Hydrogen Reservoir Research Articles

Massive stars formed in atomic hydrogen reservoirs: H I observations of gamma-ray burst host galaxies

Long gamma-ray bursts (GRBs), among the most energetic events in the Universe, are explosions of massive and short-lived stars, so they pinpoint locations of recent star formation. However, several GRB host galaxies have recently been found to be deficient in molecular gas (H2), believed to be the fuel of star formation. Moreover, optical spectroscopy of GRB afterglows implies that the molecular phase constitutes only a small fraction of the gas along the GRB line-of-sight. Here we report the first ever 21 cm line observations of GRB host galaxies, using the Australia Telescope Compact Array, implying high levels of atomic hydrogen (HI), which suggests that the connection between atomic gas and star formation is stronger than previously thought, with star formation being potentially directly fuelled by atomic gas (or with very efficient HI-to-H2 conversion and rapid exhaustion of molecular gas), as has been theoretically shown to be possible. This can happen in low metallicity gas near the onset of star formation, because cooling of gas (necessary for star formation) is faster than the HI-to-H2 conversion. Indeed, large atomic gas reservoirs, together with low molecular gas masses, stellar and dust masses are consistent with GRB hosts being preferentially galaxies which have very recently started a star formation episode after accreting metal-poor gas from the intergalactic medium. This provides a natural route for forming GRBs in low-metallicity environments. The gas inflow scenario is also consistent with the existence of the companion HI object with no optical counterpart ~19 kpc from the GRB 060505 host, and with the fact that the HI centroids of the GRB 980425 and 060505 hosts do not coincide with optical centres of these galaxies, but are located close to the GRB positions.

Effect of flowthrough cooling heat removal on the performances of MOF-5 cryo-adsorptive hydrogen reservoir for bulk storage applications

We numerically investigated the effect of flowthrough cooling heat removal on the storage and thermal performances of a 20 m3 MOF-5 cryo-adsorptive bulk hydrogen reservoir. To validate the models, detailed experimental measurements of flowthrough cooling using a 2.5 L storage tank filled with MOF-5 are used for the first time. As the hydrogen gas is charged into the large reservoir, the temperature of the system raise from 77 to 121 K. When the flowthrough cooling is active for ∼30 h, the average temperature of the adsorbent bed is cooled down to 77 K; this results in a hydrogen storage capacity of 460 kg at tank's maximum pressure of 4 MPa, which is even higher than the storage capacity of a cryo-compressed hydrogen tank equilibrated at 77 K and 4 MPa. Our work establishes that flowthrough cooling is an efficient heat removal approach for bulk hydrogen reservoirs filled with MOF-5.

English

Renewable energy sources play an important role in electrical energy generation. The drawbacks of Renewable energy sources have been overcome by the use of hybrid power generating unit. A typical hybrid renewable energy system (HRES) combines several renewable energy sources such as wind turbine (WT) and photovoltaic (PV) panels as primary energy sources and an energy storage system (ESS) based on fuel cell and battery. All of the energy sources are connected together to a central dc bus by means of power converters. This paper includes a supervisory control called hysteresis switching algorithm which determines the power that must be generated by/stored in the fuel cell and battery, taking into account the control demand by the grid, the offered power, the hydrogen reservoir point and the state-of-charge (SOC) of the battery. The proposed EMS is compared with classical EMS composed of state based supervisory control system based on states and inverter control system based on PI controller. Dynamic simulation results of the proposed EMS demonstrate the better performance than the classical EMS.

Cerium-Oxide-Modified Nickel as a Non-Noble Metal Catalyst for Selective Decomposition of Hydrous Hydrazine to Hydrogen

Hydrous hydrazine is identified as a hydrogen reservoir owing to its high content of hydrogen (8.0 wt %). Its selective decomposition under mild conditions is the key for quick H2 release. Modifying Ni nanoparticles with a small amount of CeO2 (8.0 mol %) resulted in a 3-fold increase of turnover frequency (TOF) and an enhancement of H2 selectivity from 67% to above 99%. This improvement was due to the modification of Ni with CeO2 nearby through strong metal–support interaction (e.g., Ni–O–Ce structure). Furthermore, this promoting effect was extended to other oxides which can form strong metal–support interaction with Ni, such as ZrO2, MgO, and La2O3.

Meteoritic evidence for a previously unrecognized hydrogen reservoir on Mars

Fluvial landforms on Mars suggest that it was once warm enough to maintain persistent liquid water on its surface. The transition to the present cold and dry Mars is closely linked to the history of surface water, yet the evolution of surficial water is poorly constrained. Based on in situ hydrogen isotope (D/H) analyses of quenched and impact glasses in Martian meteorites, we provide evidence for the existence of a distinct but ubiquitous water/ice reservoir (D/H=∼2–3 times Earth's ocean water) that lasted from at least the time when the meteorites crystallized (173–472 million years ago) to the time they were ejected by impacts (0.7–3.3 million years ago), but possibly much longer. The origin of this reservoir appears to predate the current Martian atmospheric water (D/H=∼5–6 times Earth's ocean water) and is unlikely to be a simple mixture of atmospheric and primordial water retained in the Martian mantle (D/H ≈ Earth's ocean water). This reservoir could represent hydrated crust and/or ground ice interbedded within sediments. Our results corroborate the hypothesis that a buried cryosphere accounts for a large part of the initial water budget of Mars.

Early solar system. Early accretion of water in the inner solar system from a carbonaceous chondrite-like source.

Determining the origin of water and the timing of its accretion within the inner solar system is important for understanding the dynamics of planet formation. The timing of water accretion to the inner solar system also has implications for how and when life emerged on Earth. We report in situ measurements of the hydrogen isotopic composition of the mineral apatite in eucrite meteorites, whose parent body is the main-belt asteroid 4 Vesta. These measurements sample one of the oldest hydrogen reservoirs in the solar system and show that Vesta contains the same hydrogen isotopic composition as that of carbonaceous chondrites. Taking into account the old ages of eucrite meteorites and their similarity to Earth's isotopic ratios of hydrogen, carbon, and nitrogen, we demonstrate that these volatiles could have been added early to Earth, rather than gained during a late accretion event.

Dynamic characteristics and mitigations of hydrogen starvations in proton exchange membrane fuel cells during start-ups

Hydrogen starvation during a start-up process in proton exchange membrane (PEM) fuel cells could result in drastic local current density variations, reverse cell voltage and irreversible cell damages. In this work, variations of local current densities and temperatures are measured in situ under both potentiostatic and galvanostatic modes. Experimental results show that when the cell starts up under potentiostatic mode with hydrogen starvation, current density undershoots occur in the downstream; while under the galvanostatic mode, local current density in the downstream almost drops to zero, but the current density near the outlet remains almost constant. The phenomenon of near constant current density near the outlet leads to a novel approach to alleviate hydrogen starvations - a hydrogen reservoir is added at the anode outlet. Experimental results show that the exit hydrogen reservoir can significantly reduce the zero current region and alleviate hydrogen starvations. A non-dimensional current-density variation coefficient is proposed to measure the magnitude of local current density changes during starvations. Experimental results show that the exit hydrogen reservoir can significantly reduce the current-density variations coefficient over the entire flow channel, indicating that adding an exit reservoir is an effective approach in mitigating hydrogen starvations.

Molecular gas content of H i monsters and implications to cold gas content evolution in galaxies

We present 12CO (J=1-0) observations of a sample of local galaxies (0.04<z<0.08) with a large neutral hydrogen reservoir, or "HI monsters". The data were obtained using the Redshift Search Receiver on the FCRAO 14 m telescope. The sample consists of 20 HI-massive galaxies with M(HI)>3e10Msun from the ALFALFA survey and 8 LSBs with a comparable M(HI) (>1.5e10Msun). Our sample selection is purely based on the amount of neutral hydrogen, thereby providing a chance to study how atomic and molecular gas relate to each other in these HI-massive systems. We have detected CO in 15 out of 20 ALFALFA selected galaxies and 4 out of 8 LSBs with molecular gas mass M(H2) of (1-11)e9Msun. Their total cold gas masses of (2-7e10Msun make them some of the most gas-massive galaxies identified to date in the Local Universe. Observed trends associated with HI, H2, and stellar properties of the HI massive galaxies and the field comparison sample are analyzed in the context of theoretical models of galaxy cold gas content and evolution, and the importance of total gas content and improved recipes for handling spatially differentiated behaviors of disk and halo gas are identified as potential areas of improvement for the modeling.

Hydrogen reservoirs, an ab-initio study on saline hydrides based on Li/Be-H compounds

Research into new materials to be used as hydrogen reservoirs is necessary, the increasing demand of energy in the world should be covered progressively by clean energies, trying not to pollute the environment. With this work we wish to contribute to the knowledge of the different saline hydrides and the possibility of using these as hydrogen reservoirs. We performed a systematic study on these materials. In this work we used different ab-initio codes to study several compounds of lithium and beryllium with hydrogen.

Calibration of an elastic recoil setup for D/H-ratios close to natural abundance

Nominally Anhydrous Minerals (NAM) in the Earth’s mantle contain trace amounts of hydrogen, as a result of the NAM’s ability to incorporate hydroxyl ions. The isotopic composition of these hydrogen reservoirs is for the Earth’s crust, well characterized. The knowledge of the isotopic composition of the Earth’s interior on the other hand is limited. It is believed that the hydrogen composition in the interior is isotopically heterogeneous and that there may exist several reservoirs of hydrogen, characterized by different deuterium/hydrogen-ratios. Characterization of these hydrogen reservoirs can provide valuable information about the mass transport of hydrogen during the evolution of the planet.In this work we present a variant of the proton–proton scattering technique with which we are capable of performing simultaneous measurements of deuterium and hydrogen. The method has been tested with a 2.9MeV deuteron beam on a polyethylene standard, with D/H ratio close to the natural abundance, and on a thin sample of Muscovite with a hydrogen concentration of 4800 wt-ppm. This is followed by a discussion about limitations and capabilities of the technique.

Searches for HCl and HF in comets 103P/Hartley 2 and C/2009 P1 (Garradd) with theHerschelSpace Observatory

HCl and HF are expected to be the main reservoirs of fluorine and chlorine wherever hydrogen is predominantly molecular. They are found to be strongly depleted in dense molecular clouds, suggesting freeze-out onto grains in such cold environments. We can then expect that HCl and HF were also the major carriers of Cl and F in the gas and icy phases of the outer solar nebula, and were incorporated into comets. We aimed to measure the HCl and HF abundances in cometary ices as they can provide insights on the halogen chemistry in the early solar nebula. We searched for the J(1-0) lines of HCl and HF at 626 and 1232 GHz, respectively, using the HIFI instrument on board the Herschel Space Observatory. HCl was searched for in comets 103P/Hartley 2 and C/2009 P1 (Garradd), whereas observations of HF were conducted in comet C/2009 P1. In addition, observations of H$_2$O and H$_2^{18}$O lines were performed in C/2009 P1 to measure the H$_2$O production rate. Three lines of CH$_3$OH were serendipitously observed in the HCl receiver setting. HCl is not detected, whereas a marginal (3.6-$\sigma$) detection of HF is obtained. The upper limits for the HCl abundance relative to water are 0.011% and 0.022%, for 103P and C/2009 P1, respectively, showing that HCl is depleted with respect to the solar Cl/O abundance by a factor more than 6$^{+6}_{-3}$ in 103P, where the error is related to the uncertainty in the chlorine solar abundance. The marginal HF detection obtained in C/2009 P1 corresponds to an HF abundance relative to water of (1.8$\pm$0.5) $\times$ 10$^{-4}$, which is approximately consistent with a solar photospheric F/O abundance. The observed depletion of HCl suggests that HCl was not the main reservoir of chlorine in the regions of the solar nebula where these comets formed. HF was possibly the main fluorine compound in the gas phase of the outer solar nebula.

NEBULAR METALLICITIES IN TWO ISOLATED LOCAL VOID DWARF GALAXIES

Isolated dwarf galaxies, especially those situated in voids, may provide insight into primordial conditions in the Universe and the physical processes that govern star formation in undisturbed stellar systems. The metallicity of H ii regions in such galaxies is key to investigating this possibility. From the SIGRID sample of isolated dwarf galaxies, we have identified two exceptionally isolated objects, the Local Void galaxy [KK98]246 (ESO 461-G036) and another somewhat larger dwarf irregular on the edge of the Local Void, MCG-01-41-006 (HIPASS J1609- 04). We report our measurements of the nebular metallicities in these objects. The first object has a single low luminosity Hii region, while the second is in a more vigorous star forming phase with several bright H ii regions. We find that the metallicities in both galaxies are typical for galaxies of this size, and do not indicate the presence of any primordial gas, despite (for [KK98]246) the known surrounding large reservoir of neutral Hydrogen.

Parallel FTIR-ATR and gravimetrical in-situ measurements on sodium alanate powder samples during hydrogen desorption

An experimental set-up has been developed to carry out in-situ measurements on hydrogen storage materials. It has been used to perform FTIR–ATR measurements on sodium alanate samples during hydrogen desorption and, in parallel, to perform gravimetrical measurements on the same sample. The ATR spectra showed the typical broad Al–H vibrational features, changing according to the phase change the material undergoes during the load cycle. It is shown that the absorbance of the material at these bands and the hydrogen content correspond to each other in a reproducible way. This behavior may be used to measure the hydrogen mass released by an alanate hydrogen reservoir by measuring the optical absorbance at defined wavelengths. In this paper the results of these experiments that may give rise to the realization of a level sensor in future hydrogen storage applications are presented.

Relationship Between Metal Dispersion, Hydrogen Desorption, and Activity for Benzene Hydrogenation Over Pd/SiO2 Catalysts

A series of Pd/SiO2 catalysts with Pd loadings from 1–10 wt% were prepared by aqueous hydrazine reduction. They were characterized by XRD, TEM, EDX, H2 chemisorption, and H2-TPD. The catalytic performances were evaluated in benzene hydrogenation in the temperature range 100–250°C. The metal dispersion (mean particle size 6.8–28.4 nm) and hydrogen reservoir increase with decreasing metal content. The catalytic activity of the Pd/SiO2 catalysts was found influenced by the reaction temperature and metal dispersion. The activity increases with metal dispersion. This might be ascribed to the Pd sites, which increase with the increase of the metal dispersion.

Room Temperature Hydrogen Production from Ethanol over CeNiXHZOY Nano‐Oxyhydride Catalysts

AbstractCeNiXHZOY nano‐oxyhydride catalysts were developed for the highly efficient sustainable hydrogen production from ethanol and water in the oxidative steam reforming reaction. After an in situ treatment in hydrogen in the temperature range of 200–300 °C, the cerium–nickel binary mixed oxides became hydrogen reservoirs, which were called oxyhydrides, in the presence of hydrogen species of the hydride nature in the anionic vacancies of mixed oxides. A novel technology was developed for the room temperature hydrogen production by using the chemical energy released from the reaction between CeNiXHZOY nano‐oxyhydride catalysts and oxygen, which completely converted ethanol specifically at 60 °C (oven temperature) and simultaneously produced hydrogen, carbon dioxide, and carbon monoxide along with small amounts of methane and ethanal. CeNiXHZOY nano‐oxyhydride catalysts demonstrated excellent catalytic stability, which was attributed to the graphitic filamentous carbon formed during the reaction. The unique activation phenomenon of the reaction (a huge variation in the temperature between the catalyst bed and the oven) was demonstrated in detail. Finally, the correlations among the catalyst properties, the catalytic performances, and the characterizations were thoroughly discussed.

Temperature dependence of the 2-butene hydrogenation over supported Pd nanoparticles and Pd(1 1 1)

The activity and induction times for 2-butene hydrogenation have been investigated over a Pd(111) single crystal surface and model Pd nanoparticles supported on Fe3O4/Pt(111) by isothermal pulsed molecular beam experiments, in the temperature range of 220–340K. C-modification of supported Pd particles induced persistent hydrogenation activity at low temperatures (220–260K). C-modification of the Pd(111) surface, in contrast, did not result in significant reactivity changes. At low temperatures (220–260K), hydrogenation activity was only maintained over the C-modified Pd particles, while at temperatures (≥280K) persistent hydrogenation was observed over all Pd catalysts at comparable rates. Two principal reaction mechanisms are discussed that could be responsible for the observed hydrogenation activity at different Pd surfaces. We show that on Pd nanoparticles, the reaction mechanism involving subsurface hydrogen species plays an important role under all investigated conditions. This subsurface-related reaction pathway relies on an effective replenishment of the subsurface hydrogen reservoir, which is affected by the presence of strongly adsorbed hydrocarbon species that are formed in the induction period. We discuss the correlation between the induction times and the hydrogenation activity of different Pd surfaces.

1,4-Hydroquinone is a Hydrogen Reservoir for Fuel Cells and Recyclable via Photocatalytic Water Splitting

Photocatalytic splitting of water was carried out in a two-phase system. Nanocrystalline titanium dioxide was used as photocatalyst and potassium hexacyanoferrate(III)/(II) as electron transporter. Generated hydrogen was chemically stored by use of a 1,4-benzoquinone/1,4-hydroquinone system, which was used as a recyclable fuel in a commercialised direct methanol fuel cell (DMFC). The electrical output of the cell was about half compared to methanol. The conversion process for water splitting and recombination in a fuel cell was monitored by UV-Vis spectroscopy and compared to a simulated spectrum. Products of side reactions, which lead to a decrease of the overall efficiency, were identified based on UV-Vis investigations. A proof of principle for the use of quinoide systems as a recyclable hydrogen storage system in a photocatalytic water splitting and fuel cell cyclic process was given.

Ignition and heat radiation of cryogenic hydrogen jets

In the present work release and ignition experiments with horizontal cryogenic hydrogen jets at temperatures of 35–65 K and pressures from 0.7 to 3.5 MPa were performed in the ICESAFE facility at KIT. This facility is specially designed for experiments under steady-state sonic release conditions with constant temperature and pressure in the hydrogen reservoir. In distribution experiments the temperature, velocity, turbulence and concentration distribution of hydrogen with different circular nozzle diameters and reservoir conditions was investigated for releases into stagnant ambient air. Subsequent combustion experiments of hydrogen jets included investigations on the stability of the flame and its propagation behaviour as function of the ignition position. Furthermore combustion pressures and heat radiation from the sonic jet flame during the combustion process were measured. Safety distances were evaluated and an extrapolation model to other jet conditions was proposed. The results of this work provide novel data on cryogenic sonic hydrogen jets and give information on the hazard potential arising from leaks in liquid hydrogen reservoirs.

ChemInform Abstract: Olefin Hydrogenation on Pd Model Supported Catalysts: New Mechanistic Insights

AbstractReview: 39 refs.

First-principles studies of lithium hydride series for hydrogen storage

The application of hydrogen as a clean energy source is based on storage of hydrogen. In metal hydrides is possible, since many metals react readily with hydrogen forming a stable metal hydride. Thus, saline hydrides such as lithium hydride have appeared as new alternatives to this, because of their high reactivity and reversibility. The first principles calculations based on density functional theory (DFT) have been used to study the physical properties of several Li–H compounds. The crystal structure, electronic properties and internal optimization parameters are treated by the LAPW method implemented in the WIEN2k code. In the present study we show the comparison of three different phases of lithium hydride compounds, in six different crystal structures, with the purpose of comparing the formation energies in all cases, and determine which is the structure, with the best structural properties for applications as hydrogen reservoir. The comparisons between the results obtained in the structures of lithium–hydride are discussed in this work.