Molecular Hydrogen Research Articles

A versatile single-photon-based quantum computing platform

AbstractQuantum computing aims at exploiting quantum phenomena to efficiently perform computations that are unfeasible even for the most powerful classical supercomputers. Among the promising technological approaches, photonic quantum computing offers the advantages of low decoherence, information processing with modest cryogenic requirements, and native integration with classical and quantum networks. So far, quantum computing demonstrations with light have implemented specific tasks with specialized hardware, notably Gaussian boson sampling, which permits the quantum computational advantage to be realized. Here we report a cloud-accessible versatile quantum computing prototype based on single photons. The device comprises a high-efficiency quantum-dot single-photon source feeding a universal linear optical network on a reconfigurable chip for which hardware errors are compensated by a machine-learned transpilation process. Our full software stack allows remote control of the device to perform computations via logic gates or direct photonic operations. For gate-based computation, we benchmark one-, two- and three-qubit gates with state-of-the art fidelities of 99.6 ± 0.1%, 93.8 ± 0.6% and 86 ± 1.2%, respectively. We also implement a variational quantum eigensolver, which we use to calculate the energy levels of the hydrogen molecule with chemical accuracy. For photon native computation, we implement a classifier algorithm using a three-photon-based quantum neural network and report a six-photon boson sampling demonstration on a universal reconfigurable integrated circuit. Finally, we report on a heralded three-photon entanglement generation, a key milestone toward measurement-based quantum computing.

Molecular Dynamics Simulation of Thermal Nonequilibrium and Chemical Reaction Processes in Hydrogen Combustion.

Using reactive force field (ReaxFF) and molecular dynamics simulation, we investigate the combustion process of hydrogen-oxygen systems in initial thermal nonequilibrium states with different translational and rovibrational temperatures for oxygen. The system studied in this work contains 300 oxygen molecules and 700 hydrogen molecules with a density of 7 times the air density. For this system, the characteristic relaxation times of oxygen and hydrogen vibrational energies are 0.173 and 0.249 ns, respectively. 0.6% of hydrogen undergoes a chemical reaction with oxygen during the thermal nonequilibrium relaxation stage. For the distribution of translational energy and vibrational energy of oxygen in the thermal nonequilibrium state, the maximum mean error of the statistical distribution in the simulation and the Boltzmann distribution at temperature calculated from the average kinetic energy of molecules is about 2.25 × 10-5. At the same time, it was observed in the simulation that many-body interactions play a certain role in the combustion process. Furthermore, we compare the ignition time and temperature rise behavior of different combustion mechanisms and molecular dynamics simulations starting from the thermal equilibrium state. These results will provide meaningful references for the construction of thermal nonequilibrium combustion chemical reaction mechanisms.

Predicting the Structure of Enzymes with Metal Cofactors: The Example of [FeFe] Hydrogenases.

The advent of deep learning algorithms for protein folding opened a new era in the ability of predicting and optimizing the function of proteins once the sequence is known. The task is more intricate when cofactors like metal ions or small ligands are essential to functioning. In this case, the combined use of traditional simulation methods based on interatomic force fields and deep learning predictions is mandatory. We use the example of [FeFe] hydrogenases, enzymes of unicellular algae promising for biotechnology applications to illustrate this situation. [FeFe] hydrogenase is an iron-sulfur protein that catalyzes the chemical reduction of protons dissolved in liquid water into molecular hydrogen as a gas. Hydrogen production efficiency and cell sensitivity to dioxygen are important parameters to optimize the industrial applications of biological hydrogen production. Both parameters are related to the organization of iron-sulfur clusters within protein domains. In this work, we propose possible three-dimensional structures of Chlorella vulgaris 211/11P [FeFe] hydrogenase, the sequence of which was extracted from the recently published genome of the given strain. Initial structural models are built using: (i) the deep learning algorithm AlphaFold; (ii) the homology modeling server SwissModel; (iii) a manual construction based on the best known bacterial crystal structure. Missing iron-sulfur clusters are included and microsecond-long molecular dynamics of initial structures embedded into the water solution environment were performed. Multiple-walkers metadynamics was also used to enhance the sampling of structures encompassing both functional and non-functional organizations of iron-sulfur clusters. The resulting structural model provided by deep learning is consistent with functional [FeFe] hydrogenase characterized by peculiar interactions between cofactors and the protein matrix.

Pseudodesulfovibrio pelocollis sp. nov. a Sulfate-Reducing Bacterium Isolated from a Terrestrial Mud Volcano.

Terrestrial mud volcanoes (TMVs), surface expressions of a deep-subterranean sedimentary volcanism, are widespread throughout the world. The methane and sulfur cycles are recognized as the most important biogeochemical cycles in these environments. Only few anaerobic bacterial strains were recovered from TMVs. We have isolated a novel sulfate-reducing bacterium (strain SB368T) from TMV located at Taman Peninsula, Russia. Optimum growth of strain SB368T was observed at 30°C, pH 8.0 and 1% NaCl. Strain SB368T utilized lactate, pyruvate and fumarate in the presence of sulfate, sulfite or thiosulfate. Growth with molecular hydrogen was observed only in the presence of acetate. Fermentative growth occurred on pyruvate. Phylogenetic analysis revealed that strain SB368T belongs to the genus Pseudodesulfovibrio but is distinct from all described species. Based on its genomic and phenotypic properties, a new species, Pseudodesulfovibrio pelocollis sp. nov. is proposed with strain SB368T (= DSM 111087T = VKM B-3585T) as a type strain.

Mechanistic study of the electrochemical oxidation of fluoroquinolones: Ciprofloxacin, danofloxacin, enoxacin, levofloxacin and lomefloxacin

The fluoroquinolones ciprofloxacin, danofloxacin, enoxacin, levofloxacin and lomefloxacin, occur in water bodies worldwide and therefore pose a threat to the aquatic environment. Advanced purification procedures, such as electrochemical oxidation, may act as a remedy since they contribute to eliminating contaminants and prevent micropollutants from entering open water bodies. By electrochemical treatment in a micro-flow reactor equipped with a boron-doped diamond (BDD) electrode, the fluoroquinolones were efficiently degraded. A total of 15 new products were identified using high-performance high-resolution chromatography coupled with high-resolution multifragmentation mass spectrometry. The ecotoxicity of the emerging transformation products was estimated through in silico quantitative structure activity relationship analysis. Almost all transformation products were predicted less ecotoxic than the initial compounds. The fluoroquinolone degradation followed three major mechanisms depending on the voltage during the electrochemical oxidation. At approximately 1 V, the reactions started with the elimination of molecular hydrogen from the piperazine moiety. At approx. 1.25 V, methyl and methylene groups were eliminated. At 1.5 V, hydroxyl radicals, generated at the BDD electrode, led to substitution at the piperazine ring. This novel finding of the three reactions depending on voltage contributes to the mechanistic understanding of electrochemical oxidation as potential remedy against fluoroquinolones in the aquatic environment.

First principles study of hydrogen storage on B-doped SiC monolayers through light transition metal atoms

In this first-principles study, based on Density Functional Theory, we assess the capacity of metal-decorated, boron-doped, graphene-like monolayers of silicon carbide (SiC) to adsorb hydrogen molecules. To enhance the binding of metal adatoms on SiC monolayers, these were substitutionally doped with boron atoms. Alkaline, alkaline-earth, and transition metal adatoms were considered and their hydrogen storage capabilities were compared. The results show that alkaline-earth metal adatoms are not suitable for hydrogen storage. On the other hand, sodium- and potassium-decorated B-doped SiC monolayers adsorb the largest number of H2 molecules per adatom, but their adsorption energies are insufficient for an adequate hydrogen storage. Titanium and scandium adatoms are the most suitable for hydrogen storage since they exhibit good adsorption energies and up to four and five H2 molecules per adatom, respectively. Moreover, the estimated potential barriers for diffusion of these two adatoms on the B-doped SiC monolayers indicate that the probability of clustering is very low. Moreover, within the ideal-gas approximation, it is estimated that hydrogen can be stored in the Ti- and Sc-decorated monolayers at room temperature and atmospheric pressure. Furthermore, if SiC monolayers were doped with boron atoms in concentrations similar to those reported for graphene, it is estimated that the gravimetric capacities could reach 5.1 wt% and 6.3 wt% for Ti-decorated and Sc-decorated monolayers, respectively, which are close to the target hydrogen-storage capacities envisioned for the near future.

Effect of Metal Carbides on Hydrogen Embrittlement: A Density Functional Theory Study

This study uses plane wave density functional theory (DFT) to investigate the effect of certain metal carbides (Niobium carbide, Vanadium carbide, Titanium carbide, and Manganese sulfide) on hydrogen embrittlement in pipeline steels. Our results predict that the interaction of hydrogen molecules with these metal carbides occurs in the long range with binding energy varying in the energy window [0.043 eV to 0.70 eV].In addition, our study shows the desorption of H2 molecules from these metal carbides in the chemisorptions. Since atomic state hydrogen interacts with NbC, VC, TiC, and MnS to cause embrittlement, we classified the strength of the hydrogen trapping as TiC + H > VC + H > NbC + H> MnS + H. In addition, our study reveals that the carbon site is a more favorable hydrogen-trapping site than the metal one.

Metal-Free Nitrogen-Doped Mesoporous Carbons for the Mild and Selective Synthesis of Pyrroles from Nitroarenes via Cascade Reaction.

The cascade synthesis of pyrroles from nitroarenes is an attractive alternative strategy. However, metal catalysts and relatively high temperatures cover the existing reported catalytic systems for this strategy. The development of nonmetallic heterogeneous catalytic systems for the one-pot synthesis of pyrrole from nitroarenes under mild conditions is both worthwhile and challenging. Herein, we describe an exceptionally efficient method for the synthesis of N-substituted pyrroles by the reductive coupling of nitroarenes and diketones over heterogeneous metal-free catalysts under mild conditions. Nonmetallic NC-X catalysts with high activity were prepared from the pyrolysis of well-defined ligands via simple sacrificing hard template methods. Hydrazine hydrate, formic acid, and molecular hydrogen can all be used as reducing agents in the hydrogenation/Paal-Knorr reaction sequence to efficiently synthesize various N-substituted pyrroles, including drugs and bioactive molecules. The catalytic system was featured with good tolerance to sensitive functional groups and no side reactions such as dehalogenation and aromatics hydrogenation. Hammett correlation studies have shown that the electron-donating substituents are beneficial for the one-pot synthesis of N-substituted pyrroles. The results established that the outstanding performance of the catalyst is mainly attributed to the contribution of graphitic N in the catalyst as well as the promotion effect of the mesoporous structure on the reaction.

Ionization Cross Sections of Hydrogen Molecule by Electron and Positron Impact.

We present ionization cross sections of hydrogen molecules by electron and positron impact for impact energies between 20 and 1000 eV. A three-body Classical Trajectory Monte Carlo approximation is applied to mimic the collision system. In this approach, the H2 molecule is modeled by a hydrogen-type atom with one active electron bound to a central core of effective charge with an effective binding energy. Although this model is crude for describing a hydrogen molecule, we found that the total cross sections for positron impact agree reasonably well with the experimental data. For the electron impact, our calculated cross sections are in good agreement with the experimental data in impact energies between 80 eV and 400 eV but are smaller at higher impact energies and larger at lower impact energies. Our calculated cross sections are compared with the scaled cross sections obtained experimentally for an atomic hydrogen target. We also present single differential cross sections as a function of the energy and angle of the ejected electron and scattered projectiles for a 250 eV impact. These are shown to agree well with available data. Impact parameter distributions are also compared for several impact energies.

A computational investigation of the thermodynamics and kinetics of multiple single-step electron transfers of various Ni- and chalcogen-containing complexes

Continued increase in green house gas emissions will lead to irreversible and unpredictable damage to the environment and biosphere. CO2 alone contributes to about two-thirds of the energy imbalance causing climate change. The bulk of these CO2 emissions can be traced to fossil fuels, which presently account for 82% of this green house gas. Developing effective renewable–alternative fuel sources is crucial to mitigate the harmful effects of fossil fuels. One such alternative fuel source is molecular hydrogen, which can be produced by the photocatalytic splitting of water using metal-based catalysts. This study investigates the thermodynamics and kinetics associated with single-step protonations and reductions of Ni[(S2C2H2)(N2C2H4)], Ni[(Se2C2H2)(N2C2H4)], and Ni[(Te2C2H2)(N2C2H4)] complexes using density functional theory. Results found diselenolene to be the least endergonic for the formation of the triply reduced, doubly protonated species with a Gibbs protonation energy of 79.6 kJ mol−1. Ditellurolene and dithiolene were slightly more endergonic with Gibbs protonation energies of 87.7 and 91.6 kJ mol−1, respectively. The most thermodynamically favorable pathways were found to be the ECCEE pathway for dithiolene and diselenolene, whereas the CECEE mechanism was found to be most favorable for ditellurolene. Kinetically, it was found that there were two feasible pathways for all three complexes. The first was a CCEEE pathway and the second was a CECEE pathway. All complexes were found to have similar Gibbs activation energies.

Can GW handle multireference systems?

Due to the infinite summation of bubble diagrams, the GW approximation of Green's function perturbation theory has proven particularly effective in the weak correlation regime, where this family of Feynman diagrams is important. However, the performance of GW in multireference molecular systems, characterized by strong electron correlation, remains relatively unexplored. In the present study, we investigate the ability of GW to handle closed-shell multireference systems in their singlet ground state by examining four paradigmatic scenarios. First, we analyze a prototypical example of a chemical reaction involving strong correlation: the potential energy curve of BeH2 during the insertion of a beryllium atom into a hydrogen molecule. Second, we compute the electron detachment and attachment energies of a set of molecules that exhibit a variable degree of multireference character at their respective equilibrium geometries: LiF, BeO, BN, C2, B2, and O3. Third, we consider a H6 cluster with a triangular arrangement, which features a notable degree of spin frustration. Finally, the dissociation curve of the HF molecule is studied as an example of single bond breaking. These investigations highlight a nuanced perspective on the performance of GW for strong correlation depending on the level of self-consistency, the choice of initial guess, and the presence of spin-symmetry breaking at the Hartree-Fock level.

Precision Measurement of Vibrational Quanta in Tritium Hydride.

Saturated absorption measurements of transitions in the (2-0) band of radioactive tritium hydride are performed with the ultrasensitive noise-immune cavity-enhanced optical-heterodyne molecular spectroscopy intracavity absorption technique in the range 1460-1510nm. The hyperfine structure of rovibrational transitions of tritium hydride, in contrast to that of hydrogen deuteride, exhibits a single isolated hyperfine component, allowing for the accurate determination of hyperfineless rovibrational transition frequencies, resulting in R(0)=203 396 426 692(22) kHz and R(1)=205 380 033 644(21) kHz. This corresponds to an accuracy 3 orders of magnitude better than previous measurements in tritiated hydrogen molecules. Observation of an isolated component in P(1) with reversed signal amplitude contradicts models for line shapes in hydrogen deuteride based on crossover resonances.

Enhanced production of hydrogen via catalytic methane decomposition on a Pt7-Ni (110) substrate: a reactive molecular dynamics investigation

Abstract Numerous researchers in the energy field are engaged in a competitive race to advance hydrogen as a clean and environmentally friendly fuel. Studies have been conducted on the different aspects of hydrogen, including its production, storage, transportation and utilization. The catalytic methane decomposition technique for hydrogen production is an environmentally friendly process that avoids generating carbon dioxide gas, which contributes to the greenhouse effect. Catalysts play a crucial role in facilitating rapid, cost-effective and efficient production of hydrogen using this technique. In this study, reactive molecular dynamics simulations were employed to examine the impact of Pt7 cluster decoration on the surface of a Ni (110) catalyst, referred to as Pt7-Ni (110), on the rates of methane dissociation and molecular hydrogen production. The reactive force field was employed to model the atomic interactions that enabled the formation and dissociation of chemical bonds. Our reactive molecular dynamics simulations using the Pt7-Ni (110) catalyst revealed a notable decrease in the number of methane molecules, specifically ~11.89 molecules per picosecond. The rate was approximately four times higher than that of the simulation system utilizing a Ni (110) catalyst and approximately six times higher than that of the pure methane, no-catalyst system. The number of hydrogen molecules generated during a simulation period of 150 000 fs was greater on the Pt7-Ni (110) surface than in both the Ni (110) and pure methane systems. This was due to the presence of numerous dissociated hydrogen atoms on the Pt7-Ni (110) surface.

Computational evaluation of Li-decorated [formula omitted]C3N2 as a room temperature reversible hydrogen storage medium

We theoretically devised a novel complex by decorating Li atoms on the α-C3N2 for hydrogen storage, employing first-principles calculations. The findings reveal that: Li can be securely adsorbed onto the α-C3N2; the Li@α-C3N2 exhibits commendable thermal stability and boasts an excellent electronic structure due to the sp2 hybridization, making it highly conducive to hydrogen adsorption; the Li@α-C3N2 can adsorb 12 H2, achieving a capacity of 5.7 wt%; the average adsorption energy (0.215 eV ∼ 0.228 eV) falls within reversible hydrogen-storage range; the corresponding desorption temperature ranges from 277 K to 293 K. Additionally, the storage capacity of the Li@α-C3N2 can be as high as 5.7 wt% at 300 K and 10 bar. The adsorption mechanism can be attributed to a combination of electrostatic interactions, orbital interactions and van der Waals interactions between the substrate and hydrogen molecules.

Cosmic hydrogen and ice loss lines

We explain the overall equilibrium-temperature-dependent trend in the exoplanet mass–radius diagram, using the escape mechanisms of hydrogen and relevant volatiles, and the chemical equilibrium calculation of molecular hydrogen (H2) break-up into atomic hydrogen (H). We identify two Cosmic Hydrogen and Ice Loss Lines (CHILLs) in the mass–radius diagram. Gas disks are well known to disperse in ten million years. However, gas-rich planets may lose some or almost all gas on a much longer timescale. We thus hypothesize that most planets that are born out of a hydrogen-gas-dominated nebular disk begin by possessing a primordial H2-envelope. This envelope is gradually lost due to escape processes caused by host-stellar radiation.

The effect of fermentation modes on the efficiency of organic waste treatment in batch bioreactors

The amount of solid organic waste is constantly growing. This is caused by the growth of industrial and agricultural capacities, and the inefficiency of existing waste processing technologies. Biotechnologies can provide effective environmentally friendly solutions for waste treatment. Therefore, the goal of our work was to compare the efficiency of strictly anaerobic fermentation of multi-component solid organic waste with hydrogen synthesis and waste treatment with pulsed air access in batch bioreactors.During fermentation, the following parameters were controlled: pH, redox potential (Eh), concentration of dissolved organics, and the content of H2, O2, and CO2 in the gas phase. The efficiency was evaluated via the process duration, calculation of the ratio of the initial and final weight of waste (Кd), and the yield of molecular hydrogen. Obtained results revealed high efficiency of organic waste degradation in both variants. The weight of waste 83-fold and 86-fold decreased, respectively. The time required for fermentation in strictly anaerobic conditions was 4 days, whereas 7 days were required for the mode with pulsed air access. The first variant provided a 2.8-fold higher hydrogen yield (54±4,1 L/kg of waste), and the second one provided a decrease in the concentration of dissolved organic compounds in the fermentation fluid. Fermentation is the effective approach for accelerated degradation of solid organic waste. Strictly anaerobic fermentation appeared to be useful in the need to accelerate the process. The mode with the pulsed air access can provide not only degradation of solid waste but also purification of the fermentation fluid.

Thermal conductivity and structural behavior of confined H2 from molecular dynamics simulation

In this work, we perform equilibrium molecular dynamics simulation to study the thermal conductivity of hydrogen molecules (H2) under extreme confinement within graphene nanochannel. We analyze the structural behavior of H2 molecules inside the nanochannel and also examine the effect of nanochannel height, the number of H2 molecules, and temperature of the system on the thermal conductivity. Our results reveal that H2 molecules exhibit a strong propensity for absorption onto the nanochannel wall, consequently forming a dense packed layer in close to the wall. This phenomenon significantly impacts the thermal conductivity of the confined system. We made a significant discovery, revealing a strong correlation between the mass density near the nanochannel wall and the thermal conductivity. This finding highlights the crucial role played by the density near the wall in determining the thermal conductivity behavior. Surprisingly, the average thermal conductivity for nanochannels with a height (h) less than 27 Å exhibited an astonishing increase of over 12 times when compared to the bulk. Moreover, we observe that increasing the nanochannel height, while the number of H2 molecules fixed, leads to a notable decrease in thermal conductivity. Furthermore, we investigate the influence of temperature on thermal conductivity. Our simulations demonstrate that higher temperature enhance the thermal conductivity due to increased phonon activity and energy states, facilitating more efficient heat transfer and higher thermal conductivity. To gain deeper insights into the factors affecting thermal conductivity, we explored the phonon density of states. Studying the behavior of hydrogen in confined environments can offer valuable insights into its transport properties and its potential for industrial applications.

Adsorption and evolution of hydrogen molecules on hexagonal boron nitride monolayer: a combined DFT and kinetic monte-carlo simulations study

Density functional theory (DFT) and kinetic Monte-Carlo (kMC) simulation code has been combinedly used to study the adsorption and evolution dynamics of hydrogen molecules over a hexagonal boron nitride (h-BN) monolayer. Maximum adsorption energy from van der Waals curve is predicted to be around 60 to 70 meV using two different DFT functionals. Repulsive lateral interaction between two hydrogen molecules plays a key role in determining the maximum number of adsorptions inside one unit cell of h-BN. Bader charge analysis, electron localization function (ELF), total and partial density of states (DOS) plots have been included to understand the weak interaction going on between the adsorbent and substrate. The input energy parameters from the DFT calculation has been used to perform the kMC simulation for describing the adsorption, desorption and the diffusion pattern of hydrogen molecules with a given time of exposure to an empty h-BN substrate along with the overall surface coverage.

A waterborne polyurethane‐based noise‐reducing material and factors influencing its damping and noise‐reducing performance

AbstractIn this study, damping coatings were used to dissipate low‐ and medium‐frequency (200–1600 Hz) traffic noise. A waterborne polyurethane/polyacrylate (WPUA) emulsion with superior damping and mechanical properties was prepared by blending polyurethane with commercial waterborne polyacrylate (SETAQUA 6754). The emulsion was combined with sound‐absorbing polyester fibers (PFs) to develop a PF/WPUA damping coating. SETAQUA 6754 improved the loss factor and mechanical properties of the waterborne resin. The composition ratio, molecular chain length, and crosslinking degree improved the damping properties of WPUA by modulating its glass transition temperature, molecular chain friction, hydrogen bonding, and molecular chain free volume. When the thickness of the waterborne damping coating was 1 cm, PF/WPUA reduced the noise by 7 dB at 200 Hz and 23 dB at 1600 Hz, indicating the effectiveness of the PF/WPUA coating in reducing reduce low‐ and medium‐frequency traffic noise.

Revisiting the rovibrational (de-)excitation of molecular hydrogen by helium

The collisional (de-)excitation of H$_ $ by He plays an important role in the thermal balance and chemistry of various astrophysical environments, making accurate rate coefficients essential for interpreting observations of the interstellar medium. Our goal is to utilize a state-of-the-art potential energy surface (PES) to provide comprehensive state-to-state rate coefficients for He-induced transitions among rovibrational levels of H$_2$. We performed quantum scattering calculations for the H$_ $-He system. Thus, we were able to provide state-to-state rate coefficients for transitions between rovibrational levels of H$_ $, with internal energies up to simeq 15 000 cm$^ for temperatures ranging from 20 to 8 000 K. Our results demonstrate a good agreement with previous calculations for pure rotational transitions between low-lying rotational levels. However, we do find significant discrepancies for rovibrational processes involving highly-excited rotational and vibrational states. We attribute these differences to two key factors: 1) the broader range of intramolecular distances covered by ab initio points and 2) the superior accuracy of the PES, resulting from the utilization of the state-of-the-art quantum chemistry methods, compared to previous lower-level calculations. Radiative transfer calculations performed with the new collisional data indicate that the population of rotational levels in excited vibrational states experiences significant modifications, highlighting the critical need for this updated dataset in models of high-temperature astrophysical environments.