Hydrogen storage potential in MIL-101 at 200 K

Hydrogen adsorption isotherms for MIL-101 metal-organic framework are reported within a wide pressure range for temperatures between 77 and 295 K. Data modeling with the modified Dubinin-Astakhov equation shows a good fitting with the experimental results. The calculated absolute adsorption allowed the evaluation of the total hydrogen storage capacity for high pressure storage tank filled with MIL-101 as sorbent. The results show that the gravimetric and volumetric storage capacities at 198 K and 70 MPa are within the present-day accepted DOE targets, even if the storage capacity is slightly decreased by 3–6% as compared to the tank without sorbent. Moreover, the calculations reveal that the dormancy time is much increased, as compared to a tank without sorbent, exceeding the ultimate DOE target of 14 days. The MIL-101 assisted cold high-pressure hydrogen storage at ∼200 K and 70 MPa, brings about an additional advantage and seems promising for both mobile and stationary applications.     

Hydrothermal conversion of water lettuce biomass at 473 or 523 K

The high moisture content of an aquatic biomass was used advantageously in a hydrothermal process. Reducing sugars, amino acids, proteins, and crude oil were extracted from water lettuce (Pistia stratiotes L.) using subcritically heated water. The highest yields of reducing sugars and amino acids were obtained after treatment at 473 K for 30 min (23.70 ± 0.52 g kg⁻¹ and 4.35 ± 0.09 g kg⁻¹ dry mass respectively), while protein was obtained at 3.60 ± 0.04 g kg⁻¹ feedstock after treatment at 523 K for 60 min. The greatest solubilization occurred at 523 K after 60 min. The solid residues could be applied as fertilizers as hemicellulose and cellulose were hydrothermally converted to humus. The crude oil components that were extracted from the liquid residues differed markedly between the two treatment temperatures. The conversion of furan compounds to cyclopentenone and its derivatives only occurred at the higher reaction temperature and was increased by a longer reaction time.     

Superior hydrogen storage properties of Mg95Ni5 + 10 wt.% nanosized Zr0.7Ti0.3Mn2 + 3 wt.% MWCNT prepared by hydriding combustion synthesis followed by mechanical milling (HCS + MM)

Significant improvement of the hydrogen storage property of the magnesium-based materials was achieved by the process of hydriding combustion synthesis (HCS) followed by mechanical milling (MM) and the addition of nanosized Zr_0.7Ti_0.3Mn₂ and MWCNT. Mg₉₅Ni₅ doped by 10 wt.% nanosized Zr_0.7Ti_0.3Mn₂ and 3 wt.% MWCNT prepared by the process of HCS + MM absorbed 6.07 wt.% hydrogen within 100 s at 373 K in the first hydriding cycle and desorbed 95.1% hydrogen within 1800 s at 523 K. The high hydriding rate remained well and the hydrogen capacity reached 5.58 wt.% within 100 s at 423 K in the 10th cycle. The dehydrogenation activation energy of this system was 83.7 kJ/mol, which was much lower than that of as-received MgH₂. A possible hydrogenation–dehydrogenation mechanism was proposed in terms of the structural features derived from the HCS + MM process and the synergistic catalytic effects of nanosized Zr_0.7Ti_0.3Mn₂ and MWCNT.     

Ammonia borane at low temperature down to 90 K and high pressure up to 15 GPa

We have studied the phase transformation behavior of the potential hydrogen storage compound ammonia borane at low temperature (from room temperature down to 90 K) and high pressure (from ambient pressure to 9.5 GPa at room temperature and up to 15 GPa at 90 K) region using the diamond anvil cell. This material shows four new phase transitions in this pressure and temperature region. The phase transition phenomenon is evidenced by the splitting of the peak and/or the appearance of the new peak in the Raman spectra as well as by the change of the pressure coefficient of the Raman modes. The phase boundaries between these phases are also established from the data collected during different cooling cycles. These results provide the information about the stability of the bonding characteristics of this potential hydrogen storage material at low temperature and high pressure region.     

Hydrogen permeation in asymmetric La28 − xW4 + xO54 + 3x/2 membranes

Asymmetric supported La_28 − xW_4 + xO_54 + 3x/2 (La/W ≈ 5.6) membranes were investigated for their hydrogen permeation properties as a function of temperature and feed gas conditions. Dense membranes of thickness 25–30 μm supported on substrates with 25 and 40 vol.% porosity were compared. Above 850 °C under dry conditions, the hydrogen permeation rate was approximately constant as a function of temperature due to low concentration of protons in the material at high temperatures. Under humid conditions and above 960 °C enhanced permeation rates were observed. A hydrogen permeation as high as 0.14 NmL min⁻¹ cm⁻² was recorded at 1000 °C with 10 vol.% H₂ (2.5 vol.% H₂O) as feed gas.     

Study of the multipeak deuterium thermodesorption in YFe2Dx (1.3 ≤ x ≤ 4.2) by DSC,TD and in situ neutron diffraction

The deuterium thermal desorption of various YFe₂D_x (x = 1.3, 2.5, 3.5, 4.2) compounds has been studied using differential scanning calorimetry (DSC) and thermal desorption (TD) experiments. These studies show that the number of desorption peaks increases with the deuterium content. In order to understand the origin of this multipeak behaviour, in situ neutron diffraction experiments during thermal desorption have been performed from 290 K to 680 K on YFe₂D_4.2. Upon heating, a multipeak TD spectrum is observed. It relates to the existence of several YFe₂D_x phases with different stabilities. The rate limiting step of this thermal desorption has been therefore attributed to several successive phase transformations rather than to different types of interstitial sites as proposed in previous TD models reported for C15-Laves phase compounds.     

Characterization of La2−xSrxCoTiO6 (0.6 ≤ x ≤ 1.0) series as new cathodes of solid oxide fuel cells

La_2−xSr_xCoTiO₆ (0.6 ≤ x ≤ 1.0) compound series is prepared by Sr-substitution in the A-site of the perovskite by a modified Pechini procedure under air. Charge compensation as Sr²⁺ content increase occurs by Co²⁺ oxidation to Co³⁺. Reduced samples are obtained by further treatment under 5%H₂/Ar and characterized by Neutron Powder Diffraction. Upon redution, Co³⁺ to Co²⁺ reduction and oxygen vacancies creation are detected. Dependence of total conductivity with temperature and pO₂ exhibits a typical p-type semiconducting behaviour. Results show that the higher the Sr content, the higher holes (Co³⁺) concentration and consequently, La_2−xSr_xCoTiO₆ (x = 1.0) shows the highest conductivity (13.23 S/cm at 1073 K in air). The negligible reactivity with YSZ, used as the electrolyte, of symmetrical cells under oxidant conditions and the moderate thermal expansion found by XRD point to their possible use as SOFC cathodes. Thus, La_1.2Sr_0.8CoTiO₆-based cathodes display polarization resistance of 0.9 Ω cm² at 1073 K in oxygen, only slightly above than the current state-of-the-art.     

Minimum ignition energy of hydrogen-air and methane-air mixtures at temperatures as low as 200 K

The primary objective of this study is to measure the minimum ignition energy (MIE) of methane-air and hydrogen-air mixtures at low temperatures and atmospheric pressure. Initial fuel-air mixture temperatures as low as 200 K were considered, for a constant equivalence ratio of 1.0 for methane-air and 0.16 for hydrogen-air. The ignition source was a spark, generated by a high-voltage pulse of 100 μs duration, applied on two pin electrodes of 0.1-mm diameter, separated by a gap distance of 1 mm. The experimental methodology was validated by comparing the results obtained with those from previous studies available in the literature. First, for methane-air mixtures, the MIE as a function of the equivalence ratio followed the same trend at 295 K and 255 K, i.e., its lowest value was obtained for a stoichiometric mixture. Second, when the temperature of the mixture was decreased, the MIE increased linearly for both fuels. The rate at which the MIE changed was higher for hydrogen-air (?7.9 μJ/K) than for methane-air (?3.4 μJ/K). Overall, this study provides valuable information on the MIE of methane-air and hydrogen-air mixtures at low temperatures, which can be useful for the design of cryogenic fuel storage systems.     

Room-temperature compressive properties of TC21 alloy processed by thermohydrogen treatment at 1123 K

The influence of hydrogen level on compressive properties of TC21 alloy processed by thermohydrogen treatment (THT) at 1123 K was studied through room-temperature compression experiments. The microstructures of TC21 alloy processed by THT at 1123 K were investigated by OM, XRD, and TEM. Results showed that hydrogen level affected apparently the microstructures and compressive properties of TC21 alloy processed by THT at 1123 K. With increasing level of hydrogen, the yield strength of TC21 alloy decreased to a minimum initially and then increased; the deformation limit of TC21 alloy decreased slightly to a minimum first, then increased to a maximum, and ultimately decreased. At a hydrogen level of 0.78 wt%, the deformation limit of TC21 alloy was the highest among all THT-processed TC21 alloys and showed an increase of 244.33% compared with the original TC21 alloy.     

Desorption properties of MgH2 composite with a composition of 40MgH2 + 37LiBH4 + 18MgF2 + 5Ti isopropoxide

In order to increase the hydrogen storage capacity of Mg-based materials, a mixture with a composition of 2LiBH₄ + MgF₂ and LiBH₄, which has a hydrogen storage capacity of 18.4 wt%, were added to MgH₂. Ti isopropoxide was also added to MgH₂ as a catalyst. A MgH₂ composite with a composition of 40 wt%MgH₂ + 25 wt%LiBH₄ + 30 wt% (2LiBH₄ + MgF₂) + 5 wt%Ti isopropoxide (corresponding to 40 wt%MgH₂ + 37 wt%LiBH₄ + 18 wt%MgF₂ + 5 wt%Ti isopropoxide) was prepared by reactive mechanical grinding. The hydrogen storage properties of the sample were then examined. Hydrogen content vs. desorption time curves for consecutive 1st desorptions of 40 wt%MgH₂ + 37 wt%LiBH₄ + 18 wt%MgF₂ + 5 wt%Ti isopropoxide from room temperature to 823 K showed that the total desorbed hydrogen quantity for consecutive 1st desorptions was 8.30 wt%.     

Speed of sound for three binary (CH4 + H2) mixtures from p = (0.5 up to 20) MPa at T = (273.16 to 375) K

Speed of sound is one of the thermodynamic properties that can be measured with least uncertainty and is of great interest in developing equations of state. Moreover, accurate models are needed by the H₂ industry to design the transport and storage stages of hydrogen blends in the natural gas network. This research aims to provide accurate data for (CH₄ + H₂) mixtures of nominal (5, 10, and 50) mol-% of hydrogen, in the p = (0.5 up to 20) MPa pressure range and with temperatures T = (273.16, 300, 325, 350, and 375) K. Using an acoustic spherical resonator, speed of sound was determined with an overall relative expanded (k = 2) uncertainty of 220 parts in 10⁶ (0.022%). Data were compared to reference equations of state for natural gas-like mixtures, such as AGA8-DC92 and GERG-2008. Average absolute deviations below 0.095% and percentage deviations between 0.029% and up to 0.30%, respectively, were obtained. Additionally, results were fitted to the acoustic virial equation of state and adiabatic coefficients, molar isochoric heat capacities and molar isobaric heat capacities as perfect-gas, together with second and third acoustic virial coefficients were estimated. Density second virial coefficients were also obtained.     

A 70 MPa hydrogen-compression system using metal hydrides

The objective of this work was to develop a 70 MPa hydride-based hydrogen compression system. Two-stage compression was adopted with AB₂ type alloys as the compression alloys. Ti_0.95Zr_0.05Cr_0.8Mn_0.8V_0.2Ni_0.2 and Ti_0.8Zr_0.2Cr_0.95Fe_0.95V_0.1 alloys were developed for the compression system. With these two alloys, a 70 MPa two-stage hydride-based hydrogen compression system was designed and built with hot oil as the heat source, and composite materials formed by mixing hydrogen storage alloys with Al fiber were used to prevent hydride bed compaction and to prevent strain accumulation. The experimental results showed that Ti_0.95Zr_0.05Cr_0.8Mn_0.8V_0.2Ni_0.2 and Ti_0.8Zr_0.2Cr_0.95Fe_0.95V_0.1 alloys could well meet the requirements of compression system. Composite materials formed by mixing hydrogen storage alloys with Al fiber were an effective way to prevent strain accumulation for hydride compression. With cold oil (298 K) and hot oil (423 K) as the cooling and heating sources, the built compression system could convert hydrogen pressure from around 4.0 MPa to over 70 MPa.     

Reversible hydrogen storage in vapour deposited Mg-5 at.% Pd powder composites

Mg-5 at.% Pd powder composites derived from multilayered films of Mg and Pd deposited in Pd/Mg/Pd/Mg/Pd layer configuration by thermal evaporation reversibly store about 3.5 wt.% hydrogen up to 15 cycles under mild conditions of pressure and temperature. Hydrogenation takes place at 0.15 MPa hydrogen pressure while dehydrogenation occurs in a dynamic rotary vacuum. Each process is completed in about three hours. The temperature of a dehydrogenation or hydrogenation step is about 5–10 K higher than the preceding hydrogenation or dehydrogenation step. The hydrogenation temperature of the first cycle is 343 K whereas the dehydrogenation temperature of the 15th cycle is 423 K. The hydrogen storage capacity of composite is the manifestation of fine-grained microstructure of Mg and the catalytic properties of Pd. It declines beyond 423 K due to the exhaustion of metallic Pd as a result of the formation of Mg–Pd intermetallic compounds. This approach presents a simple and rapid method of preparing Mg–Pd composites for hydrogen storage applications.     

Kinetics of deuterium permeation through Zircaloy-4 in the 623–773 K temperature range

Under normal operating conditions in nuclear pressurized water reactors, tritium produced by ternary fission occurring within the uranium fuel may cross the whole cladding in zirconium alloy before being released in primary water during operation, or in containers during transportation and storage. The study aims at identifying and quantifying the rate-limiting steps of this permeation process by using deuterium as isotopic tracer for tritium. A dedicated permeation device revealed that, at 773 K, deuterium permeation kinetics from the metal was limited by the surface recombination reaction. In association with gaseous deuterium charging and Thermal Desorption Spectrometry, the apparent activation energy of the deuterium desorption showed that the permeation device induced stress and strain in the specimens. A stress-free Zircaloy-4 exhibited an apparent activation energy around 240 kJ mol^?1 it dropped down to around 140 ± 10 kJ mol^?1 when under stress, in the 623 K–773 K temperature range.     

Vacuum generation by hydrogen permeation to atmosphere through austenitic and nickel-base-alloy vessel walls at temperatures from 573 K to 773 K

The permeation of hydrogen through metals is of great concern in hydrogen containment systems. In this study, hydrogen contained in seamless coiled tube vessels made of SUS 316L and Inconel 625 permeated the vessel walls at temperatures from 573 K to 773 K, and the decreasing interior pressure of the vessels was monitored for an extended period to characterize the behavior of the pressure change. It was found that the pressure became lower than the surrounding atmospheric pressure, and the vessels reached a vacuum. Hydrogen permeabilities through SUS 316L and Inconel 625 were determined from the pressure drop measurements. In order to ensure the reliability of the measurements, the permeabilities were also determined with a gas chromatograph that measured the concentration of hydrogen completely permeating the vessel wall. The permeabilities obtained with the two methods were in good agreement with each other. The pressure drop behavior was compared to, and found to be consistent with, theoretical calculations performed using the obtained permeabilities based on Fick’s law of diffusion.     

Compact and fast-response 150 kW hydrogen-oxygen steam generator

Burning of hydrogen produces high-grade heat, which can be used for zero-carbon power generation and/or heating and in heat-intensive industries. In combination with water electrolysis, hydrogen combustion provides efficient energy storage method for variable renewables. Hydrogen combustion systems are compact, powerful and highly maneuverable in comparison with fuel cells. We present experimental results of fire tests of a water-cooled hydrogen-oxygen steam generator (HOSG). This fast-response device has start-up time less than 15 s to thermal capacity of 147 kW. Temperature of generated steam is within 1173–1273 K, parameters of steam and energy conversion efficiency can be adjusted the water-to-hydrogen ratio. The maximum efficiency of conversion of chemical energy of hydrogen into enthalpy of steam is 98.7%.     

Hydrino continuum transitions with cutoffs at 22.8 nm and 10.1 nm

Classical physical laws predict that atomic hydrogen may undergo a catalytic reaction with certain species, including itself, that can accept energy in integer multiples of the potential energy of atomic hydrogen, m·27.2 eV, wherein m is an integer. The predicted reaction involves a resonant, nonradiative energy transfer from otherwise stable atomic hydrogen to the catalyst capable of accepting the energy. The product is H(1/p), fractional Rydberg states of atomic hydrogen called “hydrino atoms,” wherein n = 1/2, 1/3, 1/4,…, 1/p (p ≤ 137 is an integer) replaces the well-known parameter n = integer in the Rydberg equation for hydrogen excited states. Each hydrino state also comprises an electron, a proton, and a photon, but the field contribution from the photon increases the binding rather than decreasing it corresponding to energy desorption rather than absorption. Since the potential energy of atomic hydrogen is 27.2 eV, two H atoms formed from H₂ by collision with a third, hot H can act as a catalyst for this third H by accepting 2·27.2 eV from it. By the same mechanism, the collision of two hot H₂ provide 3H to serve as a catalyst of 3·27.2 eV for the fourth. Following the energy transfer to the catalyst an intermediate is formed having the radius of the H atom and a central field of 3 and 4 times the central field of a proton, respectively, due to the contribution of the photon of each intermediate. The radius is predicted to decrease as the electron undergoes radial acceleration to a stable state having a radius that is 1/3 (m = 2) or 1/4 (m = 3) the radius of the uncatalyzed hydrogen atom with the further release of 54.4 eV and 122.4 eV of energy, respectively. This energy emitted as a characteristic EUV continuum with a cutoff at 22.8 nm and 10.1 nm, respectively, was observed from pulsed hydrogen discharges. The continua spectra directly and indirectly match significant celestial observations.     

Hydrogen adsorption characteristics of magnesium combustion derived graphene at 77 and 293 K

Bulk graphene was prepared by the method of magnesium combustion in a CO₂ atmosphere, producing large quantities of material which had a different morphology and importantly, a more ordered carbon lattice than reduced graphene oxide and other bulk graphene synthetic methodologies. Despite a low surface area of 235.5 m²/g and ca 9 at.% of magnesium and its oxides which do not contribute to hydrogen adsorption, we observe 0.85 wt.% of H₂ at 65 bar and 77 K, and 0.9 wt.% of H₂ at 300 bar and 293 K. As this methodology readily produces many-gram quantities with cheap starting materials, we anticipate that with further enhancements to the synthetic methodology, improving both surface area and reducing reaction by-products, this material will provide a robust platform for further H₂ adsorption investigations.     

Performance calculation of single effect absorption heat pump using LiBr + LiNO3 + H2O as working fluid

In order to check the theoretical performance of the new working fluid LiBr + LiNO₃+H₂O (mole ratio of LiBr and LiNO₃ = 4:1), the theoretical coefficients of performance (COP) of this working fluid and LiBr + H₂O were calculated at various operating conditions. The improvement of crystallization problem was also checked. This proposed working fluid was proved to increase the COP by about 5% than LiBr + H₂O. The cooling water through absorber and evaporator was heated to higher temperature by this new working fluid. LiBr + LiNO₃ + H₂O was found to be an alternative to the conventional LiBr + H₂O with higher COP and less corrosivity.     

Inhibitive effect of onion mesocarp extract-nickel nanoparticles composite on simultaneous hydrogen production and pipework corrosion in 1 M HCl

Nanoscale nickel is prepared from ethanol extracts of Allium cepa and characterized. Zerovalent face centred cubic (fcc) nickel nanoparticles oriented mainly at Ni (111) plane formed rapidly within 30–45 min. The nanoparticles are stabilized by negative surface potential, non-agglomerated, monodispersed, round-shaped and distributed between sizes of 39.5–53.1 nm. The nanoparticles are used to simultaneously regulate the rates of hydrogen gas production and X80 steel corrosion in 1 M HCl solution for the first time. The nanoparticles efficiently inhibit hydrogen gas evolution and X80 steel corrosion rates especially at increased concentration. Inhibition efficiency increases as temperature increases from 303 to 323 K, remains fairly constant from 323 to 343 K and decreases drastically from 343 to 363 K. By means of O–H, N–H and C=C sites, the nanoparticles are spontaneously physically adsorbed on X80 steel surface and act as mixed type corrosion inhibitor with dominant influence on cathodic reaction involving hydrogen gas evolution. In the presence of the nanoparticles, surface roughness (measured by AFM) reduces by 76.0% and heights of peaks from the mean plane reduces by 58.2%. Comparatively, even 100 ppm of the nanoparticles showed higher inhibition efficiency at all temperatures than 1000 ppm concentration of the crude extract.