Dehydrogenation properties of the LiNH 2 BH 3 /MgH 2 and LiNH 2 BH 3 /LiBH 4 bi-component hydride systems for hydrogen storage applications

Abstract Lithium amidoborane (LiAB) is known as an efficient hydrogen storage material. The dehydrogenation reaction of LiAB was studied employing temperature-programmed desorption methods at varying temperature and H2 pressure. As the dehydrogenation products are in amorphous form, the XRD technique is not useful for their identification. The two-step decomposition temperatures (74 and 118 °C) were found to hardly change in the 1–80 bar pressure range. This is related either to kinetic effects or to thermal dependence of the reaction enthalpy. Further, the possible joint decomposition of LiNH2BH3 with LiBH4 or MgH2 was investigated. Indeed LiBH4 proved to destabilize LiAB, producing a 10 °C decrease of the first-step decomposition temperature, whereas no significant effect was observed by the addition of MgH2. The 5LiNH2BH3 + LiBH4 assemblage shows improved hydrogen storage properties with respect to pure lithium amidoborane

Correction to: Dehydrogenation properties of the LiNH2BH3/MgH2 and LiNH2BH3/LiBH4 bi-component hydride systems for hydrogen storage applications

The original version of this article is missing the below acknowledgements section

Overpressure Role in Isothermal Kinetics of H2 Desorption-Absorption: the 2LiBH4-Mg2FeH6 System

International audienceThe rates of the irreversibile LiBH4 +Mg2FeH6 → LiH + 2MgH2 + FeB + 5/2H2 and reversible (with significant sorption/desorption hysteresis) LiBH4 + 1/2Mg ↔ LiH + 1/2MgB2 + 3/2H2 reactions were measured by isothermal–isobaric experiments in a Sievert-type apparatus. Measurements were done at several temperature T and overpressure Δp/p values, deriving the rate constants k(T, Δp/p) by Avrami’s fitting of reaction advancement vs time. The results could be rationalized on the basis of the k = A exp(−Ea/RT) = A0 exp[−Ea0/RT + a(Δp/p)] kinetic formula, which couples the standard Arrhenius approach for thermal effects with an exponential dependence of the rate constant on overpressure. The empirical a coefficient varies with temperature in a way that requires the activation energy and entropy to depend linearly on Δp/p. For the first of the above reactions, Ea = −151(Δp/p) + 118 kJ mol–1 and ln(A/min–1) = −34(Δp/p) + 16; similar values are obtained for the second one. Relations of this kinetic model with the thermodynamic driving force ΔG and with equations of electrochemical kinetics, where overpressure is replaced by overvoltage, are discussed

Investigation on the kinetic mechanism of the reduction of Fe2O3/CoOFe_{2}O_{3}/CoO-decorated carbon xerogels: A non-isothermal study

The reduction of Fe2O3 and CoO oxides supported on carbon xerogels was studied to elucidate the effect of the nanoconfinement of the catalyst in carbon matrices. Resorcinol formaldehyde xerogels were synthesized, impregnated with iron and cobalt nitrates, and subsequently heated to obtain the oxides. The mechanism of oxide reduction to a metal with hydrogen was investigated by in-situ synchrotron X-ray diffraction in dynamic, non-isothermal conditions. Kinetic profiles of the reactions are obtained by plotting the diffraction intensities of selected Bragg peaks vs. temperature. The extracted Temperature-Programmed-Reduction (TPR) diagrams were best fitted by the Avrami-Erofeev and the n-order kinetic models for the iron and the cobalt oxide reduction reactions, respectively. The activation energies for the two-step reduction of Fe2O3 to FeO and then to Fe are 80 and 15.1 kJ mol−1. Such results may contribute to developing efficient and inexpensive catalysts based on non-noble metals like Fe, Co, via deposition of metal complexes on mesoporous supports

Dehydrogenation properties of the LiNH2BH3/MgH2 and LiNH2BH3/LiBH4 bi-component hydride systems for hydrogen storage applications

Abstract Lithium amidoborane (LiAB) is known as an efficient hydrogen storage material. The dehydrogenation reaction of LiAB was studied employing temperature-programmed desorption methods at varying temperature and H2 pressure. As the dehydrogenation products are in amorphous form, the XRD technique is not useful for their identification. The two-step decomposition temperatures (74 and 118 °C) were found to hardly change in the 1–80 bar pressure range. This is related either to kinetic effects or to thermal dependence of the reaction enthalpy. Further, the possible joint decomposition of LiNH2BH3 with LiBH4 or MgH2 was investigated. Indeed LiBH4 proved to destabilize LiAB, producing a 10 °C decrease of the first-step decomposition temperature, whereas no significant effect was observed by the addition of MgH2. The 5LiNH2BH3 + LiBH4 assemblage shows improved hydrogen storage properties with respect to pure lithium amidoborane

Hydrogen Storage in Propane-Hydrate: Theoretical and Experimental Study

There have been studies on gas-phase promoter facilitation of H2-containing clathrates. In the present study, non-equilibrium molecular dynamics (NEMD) simulations were conducted to analyse hydrogen release and uptake from/into propane planar clathrate surfaces at 180–273 K. The kinetics of the formation of propane hydrate as the host for hydrogen as well as hydrogen uptake into this framework was investigated experimentally using a fixed-bed reactor. The experimental hydrogen storage capacity propane hydrate was found to be around 1.04 wt% in compare with the theoretical expected 1.13 wt% storage capacity of propane hydrate. As a result, we advocate some limitation of gas-dispersion (fixed-bed) reactors such as the possibility of having un-reacted water as well as limited diffusion of hydrogen in the bulk hydrate

Multi-parameter optimization of the capacitance of Carbon Xerogel catalyzed by NaOH for application in supercapacitors and capacitive deionization systems

Carbon Xerogel is an economic choice of material for electrodes with applications in Electric Double Layer Capacitors (EDLCs) and Capacitive DeIonization systems (CDI, particularly for desalination). The objective here is to optimize Carbon Xerogel's performance, specifically its capacitance, through multi-parameter optimization using Response Surface Methodology (RSM). We choose NaOH as the catalyst and select as the optimization parameters (i) the pH of the initial Resorcinol-Formaldehyde-Catalyst (RFC) solution, (ii) Reactants to Liquid mass ratio (R/L) of the RFC solution, and (iii) the Pyrolysis Temperature (PT). For a selected range of these three parameters, we obtain an optimum capacitance of Carbon Xerogel equal to 37.6 F/g with optimized parameters PT = 800, R/L = 30% and pH = 5.7. Through comparing Carbon Xerogel samples synthesized with Na2CO3 versus NaOH as the catalyst, we show that the capacitance not only depends on the pH of the initial RFC solution, but also is a strong function of the catalyst material

A Comparison of the Role of the Chelating Agent on the Structure of Lithium Conducting Solid Electrolyte Li1.4Al0.4Ti1.6(PO4)3: Pechini vs. Modified Pechini-Type Methods

In recent years, solid lithium-ion conductors have been widely studied because of their applications as electrodes and solid electrolytes in rechargeable lithium-ion batteries. Citric acid (CA) and ethylenediaminetetraacetic acid (EDTA) were employed to synthesize the nanostructured NASICON-type Li1.4Al0.4Ti1.6(PO4)3 ceramic. The chelating agent, together with an ethylene glycol (EG) and the esterification agent were employed to form a network decorated with uniform dispersed metal ions under specific conditions: molar ratio [complexing agent/metal ions] = 1 and the molar ratio [EG/EDTA] = 6, whereas the solution pH was kept below 1. A well crystalline NASICON structure was formed following the heat treatment of the produced gel at 630 °C. Simultaneous thermal analysis (STA) revealed lower required temperature for pyrolysis and crystallization using EDTA. Powder X-ray diffraction (PXRD) showed the formation of larger crystallite size when citric acid was employed. The data from scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) have confirmed the higher apparent porosity and a larger proportion of grain boundaries in the case of EDTA-assisted synthesis

A Review of Reactor Designs for Hydrogen Storage in Clathrate Hydrates

Clathrate hydrates are ice-like, crystalline solids, composed of a three-dimensional network of hydrogen bonded water molecules that confines gas molecules in well-defined cavities that can store gases as a solid solution. Ideally, hydrogen hydrates can store hydrogen with a maximum theoretical capacity of about 5.4 wt%. However, the pressures necessary for the formation of such a hydrogen hydrate are 180–220 MPa and therefore too high for large-scale plants and industrial use. Thus, since the early 1990s, there have been numerous studies to optimize pressure and temperature conditions for hydrogen formation and storage and to develop a proper reactor type via optimisation of the heat and mass transfer to maximise hydrate storage capacity in the resulting hydrate phase. So far, the construction of the reactor has been developed for small, sub-litre scale; and indeed, many attempts were reported for pilot-scale reactor design, on the multiple-litre scale and larger. The purpose of this review article is to compile and summarise this knowledge in a single article and to highlight hydrogen-storage prospects and future challenges