Hydrogen Absorption Studies Research Articles

Investigation on nanoindentation and TOF-SIMS applications in the hydrogen and oxygen absorption behavior of Zr-Sn-Nb alloys

This paper focuses on nanoindentation and TOF-SIMS (time-of-flight secondary ion mass spectrometry) small-scale test methods in the study of hydrogen absorption and oxygenation behavior analysis of Zr-Sn-Nb oxidized at 650°C −1200 °C. The CSM (Continuous Stiffness Method) test demonstrates the hardness fluctuations caused by element proliferation in post-high temperature oxidation microstructures. The deformation resistance ability of typical microstructures is as follows: β-Zr layer > α-Zr(O) layer > ZrO2 layer. In addition, hydrogen-induced softening occurred in steam-containing hydrogen conditions (HIT=2～3Gpa), compared to steam (HIT=5～16Gpa). The 1200℃ load-displacement curve demonstrates that the pop-in (or pop-out) effect exists in the Zr-Sn-Nb alloy, related to the influence of hydrogen charge, essentially to dislocation nucleation, winding, and movement. TOF-SIMS provides an effective method for small molecular chemical elements, such as H and O, while ZrO, ZrO2, ZrO2H, ZrO3H, OH, and O2 ions also be found. Based on these results, this study also hypothesizes the OH- dominated oxidation reaction equation.

Agile soft template array fabrication of one-dimensional (1D) polyaniline nanocomposite fibers for hydrogen storage.

Polyaniline-Zn/V2O5 nanocomposites were prepared in the presence of toluene-4-sulfonic acid monohydrate as an anionic surfactant via an in situ oxidation polymerization method. The structural study of the nanocomposites was carried out using FTIR and XRD analysis, and their surface morphology was characterized through SEM analysis. The BET surface area of a 3 wt% nanocomposite was 386 m2 g-1, which is higher compared to that of PANI. The Kelvin two probe method was used to study DC conductivity, and it was found that the conductivity increases with increasing temperature. Among all the PANI nanocomposites, 3 wt% PANI-Zn/V2O5 shows a high conductivity of 13.8 S cm-1. Cyclic voltammetry results show the characteristic oxidation-reduction peaks at 0.93 V and 0.24 V for polyaniline and its nanocomposites, respectively. Hydrogen absorption studies were carried out using volumetric sorption measurement technique. At room temperature, it was found that the hydrogen adsorption capacity of polyaniline fibres is about 4.5 wt%, and its absorption capacity increases two-fold upon increasing the temperature up to 60 °C. Conversely, the 3 wt% PANI-Zn/V2O5 nanocomposite showed a high absorption capacity of 6.6 wt% compared with other compositions, which is may be due to the presence of nitrogen (N) molecules in polyaniline and its particular porous fiber architecture.

Size Matters: A Computational Study of Hydrogen Absorption in Ionic Liquids.

We combined both density functional theory and classical molecular dynamics simulations to investigate the molecular mechanisms governing hydrogen solvation in a total of 12 ionic liquids. Overall, the analysis of the structural properties under high temperature and pressure conditions revealed weak interactions between hydrogen and the ionic liquids, with a slight preference of this gas to be placed at the apolar domains. Interestingly, those ionic liquids comprising nitrate anions allow the accommodation of hydrogen molecules also in the polar areas. The study of the hydrogen velocity autocorrelation functions supports this observation. In addition, the structure of all of the tested ionic liquids was almost insensitive to the addition of hydrogen, so the available free volume and cavity formation are presumably the most important factors affecting solubility.

Experimental and numerical study of hydrogen absorption in the MmNi5−xMx compound

In this paper, the hydrogen storage properties of the MmNi4.6Al0.4 and MmNi4.6Fe0.4 compounds are compared experimentally and theoretically. The experimental curves of the activation process, experimental isotherms of absorption and the Van't Hoff's plot were first investigated. Following that, a theoretical model is contrasted with the experimental data. The mathematical equations of this model contain parameters, such as the number of hydrogen atoms per site (n1, n2), the densities of the receiving sites (N1m, N2m), and the energy parameters (P1, P2). All these parameters are obtained by numerically adjusting the experimental data. Depending on the applied temperature, the relevant parameters of the suggested model were identified and described. Entropy, internal energy, and other thermodynamic variables that govern the absorption reaction were all calculated and displayed as a function of pressure and temperature.

2D-axisymmetrical modeling and experimental study of hydrogen absorption in copper coated metal hydride

The storage of hydrogen in metal hydride reactors is examined experimentally and numerically in this paper. In this respect, as-received LaNi5 powders are coated with different amounts of copper by using copper sulphate solution to accelerate the hydrogen charging processes. The thermal conductivity of the copper-coated storage material is found to reach up to 8 times of the uncoated powders. A two-dimensional axisymmetric model regarding complex heat and mass transfer occurring during hydrogen charging process in metal hydride reactors is numerically solved at macro level. The developed model is validated by using experimental data related to the amount of hydrogen stored and the reactor temperatures. In accordance with the experimental results, the simulation results show that more homogenous temperature distribution in the reactor can be obtained with the copper coating due to improved thermal properties. Moreover, charging time is also improved by the copper coating. However, since the reactor is loaded with coated/uncoated LaNi5 powders at the same weight of 65 g, the total amount of hydrogen stored decreases with the copper coating due to reduced amount of LaNi5.

Hydrogen Absorption into Copper-Coated Titanium Measured by In Situ Neutron Reflectometry and Electrochemical Impedance Spectroscopy

One concern regarding the used nuclear fuel containers proposed for use in a Canadian deep geological repository (DGR) is the possibility that a small amount of hydrogen might be absorbed into their copper coating, potentially altering its mechanical properties. Reported herein is a study of hydrogen absorption into 50 nm of copper, coated on 4 nm of Ti using in situ neutron reflectometry (NR) and electrochemical impedance spectroscopy (EIS). NR results show that hydrogen is absorbed when the copper is cathodically polarized below the threshold for the hydrogen evolution reaction (HER), but that the hydrogen concentrates in the underlying titanium layer rather than concentrating in the copper coating. The hydrogen concentration in titanium rapidly rose when the HER was initiated and was observed to reach a steady state at TiH1.5. Over the course of 55h of cathodic polarization, the concentration of hydrogen in the copper remained below the NR detection limit (2 at %). The portion of hydrogen atoms produced that diffused through the copper layer was initially 3.2%, suggesting a possible upper limit for hydrogen uptake by the copper coating of the UFC, although definitive conclusions can only be drawn from studies on 3 mm copper-coated steel samples.

Study of hydrogen absorption in a novel three-dimensional graphene structure: Towards hydrogen storage applications

The use of a novel three-dimensional graphene structure allows circumventing the limitations of the two-dimensional nature of graphene and its application in hydrogen absorption. Here we investigate hydrogen-bonding on monolayer graphene conformally grown via the epitaxial growth method on the (0001) face of a porousified 4H-SiC wafer. Hydrogen absorption is studied via Thermal Desorption Spectroscopy (TDS), exposing the samples to either atomic (D) or molecular (D2) deuterium. The graphene growth temperature, hydrogen exposure temperature, and the morphology of the structure are investigated and related to their effect on hydrogen absorption. The three-dimensional graphene structures chemically bind atomic deuterium when exposed to D2. This is the first report of such an event in unfunctionalized graphene-based materials and implies the presence of a catalytic splitting mechanism. It is further shown that the three-dimensional dendritic structure of the porous material temporarily retains the desorbed molecules and causes delayed emission. The capability of chemisorbing atoms after a catalytic splitting of hydrogen, coupled to its large surface-to-volume ratio, make these structures a promising substrate for hydrogen storage devices.

Hydrogen influence in the UNiAl-UNiGa system: Structure and magnetism

Hydrogen absorption studies on UNiAl1-xGax were performed as part of our investigation of UTX compounds. The whole series crystallizes in the hexagonal structure of the ZrNiAl type (s.g. P-62m). The amount of hydrogen absorbed has a decreasing tendency with increasing Ga concentration. Studies of the temperature dependence of magnetic susceptibility indicate certain increase of the critical temperature of magnetic ordering in the hydrides but the increment becomes smaller with increasing Ga concentration as a result of smaller H absorption and concomitant changes in the crystal structure.

Surface microstructural controls on electrochemical hydrogen absorption at polycrystalline palladium

The ease by which hydrogen is absorbed into a metal can be either advantageous or deleterious, depending on the material and application in question. For instance, in metals such as palladium (Pd), rapid absorption kinetics are seen as a beneficial property for hydrogen purification and storage applications, whereas the contrary is true for structural metals such as steel, which are susceptible to mechanical degradation in a process known as hydrogen embrittlement. It follows that understanding how the microstructure of metals (i.e., grains and grain boundaries) influences adsorption and absorption kinetics would be extremely powerful to rationally design materials (e.g., alloys) with either a high affinity for hydrogen or resistance to hydrogen embrittlement. To this end, scanning electrochemical cell microscopy (SECCM) is deployed herein to study surface structure-dependent electrochemical hydrogen absorption across the surface of flame annealed polycrystalline Pd in aqueous sulfuric acid (considered to be a model system for the study of hydrogen absorption). Correlating spatially-resolved cyclic voltammetric data from SECCM with co-located structural information from electron backscatter diffraction (EBSD) reveals a clear relationship between the crystal orientation and the rate of hydrogen adsorption-absorption. Grains that are closest to the low-index orientations [i.e., the {100}, {101}, and {111} facets, face-centered cubic (fcc) system] facilitate the lowest rates of hydrogen absorption, whereas grains of high-index orientation (e.g., {411}) promote higher rates. Apparently enhanced kinetics are also seen at grain boundaries, which are thought to arise from physical deformation of the Pd surface adjacent to the boundary, resulting from the flame annealing and quenching process. As voltammetric measurements are made across a wide potential range, these studies also reveal palladium oxide formation and stripping to be surface structure-dependent processes, and further highlight the power of combined SECCM-EBSD for structure-activity measurements in electrochemical science.

Experimental and theoretical study of hydrogen absorption by LaNi3.6Mn0.3Al0.4Co0.7 alloy using statistical physics modeling

A monolayer model treated by statistical physics by means of the grand canonical ensemble has been developed, describing PCT isotherms for absorption of hydrogen by LaNi3.6Mn0.3Al0.4Co0.7 alloy. This model presents a high correlation with the experimental results. The experimental absorption isotherms are fitted at three temperature different (T = 293 K to T = 313 K). The physicochemical parameters involved in the model were determined from the experimental isotherms by numerical simulation. These parameters, such as two numbers of absorbed atoms per site n1 and n2, two receptor site densities N1M and N2M, and two energetic parameters, P1 and P2 are discussed in relationship with absorption process. The different thermodynamic functions which govern the absorption mechanism such as entropy (Sa), free enthalpy of Gibbs (G) and internal energy (Eint) are derived by statistical physics model calculations.

Theoretical study of hydrogen absorption and desorption in Ti1-xZrx Mn1.4 using statistical physics treatment: Microscopic investigation and thermodynamic potential interpretation

Experimental absorption and desorption isotherms of hydrogen in Ti1-xZrx Mn1.4 (x = 0, 0.1, 0.2, 0.3, 0.4) alloys at T = 293 K have been fitted using some theoretical model expressions treated by statistical physics through the grand canonical ensemble. The monolayer model with two types of sites is used to fit and interpret the experimental data. The physicochemical parameters governing the absorption-desorption processes and included into the model expressions could be numerically deduced from the relevant experimental isotherms. Six parameters of the model are fitted, namely the numbers of hydrogen atoms per site n1 and n2, the receptor site densities N1m and N2m, and the energetic parameters P1 and P2. The evolution of these parameters as function of composition x is plotted and explained in correlation with absorption-desorption processes. Finally, the thermo-dynamic potential functions which govern the sorption mechanisms such as internal energy Eint, free enthalpy of Gibbs Ga and entropy Sa were derived from statistical physics calculations based on the model adopted.

In-situ X-ray diffraction study of hydrogen absorption and desorption processes in Pd thin films: Hydrogen composition dependent anisotropic expansion and its quantitative description

The hydrogen absorption/desorption processes of (111)-textured and normal palladium (Pd) thin films of thickness ranging from 8 to 48 nm are investigated using X-ray diffractometry. The one-dimensional expansion of Pd lattice due to the substrate clamping is observed at the low hydrogen composition phase while both out-of-plane and in-plane expansions are detected at the high hydrogen composition phase. Accordingly, using a biaxial Poisson’s ratio, an anisotropic expansion factor is proposed for describing such phenomenon quantitatively and the hydrogen composition dependence on this factor is investigated.

Spontaneous Chemical Ordering in Bimetallic Nanoparticles

In most experimental studies on bimetallic nanoparticles the homogeneous alloying is consistently reported or a priori assumed. It is generally believed that at nanoscale, alloying is promoted even for otherwise immiscible systems. In this study we present evidence that Pd–Pt nanoalloys are much more susceptible to segregation than their bulk counterparts. The spontaneous segregation (chemical ordering) of Pd–Pt nanoalloys was evidenced in hydrogen absorption studies and additionally confirmed by using X-ray photoelectron spectroscopy. The results clearly show that phase segregation in bimetallic nanoparticles do occur despite the lack of the miscibility gap in the Pd–Pt phase diagram, negative heat of mixing and small lattice mismatch for both metals. Phase segregation for other bimetallic systems is also discussed. Hydrogen solubility in the investigated nanoparticles is enhanced nearly by 3 orders of magnitude with respect to H solubility in unsegregated Pd–Pt alloys. This superior solubility points out the importance of phase segregation, which is frequently overlooked, yet fundamental for systems designed for heterogeneous catalysis and hydrogen storage.

Comparative evaluation of hydrogen storage behavior of Pd doped carbon nanotubes prepared by wet impregnation and polyol methods

The present manuscript deals with the hydrogen absorption properties of multiwalled carbon nano-tubes (MWCNTs) doped with Pd nanoparticles by the conventional wet impregnation method and the polyol method. In the latter method Pd nanoparticles are doped into CNTs based on polyhydroxy organic compounds (polyol) mediated functionalization. The polyol medium reduces palladium chloride to palladium nanoparticles, and also acts as a capping agent to stabilize the Pd nanoparticles. The samples have been characterized using X-ray diffraction (XRD), Energy Dispersive X-ray (EDX) and Infrared (IR) spectroscopy. Hydrogen absorption studies clearly illustrate that Pd doped MW-CNT's prepared by polyol mediated functionalization show much higher hydrogen storage capacity compared to the sample prepared by wet impregnation route. To determine the cause of this behavior, Transmission Electron Microscopic (TEM) studies of the samples were carried out. The results indicate that the dispersion of Pd nanoparticle on the MW-CNT is much better for the sample prepared by the polyol route. An attempt was made to determine the existence of any metal-support interaction using Thermogravimetric Analysis (TGA). The investigation reveals that the higher dispersion of Pd nanoparticles on the CNT support plays a major role for the hydrogen adsorption.

Spectroscopic study of low-temperature hydrogen absorption in palladium

We report real-time detection of hydrogen (H) absorption in metallic palladium (Pd) nano-contacts immersed in liquid H2 using inelastic electron spectroscopy (IES). After introduction of liquid H2, the spectra exhibit the time evolution from the pure Pd to the Pd hydride, indicating that H atoms are absorbed in Pd nano-contacts even at the temperature where the thermal process is not expected. The IES time and bias voltage dependences show that H absorption develops by applying bias voltage 30 ∼ 50 mV, which can be explained by quantum tunneling. The results represent that IES is a powerful method to study the kinetics of high density H on solid surface.

A comprehensive investigation of structural, morphological, hydrogen absorption and magnetic properties of MmNi4.22Co0.48Mn0.15Al0.15 alloy

A comprehensive study of structural, morphological, hydrogen absorption and magnetic properties of MmNi 4.22 Co 0.48 Mn 0.15 Al 0.15 alloy as a promising hydrogen storage media was investigated. The X-ray diffraction (XRD) profiles show that the alloy maintains its crystal structure (hexagonal LaNi 5-type) even after 30 hydrogenation/dehydrogenation (H/D) cycles. However, the XRD peaks are found to be slightly broadened after cycling. SEM images reveal that particles size of the cycled sample decreases, with more uniform particle size distribution compared to noncycled ones. The pressure-composition (PC) isotherms and kinetics curves of hydrogen absorption reaction were obtained at different working temperatures by using a homemade Sievert apparatus. The enthalpy and entropy of hydride formation of the alloy were evaluated. Furthermore, the Jander diffusion and Johnson–Mehl–Avrami models as the fitting models were employed to study the kinetic mechanism of hydriding reaction and its activation energy. The room temperature magnetic measurements indicate that the milling and H/D cycling change the magnetic properties of the as-annealed alloy.

Hydrogen absorption characteristics and Mössbauer spectroscopic study of Ti0.67Nb0.33−xFex (x=0.00, 0.13, 0.20) alloys

Abstract The present study deals with the preparation and hydrogen absorption studies on Ti 0.67 Nb 0.33− x Fe x ( x = 0.00, 0.13, 0.20) alloys. From X-ray diffraction results it is inferred that the three alloys are bcc phase and get converted to fcc phase upon hydrogenation. Ti 0.67 Nb 0.13 Fe 0.20 alloy showed maximum hydrogen storage capacity (2.62 wt%) with fastest kinetics among the studied compositions. The hydrogenation kinetics of Ti 0.67 Nb 0.13 Fe 0.20 alloy was studied in detail over the temperature range from 298 K to 473 K. Two different types of rate equations were required to fit the kinetic data, indicating two different rate determining steps (rds) during the progress of hydriding reaction. The activation energies for the two rate determining steps have been calculated from hydrogen absorption kinetics study at different temperatures. 57 Fe Mossbauer spectroscopic study of Fe substituted alloys and their corresponding hydrides show the effect of hydrogenation on the electronic structure of the alloys in terms of electronic charge distribution and volume expansion.

Hydrogen absorption study of ti-based alloys performed by melt-spinning

The hydrogen absorption and desorption of Ti53Zr27Ni20 icosahedral quasicrystal (ICQ) and Ti50Ni50 shape memory alloy (SMA) melt-spun ribbons was studied. Samples were exposed to hydrogen gas at 623 K and 4 MPa for 1000 minutes. The total capacity of hydrogen obtained for Ti53Zr27Ni20 and Ti50Ni50 was 3.2 and 2.4 wt. % respectively. The Thermal Desorption Spectrometry (TDS) of the hydrogenated alloys shows that both alloys start to desorb hydrogen around 750 K. X-ray diffraction (XRD) patterns, performed after hydrogenation, indicate a complete amorphization of the Ti53Zr27Ni20 i-phase alloy, while the Ti50Ni50 alloy remained crystalline after hydride formation.

Hydrogen absorption study of high-energy reactive ball milled Mg composites with palladium additives

Abstract Hydrogenation behaviour, structure, morphology and dehydrogenation/re-hydrogenation performances of Mg–Pd nanocomposites prepared by high-energy reactive ball milling in H 2 (HRBM) of Mg in the presence of amorphous and crystalline Pd black (0.1–5 wt.%) were studied. Improvements of hydrogenation kinetics during HRBM were observed only for the materials prepared using crystalline Pd black. The obtained nanocomposites were characterised by modest improvements in their dehydrogenation and re-hydrogenation performances associated with the formation of Mg–Pd intermetallides.

Hydrogen diffusion in amorphous FeCrB ribbons

The article deals with the study of hydrogen absorption (hydrogenation) and desorption (dehydrogenation) in amorphous ferromagnetic FeCrB ribbons prepared by rapid quenching from the melt. A simple theoretical model was proposed for description of hydrogen concentration and determination of diffusion coefficient in these materials. Using this model diffusion coefficient can be calculated using experimentally obtained values of average hydrogen concentration in the sample during dehydrogenation process. The values of diffusion coefficients are comparable with those obtained by hydrogen permeation test. The proposed method is not only simple but it also makes possible to determine diffusion coefficient under the same conditions as the changes of other properties of these materials during their dehydrogenation.