Thermodynamics of Dehydrogenation of the 2LiBH4-Mg2FeH6 Composite

International audienceJoint decomposition of hydrides may be energetically favored, if stable mixed compounds are formed. This “hydride destabilization” improves the energetics of H2 release from hydrogen storage materials. The sequence of dehydrogenation reactions of the 2LiBH4–Mg2FeH6 composite was studied by PCI (pressure-composition-isotherm) and TPD (temperature-programmed-desorption) techniques in a Sievert apparatus. Produced phases were identified by ex-situ X-ray diffraction and FTIR spectroscopy. Three distinct plateaus are detected on each isotherm: A, B, and C on decreasing pressure. The A reaction, involving formation of FeB, MgH2, and LiH, occurs at higher pressure/lower temperature than dehydrogenation of either pure hydrides; these are then effectively destabilized thermodynamically. The B process is plain decomposition of MgH2, and in C, the magnesium produced reacts with left LiBH4 forming MgB2 and LiH. The B + C sequence is fully reversible, and it corresponds to two-step dehydrogenation of the LiBH4/MgH2 system. Reaction enthalpies and entropies were obtained through van’t Hoff plots of all processes, thus providing a full thermodynamic characterization of the system. Interestingly, it ensues that destabilization of pure hydrides with reaction A is due primarily to an entropic rather than enthalpic effect

Nuclear quantum effects in ab initio dynamics: theory and experiments for lithium imide

Owing to their small mass, hydrogen atoms exhibit strong quantum behavior even at room temperature. Including these effects in first principles calculations is challenging, because of the huge computational effort required by conventional techniques. Here we present the first ab-initio application of a recently-developed stochastic scheme, which allows to approximate nuclear quantum effects inexpensively. The proton momentum distribution of lithium imide, a material of interest for hydrogen storage, was experimentally measured by inelastic neutron scattering experiments and compared with the outcome of quantum thermostatted ab initio dynamics. We obtain favorable agreement between theory and experiments for this purely quantum mechanical property, thereby demonstrating that it is possible to improve the modelling of complex hydrogen-containing materials without additional computational effort

METHOD AND PLANT FOR ACTIVATING CATALYSTS

La presente invenzione si riferisce ad un metodo di attivazione di un materiale catalizzatore solido, ad un catalizzatore attivato ottenibile da detto metodo di attivazione, ad una cella a combustibile, un elettrolizzatore, una batteria metallo-aria o una marmitta catalitica contenente detto catalizzatore attivato, nonché ad un impianto per realizzare detto metodo di attivazione

Designing Nanoconfined LiBH₄ for Solid-State Electrolytes

Solid-state electrolytes are necessary for high-density and safe lithium-ion batteries. Lithium borohydride (LiBH4) is one of the hydride compounds that shows promising candidates for solid-state electrolytes and enables all-solid-state batteries. LiBH4 has good wetting properties and preferable mechanical properties when used in battery cells. The Li-ion conduction in LiBH4 can be modified with nanoconfinement as a result of distinct properties on the interfaces. The ion conductivities can be modified further by choosing property support materials, i.e., composition, textural properties, and surface chemistry. The present work briefly reviews the Li-ion conduction in nanoconfined LiBH4. A future perspective on the development of LiBH4 as a solid-state electrolyte is further elaborated in the last section.</p

Hidden in plain sight: unlocking the full potential of cyclic voltammetry with the thin-film rotating (ring) disk electrode studies for the investigation of oxygen reduction reaction electrocatalysts

Cyclic voltammetry conducted with a thin-film rotating disk electrode, or ring-disk electrode (CV-TF-R(R)DE) is a very popular \u2018ex situ\u2019 tool for the rapid screening of electrocatalysts for their activity in oxygen reduction reaction. Despite its popularity and broad use, in most instances only a small part of the information that could be accessed by CV-TFR(R)DE is actually used by scientists in their research. This work outlines both innovative and more traditional (but halfforgotten) ways of using CV-TF-R(R)DE to its optimal or full potential in the ongoing quest to study the most relevant features of oxygen reduction reaction electrocatalysts and quickly identify the most promising candidates for their applications in fuel cells or other electrochemical devices

Hydrothermal N-doped TiO2: Explaining photocatalytic properties by electronic and magnetic identification of N active sites

N-doped TiO2 nanocrystals with high photoactivity in the visible range, were successfully synthesized by hydrothermal method, followed by thermal annealing at different temperatures (350–600 8C), in order to allow differential nitrogen diffusion into the TiO2 lattice. Optical and magnetic properties, studied by diffuse reflectance spectroscopy, electron paramagnetic resonance and X-ray photoelectron spectroscopy analysis, revealed that TiO2 was effectively doped. The thermal treatment induces insertion of nitrogen into TiO2 lattice in the form of nitride anion NÀ, detected as N by EPR, whose ionic character varies with the temperature of annealing. The amount of N increases till 450 8C, then it decreases. Similar trend was observed for the photomineralization of phenol under visible light irradiation (l > 385 nm): the photoactivity of N-doped samples becomes maximum for N–TiO2 annealed at 450 8C. The overall results suggest that the efficacy of the catalyst depends on the ability of NÀ centers to trap photogenerated holes. This effect lowers the rate of electron–hole recombination and allows the N (NÀ + h+) center acts as strong oxidizing agent

New membrane-electrode assembly (MEA) and methods of producing the same

The present invention describes devices aimed mainly, but not exclusively, at improving the performance of membrane-electrode assemblies ("membrane-electrode assembly", MEA) for application in fuel cells. These findings have been conceived mainly, but not exclusively, for MEAs that include electrocatalyst materials comprising a carbon nitride matrix. The findings described in the present invention allow: (i) to improve the mutual compatibility between the various layers of which the MEA is composed, facilitating the migration of the ionic species; and (ii) improve the accessibility of the active sites of the electrocatalyst to the reagents and products of the electrochemical processes necessary for the operation of the MEA