Papers by Keyword: Hydrogen Storage

Abstract: Nitrogen-doped ordered mesoporous carbon has been synthesized and used to confine LiBH₄ to improve its dehydrogenation properties. The carbon has a high BET specific surface up to 448.25 m²/g with pore size centered at 1.2 and 4.1 nm. The effects of ball milling time and speed on de-hydrogenation were investigated. The onset hydrogen desorption temperature of LiBH₄ is reduced to 100 °C by addition 40 wt% carbon, and it can release hydrogen of 8.3 wt% at 380 °C. Furthermore, cyclic dehydrogenation is studiedto estimate the stability of the samples in the present work.

Abstract: Microstructure, hydrogen storage properties and thermal stabilities of V-Ti-Fe alloys prepared by arc-melting were studied in this work. It was confirmed that V₆₀Ti₃₀Fe₁₀, V₇₀Ti₂₀Fe₁₀ and V₈₀Ti₁₀Fe₁₀ alloys are a body-centered cubic (bcc) single phase, while V₇₅Ti₁₀Fe₁₅ alloy consists of the bcc main phase and C14-typed Laves secondary phase. Experimental results show that the V₈₀Ti₁₀Fe₁₀ alloy reached the largest hydrogen absorption capacities which were about 1.9 wt.% and 1.62 wt.% at 423 K and 473 K, while V₇₅Ti₁₀Fe₁₅ alloy with C14-typed Laves phase showed better hydrogen desorption capacities with 1.31 wt.% at 423 K and 1.35 wt.% at 473 K, respectively. In addition, the DSC measurements indicate that the thermal stability of V₇₅Ti₁₀Fe₁₅ alloy with C14-typed Laves phase decreased, which is very beneficial to the improvement of dehydrogenation rate in the alloy.

Abstract: In this study, a first-principles investigation of hydrogen storage in the FeTi intermetallic is carried out. The structural and electronic changes due to hydrogen insertion into the FeTi intermetallic are determined using DFT and pseudo-potential calculations through the code SIESTA (Spanish Initiative for Electronic Simulation of Thousand of Atoms). The pseudopotentials are constructed using Troullier and Martins parametrization which describes correctly the ion-electron interactions. To define the real-space grid, necessary for numerical calculations of the electron density, detailed tests were performed in order to choose the appropriate basis set, the energy cutoff and the k-grid cutoff. The exchange-correlation potential is treated with the generalized gradient approximation (GGA). Lattice data, bonding properties and the density of states provide an explanation for the role played by hydrogen in the chemical bond with the Ti and Fe constituents.

Abstract: Hydrogen is the lightest and most abundant element in the universe and an energy carrier. It can be produced from several sources using various methods, such as, electrolysis of water or reforming of hydrocarbons like, natural gas can produce hydrogen in a big plant or fuelling stations. When it is produced using renewable energy sources such as wind, solar, geothermal, or hydroelectric power, it supports the zero emissions approach. Hydrogen powdered electricity generation, whether it is for vehicles, or others, it can be carried out mainly in two ways: burning hydrogen in an internal combustion engine, or reacting hydrogen with oxygen in a fuel cell. Above all, we need to have proper storage facility available at the production and as well as at the utilization site. There are several hydrogen storage technology available such as compressed storage; liquid hydrogen storage; metal hydrides, chemical hydride and by sorption in some porous medium. In this review article, some of the important finding in hydrogen storage materials for physical absorption methods has been discussed.

Abstract: Nanostructured Mg₂Ni intermetallic compounds were synthesised by high energy ball milling. Effect of milling time on structure and surface morphology of milled powders were studied using X-ray diffraction and scanning electron microscopy. Crystallite size and degree of crystallinity were confirmed using transmission electron microscopy and selective area electron diffraction analysis. In order to understand the effect of milling time on reaction rates, Differential Thermal Analysis is performed. Thermal profiles of 30 h milled powders indicate lower activation energy. Cyclic voltammetry, electrochemical impedance spectroscopy and charge-discharge studies were carried out to understand the electrochemical performance of prepared electrode materials. 30 h milled electrode material delivers maximum discharge capacity with superior capacity retention after 20 cycles at 20 mA g^-1.

Abstract: The paper presents the experimental results of saturation of the carbon material containing nanotubes with hydrogen from the gas. The dependences of hydrogen concentration from pressure (from 0 to 8 atmospheres), at the same temperature for adsorption (-30 degrees Celsius) and different temperatures for desorption were obtained. The temperature has an influence on sorption-desorption process and sorption properties of carbon material. The amount of residual hydrogen depends on saturation parameters.

Abstract: Graphene oxide (GO) is extracted from graphite oxide synthesized using modified Hummers method. The extracted GO solution is then drop casted onto a p type silicon substrate and dried in hot air oven. The dried solution is annealed at a temperature of about 200 degree Celsius for about one hour to obtain thermally reduced graphene oxide (RGO). Such thermally synthesized RGO usually have a lot of structural defects which can act as a binding site for hydrogen. The binding efficiency of hydrogen to defect centers can be increased by applying electric field to RGO as it changes the carrier concentration (doping) on the surface. This induces more polarization in the hydrogen molecule resulting in strong binding force, thereby increasing its hydrogen storage efficiency. In our experiment we have demonstrated room temperature electric field doping in RGO films by modulating the channel current by changing the back gate voltage which is a precursor for employing RGO in hydrogen storage applications.Keywords Graphene oxide, Reduced graphene oxide, Field effect, Hydrogen storage, and Defects

Abstract: Effect of small addition of tin (1.7 at.%) into LaNi_4.5Co_0.5 alloy on gas phase and cathodically charged hydrogen absorption ability as well as its corrosion resistance in 6M KOH solution is discussed. To reveal the effect of Sn doping three alloys have been selected: LaNi_4.5Co_0.5 (precursor), LaNi_4.5Co_0.5Sn_0.1 and LaNi₅ - as a parent compound. The room temperature p-C isotherms indicate to beneficial effect of Sn addition which causes decrease of H₂ equilibrium pressure and does not limit atomic hydrogen solubility. Discharge capacities (Q_disch), exchange current densities of H₂O/H₂ system () as well as corrosion rates () have been determined for the tested alloys on the basis of cyclic galvanostatic measurements (at –0.5C/+0.5C rates). It has been shown that for N > 3 cycle the discharge capacity of LaNi_4.5Co_0.5 is ca twofold greater than that for LaNi₅ reference. Addition of 1.7 at.% Sn into Co-containing alloy expands the discharge capacity by 30-40%. The Co containing alloys reveal twice as great exchange current densities of H₂O/H₂ system compared to LaNi₅, however, Sn addition slightly decreases the , especially for latest cycles. The partial cobalt substitution for Ni accelerates alloy corrosion in alkaline solution, however, tin addition fully eliminates this effect.

Abstract: The paper presents the theoretical foundations of carbon nanotubes, as well as the methods of the saturation of carbon materials containing nanotubes with hydrogen from the gaseous phase. The dependences of hydrogen storage concentration on the pressure (between 0 and 8 atmospheres) at the same temperature for adsorption (–30 degrees Celsius) and different temperatures for desorption have been obtained. Obviously, at 8 atmospheres the concentration of hydrogen storage varies with the change of the temperature. Particular attention was paid to the influence of the temperature on the rate of desorption.

Abstract: We report on the preparation and hydrogen desorption/absorption kinetics of nanocrystalline magnesium hydride (MgH₂) added commercial Ti by high-energy ball milling. The phase and composition of the as-milled powders are characterized by X-ray diffraction (XRD). The results show that the milled sample contained MgH₂ phase, Ti phase and small amount of MgO phase. When the milling time is 30 h, the hydrogen desorption property of MgH₂ has been investigated and found that the sample releases 0.43, 0.86 and 0.90 wt% H₂ in 200 minutes at 280, 290 and 300 ^oC , respectively. Moreover, the sample absorbs 0.48, 0.0.58 and 0.61 wt% H₂ in 15 minutes at 280, 290 and 300 ^oC , respectively. It can be seen that the kinetics of hydrogen desorption/absorption of MgH₂-Ti composite has been greatly enhanced compared to the pure MgH₂.