Publications (9)36.28 Total impact
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Article: Hydrogen storage in hybrid nanostructured carbon/palladium materials: Influence of particle size and surface chemistry
International Journal of Hydrogen Energy 01/2013; · 4.05 Impact Factor -
Article: Tunable synthesis of (Mg–Ni)-based hydrides nanoconfined in templated carbon studied by in situ synchrotron diffraction
Nano Energy. 01/2013; -
Article: Synthesis, structural and hydrogenation properties of Mg-rich MgH2-TiH2 nanocomposites prepared by reactive ball milling under hydrogen gas.
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ABSTRACT: MgH(2)-TiH(2) nanocomposites have been obtained by reactive ball milling of elemental powders under 8 MPa of hydrogen pressure. The composites consist of a mixture of β-rutile MgH(2), γ-orthorhombic high pressure MgH(2) and ε-tetragonal TiH(2) phases with nanosized crystallites ranging from 4 to 12 nm. In situ hydrogen absorption curves on milling reveal that nanocomposite formation occurs in less than 50 min through the consecutive synthesis of the TiH(2) and MgH(2) phases. The abrasive and catalytic properties of TiH(2) speed up the formation of the MgH(2) phase. Thermodynamic, kinetic and cycling hydrogenation properties have been determined for the 0.7MgH(2)-0.3TiH(2) composite and compared to nanometric MgH(2). Only the MgH(2) phase desorbs hydrogen reversibly at moderate temperature (523 to 598 K) and pressure (10(-3) to 1 MPa). The presence of TiH(2) does not modify the thermodynamic properties of the Mg/MgH(2) system. However, the MgH(2)-TiH(2) nanocomposite exhibits outstanding kinetic properties and cycling stability. At 573 K, H-sorption takes place in less than 100 s. This is 20 times faster than for a pure nanometric MgH(2) powder. We demonstrate that the TiH(2) phase inhibits grain coarsening of Mg, which allows extended nucleation of the MgH(2) phase in Mg nanoparticles before a continuous and blocking MgH(2) hydride layer is formed. The low crystallinity of the TiH(2) phase and its hydrogenation properties are also compatible with a gateway mechanism for hydrogen transfer from the gas phase to Mg. Mg-rich MgH(2)-TiH(2) nanocomposites are an excellent media for hydrogen storage at moderate temperatures.Physical Chemistry Chemical Physics 12/2011; 14(3):1200-11. · 3.57 Impact Factor -
Article: Effect of NH2 and CF3 functionalization on the hydrogen sorption properties of MOFs.
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ABSTRACT: The hydrogen adsorption capacity and heat of adsorption at 77 K have been evaluated for several porous metal terephthalate MOFs (MIL-53(Fe), MIL-125(Ti) and UiO-66(Zr)), as well as in their -NH(2) and -(CF(3))(2) functionalized isoreticular structures. The capacity of hydrogen is basically related to the textural properties of the solids and not to their composition. The heats of adsorption at low coverage are on the whole close to those usually reported for MOFs (6-7 kJ mol(-1)), except for the UiO-66(Zr) and MIL-53(Fe)-(CF(3))(2) analogues, whereas the presence of Lewis acid sites and/or a confinement effect enhances significantly the strength of interaction with hydrogen.Dalton Transactions 03/2011; 40(18):4879-81. · 3.84 Impact Factor -
Article: Synthesis of small metallic Mg-based nanoparticles confined in porous carbon materials for hydrogen sorption.
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ABSTRACT: MgH2, Mg-Ni-H and Mg-Fe-H nanoparticles inserted into ordered mesoporous carbon templates have been synthesized by decomposition of organometallic precursors under hydrogen atmosphere and mild temperature conditions. The hydrogen desorption properties of the MgH2 nanoparticles are studied by thermo-desorption spectroscopy. The particle size distribution of MgH2, as determined by TEM, is crucial for understanding the desorption properties. The desorption kinetics are significantly improved by downsizing the particle size below 10 nm. Isothermal absorption/desorption cycling of the MgH2 nanoparticles shows a stable capacity over 13 cycles. The absorption kinetics are unchanged though the desorption kinetics are slower on cycling.Faraday Discussions 01/2011; 151:117-31; discussion 199-212. · 5.00 Impact Factor -
Article: Size-dependent hydrogen sorption in ultrasmall Pd clusters embedded in a mesoporous carbon template.
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ABSTRACT: Hydrogen sorption properties of ultrasmall Pd nanoparticles (2.5 nm) embedded in a mesoporous carbon template have been determined and compared to those of the bulk system. Downsizing the Pd particle size introduces significant modifications of the hydrogen sorption properties. The total amount of stored hydrogen is decreased compared to bulk Pd. The hydrogenation of Pd nanoparticles induces a phase transformation from fcc to icosahedral structure, as proven by in situ XRD and EXAFS measurements. This phase transition is not encountered in bulk because the 5-fold symmetry is nontranslational. The kinetics of desorption from hydrogenated Pd nanoparticles is faster than that of bulk, as demonstrated by TDS investigations. Moreover, the presence of Pd nanoparticles embedded in CT strongly affects the desorption from physisorbed hydrogen, which occurs at higher temperature in the hybrid material compared to the pristine carbon template.Journal of the American Chemical Society 06/2010; 132(22):7720-9. · 9.91 Impact Factor -
Article: Pd nanoparticles embedded into a metal-organic framework: synthesis, structural characteristics, and hydrogen sorption properties.
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ABSTRACT: The metal-organic framework MIL-100(Al) has been used as a host to synthesize Pd nanoparticles (around 2.0 nm) embedded within the pores of the MIL, showing one of the highest metal contents (10 wt %) without degradation of the porous host. Textural properties of MIL-100(Al) are strongly modified by Pd insertion, leading to significant changes in gas sorption properties. The loss of excess hydrogen storage at low temperature can be correlated with the decrease of the specific surface area and pore volume after Pd impregnation. At room temperature, the hydrogen uptake in the composite MIL-100(Al)/Pd is almost twice that of the pristine material. This can be only partially accounted by Pd hydride formation, and a "spillover" mechanism is expected to take place promoting the dissociation of molecular hydrogen at the surface of the metal nanoparticles and the diffusion of monatomic hydrogen into the porosity of the host metal-organic framework.Journal of the American Chemical Society 02/2010; 132(9):2991-7. · 9.91 Impact Factor -
Article: Occurrence of Uncommon Infinite Chains Consisting of Edge-Sharing Octahedra in a Porous Metal Organic Framework-Type Aluminum Pyromellitate Al4(OH)8[C10O8H2] (MIL-120): Synthesis, Structure, and Gas Sorption Properties
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ABSTRACT: A new metal organic framework (MOF)-type aluminum pyromellitate or Al4(OH)8[C10O8H2]·4.8−5H2O (called MIL-120) has been hydrothermally synthesized at 210 °C for 24 h. Its structure was analyzed by single-crystal microdiffraction using the synchrotron radiation beamline at ID13 station (ESRF, Grenoble). It consists of infinite chains of aluminum centers in octahedral coordination connected to each other through the pyromellitate linker. The structural feature is the existence of the AlO2(OH)4 octahedra linked to each other via a common edge consisting of two μ2-hydroxo groups, along the [102] direction. The different positions of the common edge in the two distinct Al crystallographical sites induce a cis−trans connection mode of the octahedral units, and zigzag chains are generated. All the carboxylate groups of the pyromellitate molecules are perpendicularly connected to the inorganic chains, and it results in the formation of channels running along the c axis (5.4 × 4.7 Å), in which water molecules are encapsulated. 27Al solid state NMR revealed two well resolved signals with two distinct quadrupolar coupling constants (CQ = 8.07 and 4.77 MHz) related to two Al sites. Brunnauer-Emmett-Teller (BET) surface area is 308(4) m2 g−1 (Langmuir: 432(1) m2 g−1). H2 adsorption is 1.3 wt % at 77 K and 3 MPa. CH4 or CO2 adsorptions are 1.8 mmol g−1 and 4.8 mmol g−1, respectively, at 303 K (under 1 MPa).12/2009; -
Article: Elaboration and characterization of magnesium-substituted La5Ni19 hydride forming alloys as active materials for negative electrode in Ni-MH battery
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ABSTRACT: The crystallographic structure as well as the thermodynamic and electrochemical properties of the hydrogen absorbing compounds La5Ni19 and La4MgNi19 have been determined. X-ray diffraction and microprobe analysis have shown the presence of a single hexagonal (P63/mmc) phase for the Mg-free binary compound whereas only one composition but two different crystallographic structures, hexagonal (P63/mmc) and rhombohedral (R-3m), are observed for La4MgNi19. Each phase can be described as the stacking along the c-axis of n[A2B4]/m[AB5] sub-units with n = 1 and m = 3 and A = La, Mg; B = Ni. Depending on the stacking sequence, either the hexagonal or the rhombohedral phase is obtained. Thermodynamic properties toward hydrogen uptake (capacity and equilibrium pressure) and electrochemical properties (cycling behavior) in alkaline medium have been measured and are compared for these compounds with and without magnesium. It is observed that the Mg-free compound exhibits a much lower reversible hydrogen capacity than the Mg-containing one. However, despite larger capacity, this latter compound remains to be optimized in term of cycle life.Electrochimica Acta.
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Institutions
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2010–2011
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Institut de Chimie et des Matériaux de Paris Est
Thiais, Ile-de-France, France
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