Binding Energy Of Hydrogen Atom Research Articles

Coulomb-Zeeman-Stark problem in two dimensions

Coulomb-bound systems in reduced dimensions are sensitive probes of increased confinement. For example, the ground-state binding energy of hydrogen atoms increases by a factor of 4 when passing from three to two dimensions. Recently, quasi--two-dimensional hydrogen has been realized experimentally in the form of low-dimensional excitons. Their sensitivity to external electric and magnetic perturbations is reduced by the confinement. To quantify the reduction, we consider in the present work two-dimensional hydrogen in crossed electric and magnetic fields. We compare analytical, numerical, and variational results for the binding energy and dipole polarizability in arbitrary magnetic fields. Our analytical expressions for both weak and strong magnetic fields are supplemented by accurate variational and hypergeometric resummation results, thereby covering arbitrary magnetic fields.

Nickel hydroxide array coated with NiFe alloy nanosheets for overall mixed water splitting

In this study, Ni(OH) 2 coated NiFe alloy with Mott-Schottky structure is successfully prepared by hydrothermal and in-situ electrodeposition methods. The materials are characterized by physical and electrochemical characterizations, and the results show that Ni(OH) 2 @NiFe/NF has better catalytic activities than other monomers. Furthermore, the Ni/Fe ratio in the electrodeposition step and the CV deposition cycles could affect the performances. While the sample with Ni/Fe= 2:2 and 60 CV deposition cycles (Ni(OH) 2 @Ni 2 Fe 2 /NF-60) exhibits the best activities towards hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and urea oxidation reaction (UOR). Furthermore, the two-electrode electrolyzer composed of Ni(OH) 2 @Ni 2 Fe 2 /NF-60 exhibits the smallest driving potential (1.696 V (HER&OER) and 1.601 V (HER&UOR) at 50 mA·cm −2 ), with excellent stability. These may be due to the Mott-Schottky structure (metal-semiconductor interface) could reduce the binding energy of hydrogen atoms, promote charge transfer and generate abundant active sites, while producing a synergistic effect and promoting electrocatalytic reactions. • The Mott-Schottky structure is constructed. • The Ni(OH) 2 @NiFe displays worth catalytic activity for HER/OER/UOR. • The electrolyzer delivers 1.601 V (OUS) and 1.696 V (OWS) at 50 mA·cm −2 . • The catalytic performance of this electrode is comparable to that of noble metals.

Effect of uniaxial tensile strain on binding energy of hydrogen atoms to vacancy-carbon-hydrogen complexes in α-iron

• The hydrogen binding energy to vacancies under uniaxial tensile strain was calculated. • The binding energy of hydrogen atoms to vacancies decreased with increasing strain. • The binding energy of hydrogen to vacancy-C complexes increased with increasing strain. • The hydrogen retention was estimated under uniaxial tensile strain. The hydrogen binding energy to vacancies or vacancy-carbon complexes in α -Fe under uniaxial tensile strain was calculated using the density functional theory. The solution energies of hydrogen and carbon decreased with an increase in the uniaxial tensile strain. With increasing strain, the binding energy of hydrogen atoms to vacancies also decreases; however, the binding energy of the vacancy-carbon complexes increases. The hydrogen retention was estimated under exposure to hydrogen gas. In the strained area, both the hydrogen concentration of the interstitial hydrogen atoms and the number of hydrogen atoms trapped in the vacancies increased. Therefore, hydrogen retention increased with increasing strain; however, the change in the hydrogen binding energy did not have a strong impact on the hydrogen retention. The presence of vacancies affects hydrogen retention more strongly. Although the binding energy of hydrogen atoms to vacancy-carbon complexes increased, the hydrogen retention in the Fe-C alloy was lower than that in pure Fe.

First-principles investigations of hydrogen trapping in Y2O3 and the Y2O3|bcc Fe interface

Based on first-principles calculations, the binding energy of hydrogen atom to Y2O3 and Y2O3|bcc Fe interface (relative to bcc Fe side) with cube-on-cube orientation is at least 0.45 eV, if hydrogen substitutional is considered, or at least 0.26 eV if only hydrogen interstitial is considered. The calculated binding energies do not have a unique fixed value, because they are dependent on the interface structure, the Fermi level of Y2O3 near the interface and the chemical potential of Y/O. Hydrogen substitutional is more stable than hydrogen interstitial near the interface for Fermi level around calculated Schottky barrier height (SBH) at equilibrium. The Y2O3 particle interior can be an effective trapping site for hydrogen. Hydrogen interstitial, hydrogen substitutional and Y/O vacancy have a much lower energy near the interface than within the Y2O3 particle, presumably due to image charge interaction related to their non-zero charge state. For neutral impurities or defects, the energy near interface and that far away from the interface are similar (⩽0.1 eV difference) for a perfect coherent interface. The Y2O3|bcc Fe interface should provide effective trapping sites for hydrogen atoms in oxide dispersion strengthened (ODS) steels.

New insights into the anti-disproportionation mechanism of ZrCo alloying with Ti, Hf, Sc, Cu, and Fe elements

First-principles calculations were performed to investigate the effects of alloying substitutions (i.e. Ti, Hf, Sc, Cu and Fe) on the anti-disproportionation ability of ZrCo alloy. For the first time, we revealed the disproportionation mechanism from the energy point of view and provided a new theoretical method to predict whether the substitution element has the ability to enhance the anti-disproportionation performance of ZrCo alloy. Based on the hydrogen atom occupancy behavior in ZrCoH3 and the results of our calculation of binding energy, the hydrogen atom migration model during hydrogenation and theoretical computational model were established. Through structural optimization, a series of stable 2 × 1 × 2 ZrCoH3 supercells were obtained, which contain four hydrogen atoms occupying 8e site and various substitution atoms with different amounts except for pure system. The binding energy of hydrogen atom in the 8e site and activation energy of diffusing from 8e site to 4c2 site of these ZrCoH3 supercells were calculated. The results showed that the substitution of Ti and Hf increased the binding energy of hydrogen atom in the 8e site, while the substitution of Fe, Cu and Sc decreased the binding energy of hydrogen atom in the 8e site. Meanwhile, both of Ti and Hf substitution reduced the activation energy of diffusing from 8e site to 4c2 site, while all of Fe, Cu and Sc substitution increased the activation energy of diffusing from 8e site to 4c2 site. These results indicated that hydrogen-induced disproportionation was the inherent property of ZrCo alloy, and element substitution can restrain or accelerate disproportionation by affecting both the binding energy and activation energy. With simultaneous consideration of the binding energy and activation energy, the effect of these alloying substitutions on the anti-disproportionation ability could be ascertained and the results were in good agreement with the previous theoretical and experimental results.

INTERACTION OF HYDROGEN IMPURITY WITH NANOCRYSTALLINE PALLADIUM AND NICKEL

The interaction of hydrogen atoms with nanocrystalline palladium and nickel in the work was studied by the molecular dynamics method. The nanocrystalline structure of palladium and nickel was created in the model by crystallization from the liquid state at the presence of several specially introduced crystalline embryos. After solidification, the calculation blocks, in addition to the crystalline phase, contained grain boundaries and triple junctions of grain boundaries. The interactions of metal atoms with each other were described by the multi-particle Cleri-Rosato potential constructed in the framework of the tight-binding model. Morse potentials were used to describe the interactions of hydrogen atoms with metal atoms and with each other. The parameters of Morse potentials were calculated from the experimental data of theabsorption energy, the activation energy of the above-barrier diffusion of hydrogen in a metal (at normal and high temperatures), the binding energy with a vacancy, dilatation. According to the results obtained in the present work, at a high concentration of hydrogen (the concentration of 10% from the metal atoms was considered), the hydrogen atoms combine into aggregates, which are formed predominantly near the surface of the metal. The aggregates contained, as a rule, several dozen hydrogen atoms and had low diffusion activity. The binding energy of hydrogen atoms with these aggregates was greater than with the metal crystal lattice or grain boundaries in it. In palladium, hydrogen aggregates were formed farther from the surface than in nickel. Apparently, this is due not so much to the relatively low energy of hydrogen absorption by palladium (–0.1 eV) in comparison with nickel (0.16 eV), but rather to the difference in lattice parameters of the metals under consideration: 3.89 Å for Pd and 3.524 Å for Ni. For the same reason, conspicuously, hydrogen aggregates in a pure crystal lattice were more often observed in Pd than in Ni. In Ni, aggregates, as a rule, were formed in defect areas containing an excess free volume: near the free surface, in grain boundaries and in triple junctions.

Ab initio study of Be and Be12Ti for fusion applications

The paper applies ab initio methods for investigation of possible origin of the easier tritium release from titanium beryllide Be12Ti as compared with that of beryllium. Both materials are considered as neutron multiplier materials in some design concepts of tritium breeding blanket of future fusion reactor. The only stable tetragonal crystal structure of Be12Ti was studied in this work. Hydrogen solution energy in all non-equivalent interstitial positions of Be12Ti was found to be lower than that for beryllium suggesting easier dissolution of hydrogen atoms in Be12Ti. Maximal binding energy of hydrogen atoms in vacancy linearly decreases with the number of hydrogen atoms both in beryllium and Be12Ti. The highest hydrogen binding in a vacancy is 0.4 eV lower in Be12Ti, predicting easier release of hydrogen from beryllide with respect to beryllium. No formation of chemical bonds between hydrogen atoms inside both beryllium and Be12Ti vacancies was observed.

Hydrogen atom addition to the surface of graphene nanoflakes: A density functional theory study

Polycyclic aromatic hydrocarbons (PAHs) provide a 2-dimensional (2D) reaction surface in 3-dimensional (3D) interstellar space and have been utilized as a model of graphene surfaces. In the present study, the reaction of PAHs with atomic hydrogen was investigated by means of density functional theory (DFT) to systematically elucidate the binding nature of atomic hydrogen to graphene nanoflakes. PAHs with n=4–37 were chosen, where n indicates the number of benzene rings. Activation energies of hydrogen addition to the graphene surface were calculated to be 5.2–7.0kcal/mol at the CAM-B3LYP/6-311G(d,p) level, which is almost constant for all PAHs. The binding energies of hydrogen atom were slightly dependent on the size (n): 14.8–28.5kcal/mol. The absorption spectra showed that a long tail is generated at the low-energy region after hydrogen addition to the graphene surface. The electronic states of hydrogenated graphenes were discussed on the basis of theoretical results.

Adsorption of hydrogen atoms on graphene with TiO2 decoration

Graphene-based nanocomposites are regarded as potential candidate for hydrogen storage. In this work, the energetics of the hydrogen adsorption on graphene with TiO2 decoration is systematically investigated based on first-principles total energy calculations. TiO2 cluster is chemisorbed on graphene via O–C bonds. The C atoms near TiO2 cluster act as the nucleation positions for the hydrogen atom adsorption, and the binding energy of hydrogen atoms on graphene is significantly enhanced due to the decoration of TiO2 clusters, which is larger than the binding energy of hydrogen atoms in hydrogen molecules. It can be deduced that the hydrogen storage capacity could reach 7.3 wt. %, provided that the content of TiO2 in graphene is 5 wt. %. The results give a comprehensive understanding on electrochemical hydrogen storage behavior of graphene-based nanocomposites.

Hydrogen spillover storage on Ca-decorated graphene

In this work, first-principles total energy calculations were performed in order to study the structure and hydrogen storage behavior on Ca-decorated graphene. On the stable structure of Ca-decorated graphene with 3×3−300 reconstruction, the first hydrogen molecule adsorbed is dissociative, with the energy barrier of only 0.05 eV. The electrons of H atoms saturate the electronic states of Ca around the Fermi level and enhance the system stability. Further adsorption of hydrogen molecules on Ca-adsorbed graphene is weak, which indicates Ca-adsorbed graphene does not suit for the hydrogen storage via physical adsorption of hydrogen molecules. On the other hand, hydrogen spillover mechanism could exist on Ca-decorated graphene. On the graphene with one Ca dimer adsorbed, one of the four H atoms adsorbed on the Ca dimer adsorbes chemically on C in graphene more stably by 0.37 eV than on the Ca dimer. With the number of hydrogen atoms adsorbed on Ca-decorated graphene increases, the binding energy of hydrogen atoms tends to increase. Thus, the spillover process is energetically favorable. The hydrogen storage capacity via the spillover mechanism in Ca-adsorbed graphene depends on the Ca content and could approach 7.7 wt.%.

Density functional study of hydrogen adsorption and dissociation on small Pd n ( n = 1–7) clusters

Density functional theory has been performed to investigate the interaction of H 2 and Pd n clusters ( n = 1–7). The local minima configurations for different H 2 molecule approach modes towards Pd n clusters are presented. Our results show that in some cases H 2 is physically adsorbed around Pd atom, and in other cases H 2 is dissociated to be H atoms. Except for PdH2, Pd n clusters with H atoms dissociatively adsorbed are most stable. For these most stable PdnH2 clusters ( n ⩾ 2), the binding energy of hydrogen atom decreases as the number of Pd atom increases until n = 4, and when n ⩾ 4, the binding energy almost keeps constant with the H atoms bound sites changing from Pd–Pd bonds to Pd triangle planes. Besides, the adsorption of H 2 on other low-lying isomers of Pd n clusters is also discussed.

High coverage of hydrogen on a (10,0) single-walled boron nitride nanotube

The binding energy of hydrogen atoms to a (10,0) single-walled boron nitride nanotube (SWBNNT) is calculated at 25%, 50%, 75%, and 100% coverage using the density functional theory. The average binding energy is highest at 50% coverage when the H atoms are adsorbed on the adjacent B and N atoms along the tube axis and the value is $\ensuremath{-}53.93\phantom{\rule{0.3em}{0ex}}\mathrm{kcal}∕\mathrm{mol}$, which is similar to half of the $\mathrm{H}\mathrm{H}$ binding energy. Also, the band gap $(\ensuremath{-}4.29\phantom{\rule{0.3em}{0ex}}\mathrm{eV})$ of the pristine (10,0) SWBNNT is decreased up to $\ensuremath{-}2.01\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ for the H-adsorbed BNNT with 50% coverage.

Calculation of enthalpy of metal hydride formation and prediction of hydrogen site occupancy

AbstractA model is presented for calculating the enthalpy of formation of metal hydrides. The model takes into account the effect of the bond number formed between the hydrogen and metal atoms. Site occupancies of hydrogen atoms in pure metals calculated using this model are in good agreement with experimental observations. A method for calculating the binding energy of hydrogen atoms at different sites in hydrogen storage alloys is also presented, and is shown to predict accurately the site occupancy of hydrogen atoms in CI5 Laves phase alloys.MST/7I9

Calculation of surface binding energy for hydrogen, oxygen, and carbon atoms on metallic surfaces

The model of Polar Covalence developed by Sanderson was used to calculate binding energies at zero coverage for H, O, and C atoms adsorbed on metal surfaces. For 11 single crystal metals, the average absolute difference between the experimental and calculated binding energies of hydrogen atoms was 3–4 kcal mol . The model correctly predicts the weak binding of H on sp metals, e.g., Hg and Cd. Very similar agreement, 3–4 kcal mol , was obtained for O atoms on 8 single crystal metals. In the case of carbon atoms, the binding energy on Ru and Ni was calculated to be less than the atomization energy of graphite, in agreement with experiment. A similar effect on Pd surfaces is predicted. The calculated low binding energy, 40 kcal mol , of H atoms on top of Pd is supported by a combination of thermodynamic, quantum mechanical, spectroscopic and thermal desorption data. These calculations represent the first attempt to apply Sanderson's method to first, second, and third row transition metals and to surface thermodynamics.

On the location of a hydrogen atom in body-centered cubic 3d transition metal lattices

Extended Hückel molecular orbital calculations were carried out for 22-atom clusters simulating the b.c.c. forms of vanadium, chromium, iron and cobalt. In each study the Hiickel parameter K was optimized to reproduce the observed cohesive energy of the isolated metal. Results indicate that in all cases a hydrogen atom implanted in the cluster is more stable in a site of distorted tetrahedral symmetry than in a site of distorted octahedral symmetry, and that a hydrogen atom in either site is stabilized by an adjacent lattice vacancy. An inverse relationship is observed between the computed binding energies of hydrogen atoms in both tetrahedral and octahedral sites and the d electron repulsive potential.

Electron-electron correction to the chemical binding energy of hydrogen atoms in α-palladium hydrides

We show that the modification of the electron-electron term resulting from the binding of a pair of hydrogen impurities in α-palladium hydrides cancels the corresponding modification of the one-electron band energies.