobin (Mb) is characterized. Hydrogen has been implicated in a number of physiologically relevant processes, including cellular aging or inflammation. Here, the internal diffusion through the protein matrix was characterized, and the vibrational spectroscopy was investigated using conventional empirical energy functions and improved models able to describe higher-order electrostatic moments of the ligand. Depending on the energy function used, H2 can occupy the same internal defects as already found for Xe or CO (Xe1 to Xe4 and B-state). Furthermore, four additional sites were found, some of which had been discovered in earlier simulation studies. Simulations using a model based on a Morse oscillator and distributed charges to correctly describe the molecular quadrupole moment of H2 indicate that the vibrational spectroscopy of the ligand depends on the docking site it occupies. This is consistent with the findings for CO in Mb from experiments and simulations. For H2, the maxima of the absorption spectra cover ∼20 cm−1 which are indicative of a pronounced Stark effect of the surrounding protein matrix on the vibrational spectroscopy of the ligand. Electronic structure calculations show that H2 forms a stable complex with the heme iron (stabilized by ∼−12 kcal/mol), but splitting of H2 is unlikely due to a high activation energy (∼50 kcal/mol).

The Adsorption and Sensing Characteristics of Metal‐Calix[4]Arenes Toward Hydrogen Molecule: Density Functional Theory, Perturbation Theory and Molecular Dynamics Approaches

AbstractCalixarenes, which can be functionalized in a wide range of derivatives, are one of the chemicals that should be considered for safe energy storage. This research focused on utilization Density Functional Theory (DFT) method to investigate the hydrogen sensing and adsorption characteristics of two distinct calix[4]arene compounds and their corresponding metal complexes. In the study, electronic sensor properties were investigated by using different approaches. In addition, the dynamic stability was determined by Molecular dynamics (MD) calculations. Perturbation theory analysis has revealed the importance of the relationship between Fe and S atoms. The adsorption energy on the C1 structure with the best adsorption ability was calculated as −10.3 kJ/mol. According to RDG analysis, weak van der Waals interactions play a role in adsorption. The C2‐Fe complex with a substantial decrease in the HOMO–LUMO gap has been identified and explained as an applicant material for electronic sensor against hydrogen molecule. Moreover, it was also determined that the C2‐Fe complex has work function type gas sensor property against hydrogen molecule. According to the results, metal‐calixarene complexes can play an important role in hydrogen safety in the future.

Hydrogen Gas Inhalation Alleviates Airway Inflammation and Oxidative Stress on Ovalbumin-Induced Asthmatic BALB/c Mouse Model

Airway inflammatory diseases, such as asthma, are a global public health concern owing to their chronic inflammatory effects on the respiratory mucosa. Molecular hydrogen (H2) has recently been recognized for its antioxidant and anti-inflammatory properties. In this study, we examined the therapeutic potential of H2 in airway inflammation using an ovalbumin (OVA)-induced BALB/c mouse model of allergic asthma. Female BALB/c mice were sensitized and challenged with OVA to induce airway inflammation, and 30 mice were randomly divided into five groups: NT (non-treatment), HTC (3% H2 treatment only), NC (negative control, OVA only), PC (positive control, OVA + intranasal 1 mg/mL salbutamol 50 μL), and HT (H2 treatment, OVA + inhaled 3% H2). Various inflammatory and oxidative stress (OS)-induced markers such as white blood cells (WBCs) and their differential counts, lung histology, cytokine levels such as interleukin (IL)-4, (IL)-5, (IL)-13, interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), granulocyte-macrophage colony-stimulating factor (GM-CSF), (IL)-10, reactive oxygen species (ROS), nitric oxide (NO), glutathione peroxidase (GPx), and catalase (CAT), and total immunoglobulin E (IgE) levels were investigated. Our results showed that inhaled H2 significantly reduced inflammatory cell infiltration, OS markers, and pro-inflammatory cytokine expression while upregulating antioxidant enzyme activity. Furthermore, H2 also significantly decreased serum IgE levels, a marker of allergic inflammation. Collectively, our findings suggest that H2 inhalation is a promising treatment option for airway inflammation, offering a novel approach with potential clinical applications.

Computational Exploration of Adsorption-Based Hydrogen Storage in Mg-Alkoxide Functionalized Covalent-Organic Frameworks (COFs): Force-Field and Machine Learning Models.

Hydrogen is a clean-burning fuel that can be converted to other forms. of energy without generating any greenhouse gases. Currently, hydrogen is stored either by compression to high pressure (>700 bar) or cryogenic cooling to liquid form (<23 K). Therefore, it is essential to develop safe, reliable, and energy-efficient storage technology that can store hydrogen at lower pressures and temperatures. In this work, we systematically designed 2902 Mg-alkoxide-functionalized covalent-organic frameworks (COFs) and performed high-throughput (HT) computational screening for hydrogen storage applications at 111, 231, and 296 K. To accurately model the interaction between Mg-alkoxide sites and molecular hydrogen, we performed MP2 calculations to compute the hydrogen binding energy for different types of functionalized models, and the data were subsequently used to fit modified-Morse force field (FF) parameters. Using the developed FF models, we conducted HT grand canonical Monte Carlo (GCMC) simulations to compute hydrogen uptakes for both original and functionalized COFs. The generated data were subsequently used to evaluate the materials' gravimetric and volumetric storage performance at various temperatures (111, 231, and 296 K). Finally, we developed machine learning (ML) models to predict the hydrogen storage performance of functionalized structures based on the features of the original structures. The developed model showed excellent performance with a mean absolute error (MAE) of 0.061 wt % and 0.456 g/L for predicting the gravimetric and volumetric deliverable capacities, enabling a quick evaluation of structures in a hypothetical COF database. The screening results demonstrated that the Mg-alkoxide functionalization yields greater improvements in volumetric H2 storage capacities for COFs with smaller pores compared to those with larger (mesoporous) pores.

Lineshape of Amplitude-Modulated Stimulated Raman Spectra

The amplitude modulation of a pump field and the phase-sensitive detection of a pump-induced intensity change of a probe field encompass a common practice in nonlinear spectroscopies to enhance the detection sensitivity. A drawback of this approach arises when the modulation frequency is comparable to the width of the spectral feature of interest, since the presence of sidebands in the amplitude-modulated pump field provides distortion to the observed spectral lineshape. This represents a problem when accurate measurements of spectral lineshapes and line positions are pursued, as recently happened in our group with the metrology of the Q(1) line in the 1-0 band of molecular hydrogen. The measurement was performed with a Stimulated Raman Scattering spectrometer that was calibrated, for the first time, against an optical frequency comb. In this work, we develop an analytical tool for nonlinear Stimulated Raman spectroscopies that allows us to precisely quantify spectral distortions arising from high-frequency amplitude modulation in one of the interacting fields. Once they are known, spectral distortions can be deconvolved from the measured spectra to retrieve unbiased data. The application of this tool to the measured spectra is discussed.