Hydrogen Desorption Behavior Research Articles

Reversible hydrogen storage in Y2C MXene under the influence of functional groups (F, Cl, OH)

The hydrogen storage potential of the bare MXenes Y2C and terminated Y2CT2, where T is O, OH, or F, were studied using density functional theory (DFT). Hydrogen adsorption and desorption behaviors are simulated by ab initio molecular dynamic simulations. The interaction of the H2-molecules on the Y2C-family was investigated within the projected density of states. Only bare Y2C and Y2C(OH)2 provided Kubas-type interactions. The calculated maximum capacity of H2 in bare Y2C can reached up to 5.041 wt%, whereas the reversible capacity of H2 was up to 2.036 wt%. In Y2C(OH)2, the maximum capacity of H2 storage is 3.477 wt% and the reversible capacity was 1.769 wt%. This indicated that Y2C and Y2C(OH)2 are practical candidates for hydrogen storage applications.

Enhancing hydrogen storage efficiency: Computational insights into scandium-decorated 2D polyaramid

This study explores hydrogen storage in 2D polyaramid (2DPA) and its enhancement via scandium decoration for onboard storage in fuel cell vehicles. Sc decoration in 2DPA is accompanied by a net 1.6 e charge transfer from Sc to 2DPA. Hydrogen binding in 2DPA + Sc proceeds with a net charge transfer of 0.32 e from Sc towards H2. 2DPA + Sc demonstrates a maximum hydrogen loading capacity of 8.589 wt% with an average adsorption energy of −0.376 eV/H2. These findings meet the stipulated criteria by the US Department of Energy for solid-state hydrogen storage in light-duty vehicles. Feasibility studies were conducted considering practical limitations in transition metal-modified carbon nanomaterials, including Sc-Sc clustering tendencies, stability, and hydrogen desorption behavior via ab initio molecular dynamics simulations, phonon dispersion, and diffusion studies. The highest barrier height for hydrogen desorption from 2DPA + Sc is 0.48 eV, and desorption is predicted to occur at 412 K (5 bar) indicating possibility of room temperature and reversible hydrogen storage. Our findings indicate that 2DPA + Sc is a promising hydrogen storage substrate material and should be explored in experimental trials.

Microstructural study on the slope of plateau pressure in TiFe0.8Al0.2 hydrogen storage alloy

In the TiFe0.8Al0.2 alloy, the Ti2Fe phase was precipitated, and the B2 phase was separated into two B2 phases. The alloy absorbed hydrogen at room temperature without any thermal activation process by forming the Ti2Fe phase. The hydrogen absorption and desorption behaviors were examined, and the slope of the plateau pressure was severely formed. The two B2 phases had different compositions. The hydride-forming enthalpies of the two B2 phases were calculated through a density function theory calculation, and the values of the two B2 phases were different. Therefore, it was confirmed that the slope of the plateau pressure was severely formed because of the separation of the B2 phase.

Growth Behavior of Pores and Hydrogen Desorption Behavior in Pure Aluminum and A6061 Aluminum Alloys

Growth Behavior of Pores and Hydrogen Desorption Behavior in Pure Aluminum and A6061 Aluminum Alloys

Microstructure and hydrogen storage properties of MgH2/MIL-101(Cr) composite

In this paper, a new hydrogen storage composite based on magnesium hydride and metal-organic framework MIL-101(Cr) (an acronym for Material Institute Lavoisier) has been mechanically synthesized and investigated. The hydrogen sorption and desorption behavior in the composite was investigated for the temperature and pressure ranges of (593−653) K and (0−3) MPa, respectively. According to the pressure-composition-temperature isotherms of hydrogen sorption/desorption, the MgH2–5 wt%MIL-101(Cr) composite starts to absorb hydrogen at a lower pressure at 593 K. In addition, the hydrogen release peak for composite shifts to lower temperatures by about 140 K compared to the pure milled MgH2 during temperature programmed desorption at a heating rate of 6 K/min. The activation energy of hydrogen desorption from the composite is 120 ± 2 kJ/mol, which is 36% lower than the activation energy of hydrogen desorption from magnesium hydride (189 ± 2 kJ/mol). The enthalpy of hydrogen absorption was found to be 73 kJ/mol H2 and 60 kJ/mol H2 for milled MgH2 and MgH2–5 wt%MIL-101(Cr) composites, respectively. It is showed that the MIL-101(Cr) MOF structures decompose during ball milling and the chromium oxide nanoparticles form a core-shell structure with MgH2 particles. Thus, composite has better sorption and desorption properties than pure magnesium/magnesium hydride due to the nanoconfinement of MgH2. The chromium oxide nanoparticles act as active sites on the surface of the magnesium particles and facilitate the dissociative chemisorption or recombinative desorption of hydrogen. The main regularities of the phase transition in the magnesium-hydrogen system for the composite and magnesium hydride during dehydrogenation have been studied for temperatures in the range of 298–750 K. The in situ analysis of the phase transitions during the dehydrogenation of MgH2 and MgH2–5 wt%MIL-101(Cr) composite indicates a pronounced catalytic effect of the addition of MIL-101(Cr) to the Mg/MgH2. Based on the experimental results and ab initio calculations, a mechanism for the sorption and desorption of hydrogen by the composite has been proposed.

Investigation on Nonisothermal Dehydrogenation Behavior of Mg–Ni–La–H Materials Prepared by Mechanochemical Reaction

Mg10NixLa–H alloys are synthesized by mechanochemical reaction starting with Mg–Ni–La multiphase polycrystalline alloys prepared by resistance melting furnace. The nonisothermal hydrogen desorption behaviors are investigated herein. All prepared samples are characterized by scanning electron microscopy, X‐ray diffraction, fully automatic fast surface and porosity analysis meter Brunauer–Emmett–Teller (BET), differential scanning calorimetry, and thermogravimetric analyzer to get information of phase compositions, microstructure, BET surface area, and dehydrogenation properties. The results demonstrate that Mg10NixLa–H exhibits enhanced nonisothermal hydrogen desorption behavior owing to the synergistic effects among hydrides. The main peak dehydrogenation temperatures for Mg10Ni5La–H, Mg10Ni10La–H, and Mg10Ni15La–H alloys are 375.3, 374.4, and 359.7 °C at 5 °C min−1, respectively. And the apparent activation energy for Mg10Ni5La–H, Mg10Ni10La–H, and Mg10Ni15La–H is 111.7, 275.5, and 184.7 kJ mol−1, respectively. However, the actual hydrogen release capacities of Mg10Ni5La–H, Mg10Ni10La–H, and Mg10Ni15La–H are about 5.09, 3.98, and 4.49 wt%, respectively. Mg10Ni15La–H exhibits the lowest onset dehydrogenation temperature due to its reduced particle size and uniformly distributed hydride phase. The modification of Mg‐based hydrogen storage materials by combining mechanochemical reaction and multiple microalloying is essential for further improvement of thermal properties.

Study on the microstructure and hydrogen storage property changes of cast TiFe0.9Cr0.1 alloy by homogenization annealing

This study investigated the changes in the microstructure and hydrogen storage properties of cast TiFe0.9Cr0.1 alloys by homogenization annealing. The as-cast and homogenized samples consisted of B2 and C14 Laves phase. After annealing, compositions of the B2 phase in both samples were similar, while the Laves phase fraction decreased and the Cr concentration in the Laves phase increased. To understand the microstructure changes caused by annealing, the fraction and the composition of the phases in the equilibrium state were derived using thermodynamic calculation, where the microstructure of the as-cast sample changed to the direction in the equilibrium state by annealing. The first hydrogenation kinetics were examined in the as-cast and homogenized samples, which slowed in the latter as the Laves phase fraction decreased. The hydrogen absorption and desorption behaviors were compared using a pressure-composition-temperature diagram at 50 °C. Since the compositions of the B2 phase in the two samples were almost the same, the two samples represented similar hydrogen storage behaviors. From the first-principles density functional theory calculation, the hydride-forming enthalpy of the B2 phase was calculated. By using an equation to predict the desorption plateau pressure from the hydride-forming enthalpy, the desorption pressure was predicted to be 1.34 bar, a value similar to the desorption pressure obtained from the experiment.

Effect of Tempering Temperature on Hydrogen Embrittlement of SCM440 Tempered Martensitic Steel.

The effect of tempering temperature on the hydrogen embrittlement characteristics of SCM440 tempered martensitic steels was investigated in terms of their microstructure and hydrogen desorption behavior. The microstructures were characterized using scanning and transmission electron microscopy, as well as X-ray diffraction and electron backscattered diffraction analysis. Thermal desorption analysis (TDA) was performed to examine the amount and trapping behavior of hydrogen. The cementite morphology of the SCM440 tempered martensitic steels gradually changed from a long lamellar shape to a segmented short-rod shape with an increasing tempering temperature. A slow strain rate tensile test was conducted after electrochemical hydrogen charging to evaluate the hydrogen embrittlement resistance. The hydrogen embrittlement resistance of the SCM440 tempered martensitic steels increased with an increasing tempering temperature because of the decrease in the fraction of the low-angle grain boundaries and dislocation density. The low-angle grain boundaries and dislocations, which acted as reversible hydrogen trap sites, were critical factors in determining the hydrogen embrittlement resistance, and this was supported by the decreased diffusible hydrogen content as measured by TDA. Fine carbides formed in the steel tempered at a relatively higher temperature acted as irreversible hydrogen trap sites and contributed to improving the hydrogen embrittlement resistance. Our findings can suggest that the tempering temperature of SCM440 tempered martensitic steel plays an important role in determining its hydrogen embrittlement resistance.

高純度アルミニウムおよびA6061アルミニウム合金におけるポアの成長挙動と水素脱離挙動

An increase in the volume fraction of pores in aluminum alloys causes a decrease in the elongation and the strength of alloys. To improve the mechanical properties of aluminum alloys, it is important to understand the growth and shrinkage behavior of pores. In this study, we analyzed the relationship between hydrogen desorption behavior and the growth/shrinking behavior of pores in A6061 alloys and pure aluminum using thermal desorption analysis and synchrotron radiation X-ray tomography. In pure aluminum, the fine pores began to annihilate at temperatures above 500°C and the relatively large pores coarsened. In contrast, the pores shrank with increasing temperature in A6061 alloy. The influence of second-phase particles has been discussed as a possible explanation for the difference in the nature of pores at elevated temperatures in pure aluminum and A6061 alloys. As in the A6061 alloy, much of the hydrogen desorbed from the pores due to heating is released externally from the second-phase particles on the aluminum surface, resulting in pore shrinkage due to the internal pressure drop of pores.

The phase transitions behavior and defect structure evolution in magnesium hydride/single-walled carbon nanotubes composite at hydrogen sorption-desorption processes

The development of hydrogen storage methods is one of the important areas of research in the field of hydrogen energy, while metal hydrides and composites based on them are the most preferred candidates for this. In this paper, one of the composite hydrogen storage materials based on magnesium hydride and single-walled carbon nanotubes was considered. The hydrogen sorption and desorption behavior in composite have been investigated for temperatures and pressures ranges (593−653) K and (0−3) MPa, respectively. Using scanning electron microscopy, it was shown that carbon nanotubes are homogeneously distributed on the surface of MgH2 particles and some of nanotubes are partially embedded in the bulk of MgH2. According to pressure-composition-temperature curves and Van’t Hoff plots it was determined that the enthalpy value of hydrogen absorption process was 69 KJ/mol H2 and 62 KJ/mol H2 for milled MgH2 and MgH2 with 5 wt% single-walled carbon nanotubes, respectively. The main regularities of phase transition in the magnesium-hydrogen system for composite and magnesium hydride during dehydrogenation have been researched for temperatures in the range of 298–750 K. The in situ analysis of the phase transitions during dehydrogenation of MgH2 and composite based on MgH2 and 5 wt% of single-walled carbon nanotubes in argon atmosphere indicates pronounced catalytic effect of carbon nanotubes on the hydrogen desorption. The thermally stimulated desorption curves showed that hydrogen begins to release from the composite where the MgH2 decomposition is minimal. An in situ Doppler broadening spectroscopy study revealed that this is caused by a significant changes magnesium defect structure as a result of the carbon nanotubes/nanoparticles embedding, and the low-temperature hydrogen release follows from the decomposition of associated defects (dislocation-hydrogen or vacancy-hydrogen complexes) as well as its effective diffusion to the surface.

Positive correlation of Nb/Cr doping with dehydrogenation performance of ZrCo-based hydrides

It is well known that element substitution is vital to an improvement of hydrogen storage capacity degraded by hydrogen-induced disproportionation of zirconium-cobalt (ZrCo) alloy. Contrary to other studies, this work is devoted to investigating the hydrogen desorption behavior of Zr1-xNbxCo1-yCryH3 (x = 0–0.25 and y = 0–0.125) systems formed by Nb substitution and Nb/Cr co-substitution in the ZrCoH3 crystal using the first-principles calculations based on the density functional theory. Firstly, the preferred positions of Nb and Nb/Cr substitutions are determined through the minimum total energy. Lattice constants and the density of states are employed to characterize the bonding behavior between atoms. The thermodynamic properties of Zr1-xNbxCo1-yCryH3 are also assessed by the enthalpy of formation and equilibrium hydrogen pressure. It is shown that both the thermodynamic stability and dehydrogenation temperature of ZrCoH3 decrease by increasing the Nb content, which is attributed to the fact that the Zr–H and Co–H binding capabilities are weakened by the presence of Nb. In addition, there are weaker thermal stability, lower dehydrogenation temperature, smaller volume of 8e site, and comparable volume of the hydride after ZrCoH3 is co-substituted by Nb and Cr, thereby promoting the hydrogen release and enhancing the anti-disproportionation performance. Clearly, both Nb doping and Nb/Cr co-doping possess a positive effect on the hydrogen desorption ability of ZrCoH3. More importantly, it is discoverable that compared to other substitution systems, the dehydrogenation temperature is the least for the Zr0.75Nb0.25Co0.875Cr0.125 hydride, highlighting that Nb and Cr co-substitution is more beneficial to improving the dehydrogenation performance of ZrCo-based alloy.

Air exposure improving hydrogen desorption behavior of Mg–Ni-based hydrides

It is well established that H2O and O2 have an inauspicious influence on hydrogen reactivity of hydrogen storage alloys. In this work, an unexpected improvement of the desorption behavior was discovered by just exposing the magnesium rich Mg–Ni hydrides into the air for a certain period. Upon an exposure duration of 4 months, the dehydrogenation peak and onset temperature were sharply lowered by 150 °C and 130 °C. Furthermore, the air-exposed sample could quickly absorb 3.08 wt% H2 and desorb 2.81 wt% H2 within 400 s at 300 °C. Besides the refinement of the powders due to the spontaneous hydrolysis reaction, the in-situ formed magnesium hydroxide layer and Ni are thought to be responsible for the remarkable improvement. This work gives interesting insights that the self-generating surface passivation is not necessarily harmful in the solid-state hydrogen storage area, especially for the cases where active sites of catalysis are present.

Short-Range Nanoreaction Effect on the Hydrogen Desorption Behaviors of the MgH2–Ni@C Composite

Doping a catalyst can efficiently improve the hydrogen reaction kinetics of MgH2. However, the hydrogen desorption behaviors are complicated in different MgH2-catalyst systems. Here, a carbon-encapsulated nickel (Ni@C) core-shell catalyst is synthesized to improve the hydrogen storage properties of MgH2. The complicated hydrogen desorption mechanism of the MgH2-Ni@C composite is elucidated. The experimental and theoretical calculation results indicate a short-range nanoreaction effect on the hydrogen desorption behaviors of the MgH2-Ni@C composite. The Ni@C catalysts and the adjacent MgH2 form nanoreaction sites along with preferential hydrogen desorption. The new interface between the in situ formed Mg and residual MgH2 contributes to the subsequent hydrogen desorption. With the nanoreaction sites increased via adding more catalyst, the short-range nanoreaction effect is more prominent; as a comparison, the interface effect becomes weaker or even disappears. In addition, the core-shell structure catalyst shows ultrahigh structural stability and catalytic activity, even after 50 hydrogen absorption and desorption cycles. Hence, this study provides new insights into the complicated hydrogen desorption behaviors and comes up with the short-range nanoreaction effect in the MgH2-catalyst system.

Investigation of Physical and Mechanical Characteristics of Rubber Materials Exposed to High-Pressure Hydrogen.

Rubber materials play a key role in preventing hydrogen gas leakage in high-pressure hydrogen facilities. Therefore, it is necessary to investigate rubber materials exposed to high-pressure hydrogen to ensure operational safety. In this study, permeation, volume swelling, hydrogen content, and mechanical characteristics of acrylonitrile butadiene rubber (NBR), ethylene propylene diene monomer (EPDM), and fluorocarbon (FKM) samples exposed to pressures of 35 and 70 MPa were investigated. The results showed that the volume recovery and hydrogen desorption behavior of EPDM with the highest permeation were fast whereas those of FKM with the lowest permeation were slow. The volume of NBR with the highest hydrogen content expanded after decompression. In contrast, FKM swelled the most despite having the lowest hydrogen content. After exposure to high-pressure hydrogen, the compression set (CS) slightly increased due to internal cracks, but the tensile strength decreased significantly with increasing pressure despite the absence of cracks in the fracture area of all tensile specimens. It was concluded that the decrease in tensile strength is closely related to the volume increase because of the relationship between the relative true strength and the volume ratio.

Hydrogen absorption due to wear between Ni–Ti superelastic alloys in water

Hydrogen absorption behavior has been investigated during wear between Ni–Ti superelastic alloys in purified water at room temperature by a hydrogen thermal desorption analysis. For the present wear test under a rotation speed of 100 rpm and an applied load of 2.0 N, the amounts of mass and thickness losses of a specimen increase without marked corrosion with increasing wear time. Even after 0.5 h, there is sufficient hydrogen absorption (approximately 12 mass ppm) to be detected. The amount of desorbed hydrogen (absorbed hydrogen) increases with increasing wear time. The hydrogen desorption behavior of wear specimens is not necessarily the same as those of cathodically hydrogen-charged specimens and specimens that absorbed hydrogen in acid solutions, as reported previously. The residual martensite phase and hydride are observed after the wear test. The present results indicate that Ni–Ti superelastic alloy absorbs a substantial amount of hydrogen, which causes hydrogen embrittlement, during wear in water within a short time.

Thermal migration towards constructing W-W dual-sites for boosted alkaline hydrogen evolution reaction

Tungsten carbides, featured by their Pt-like electronic structure, have long been advocated as potential replacements for the benchmark Pt-group catalysts in hydrogen evolution reaction. However, tungsten-carbide catalysts usually exhibit poor alkaline HER performance because of the sluggish hydrogen desorption behavior and possible corrosion problem of tungsten atoms by the produced hydroxyl intermediates. Herein, we report the synthesis of tungsten atomic clusters anchored on P-doped carbon materials via a thermal-migration strategy using tungsten single atoms as the parent material, which is evidenced to have the most favorable Pt-like electronic structure by in-situ variable-temperature near ambient pressure X-ray photoelectron spectroscopy measurements. Accordingly, tungsten atomic clusters show markedly enhanced alkaline HER activity with an ultralow overpotential of 53 mV at 10 mA/cm2 and a Tafel slope as low as 38 mV/dec. These findings may provide a feasible route towards the rational design of atomic-cluster catalysts with high alkaline hydrogen evolution activity.

Optimizing Hydrogen Adsorption by d–d Orbital Modulation for Efficient Hydrogen Evolution Catalysis

AbstractUnraveling the essence of hydrogen adsorption and desorption behaviors can fundamentally guide catalyst design and promote catalytic performance. Herein, the regulation of hydrogen adsorption is systematically investigated by d–d orbital interaction of metallic tungsten dioxide (WO2). Theoretical simulations show that the incorporation of post‐transition metal atoms including Fe, Co, Ni, and Cu can gradually reduce the bond order of W—M sites, consequently weakening the hydrogen adsorption and accelerating the hydrogen evolution reaction (HER) process. Under that theoretical guidance, various 3d metal doped WO2 electrocatalysts are systematically screened for HER catalysis. Among them, the Ni‐WO2/nickel foam exhibits an overpotential of 41 mV (−10 mA cm−2) and Tafel slope down to 47 mV dec−1 representing the best tungsten‐based HER catalysts so far. This work demonstrates that optimizing hydrogen adsorption via d–d orbital modulation is an effective approach to developing efficient and robust catalysts.

Unveiling the promotion of accelerated water dissociation kinetics on the hydrogen evolution catalysis of NiMoO4 nanorods

Nickel molybdate (NiMoO4) attracts superior hydrogen desorption behavior but noticeably poor for efficiently driving the hydrogen evolution reaction (HER) in alkaline media due to the sluggish water dissociation step. Herein, we successfully accelerate the water dissociation kinetics of NiMoO4 for prominent HER catalytic properties via simultaneous in situ interfacial engineering with molybdenum dioxide (MoO2) and doping with phosphorus (P). The as-synthesized P-doped NiMoO4/MoO2 heterostructure nanorods exhibit outstanding HER performance with an extraordinary low overpotential of −23 mV at a current density of 10 mA cm−2, which is highly comparable to the performance of the state-of-art Pt/C coated on nickel foam (NF) catalyst. The density functional theory (DFT) analysis reveals the enhanced performance is attributed to the formation of MoO2 during the in situ epitaxial growth that substantially reduces the energy barrier of the Volmer pathway, and the introduction of P that provides efficient hydrogen desorption of NiMoO4. This present work creates valuable insight into the utilization of interfacial and doping systems for hydrogen evolution catalysis and beyond.

Hydrogen Absorption and Desorption Behavior on Aluminum-Coated Hot-Stamped Boron Steel during Hot Press Forming and Automotive Manufacturing Processes.

Our study mainly focused on diffusible hydrogen in aluminum–silicon-coated hot-stamped boron steel during a hot press forming process and in pre-treatment sequential lines of the automotive manufacturing process using a thermal desorption spectroscopy (TDS) technique. First, in the hot stamping procedure, as the soaking time increased in the heating furnace at a specific dew point when austenitizing, a high concentration of diffusible hydrogen was absorbed into the hot-stamped boron steel. Based on the TDS analysis of hydrogen absorbed from hot stamping, the activation energy value of hydrogen trapping in 1.8 GPa grade steel is lower than that of 1.5 GPa grade steel. This means that diffusible hydrogen can be more easily diffused into defective sites of the microstructure at a higher level of the tensile strength grade. Second, in sequential pre-treatment lines of the automotive manufacturing process, additional hydrogen did not flow into the surface, and an electro-deposition process, including a baking procedure, was effective in removing diffusible hydrogen, which was similar to the residual hydrogen of the as-received state (i.e., initial cold rolled blank). Based on these results, the hydrogen absorption was facilitated during hot press forming, but the hydrogen was sequentially desorbed during automotive sequential lines on aluminum-coated hot-stamped steel parts.

Effects of Cr on microstructure, mechanical properties and hydrogen desorption behaviors of ZrTiNbMoCr high entropy alloys

Phase constitution, mechanical properties and hydrogen desorption behaviors of the as-cast (ZrTiNbMo)100-xCrx (x = 0, 2, 5, 10, 15, 20) high entropy alloys (HEAs) have been investigated. ZrTiNbMo alloy has a body-centered cubic (BCC) single phase structure, and the Cr addition leads to the formation of Laves phase. The HEAs can be strengthened by Cr addition due to more formation of Laves phase and solution strengthening. Zr20Ti20Nb20Mo20Cr20 HEA shows the maximum Vickers hardness of 564 HV and maximum compressive yield strength of 1479 MPa, respectively. In contrary, the ductility can be retained when x = 2, but obviously decreases with further increasing Cr content. Thermal stability and hydrogen desorption capacity of the hydrogenated HEAs decreases with Cr addition, which may be mainly ascribed to the reduction of cell volume and much less stability of hydrogen atoms in solid solution with increasing Cr content.