Molecular Hydrogen Research Articles

Investigation of hydrogen uptake capacity for FAU, MOR, MTW, MWW

In this study, the hydrogen storage properties of various synthetic zeolites, including Zeolite Y (FAU), Mordenite (MOR), ZSM-12 (MTW), and MCM-22 (MWW) are determined at 77 K and atmospheric pressure. The structures of the zeolites are characterized by XRD, ICP-OES, FE-SEM, TGA and N2 adsorption-desorption isotherms. The results show that H-MCM-22 zeolite has the highest hydrogen storage capacity at 1.0 bar with 1.19 wt%, followed by H-MOR zeolite with 1.05 wt%, H–Y zeolite with 0.75 wt% and H-ZSM-12 zeolite with 0.60 wt%. The hydrogen adsorption data on FAU, MOR, MTW, and MWW at 77 K obey the Sips isotherm model. The experimental data show that the ultra-micropore volume of the zeolite is effective in hydrogen adsorption at low-pressure ranges. In addition, increasing the aluminum content of the zeolite increases the hydrogen adsorption capacity of the zeolite at atmospheric pressure. Therefore, zeolites with channel sizes close to the kinetic diameter of a hydrogen molecule, large cage volumes, and high aluminum content are potential candidates for energy storage applications.

Molecular Hydrogen Protects against Various Tissue Injuries from Side Effects of Anticancer Drugs by Reducing Oxidative Stress and Inflammation

Molecular Hydrogen Protects against Various Tissue Injuries from Side Effects of Anticancer Drugs by Reducing Oxidative Stress and Inflammation

Revealing the atomic and electronic mechanism of human manganese superoxide dismutase product inhibition

Human manganese superoxide dismutase (MnSOD) is a crucial oxidoreductase that maintains the vitality of mitochondria by converting superoxide (O2●−) to molecular oxygen (O2) and hydrogen peroxide (H2O2) with proton-coupled electron transfers (PCETs). Human MnSOD has evolved to be highly product inhibited to limit the formation of H2O2, a freely diffusible oxidant and signaling molecule. The product-inhibited complex is thought to be composed of a peroxide (O22−) or hydroperoxide (HO2−) species bound to Mn ion and formed from an unknown PCET mechanism. PCET mechanisms of proteins are typically not known due to difficulties in detecting the protonation states of specific residues that coincide with the electronic state of the redox center. To shed light on the mechanism, we combine neutron diffraction and X-ray absorption spectroscopy of the product-bound, trivalent, and divalent states of the enzyme to reveal the positions of all the atoms, including hydrogen, and the electronic configuration of the metal ion. The data identifies the product-inhibited complex, and a PCET mechanism of inhibition is constructed.

Electric field-induced electronic structure and intersubband transitions of a hydrogen molecular ion in a gaussian-type quantum ring

In this work, the influence of an external electric field on the electronic structure and intersubband transitions of a singly ionized double-donor system in a GaAs quantum ring defined by Gaussian-type potentials is investigated theoretically. Within the framework of the effective mass approach, the two-dimensional diagonalization method is used for the solution of the Schrödinger equation to obtain the eigen energies and corresponding wave functions. Numerical results reveal that the electronic energy spectrum and the linear optical absorption coefficient of the ring are remarkably affected by the strength of the lateral electric field, internuclear distance and parameters defining the confinement potential. Also, it has been shown that beyond the anti-crossing point, the wave functions exchange their symmetries without mixing, which is a characteristic feature of energy-level anti-crossing.

Benchmarking of machine learning interatomic potentials for reactive hydrogen dynamics at metal surfaces

Simulations of chemical reaction probabilities in gas surface dynamics require the calculation of ensemble averages over many tens of thousands of reaction events to predict dynamical observables that can be compared to experiments. At the same time, the energy landscapes need to be accurately mapped, as small errors in barriers can lead to large deviations in reaction probabilities. This brings a particularly interesting challenge for machine learning interatomic potentials, which are becoming well-established tools to accelerate molecular dynamics simulations. We compare state-of-the-art machine learning interatomic potentials with a particular focus on their inference performance on CPUs and suitability for high throughput simulation of reactive chemistry at surfaces. The considered models include polarizable atom interaction neural networks (PaiNN), recursively embedded atom neural networks (REANN), the MACE equivariant graph neural network, and atomic cluster expansion potentials (ACE). The models are applied to a dataset on reactive molecular hydrogen scattering on low-index surface facets of copper. All models are assessed for their accuracy, time-to-solution, and ability to simulate reactive sticking probabilities as a function of the rovibrational initial state and kinetic incidence energy of the molecule. REANN and MACE models provide the best balance between accuracy and time-to-solution and can be considered the current state-of-the-art in gas-surface dynamics. PaiNN models require many features for the best accuracy, which causes significant losses in computational efficiency. ACE models provide the fastest time-to-solution, however, models trained on the existing dataset were not able to achieve sufficiently accurate predictions in all cases.

Significant Promotional Effect of Nb Doping in Bifunctional Pd/WOx Nanocatalysts on One‐Step Benzene Hydroalkylation

AbstractThe development of high‐efficiency heterogeneous bifunctional metal‐acid catalysts with an appropriate metal‐acid balance for the production of cyclohexylbenzene (CHB) via the one‐step tandem benzene hydroalkylation still faces a dilemma because of the difficulty in inhibiting the over hydrogenation of benzene substrate and cyclohexene intermediate and controlling target product selectivity. In this study, Nb‐doped WOx supported Pd nanocatalysts were developed. It has been shown that doping Nb into WOx supports altered surface properties and microstructures of catalysts, resulting in the generation of more surface acidic sites and defective W−Ov−Nb structures (Ov: oxygen vacancies). As‐constructed Pd‐based nanocatalyst with only 0.1 wt % Pd loading and a Nb/(Nb+W) molar ratio of 0.25 exhibited superior catalytic benzene hydroalkylation performance to undoped supported Pd catalyst, with a much higher yield of CHB (35.6 %) at 220 °C. It was authenticated that highly dispersed Pd sites facilitated the dissociation of hydrogen molecules, defective W−Ov−Nb structures were conductive to the surface transfer of active hydrogen species, a large number of acidic sites favored benzene/cyclohexene intermediate adsorption, and abundant Brønsted acidic sites promoted the alkylation between cyclohexene intermediate formed and benzene. Accordingly, excellent cooperative catalysis between Pd sites, acidic sites, and oxygen vacancies contributed to improved catalytic performance of Nb‐doped WOx supported Pd catalysts in benzene hydroalkylation. This research presents an alternative for the creation of low‐cost practical bifunctional metal‐acid catalysts for highly efficient benzene hydroalkylation.

Unlocking the Potential of MXene in Catalysis: Decorated Mo2CTx Catalyst for Ammonia Synthesis under Mild Conditions.

Ammonia, which is one of the most important chemicals for the synthesis of dyes, pharmaceuticals, and fertilizers, is produced by the reaction of molecular hydrogen with nitrogen, over an iron-based catalyst at 400-500 °C under pressure of over 100 bar. Decreasing the operating temperature and pressure of this highly energy-intensive process, developed by Haber and Bosch over 100 years ago, would decrease energy consumption in the world. In this work, we used two-dimensional Mo2CTx MXene as a support for a cobalt-based catalyst. The MXene functionalized by Co showed catalytic activity for ammonia synthesis from H2 and N2 at temperatures as low as 250 °C, without any pretreatment. The developed catalyst was highly active for ammonia synthesis, demonstrating a high rate of up to 9500 μmol g-1activephase h-1 at 400 °C under ambient pressure in steady-state conditions, and did not suffer from any deactivation after 15 days of reaction. The apparent activation energy (Ea) was found to be in the range of 68-74 kJ mol-1, which is in line with values reported for highly active catalysts. This improved catalyst may decrease the energy consumption in the synthesis of ammonia and its derivatives, as well as facilitate the use of ammonia as a hydrogen carrier for renewable energy storage.

Radio Observations of Tidal Disruption Events Around Direct Collapse Black Holes at Cosmic Dawn

Primordial haloes immersed within intermediate Lyman-Werner (LW) UV backgrounds are theorisedto be the seeds of supermassive primordial stars (SMSs) that could be the origin of the first quasars in our universe. Only extreme levels of LW fluxes however will destroy the molecular hydrogen H2 in these haloes, resulting in much less massive stars in the early stages of our universe. This investigation considers the collapse in haloes within weaker LW background that were much more common in the primordial universe, and allowed for the survival of some H2 within these haloes. The survival of H2 along with Tvir ∼ 104 K allows the atomic cooling of H2 to begin, triggering the baryonic collapse within these haloes. These flows are predicted to result in SMSs on the order of a few × 105 M⊙ before collapsing to a DCBH due to general relativistic instabilities within their cores. The stars formed through these mechanisms could be the origin seeds of intermediate mass black holes found within dwarf galaxies today, or even create a secondary tier of less massive but still highly luminous quasars at a redshift z > 7. Some of these stars form in binaries and small clusters, raising the possibility of future detections of gravitational waves from BH mergers by LISA. This investigation considers the tidal disruption events (TDEs) of lower mass Pop III stars that form within the nuclear accretion disc of these DCBHs, the potential observation of these TDE afterglows in the radio, and thesubsequent identification of their host DCBHs. We find that the radio observation of the afterglow of 15 M⊙ and 40 M⊙ TDEs due to 104 M⊙ DCBHs would be visible up to z = 20 by SKA and ngVLA.

Implications for the Hydrogenation of Propyne and Propene with Parahydrogen due to the in situ Transformation of Rh2C to Rh0/C.

NMR spectroscopy studies using parahydrogen-induced polarization have previously established the existence of the pairwise hydrogen addition route in the hydrogenation of unsaturated hydrocarbons over heterogeneous catalysts, including those based on rhodium (Rh0). This pathway requires the incorporation of both hydrogen atoms from one hydrogen molecule to the same product molecule. However, the underlying mechanism for such pairwise hydrogen addition must be better understood. The involvement of carbon, either in the form of carbonaceous deposits on the surface of a catalyst or as a metal carbide phase, is known to modify catalytic properties significantly and thus could also affect the pairwise hydrogen addition route. Here, we explored carbon's role by studying the hydrogenation of propene and propyne with parahydrogen on a Rh2C catalyst and comparing the results with those for a Rh0/C catalyst obtained from Rh2C via H2 pretreatment. While the catalysts Rh2C and Rh0/C differ notably in the rate of conversion of parahydrogen to normal hydrogen as well as in terms of hydrogenation activity, our findings suggest that the carbide phase does not play a significant role in the pairwise H2 addition route on rhodium catalysts.

The Impact of Hydrogen Inhalation Therapy on Blood Reactive Oxygen Species Levels: A Randomized Controlled Study

Reactive Oxygen Species (ROS) play a key role in physiological processes. However, the imbalance between ROS and antioxidants in favor of the former causes oxidative stress linked to numerous pathologies. Due to its unique attributes, including distinguished permeability and selective antioxidant capability, molecular hydrogen (H2) has become an essential therapeutic agent. Hydrogen Inhalation Therapy (HIT) has come to light as a promising strategy to counteract oxidative stress. In this randomized controlled study, we aimed to evaluate the effectiveness of HIT in reducing blood ROS levels. 37 participants with elevated ROS levels (d-ROMs value > 350 U.CARR) were enrolled in the study. Participants were divided into test and control groups. The test group participants received HIT, and then their blood ROS levels were measured immediately post-treatment and after 24 hours. Their results were compared to those of the control group participants who did not undergo HIT. The test group demonstrated a significant reduction in blood ROS levels after the treatment. These findings suggested the efficacy of HIT in reducing oxidative stress.

Screening, Synthesis, and Characterization of a More Rapidly Dissolving Celecoxib Crystal Form.

The prevalence of poor solubility in active pharmaceutical ingredients (APIs) such as celecoxib (CEL) is a major bottleneck in the pharmaceutical industry, leading to a low concentration gradient, poor passive diffusion, and in vivo failure. This study presents the synthesis and characterization of a new cocrystal of the API CEL. CEL is a nonsteroidal anti-inflammatory drug used for the treatment of osteoarthritis and rheumatoid arthritis. Computational screening was completed for CEL against a large library of generally recognized as safe (GRAS) coformers, based on molecular complementarity and hydrogen bond propensity (HBP). The generated list of 17 coformers with a likelihood for cocrystallization with CEL were experimentally screened using four techniques: liquid-assisted grinding (LAG), solvent evaporation (SE), gas antisolvent crystallization (GAS), and supercritical enhanced atomization (SEA). One new crystalline form was isolated, employing the liquid coformer N-ethylacetamide (NEA). This novel form, celecoxib-di-N-ethylacetamide (CEL·2NEA), was characterized by a variety of different techniques. The crystal structure was determined through single-crystal X-ray diffraction. Both NEA molecules are evolved from the crystal structure at a desolvation temperature of approximately 65 °C. The CEL·2NEA cocrystal exhibited a dissolution rate, with more than a twofold improvement in comparison to as-received CEL after only 15 min.

A density functional theory study of defective and doped structures of MgB2 and their interaction with hydrogen

The LiBH4+MgH2 system exhibits promising potential for solid-state hydrogen storage, yet the sluggish rehydrogenation of MgB2 poses a significant challenge. In this study, we utilize density functional theory (DFT) simulations to investigate the energetics of hydrogen in pure, defective, and doped MgB2 in equilibrium with molecular hydrogen. Our findings reveal that the B-Frenkel defect process is the thermodynamically most favorable in MgB2. The calculated solution energy for hydrogen at the interstitial site indicates low hydrogen solubility, even at mild temperatures. Incorporating hydrogen into a pre-existing B vacancy enhances the process, facilitated by doping of O on the B site. Additionally, Li doping on the Mg site enhances incorporation by forming strong Li–H bonds, predicting lower activation barriers for hydrogen dissociation and diffusion. Doping MgB2 with O and F at the B site significantly enhances hydrogen solubility. These dopants make MgB2 a promising material for high-capacity and fast-kinetics hydrogen storage applications, and further research into these effects can lead to advancements in energy storage technology.

Hydrogen storage in Ti doped 4-6-8 biphenylene (Ti.C468): Insights from density functional theory

Hydrogen storage exploration in carbon-based materials is pivotal for advancing energy technologies. This study employs first-principles Density Functional Theory (DFT) calculations, utilizing the PBE functional with the VASP code, to investigate the 4-6-8 biphenylene (C468) and its derivatives, a distinctive 2D carbon structure. Both pristine C468 and its titanium-decorated variants (1TiC468 and 2TiC468) are analyzed. 1TiC468 and 2TiC468 exhibit maximum hydrogen molecule accommodation of up to 12 and 24, achieving gravimetric densities of 6.713 wt% and 11.188 wt%, respectively, with adsorption energies ranging from −0.132 eV/H2 to −0.399 eV/H2. These gravimetric values align with or surpass DOE guidelines. Additionally, comparative analysis indicates enhanced hydrogen adsorption due to Ti presence in C468. Molecular dynamics (MD) and phonon dispersion studies confirm the stability of mTiC468 (m = 1 and 2) systems at 300K. These findings underscore the potential of Ti-decorated C468 as hydrogen storage candidates, expanding the applications of carbon-based materials in energy storage.

The effects of cryopreservation and molecular hydrogen on the ultrastructure of bull spermatozoa

The effects of cryopreservation and molecular hydrogen on the ultrastructure of bull spermatozoa

Nonadiabatic Molecular Dynamics with Fermionic Subspace-Expansion Algorithms on Quantum Computers.

We introduce a novel computational framework for excited-state molecular quantum dynamics simulations driven by quantum-computing-based electronic-structure calculations. This framework leverages the fewest-switches surface-hopping method for simulating the nuclear dynamics and calculates the required excited-state transition properties with different flavors of the quantum subspace expansion and quantum equation-of-motion algorithms. We apply our method to simulate the collision reaction between a hydrogen atom and a hydrogen molecule. For this system, we critically compare the accuracy and efficiency of different quantum subspace expansion and equation-of-motion algorithms and show that only methods that can capture both weak and strong electron correlation effects can properly describe the nonadiabatic effects that tune the reactive event.

Limits of the harmonic approach for the Morse potential

This paper presents the solution of the Morse potential via the Variational Method using a trial eigenfunction based on the harmonic oscillator and without variational parameters. The first fundamental state and the first nine excited states for the diatomic molecules of hydrogen, lithium hydride, sodium hydride, oxygen, carbon monoxide and silicon monoxide are calculated. The results obtained by the variational method are compared with the values obtained by the exact solution of the same potential in order to establish a percentage error for each energy level of the molecules analyzed and to verify up to which level the chosen trial eigenfunction describes the original system well. That shows that the approximation of the trial eigenfunction is reasonable for the first excited states. From the fourth or fifth excited state, depending on the molecule, the discrepancy no longer reasonable.

Tertiary phosphine‐supported diiron model complexes relevant to [FeFe]‐hydrogenases

In an effort to better probe the structure–function relationship on the biological [Fe4S4] cluster of [FeFe]‐hydrogenases, a new library of tertiary phosphine‐supported diiron dithiolate complexes [Fe2(μ‐adtNR)(CO)5{P(C6H4X)3}] (1–3) with various substituents (X = F vs. H vs. Me), wherein adtNR is denoted as abbreviation for the (SCH2)2N(C6H4C2H4OC(O)CH2C6H4Me) unit, is prepared as the active site mimics of [FeFe]‐hydrogenases. Notably, the substituent influences of tertiary phosphines on the structures and electrochemical behaviors of 1–3 are studied by spectroscopic and crystallographic techniques as well as cyclic voltammetry. For example, the electronic effect of tertiary phosphines [P(C6H4X)3] is responsible for the electron density around diiron center and the key Fe–Fe as well as Fe–P lengths in 1–3 as revealed by IR spectroscopy and crystallographic analysis. Further, complexes 1–3 show the electrochemical activity for proton reduction into molecular hydrogen (H2) using acetic acid (AcOH) as a proton source. Noticeably, F‐substituent‐containing diiron model complex 1 exhibits greater turnover frequency (i.e., turnover frequency value) and similar overpotential for electrocatalytic H2 evolution relative to H‐ or Me‐substituent‐bearing diiron homologs 2 or 3.

Dissolution dynamics of partially protected poly(4-hydroxystyrene) in organic developers investigated by quartz crystal microbalance (QCM) method

Abstract Poly(4-hydroxystyrene) (PHS) molecules in solid films are connected each other through polar and nonpolar molecular interaction and hydrogen bonds. Although the dissociation of phenolic hydroxyl groups plays the major role in the dissolution of PHS films in tetramethylammonium hydroxide (TMAH) aqueous developer, it is important to clarify the effects of other interactions. In this study, we investigated the dissolution dynamics of partially protected PHS in organic developers by a quartz crystal microbalance method to deepen the fundamental understanding of the dissolution dynamics of chemically amplified resists. The dissolution dynamics in the solvents, in which the phenolic hydroxyl groups are hardly dissociated, was measured. In 50 vol% methanol aqueous developer, a large swelling was observed. By decreasing the polarity of developer, the dissolution dynamics was significantly changed. In the hexyl acetate, the dissolution kinetics of PHS films became similar to that in TMAH aqueous developer although the dissolution mechanism is different.

PDRs4All

Context. One of the main problems in astrochemistry is determining the amount of sulfur in volatiles and refractories in the interstellar medium. The detection of the main sulfur reservoirs (icy H2S and atomic gas) has been challenging, and estimates are based on the reliability of models to account for the abundances of species containing less than 1% of the total sulfur. The high sensitivity of the James Webb Space Telescope provides an unprecedented opportunity to estimate the sulfur abundance through the observation of the [S I] 25.249 µm line. Aims. Our aim is to determine the amount of sulfur in the ionized and warm molecular phases toward the Orion Bar as a template to investigate sulfur depletion in the transition between the ionized gas and the molecular cloud in HII regions. Methods. We used the [S III] 18.7 µm, [S IV] 10.5 µm, and [S l] 25.249 µm lines to estimate the amount of sulfur in the ionized and molecular gas along the Orion Bar. For the theoretical part, we used an upgraded version of the Meudon photodissociation region (PDR) code to model the observations. New inelastic collision rates of neutral atomic sulfur with ortho-and para- molecular hydrogen were calculated to predict the line intensities. Results. The [S III] 18.7 µm and [S IV] 10.5 µm lines are detected over the imaged region with a shallow increase (by a factor of 4) toward the HII region. This suggests that their emissions are partially coming from the Orion Veil. We estimate a moderate sulfur depletion, by a factor of ~2, in the ionized gas. The corrugated interface between the molecular and atomic phases gives rise to several edge-on dissociation fronts we refer to as DF1, DF2, and DF3. The [S l] 25.249 µm line is only detected toward DF2 and DF3, the dissociation fronts located farthest from the HII region. This is the first ever detection of the [S l] 25.249 µm line in a PDR. The detailed modeling of DF3 using the Meudon PDR code shows that the emission of the [S l] 25.249 µm line is coming from warm (>40 K) molecular gas located at AV ~1–5 mag from the ionization front. Moreover, the intensity of the [S l] 25.249 µm line is only accounted for if we assume the presence of undepleted sulfur. Conclusions. Our data show that sulfur remains undepleted along the ionic, atomic, and molecular gas in the Orion Bar. This is consistent with recent findings that suggest that sulfur depletion is low in massive star-forming regions because of the interaction of the UV photons coming from the newly formed stars with the interstellar matter.

A Density Functional Theory Study of Defective and Doped Structures of MgB2 and Their Interaction with Hydrogen

The LiBH4+MgH2 system exhibits promising potential for solid-state hydrogen storage, yet the sluggish rehydrogenation of MgB2 poses a significant challenge. In this study, we utilize density functional theory (DFT) simulations to investigate the energetics of hydrogen in pure, defective, and doped MgB2 in equilibrium with molecular hydrogen. Our findings reveal that the B-Frenkel defect process is the thermodynamically most favorable in MgB2. The calculated solution energy for hydrogen at the interstitial site indicates low hydrogen solubility, even at mild temperatures. Incorporating hydrogen into a pre-existing B vacancy enhances the process, facilitated by doping of O on the B site. Additionally, Li doping on the Mg site enhances incorporation by forming strong Li-H bonds, predicting lower activation barriers for hydrogen dissociation and diffusion. Doping MgB2 with O and F at the B site significantly enhances hydrogen solubility. These dopants make MgB2 a promising material for high-capacity and fast-kinetics hydrogen storage applications, and further research into these effects can lead to advancements in energy storage technology.