3D Hydrogen Research Articles

A hybrid expert neural network for predicting hydrogen concentration under the ceiling in underground garage

In the event of a hydrogen leak, the build-up of hydrogen near the ceiling of an underground garage poses a significant safety risk. Fast and accurate estimation of hydrogen concentration distribution is crucial for risk assessment. This study proposes a novel neural network named multi-expert variational hybrid network (MEVHN) to predict the distribution of hydrogen concentration under the ceiling when the peak concentration reaches its maximum value during a leakage event. The model utilizes data from discrete sensors to make predictions. It incorporates a mixture of experts (MoE) framework to transform the sensor data into latent variables, which are then used by a variational autoencoder (VAE) decoder to predict the hydrogen concentration distribution. Constraints are added to the loss function to improve the prediction accuracy further. The results show that the MEVHN has an inference time of 1.3 seconds, a coefficient of determination (R²) of 0.977, a mean absolute error (MAE) of 1.86E-3, and a mean squared error (MSE) of 3.15E-5. These results indicate that the model performs well in predicting the 2D hydrogen concentration distribution.

Topological Co(II)-malonate polymorph: Degradation properties of Naproxen and colorimetric recognition of acetone, Cr2O72−, and Fe3+

Two Co(II)coordination polymers namely, [Co(mal)(4,4`-bpy)0.5 (H2O)]n(1) and [Co(mal)(4,4`-bpy)0.5 (H2O)]n(2)are synthesized at ambient temperature, both complexes are based on {Co(RCOO)2}unitserving as 3D network along with sqc and fes topology and corroborated by many analytical techniques. CPs(1) crystallized in a 2D manner and then constructed a 3D hydrogen bonding network which was demonstrated monoclinic crystal system while(2)is a 3D supramolecular network that possesses a tetrahedral crystal system, according to topological analysis CPs(1) shows 5-C net and CPs(2) elaborates a 3-C net which proves both are completely different. A luminescence investigation was performed using both coordination polymers (CPs), which demonstrated effective colorimetric detection of acetone, Cr₂O₇²⁻, and Fe³⁺, with corresponding detection limits of 1.91, 2.57, and 0.29 ppm, respectively, in an ethanolic medium. Additionally, the catalytic degradation of Naproxen was evaluated for both catalysts, revealing significant degradation efficiencies of 90 % for catalyst (1) and 38 % for catalyst (2).

3D hydrogen-like screening effect on excitons in hBN-encapsulated monolayer transition metal dichalcogenides

We observe both s-series and p-series excitons by using sum frequency generation spectroscopy on monolayer (1L-)MX2 (M = Mo, W, X = S, Se) encapsulated by hexagonal boron nitride (hBN). Moreover, we perform numerical calculations with the Rytova-Keldysh potential and obtain the relative dielectric constant of hBN among other parameters. The obtained relative dielectric constant can be approximated by the high-frequency limit of the infrared dispersion even though the exciton binding energies are almost on the phonon resonances in hBN. This suggests that the theoretically indicated modification of the exciton level structure due to the phonon resonances is negligible. The power-law scaling of exciton binding energies indicates that dielectric screening of 1L-MX2 exciton levels other than 1s can be approximated by that of a 3D hydrogen model with the dielectric constant of hBN.

Comparison of terrestrial exospheric hydrogen 3D distributions at solar minimum and maximum using TWINS Lyman-α observations

Remote sensing observations of far-ultraviolet (FUV) emissions have been used to estimate 3D neutral hydrogen (H) density models of the terrestrial exosphere under solar minimum (2008) and solar maximum (2013 and 2015) conditions. Specifically, we used Lyman-alpha (Lyman-α, FUV at 121.6 nm) radiance data acquired by the Lyman-alpha detectors (LADs) onboard NASA’s TWINS satellites, collected over several days for each of the 3 years to provide sufficient coverage of the exospheric region. The datasets included Lyman-α measurements taken only above Earth radii (Re) of 3.75, assumed to be the optically thin region of the exosphere, where the measured Lyman-α intensity along a line of sight (LOS) is linearly proportional to the atomic hydrogen column density. Based on the calibration using multiple UV-bright stars, a significant decrease in TWINS1 LAD1/2 sensitivities was found for 2013 (LAD2 ∼1/2, LAD ∼1/3) and 2015 (LAD2 ∼1/3, LAD ∼1/7) compared to 2008. The calibration uncertainty was derived to be, on average, 5%. We estimated the 3D global hydrogen density distributions from these radiance data using two different tomographic inversion methods: first, a parametric fitting method based on a spherical harmonic function of order 3 and second, a high degree-of-freedom retrieval approach to validate our retrievals of H density. Both inversion methods consistently incorporate the effects of Lyman-α absorption within the exosphere and Lyman-α re-emission from Earth’s albedo. Our results reveal that H densities during solar maximum conditions are, on average, 30%–40% higher than those during solar minimum. All models showed a high concentration of atomic H on the dayside and nightside near the Sun–Earth line, which determines a nose/geotail structure consistent with theoretical effects from the solar radiation pressure. Furthermore, we identified that H-density enhancements during solar maximum with respect to solar minimum conditions occur at mid-to-high latitudes, particularly on the dusk side, while no significant enhancement seems to occur near the dayside nose.

Plasticization of a stiff pharmaceutical solid for better tabletability via cocrystallization: Shape synthons as supramolecular protecting groups

Extremely high particle stiffness and very low hardness is a serious concern in various mechanical processes in pharmaceutical manufacturing. Here we report an exceptionally high Young’s modulus (E) of ∼ 18 GPa in a drug, isoniazid (INH). This is one of the highest experimentally determined values among all reported pharmaceutical molecular crystals, which we attribute to the presence of a strong three-dimensional (3D) hydrogen bonding network (HBN). Further, we successfully reduced the 3D HBN in INH to 2D in its cocrystal using a co-former, 3,4-dimethylbenzoic acid (DMBA), where its two hydrophobic groups act like protecting groups at supramolecular level and prevent the extension of HBN. This reduced the E in the 1:1 cocrystal, INH-DMBA, by many folds and markedly improved its powder tabletability. To the best of our knowledge, this is the first reliable molecular level approach to alter the stiffness of pharmaceutical crystals and tabletability improvement in a predictable manner, hence, is important in the context of crystal engineering.

Slowdown of solvent structural dynamics in aqueous DMF solutions

This study presents a comprehensive investigation into the molecular dynamics of solvation environments through an integrated approach combining Fourier-transform infrared (FTIR) spectroscopy, molecular dynamics (MD) simulations, and two-dimensional infrared (2D IR) spectroscopy. We explore the solvation of an ionic solute (ammonium thiocyanate) in various solvent systems, including N,N-dimethylformamide (DMF), water, and a 0.5 mole fraction of DMF in water, aiming to unravel the intricate interplay between solute-solvent interactions and solvent dynamics across diverse solvation environments. By integrating FTIR spectral analysis with radial distribution functions and coordination numbers obtained from MD simulations, we decipher the solvent composition around the solute molecule. Analysis of 2D IR spectra and hydrogen bond, as well as dipolar autocorrelation function from MD simulations, further elucidates the nuances of solute-solvent interactions, highlighting the impact of solvent dynamics on solvation structures. Our results reveal a significant slowdown of the solvent structural dynamics in the equimolar binary solvent mixture compared to the neat solvents. This slowdown underscores the complex relationship between solute-solvent interactions and solvent dynamics. The integration of FTIR, MD simulations, and 2D IR spectroscopy provides a unified framework for obtaining a holistic understanding of solvation dynamics, offering valuable insights into the underlying molecular mechanisms governing solute-solvent interactions in complex systems. These results pave the way for future studies to delve deeper into the molecular intricacies of solvation phenomena.

2D hydrogen bonded organic framework (2D-HOF) in benzodioxane-coupled-pyridine as a charge carrier: Synthesis, structural, quantum computational investigation

This research presents a comprehensive investigation into the synthesis, structural features, and charge carrier properties of a novel 2D Hydrogen-Bonded Organic Framework (2D-HOF) formed by Benzodioxane-Coupled-Pyridine. The synthesis involves the reaction of 2,3-dihydrobenzo[b][1,4]dioxin-6-carbaldehyde with pyridine-2-carbohydrazide in the presence of acetic acid and ethanol solvent, leading to the formation of (E)-2-(2-((2,3-dihydrobenzo[b][1,4]dioxin-6-yl)methylene)hydrazinyl)pyridine (DDMP). Single crystal X-ray diffraction analysis reveals the monoclinic crystal system with the P21/n space group, showcasing a non-planar structure due to a distinctive twisting motion in the dioxane ring. The crystal packing is governed by a complex network of intermolecular interactions, including hydrogen bonds, short contacts, and π-stacking, ultimately forming a stable 2D-HOF. Hirshfeld Surface (HS) analysis provides insights into key interactions, emphasizing the significance of hydrogen bonding, short contacts, and stacking interactions in molecular packing. The 2D fingerprint (FP) plots quantitatively highlight crucial interatomic contacts, with hydrogen bonding, CH…H, and O…H interactions dominating. Molecular Electrostatic Potential (MEP) analysis reveals potential sites for electrophilic and nucleophilic attacks, aiding in predicting reactive sites and charge carrier behavior. Energy framework analysis sheds light on the pairwise interaction energies within the crystal structure, emphasizing the role of dispersive forces in stabilizing the crystal lattice. Density functional theory calculations indicate the molecule's charge transfer capabilities, suggesting its suitability for applications such as batteries, supercapacitors, and solar cells. Additionally, global reactivity parameters suggest that the 2D HOF material has electron and proton conduction capabilities, making it versatile for various applications. Atoms-in-molecules (AIM) topology analysis, particularly non-covalent interaction (NCI) analysis, provides a detailed understanding of intra and intermolecular interactions, highlighting hydrogen bonding and π…π interactions. H-bond binding energy analysis confirms the non-covalent nature of identified interactions, emphasizing their strength and significance.

An Ultra‐Robust and 3D Proton Transport Pathways iHOF with Single‐Crystal Superprotonic Conductivity Around 0.4 S cm−1

AbstractThe weak intermolecular forces of hydrogen‐bonded organic frameworks (HOFs) make it relatively difficult to synthesize and design HOFs with superprotonic conductivity and robustness. The self‐assembly of ionic hydrogen bonding organic frameworks (iHOFs) through acid–base pairing strategies are possible on account of the rich hydrogen bonding, strong ionic bonding, and π–π stacking interactions and so on. Herein, a case of iHOF (iHOF‐16) with a three‐dimensional (3D) hydrogen bonding network is reported, the doughty ionic bond interactions in the structure and π–π stacking interactions between layers make it exhibits excellent thermal and chemical stability, it can maintain high crystallinity and robust structure even under extreme conditions. Importantly, iHOF‐16 exhibits highly anisotropic proton conductivity of 0.388, 5.56 × 10−3, and 3.25 × 10−4 S cm−1 in the direction of a‐axis, b‐axis, and c‐axis, respectively. The proton transfer paths of single crystal on each axis are calculated using density functional theory (DFT) and, supported by joint experimental–theoretical calculations, protons are most easily transported in the a‐axis direction resulting in superprotonic conductivity. The present study provides a promising approach for the design of stable superprotonic conductivity materials through a simple yet effective charge‐assisted synthesis strategy.

Biodegradable Ferroelectric Molecular Plastic Crystal HOCH2(CF2)7CH2OH Structurally Inspired by Polyvinylidene Fluoride.

Ferroelectric materials, traditionally comprising inorganic ceramics and polymers, are commonly used in medical implantable devices. However, their nondegradable nature often necessitates secondary surgeries for removal. In contrast, ferroelectric molecular crystals have the advantages of easy solution processing, lightweight, and good biocompatibility, which are promising candidates for transient (short-term) implantable devices. Despite these benefits, the discovered biodegradable ferroelectric materials remain limited due to the absence of efficient design strategies. Here, inspired by the polar structure of polyvinylidene fluoride (PVDF), a ferroelectric molecular crystal 1H,1H,9H,9H-perfluoro-1,9-nonanediol (PFND), which undergoes a cubic-to-monoclinic ferroelectric plastic phase transition at 339 K, is discovered. This transition is facilitated by a 2D hydrogen bond network formed through O-H···O interactions among the oriented PFND molecules, which is crucial for the manifestation of ferroelectric properties. In this sense, by reducing the number of -CF2- groups from ≈5000 in PVDF to seven in PFND, it is demonstrated that this ferroelectric compound only needs simple solution processing while maintaining excellent biosafety, biocompatibility, and biodegradability. This work illuminates the path toward the development of new biodegradable ferroelectric molecular crystals, offering promising avenues for biomedical applications.

Cosmic string influence on a 2D hydrogen atom and its relationship with the Rytova–Keldysh logarithmic approximation in semiconductors

A two-dimensional hydrogen atom offers a promising alternative for describing the quantum interaction between an electron and a proton in the presence of a cosmic string. Reducing the hydrogen atom to two dimensions enhances its suited to capture the cylindrical/conical symmetry associated with the cosmic string, providing a more appropriate description of the physical system. After solving Schrd̈inger’s equation, we calculate the eigenenergies, probability distribution function, and expected values for the hydrogen atom with logarithmic potential under the influence of the topological defect. The calculations for the 2D hydrogen atom are performed for the first time using the Finite Difference Method. The results are presented through graphics, tables, and diagrams to elucidate the system’s physical properties. We have verified that our calculations agree with a linear variational method result. Our model leads to an interesting analogy with excitons in a two-dimensional monolayer semiconductor located within a specific semiconductor region. To elucidate this analogy, we present and discuss some interaction potentials and their exciton eigenstates by comparing them with the results from the literature.

Landau Levels versus Hydrogen Atom

The Landau problem and harmonic oscillator in the plane share a Hilbert space that carries the structure of Dirac’s remarkable so(2,3) representation. We show that the orthosymplectic algebra osp(1|4) is the spectrum generating algebra for the Landau problem and, hence, for the 2D isotropic harmonic oscillator. The 2D harmonic oscillator is in duality with the 2D quantum Coulomb–Kepler systems, with the osp(1|4) symmetry broken down to the conformal symmetry so(2,3). The even so(2,3) submodule (coined Rac) generated from the ground state of zero angular momentum is identified with the Hilbert space of a 2D hydrogen atom. An odd element of the superalgebra osp(1|4) creates a pseudo-vacuum with intrinsic angular momentum 1/2 from the vacuum. The odd so(2,3)-submodule (coined Di) built upon the pseudo-vacuum is the Hilbert space of a magnetized 2D hydrogen atom: a quantum system of a dyon and an electron. Thus, the Hilbert space of the Landau problem is a direct sum of two massless unitary so(2,3) representations, namely, the Di and Rac singletons introduced by Flato and Fronsdal.

High conductivity of 2D hydrogen substituted graphyne nanosheets for fast recovery NH3 gas sensors at room temperature

The current two-dimensional (2D) material based NH3 sensors generally suffer from low response values and sluggish recovery dynamics, which is resulted from their inferior conductivity. Herein, high conductivity (0.045 S/m) of 2D hydrogen substituted graphyne (HsGY) nanosheets are successfully synthesized employing aqueous/organic interface method and using them for the first time for the detection of NH3 at room temperature. The resultant gas sensing performance shows that the 2D HsGY nanosheets exhibit a high gas response value (4.9) to 100 ppm NH3 and fast recovery time (108 s) at the room temperature. The NH3 gas sensing mechanism is discussed by utilizing density functional theory (DFT) calculations. The present study provides novel gas sensing material for the development of high-performance room temperature NH3 sensors.

HBCalculator: A Tool for Hydrogen Bond Distribution Calculations in Molecular Dynamics Simulations.

Hydrogen bonds, crucial noncovalent interactions in molecular systems, significantly impact biological, chemical, and energy-related processes; therefore, characterizing hydrogen bond information is of importance to fundamental studies. This work introduces the HBCalculator, a Tcl-based tool integrated with VMD for calculating 1D and 2D distributions of hydrogen bond density and strength. The tool facilitates spatial analysis, overcoming limitations in existing packages that lack direct spatial distribution output. By employing HBCalculator in MD simulations, three systems of cellulose/water and graphene/water interfaces, were tested to showcase its functionality. The 1D and 2D hydrogen bond distributions reveal insights into interfacial properties, reflecting the impact of material hydrophobicity. The simplicity of usage, along with its potential for diverse molecular systems, positions HBCalculator as a valuable tool for researchers exploring hydrogen bond networks.

Phase-Transition of Mo2C Induced by Tungsten Doping as Heterointerface-Rich Electrocatalyst for Optimizing Hydrogen Evolution Activity.

Electrochemical hydrogen evolution reaction (HER) from water splitting driven by renewable energy is considered a promising method for large-scale hydrogen production, and as an alternative to noble-metal electrocatalysts, molybdenum carbide (Mo2C) has exhibited effective HER performance. However, the strong bonding strength of intermediate adsorbed H (Hads) with Mo active site slows down the HER kinetics of Mo2C. Herein, using phase-transition strategy, hexagonal β-Mo2C could be easily transferred to cubic δ-Mo2C through electron injection triggered by tungsten (W) doping, and heterointerface-rich Mo2C-based composites, including β-Mo2C, δ-Mo2C, and MoO2, are presented. Experimental results and density functional theory calculations reveal that W doping mainly contributes to the phase-transition process, and the generated heterointerfaces are the dominant factor in inducing remarkable electron accumulation around Mo active sites, thus weakening the Mo─H coupling. Wherein, the β-Mo2C/MoO2 interface plays an important role in optimizing the electronic structure of Mo 3d orbital and hydrogen adsorption Gibbs free energy (ΔGH*), enabling these Mo2C-based composites to have excellent intrinsic catalytic activity like low overpotential (η10 = 99.8mV), small Tafel slope (60.16 dec-1), and good stability in 1m KOH. This work sheds light on phase-transition engineering and offers a convenient route to construct heterointerfaces for large-scale HER production.

First-principles study on a Li-decorated two-dimensional g-C6N6 monolayer: A promising ambient temperature reversible H2 storage material

Designing novel materials that exhibit superior reversibility and function under ambient conditions can facilitate the development of hydrogen energy applications. Two-dimensional (2D) g-C6N6 monolayers show great potential for use in hydrogen storage owing to their nanoporous structure, ultralight mass, and flexible electronic structure. However, the hydrogen storage potential of these materials is limited by the naturally weak interaction between 2D materials and hydrogen molecules caused by van de Waals forces. To address this issue, we studied the hydrogen storage performance of the complex by decorating active Li ions on a 2D g-C6N6 substrate through first-principles calculations. Our results showed that modifying the Li ions did not cause the original planar structure to deform but rather induced more active sites for hydrogen adsorption by establishing an electrostatic field between the Li ions and the g-C6N6 monolayer. Through this modification, reversible hydrogen storage was achieved under ambient conditions with an average adsorption energy of −0.197 eV/H2 and a high gravimetric capacity of 5.88 wt%. The electronic properties of the material were systematically investigated, and the results suggested that the enhanced capacity of the Li@ g-C6N6 system to store hydrogen resulted from the formation of a polarization field and the induced electrostatic effect. Our research offers a new possibility for achieving reversible hydrogen energy storage at room temperature.

Glucose detection via photoelectrochemical sensitivity of 3D CuO-TiO2 heterojunction nanotubes/Ti combined with chemometric tools

High sensitivity and low detection limit are important targets for biosensors. Using 3D hydrogen titanate nanotubes/Ti as precursor, CuO-TiO2 heterojunction nanotubes/Ti (CuO-TiO2NTs/Ti) photoelectrode was prepared to fabricate photoelectrochemical (PEC) glucose sensor. The prominent Ti foil substrate, 3D mesoporous structure, and CuO-TiO2 heterojunction of this PEC sensor can effectively improve the separation efficiency of charge carriers, facilitate electron transfer, and generate strong photoelectronic signals. Under visible light irradiation, the CuO-TiO2NTs/Ti electrode exhibited high sensitivity, low LOD, and good selectivity. Through density functional theory simulation, the enhanced electron-hole separation and improved PEC properties were illuminated in the CuO-TiO2 heterojunction. Associated with chemometric tools, the accuracy of the sensitivity was significantly improved, which could enhance the practical application capability of PEC biosensors.

High-accuracy solution of the Dirac equation for three-dimensional hydrogen atom using a variationally optimized diagonalization method

High-accuracy solution of the Dirac equation for three-dimensional (3D) hydrogen atom is theoretically presented using a variationally optimized diagonalization method. By imposing the asymptotical conditions, a complete set of orthogonal Laguerre basis functions is constructed explicitly for the solution of the Dirac equation, which eliminates the singularity difficulty at the point nucleus and gives a convergent integral. A fully explicit expression of the matrix elements of the Dirac Hamiltonian has been derived from the method of the generating function of Laguerre polynomials. The relative errors of the relativistic energies are ranged from 11 to 14 digits, showing that the calculated relativistic energies are in excellent agreement with the exact energies. These results show that my proposed orthogonal Laguerre basis set is extremely efficient and stable in calculating high-accuracy solution of the Dirac equation for 3D hydrogen atom.

NO measurements in high temperature hydrogen flames: The crucial role of the hydrogen oxidation chemistry for accurate NO predictions

The current work investigates the formation of Nitric Oxide (NO) in hydrogen–air flames, over a wide range of flame temperatures. The use of hydrogen allows improved focus on the thermal-NO pathway by removing the complexity introduced by the prompt-NO pathway, which has been shown to be an important contributor to inaccurate predictions of absolute post-flame NO concentrations in hydrocarbon flames. This experimental study is conducted at atmospheric pressure using stoichiometric, premixed, laminar stagnation flames. Adiabatic flame temperatures ranging from 1600K to 2300K are achieved by varying the argon concentration in air. One-dimensional velocity, temperature, and NO concentration profiles are measured using non-intrusive laser diagnostics: Particle Tracking Velocimetry (PTV), NO multiline thermometry, and NO Laser Induced Fluorescence (NO-LIF), respectively. Results show that the experimental velocity profiles are incorrectly captured by the studied mechanisms, especially at low and high temperatures. This suggests that major inaccuracies are present in the hydrogen oxidation chemistry of the thermochemical models, regardless of their optimisation methodology. Furthermore, NO-LIF profiles show major discrepancies between all the studied mechanisms and the experiments, especially at elevated temperatures. The disagreement stems from an inaccurate description of the base chemistry of the models. These inaccuracies arise specifically from the description of the radical pool driving the flame behaviour and NO formation. This study demonstrates the need for model optimisation on experimental measurements using pure hydrogen 1D flames to obtain an accurate description of the hydrogen oxidation chemistry at play. This would lead to an improved description of the NOx sub-chemistry of any hydrogen, or hydrocarbon, combustion system.

Metalloporphyrin-based highly conjugated three-dimensional covalent organic frameworks for the electrochemical hydrogen evolution reaction

A diagram of a metalloporphyrin-based highly conjugated 3D COF electrocatalytic hydrogen evolution process.

Molecular Engineering of Ordered Piezoelectric Sulfonic Acid-Containing Assemblies.

Sulfonic acid-containing bioorganic monomers with wide molecular designability and abundant hydrogen bonding sites hold great potential to design diverse functional biocrystals but have so far not been explored for piezoelectric energy harvesting applications due to the lack of strategies to break the centrosymmetry of their assemblies. Here, a significant molecular packing transformation from centrosymmetric into non-centrosymmetric conformation by the addition of an amide terminus in the sulfonic acid-containing bioorganic molecule is demonstrated, allowing a high electromechanical response. The amide-functionalized molecule self-assembles into a polar supramolecular parallel β-sheet-like structure with a high longitudinal piezoelectric coefficient d11 = 15.9 pm V-1 that produces the maximal open-circuit voltage of >1V and the maximal power of 18 nW in nanogenerator devices pioneered. By contrast, molecules containing an amino or a cyclohexyl terminus assemble into highly symmetric 3D hydrogen bonding diamondoid-like networks or 2D double layer structures that show tunable morphologies, thermostability, and mechanical properties but non-piezoelectricity. This work not only presents a facile approach to achieving symmetry transformation of bioorganic assemblies but also demonstrates the terminal group and the property correlation for tailor-made design of high-performance piezoelectric biomaterials.