H2 Absorption Research Articles

Physical conditions in the diffuse interstellar medium of local and high-redshift galaxies: measurements based on the excitation of H2 rotational and C i fine-structure levels

ABSTRACT We present the results of an analysis of the physical conditions (number density, intensity of UV field, kinetic temperature) in the cold H2-bearing interstellar medium of local and high-redshift galaxies. Our measurements are based on the fit to the observed population of H2 rotational levels and C i fine-structure levels with the help of grids of numerical models calculated with the photon-dominated region (PDR) Meudon code. A joint analysis of low H2 rotational levels and C i fine-structure levels breaks the degeneracy in the IUV−nH plane and provides significantly tighter constraints on the number density and intensity of the UV field. Using archive data from the VLT/UVES, KECK/HIRES, HST/STIS and FUSE telescopes, we selected 12 high-redshift damped Lyα systems (DLAs) in quasar spectra and 14 H2 absorption systems along the lines of sight towards stars in the Milky Way and the Magellanic Cloud galaxies. These systems have strong H2 components, with a column density log N(H2)/[cm−2] > 18 and associated C i absorptions. We find that H2-bearing media in high-redshift DLAs and in local galaxies have similar values of the kinetic temperatures Tkin ∼ 100 K and number density 10−500 cm−3. However, the intensity of incident UV radiation in DLAs varies in a wide range (0.1−100 units of the Mathis field), while it is ∼0.1−3 units of the Mathis field for H2 systems in the Milky Way and Large and Small Magellanic Cloud galaxies. The large dispersion of measured UV flux in DLAs is probably a consequence of the fact that the DLA sample probes galaxies selected from the overall galaxy population at high redshift, and therefore corresponds to a wide range of physical conditions.

A Novel Hydrogen Sensor Based on a Guided-Mode Resonance Filter

In this study, we demonstrated a hydrogen (H2) sensor based on a guided-mode resonance (GMR) filter coated with a layer of palladium (Pd). The sensor consists of three key layers, namely the substrate (replicated grating structure on an optical adhesive), waveguiding layer of TiO2, and active-sensing layer of Pd. The sensor functions as an optical resonator. On absorption of H2, the change of the refractive index in Pd changes the optical response of the sensor. To monitor the output optical response, a transmission setup was used, and two detection modalities—the change in transmission efficiency at a specific wavelength and the shift in the resonant wavelength—were demonstrated. Upon injection of a mixture of 4% H2 and 96% argon, the resonant wavelength shifted 6.38 nm, and transmission efficiency increased by 45% in 24 s.

Induction Heating in Nanoparticle Impregnated Zeolite.

The ultra-stable Y (H-USY) zeolite is used as catalyst for the conversion of plastic feedstocks into high added value products through catalytic cracking technologies. However, the energy requirements associated with these processes are still high. On the other hand, induction heating by magnetic nanoparticles has been exploited for different applications such as cancer treatment by magnetic hyperthermia, improving of water electrolysis and many other heterogeneous catalytic processes. In this work, the heating efficiency of γ-Fe2O3 nanoparticle impregnated zeolites is investigated in order to determine the potential application of this system in catalytic reactions promoted by acid catalyst centers under inductive heating. The γ-Fe2O3 nanoparticle impregnated zeolite has been investigated by X-ray diffraction, electron microscopy, ammonia temperature program desorption (NH3-TPD), H2 absorption, thermogravimetry and dc and ac-magnetometry. It is observed that the diffusion of the magnetic nanoparticles in the pores of the zeolite is possible due to a combined micro and mesoporous structure and, even when fixed in a solid matrix, they are capable of releasing heat as efficiently as in a colloidal suspension. This opens up the possibility of exploring the application at higher temperatures.

Estimation of the Absorption Cross Section of the Forbidden Vibrational Band of Hydrogen in Nanoporous Aerogel

Measurement results of the concentration of H2 molecules into aerogel (SiO2) nanopores with diameter 20 nm are presented. The standard gasometric method is used. The experimental data on H2 molecule concentration together with the data on integral intensity of collision-induced H2 absorption 0–1 band are used for estimation of the absorption cross section at the band maximum.

Spin‐Torque Manipulation for Hydrogen Sensing

AbstractExternal manipulation of spin‐orbit torques (SOTs) promises not only energy‐efficient spin‐orbitronic devices but also versatile applications of spin‐based technologies in diverse fields. However, the external electric‐field control, widely used in semiconductor spintronics, is known to be ineffective in conventional metallic spin‐orbitronic devices due to the very short screening length. Here, an alternative approach to control the SOTs by using gases is shown. It is demonstrated that the spin‐torque generation efficiency of a Pd/Ni81Fe19 bilayer can be reversibly manipulated by the absorption and desorption of H2 gas, which appears concomitantly with the change of the electrical resistance. It is found that compared with the change of the Pd resistance induced by the H2 absorption, the change of the spin‐torque generation efficiency is almost an order of magnitude larger. This result provides a new method to externally manipulate the SOTs and paves a way for developing more sensitive hydrogen sensors based on the spin‐orbitronic technology.

Ag(I)-Hived Fullerene Microcube as an Enhanced Catalytic Substrate for the Reduction of 4-Nitrophenol and the Photodegradation of Orange G Dye.

We report a facile approach to fabricate an Ag-embedded fullerene (C60) catalyst by the chemical reduction of the AgNO3 complex encapsulated fullerene microcrystal, which showed an enhanced catalytic reduction of 4-nitrophenol because of the strong absorption and propagation of H2 along the fullerene surface. With the aid of visible-light radiation, photodegradation of orange G dye is achieved through the formation of an electron donor-acceptor dyad between plasmon Ag nanostructures and fullerene molecules, which effectively offsets the "electron-hole" recombination. Neither Ag nanoparticle nor fullerene crystal used in isolation could perform this chemical conversion, implying that the metal-fullerene hybrid structure is imperative for performing the catalytic reaction. The obtained Ag-embedded fullerene crystal is characterized by scanning electron microscopy (SEM), associated energy-dispersive X-ray spectroscopy (EDX) imaging, and X-ray photoelectron spectroscopy (XPS) and demonstrates that the present hybrid materials would add a supplemental member to a family of photocatalysts toward the organic synthesis and wastewater remediation.

Observational estimate of the partial covering probability of quasar emission regions by distant H2 absorption clouds

ABSTRACT We have searched high spectral resolution spectra of quasars known to exhibit high redshift (z > 1.7) intervening H2-bearing damped Lyman-α (DLA) systems for partial coverage of the quasar emission by intervening H2 clouds. Partial coverage manifests itself by the presence of non-zero residual flux in the core of saturated H2 absorption lines. The residual flux can be observed either only at the bottom of absorption lines redshifted on top of quasar emission lines, in which case part of the broad line region (BLR) is not covered, or in all absorption lines, in case some continuum source is not covered. Among 35 H2 absorption clouds in 14 quasar spectra obtained with the VLT-UVES or Keck-HIRES spectrographs, we detect partial coverage of the BLR for 13 clouds. This result suggests that the probability of partial coverage of the QSO BLR by a distant H2 absorption cloud is about 40 per cent. For four systems towards Q 0013−0029, Q 0405−4418, Q 0812+3208, and J 2100−0641, partial coverage is detected for the first time. We determine the theoretical probability of partial coverage of the BLR by a distant H2 cloud as a function of the ratio between the cloud and the BLR sizes. Using this model, we obtain an estimate of the characteristic BLR radius of $50^{+19}_{-23}\,\rm{light \,days}$. This is similar to the estimate of the BLR size obtained by reverberation-mapping analysis $({\sim}100\,\rm{light\, days})$.

H2+阿秒瞬态吸收中的量子路径干涉

H2+阿秒瞬态吸收中的量子路径干涉

Hydrogen Sensor Based on Tunable Diode Laser Absorption Spectroscopy.

A laser-based hydrogen (H2) sensor using wavelength modulation spectroscopy (WMS) was developed for the contactless measurement of molecular hydrogen. The sensor uses a distributed feedback (DFB) laser to target the H2 quadrupole absorption line at 2121.8 nm. The H2 absorption line exhibited weak collisional broadening and strong collisional narrowing effects. Both effects were investigated by comparing measurements of the absorption linewidth with detailed models using different line profiles including collisional narrowing effects. The collisional broadening and narrowing parameters were determined for pure hydrogen as well as for hydrogen in nitrogen and air. The performance of the sensor was evaluated and the sensor applicability for H2 measurement in a range of 0–10 %v of H2 was demonstrated. A precision of 0.02 %v was achieved with 1 m of absorption pathlength (0.02 %v∙m) and 1 s of integration time. For the optimum averaging time of 20 s, precision of 0.005 %v∙m was achieved. A good linear relationship between H2 concentration and sensor response was observed. A simple and robust transmitter–receiver configuration of the sensor allows in situ installation in harsh industrial environments.

In-situ synthesis of Mg2Ni-Ce6O11 catalyst for improvement of hydrogen storage in magnesium

To decrease the hydrogen sorption temperature and increase the hydrogen sorption rate is important for the practical application of magnesium for hydrogen storage. The binary nano-catalysts Mg2Ni and Ce6O11 with oxygen vacancy defects was in-situ synthesized on Mg surface via the hydrogen activation of Mg-Ni-CeO2. The hydrogen storage material Mg-20Ni-CeO2 can release 4.19 wt% H2 in 5 min at 320 °C, which is significantly higher than that of Mg with 10 wt% Ni (3.44 wt% H2) or 10 wt% CeO2 (0.34 wt% H2). The peak temperature and apparent activation energy for hydrogen desorption of Mg-20Ni-CeO2 are reduced by 115.8 °C and 63.89 kJ/mol respectively comparing with that without catalyst. Structural analysis suggests that Mg2Ni and Ce6O11 can be in-situ synthesized on Mg surface, which shows a synergistic catalysis for hydrogen storage. During H2 absorption, the oxygen vacancy defects on Ce6O11 surface can trap H2 molecules, while the Mg2Ni on Mg/Mg2Ni interface can promote H2 dissociation. For H2 desorption, the Mg2Ni can weaken the Mg-H bond and act as “hydrogen pump” to transfer H for H2 formation with the assistance of Ce3+/Ce4+ transformation in Ce6O11. The results of this study provide a new horizon for a novel binary catalyst design for hydrogen storage.

Barium-Promoted Ruthenium Catalysts on Yittria-Stabilized Zirconia Supports for Ammonia Synthesis

The cost-effective, small-scale, distributed synthesis of ammonia depends on effective catalysts and processes that operate under modest elevated pressure (i.e., p < 20 bar) conditions. The present paper considers Ru as the active catalyst supported on yittria-stabilized zirconia (YSZ). The addition of alkali and alkaline-earth metal promoters is found to increase synthesis rates by an order of magnitude. The rate enhancement is largely insensitive to the promoter concentration, with Cs outperforming Ba and K by a factor of 2. However, Ba is found to be stable whereas Cs degrades more rapidly, which is attributed to the low melting point of its oxide. At 400 °C and 1.0 MPa, the specific synthesis rate over Ba–Ru is measured to be approximately 1410 mmol gRu–1 h–1, higher than the most active oxide-supported Ru catalysts reported in the literature. The rate becomes inhibited by H2 absorption at low temperature (below 350 °C), but lower H2/N2 ratios enable the rate to remain comparable to what is observed i...

Effects of graphite addition and air exposure on ball-milled Mg–Al alloys for hydrogen storage

Magnesium hydride (MgH2) is a promising candidate as a hydrogen storage material. However, its hydrogenation kinetics and thermodynamic stability still have room for improvement. Alloying Mg with Al has been shown to reduce the heat of hydrogenation and improve air resistance, whereas graphite helps accelerating hydrogenation kinetics in pure Mg. In this study, the effects of simultaneous Al alloying and graphite addition on the kinetics and air-exposure resistance were investigated on the Mg60Al40 system. The alloys were pulverized through high-energy ball milling (hereinafter HEBM). We tested different conditions of milling energy, added graphite contents, and air exposure times. Structural characterization was conducted via X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). H2 absorption and desorption properties were obtained through volumetry in a Sieverts-type apparatus and Differential Scanning Calorimetry (DSC). The desorption activation energies were calculated using DSC curves through Kissinger analysis. Mg60Al40 with 10 wt% graphite addition showed fast activation kinetics, even after 2 years of air exposure. Graphite addition provided a catalytic effect on ball-milled Mg–Al alloys by improving both absorption and desorption kinetics and lowering the activation energy for desorption from 189 kJ/mol to 134 kJ/mol. The fast kinetics, reduced heat of reaction, and improved air resistance of these materials make them interesting candidates for potential application in hydride-based hydrogen storage tanks.

Theoretical investigation on interactions of H2 absorption to CuXe cations I and II

Geometries, stabilities and interactions of H2-absorption to CuXe cations at CCSD(T) theoretical level were investigated. T-shaped stable structures of H2-absorption to Cu or Xe atoms with different dissociation energies were found for CuXe+. Analysis of electron density functions, delocalization index and AIM theory suggest the partial covalent character and vdW character for three-atom Cu⋯H2 and Xe⋯H2 interactions. For CuXe2+, investigations show the break of H–H bonding upon H2-absorption and it could be considered as H2XeCu2+. All the interactions were visualized by independent gradient model analysis.

Proximate molecular quasar absorbers

We present results from a search for strong H2 absorption systems proximate to quasars (zabs ≈ zem) in the Sloan Digital Sky Survey (SDSS) Data Release 14. The search is based on the Lyman-Werner band signature of damped H2 absorption lines without any prior on the associated metal or neutral hydrogen content. This has resulted in the detection of 81 systems with N(H2) ∼ 1019 − 1020 cm−2 located within a few thousand km s−1 from the quasar. Compared to a control sample of intervening systems, this implies an excess of proximate H2 systems by about a factor of 4 to 5. The incidence of H2 systems increases steeply with decreasing relative velocity, reaching an order of magnitude higher than expected from intervening statistics at Δv &lt; 1000 km s−1. The most striking feature of the proximate systems compared to the intervening ones is the presence of Ly − α emission in the core of the associated damped H I absorption line in about half of the sample. This puts constraints on the relative projected sizes of the absorbing clouds to those of the quasar line emitting regions. Using the SDSS spectra, we estimate the H I, metal and dust content of the systems, which are found to have typical metallicities of one tenth Solar, albeit with a large spread among individual systems. We observe trends between the fraction of leaking Ly − α emission and the relative absorber-quasar velocity as well as with the excitation of several metal species, similar to what has been seen in metal-selected proximate DLAs. With the help of theoretical H I-H2 transition relations, we show that the presence of H2 helps to break the degeneracy between density and strength of the UV field as main sources of excitation and hence provides unique constraints on the possible origin and location of the absorbing clouds. We suggest that most of these systems originate from galaxies in the quasar group, although a small fraction of them could be located in the quasar host as well. We conclude that follow-up observations are still required to investigate the chemical and physical conditions in individual clouds and to assess the importance of AGN feedback for the formation and survival of H2 clouds.

Hydrogen isotope effect in a Ni32Nb28Zr30Cu10 amorphous membrane

The pressure-composition isotherms and the absorption kinetics of both hydrogen and deuterium were investigated for an amorphous membrane, potentially useful for hydrogen purification and separation in membrane reactors, with atomic composition Ni32Nb28Zr30Cu10. In the temperature range between 294 and 394 °C, the equilibrium pressure between the gas and the solid was higher for deuterium than for hydrogen, with a typical ratio P(D2)/P(H2)≈1.5. Moreover, the absorption of H2 is faster than that of D2. Both behaviors of the presently investigated amorphous membrane closely resemble those of the Pd–Ag alloys, that are currently used in membrane reactors and separators.

High-Sensitivity Fiber-Optic Sensor for Hydrogen Detection in Gas and Transformer Oil

This paper reports on the characterization of a palladium (Pd)-based fiber-optic hydrogen (H2) sensor for health monitoring of distribution and power transformers in the electrical grid. The sensor consists of a Pd foil, which expands due to H2 absorption, and a fiber Bragg grating that measures this expansion. Fifteen sensors were manufactured and characterized in gas and oil environments at various H2 concentrations and temperatures. In gas, the sensors were evaluated at 60 °C, 75 °C, 90 °C, 105 °C, and 120 °C and H2 concentrations from 0.01% to 5%. In oil, the same sensors were evaluated at 90 °C and dissolved H2 concentrations from 5 to 2700 ppm. Furthermore, the influence of carbon monoxide (CO), which is often present in transformers and can impact H2 response of the sensor, was investigated. At 90 °C in gas, the response to 0.01% and 5% H2 was on average 28 and 719 pm, respectively. At 90 °C in oil, the response to 5 and 2700 ppm dissolved H2 was on average 11 and 763 pm, respectively. The average, relative accuracy is better than 20% over the whole measurement range in gas and for measurements above 100 ppm in oil. These specifications make the sensor a promising candidate for online monitoring of H2 in transformers.

Experimental studies on industrial scale metal hydride based hydrogen storage system with embedded cooling tubes

Abstract The present article reports the activation and testing of large scale metal hydride based hydrogen storage system (MHHSS) for industrial application. The metal hydride reactor is fabricated using SS316 material with 99 embedded cooling tube and filled with 40 kg of LaNi4.7Al0.3. The activation was carried out by successive absorption and desorption processes. In the third absorption cycle, MHHSS had absorbed 552.356 g of hydrogen to reach a maximum storage capacity of 1.4 wt% at 40 bar pressure and 30 °C temperature. The testing of MHHSS was carried out by varying H2 supply pressure, absorption and desorption temperatures and heat transfer fluid (HTF) flow rate. It was observed that the supply pressure has significant effect on absorption rate, and the optimum supply pressure was observed in the range of 10–15 bar. Similarly, during the desorption cycle, optimum desorption temperature was found in the range of 80–90 °C. The optimum flow velocity for HTF was observed in the range of 20–30 lpm.

Kinetic improvement of H2 absorption and desorption properties in Mg/MgH2 by using niobium ethoxide as additive

The hydrogen absorption and desorption properties of a MgH2 – 1 mol.% Nb(V) ethoxide mixture are reported. The material was prepared by hand mixing the additive with previously ball-milled MgH2. Nb ethoxide reacts with MgH2 during heating, releasing C2H6 and H2, and producing MgO and Nb or Nb hydride. Hydriding and dehydriding are greatly enhanced by the use of the alkoxide. At 250 °C the material with Nb takes up 1.8 wt% in 30 s compared with 0.1 wt% of pure Mg, and releases 4.2 wt% in 30 min, whereas MgH2 without Nb does not appreciably desorb hydrogen. The absorption and desorption activation energies are reduced from 153 kJ/mol H2 to 94 kJ/mol H2, and from 176 kJ/mol H2 to 75 kJ/mol H2, respectively. The hydrogen sorption properties remain stable after 10 cycles at 300 °C. The kinetic improvement is attributed to the fine distribution of amorphous/nanometric NbHx achieved by the dispersion of the liquid additive.

Implications of Revised CO2–CH4 and CO2–H2 Absorption for Outer Edge Habitable Zone Planets

Implications of Revised CO₂–CH₄ and CO₂–H₂ Absorption for Outer Edge Habitable Zone Planets

Nanostructured hydrogen storage materials prepared by high-energy reactive ball milling of magnesium and ferrovanadium

Hydrogen storage nanocomposites prepared by high energy reactive ball milling of magnesium and vanadium alloys in hydrogen (HRBM) are characterised by exceptionally fast hydrogenation rates and a significantly decreased hydride decomposition temperature. Replacement of vanadium in these materials with vanadium-rich Ferrovanadium (FeV, V80Fe20) is very cost efficient and is suggested as a durable way towards large scale applications of Mg-based hydrogen storage materials. The current work presents the results of the experimental study of Mg–(FeV) hydrogen storage nanocomposites prepared by HRBM of Mg powder and FeV (0–50 mol.%). The additives of FeV were shown to improve hydrogen sorption performance of Mg including facilitation of the hydrogenation during the HRBM and improvements of the dehydrogenation/re-hydrogenation kinetics. The improvements resemble the behaviour of pure vanadium metal, and the Mg–(FeV) nanocomposites exhibited a good stability of the hydrogen sorption performance during hydrogen absorption – desorption cycling at T = 350 °C caused by a stability of the cycling performance of the nanostructured FeV acting as a catalyst. Further improvement of the cycle stability including the increase of the reversible hydrogen storage capacity and acceleration of H2 absorption kinetics during the cycling was observed for the composites containing carbon additives (activated carbon, graphite or multi-walled carbon nanotubes; 5 wt%), with the best performance achieved for activated carbon.