David Antonelli

University of South Wales, Понтиприте, Wales, United Kingdom

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Publications (69)375.05 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Proton conductivity in a series of mesoporous niobium and tantalum metal oxide (mX2O5) composites of naphthalene sulfonic acid formaldehyde resin (NSF) that are resistant to moisture loss at temperatures greater than 50 °C is reported. The investigation focuses on the effect to proton conductivity by changing pore size and metal in the mesostructure of the mX2O5 system and thus, a series of mX2O5-NSF composites were synthesized with C6, C12, and C18 templates. These were characterized by XRD, thermogravimetric analysis, nitrogen adsorption, and scanning TEM and then studied using impedance spectroscopy to establish proton conductivity values at various temperatures ranging from 25 to 150 °C. The most promising sample displayed a conductivity of 21.96 mS cm−1 at 100 °C, surpassing the literature value for Nafion 117 (ca. 8 mS cm−1). 1H and 13C solid state NMR studies the mX2O5-NSF composites demonstrate that the oligomeric nature of the NSF is preserved while in contact with the mX2O5 surface, thus facilitating conductivity.
    ChemSusChem 09/2014; · 7.48 Impact Factor
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    Microporous and Mesoporous Materials 08/2014; 194:52–59. · 3.37 Impact Factor
  • Microporous and Mesoporous Materials 05/2014; 190:284–291. · 3.37 Impact Factor
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    ABSTRACT: An amorphous Fe(II) hydride material approximating FeH2 in composition (FeH2−xRx(Et2O)y where R = mesityl) has been isolated as a bulk powder in the solid state. This was accomplished under moderate reaction conditions by the reaction of bis(mesityl) iron(II) in toluene and hydrogen gas at 100 bar and 298 K to give a 1:5 mixed phase amorphous material of Fe(0) and the iron (II) hydride. This represents an important advance because FeH2 has never been synthesised in bulk form. The material shows ferromagnetic behaviour with a magnetic susceptibility of 1.25 Bohr magnetons per formula unit at 10 K.
    Journal of Alloys and Compounds 01/2014; 590:199–204. · 2.73 Impact Factor
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    ABSTRACT: doi: 10.1021/cm402853k
    Chemistry of Materials 11/2013; · 8.24 Impact Factor
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    ABSTRACT: Models of two linked M(III) and M(II) (M = Ti, V, Cr) binding sites in hydrazine-linked hydrogen storage materials have been studied quantum chemically using density functional theory. The results compare favorably with previous experimental and computational results. Strong evidence is observed that the H2 molecules bind to the metal in a Kubas manner. As seen previously in monometallic analogues,(1, 2) altering the transition metal across the first row of the periodic table reduces the number of H2 molecules that can be bound, and replacing a hydrazide ligand with a hydride increases the M-H2 interaction energy. Evidence is presented for metal–metal interactions, which can influence the H2 binding enthalpy and may help to explain the observed metallic properties and rising H2 binding enthalpies with coverage of the experimental materials. An alternate explanation for the rising enthalpies is also proposed, involving a pressure-induced deformation of the structure with concomitant twisting of the bonds into conformations that allow more optimal binding of an H2 ligand.
    The Journal of Physical Chemistry C. 09/2012; 116(36):19134–19144.
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    ABSTRACT: The Cr(II) binding sites of an experimentally realised hydrazine linked hydrogen storage material have been studied computationally using density functional theory. Both the experimentally determined rise in H(2) binding enthalpy upon alteration of the ancillary ligand from bis[(trimethylsilyl)methyl] to hydride, and the number of H(2) molecules per Cr centre, are reproduced reasonably well. Comparison with analogous Ti(II), V(II) and Mn(II) systems suggests that future experiments should focus on the earliest 3d metals, and also suggests that 5 and 7 wt% H(2) storage may be possible for V(II) and Ti(II) respectively. Alteration of the metal does not have a large effect on the M-H(2) interaction energy, while alteration of the ancillary ligand bound to the metal centre, from bis[(trimethylsilyl)methyl] or hydride to two hydride ligands, THF and only hydrazine based ligands, indicates that ancillary ligands that are poor π-acceptors give stronger M-H(2) interactions. Good evidence is found that the M-H(2) interaction is Kubas type. Orbitals showing σ-donation from H(2) to the metal and π-back-donation from the metal to the dihydrogen are identified, and atoms-in-molecules analysis indicates that the electron density at the bond critical points of the bound H(2) is similar to that of classical Kubas systems. The Kubas interaction is dominated by σ-donation from the H(2) to the metal for Cr(II), but is more balanced between σ-donation and π-back-donation for the Ti(II) and V(II) analogues. This difference in behaviour is traced to a lowering in energy of the metal 3d orbitals across the transition series.
    Dalton Transactions 05/2012; 41(28):8515-23. · 3.81 Impact Factor
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    ABSTRACT: doi: 10.1021/cm300425z
    Chemistry of Materials 04/2012; 24(9):1629-1638. · 8.24 Impact Factor
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    ABSTRACT: Supporting evidence: Supported dihydrogen-metal complexes have been proposed for room-temperature hydrogen storage, however, there has been little experimental evidence to support such predictions. Using inelastic neutron scattering and ab initio DFT, direct evidence is provided for activated formation of a dihydrogen complex in a silica-supported Ti(III) organometallic compound.
    Chemistry 03/2012; 18(14):4170-3. · 5.93 Impact Factor
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    ABSTRACT: Molecular models of the M-H(2) binding sites of experimentally characterised amorphous vanadium hydrazide gels are studied computationally using gradient corrected density functional theory, to probe the coordination number of the vanadium in the material and the nature of the interaction between the metal and the H(2) molecules. The H(2) is found to bind to the vanadium through the Kubas interaction, and the first quantum theory of atoms-in-molecules analysis of this type of interaction is reported. Strong correlation is observed between the electron density at the H-H bond critical point and the M-H(2) interaction energy. Four coordinate models give the best reproduction of the experimental data, suggesting that the experimental sites are four coordinate. The V-H(2) interaction is shown to be greater when the non-hydrazine based ligand, THF, of the experimental system is altered to a poorer π-acceptor ligand. Upon altering the metal to Ti or Cr the M-H(2) interaction energy changes little but the number of H(2) which may be bound decreases from four (Ti) to two (Cr). It is proposed that changing the metal from V to Ti may increase the hydrogen storage capacity of the experimental system. A 9.9 wt% maximum storage capacity at the ideal binding enthalpy for room temperature performance is predicted when the Ti metal is combined with a coordination sphere containing 2 hydride ligands.
    Chemistry 02/2012; 18(6):1750-60. · 5.93 Impact Factor
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    ABSTRACT: Hydrogen is the ideal fuel because it contains the most energy per gram of any chemical substance and forms water as the only byproduct of consumption. However, storage still remains a formidable challenge because of the thermodynamic and kinetic issues encountered when binding hydrogen to a carrier. In this study, we demonstrate how the principal binding sites in a new class of hydrogen storage materials based on the Kubas interaction can be tuned by variation of the coordination sphere about the metal to dramatically increase the binding enthalpies and performance, while also avoiding the shortcomings of hydrides and physisorpion materials, which have dominated most research to date. This was accomplished through hydrogenation of chromium alkyl hydrazide gels, synthesized from bis(trimethylsilylmethyl) chromium and hydrazine, to form materials with low-coordinate Cr hydride centers as the principal H(2) binding sites, thus exploiting the fact that metal hydrides form stronger Kubas interactions than the corresponding metal alkyls. This led to up to a 6-fold increase in storage capacity at room temperature. The material with the highest capacity has an excess reversible storage of 3.23 wt % at 298 K and 170 bar without saturation, corresponding to 40.8 kg H(2)/m(3), comparable to the 2015 DOE system goal for volumetric density (40 kg/m(3)) at a safe operating pressure. These materials possess linear isotherms and enthalpies that rise on coverage, retain up to 100% of their adsorption capacities on warming from 77 to 298 K, and have no kinetic barrier to adsorption or desorption. In a practical system, these materials would use pressure instead of temperature as a toggle and can thus be used in compressed gas tanks, currently employed in the majority of hydrogen test vehicles, to dramatically increase the amount of hydrogen stored, and therefore range of any vehicle.
    Journal of the American Chemical Society 08/2011; 133(39):15434-43. · 10.68 Impact Factor
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    ABSTRACT: Oxalic acid, oxamide, glycolic acid, and glycolamide were employed as 2-carbon linkers to synthesize a series of one-dimensional V(III) polymers from trismesityl vanadium(III)·THF containing a high concentration of low-valent metal sites that can be exploited for Kubas binding in hydrogen storage. Synthesized materials were characterized by powder X-ray diffraction (PXRD), nitrogen adsorption (BET), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR), Raman spectroscopy, thermogravimetric analysis, and elemental analysis. Because each of these organic linkers possesses a different number of protons and coordinating atoms, the products in each case were expected to have different stoichiometries with respect to the number of mesityl groups eliminated and also a different geometry about the V(III) centers. For example, the oxalate and glycolate polymers contained residual mesityl groups; however, these could be exchanged with hydride via hydrogenolysis. The highest adsorption capacity was recorded on the product of trismesityl vanadium(III)·THF with oxamide (3.49 wt % at 77 K and 85 bar). As suggested by the high enthalpy of adsorption (17.9 kJ/mol H(2)), a substantial degree of performance of the vanadium metal centers was retained at room temperature (25%), corresponding to a gravimetric adsorption of 0.87 wt % at 85 bar, close to the performance of MOF-177 at this temperature and pressure. This is remarkable given the BET surface area of this material is only 9 m(2)/g. A calculation on the basis of thermogravimetric results provides 0.88 hydrogen molecule per vanadium center under these conditions. Raman studies with H(2) and D(2) showed the first unequivocal evidence for Kubas binding on a framework metal in an extended solid, and IR studies demonstrated H(D) exchange of the vanadium hydride with coordinated D(2). These spectroscopic observations are sufficient to assign the rising trends in isosteric heats of hydrogen adsorption observed previously by our group in several classes of materials containing low-valent transition metals to the Kubas interaction.
    Journal of the American Chemical Society 03/2011; 133(13):4955-64. · 10.68 Impact Factor
  • Chaoyang Yue, Michel L Trudeau, David Antonelli
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    ABSTRACT: Mesoporous tantalum oxide, Fe3+-doped mesoporous tantalum oxide, and bis(toluene) titanium reduced mesoporous tantalum oxide were used for the first time as Schrauzer-type photocatalysts for the conversion of dinitrogen to ammonia. The materials were characterized by XRD, TEM, XPS, and nitrogen absorption before and after catalytic runs. The results showed low to moderate activities depending on the composition. In contrast to previously studied Ti catalysts, Fe doping and heat pretreatment were not prerequisites for photocatalytic activity, but did improve the turnover rates by up to a factor of two. The optimal Fe loading for the tantalum oxides was found to be 1 wt% and the optimal heating condition at 300 °C for 3 h. Increased surface area and heat treatment were also found to improve activities. Contrary to our expectations, reduction of the mesostructure with bis(toluene) titanium had little effect on the catalytic activity. In spite of the dramatically higher surface areas of the mesoporous tantalum oxides as compared with bulk titanias used previously in this process, the overall catalytic activities were still less than those obtained in the Schrauzer system. This suggests that the increase in diffusion and surface area offered by the mesoporous structure is offset by the smaller crystalline domain sizes in the walls of the structure, leading to poor electron-hole separation and a reduction in catalytic efficiency. Key words: mesoporous, Schrauzer, ammonia, photocatalysis, tantalum oxide.
    Canadian Journal of Chemistry 02/2011; 83(4):308-314. · 0.96 Impact Factor
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    B O Skadtchenko, D M Antonelli
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    ABSTRACT: The flexible oxidation states of mesoporous Nb, Ta, and Ti oxides make them unique amongst porous materials allowing reaction pathways and cascades that are not possible for mesoporous silica or microporous materials such as zeolites. This electronic activity coupled with the 20–30 Å pores and the amorphous wall structure, which provides greater bandwidth (W) and hence an even greater range of redox potentials, leads to a rich variety of host–guest inclusion chemistry, which serves as an unprecedented 1-D analogue to layered 2-D host–guest inclusion reactions studied for decades. In this paper we survey a series of reactions between these mesoporous hosts and a wide variety of organic and organometallic guest species including alkali fullerides, cobaltocene, and other organometallic sandwhich species, and discuss the electronic and magnetic properties of the resulting composites.Key words: mesoporous materials, semiconductors, fullerides, superconductors, oxides, nanomaterials, metallocenes.
    Canadian Journal of Chemistry 02/2011; 84(3):371-383. · 0.96 Impact Factor
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    ABSTRACT: To verify the role of the Kubas interaction in transition metal grafted mesoporous silicas, and to rationalize unusual rising enthalpy trends with surface coverage by hydrogen in these systems, computational studies have been performed. Thus, the interaction of H(2) with the titanium centers in molecular models for experimentally characterized mesoporous silica-based H(2) absorption materials has been studied quantum chemically using gradient corrected density functional theory. The interaction between the titanium and the H(2) molecules is found to be of a synergic, Kubas type, and a maximum of four H(2) molecules can be bound to each titanium, in good agreement with previous experiments. The average Ti-H(2) interaction energies in molecules incorporating benzyl ancillary ligands (models of the experimental systems) increase as the number of bound H(2) units increases from two to four, in agreement with the experimental observation that the H(2) adsorption enthalpy increases as the number of adsorbed H(2) molecules increases. The Ti-H(2) interaction is shown to be greater when the titanium is bound to ancillary ligands, which are poor π-acceptors, and when the ancillary ligand causes the least steric hindrance to the metal. Extension of the target systems to vanadium and chromium shows that, for molecules containing hydride ancillary ligands, a good relationship is found between the energies of the frontier molecular orbitals of the molecular fragments, which interact with incoming H(2) molecules, and the strength of the M-H(2) interaction. For the benzyl systems, both the differences in M-H(2) interaction energies and the energy differences in frontier orbital energies are smaller than those in the hydrides, such that conclusions based on frontier orbital energies are less robust than for the hydride systems. Because of the high enthalpies predicted for organometallic fragments containing hydride ligands, and the low affinity of Cr(III) for hydrogen in this study, these features may not be ideal for a practical hydrogen storage system.
    Journal of the American Chemical Society 11/2010; · 10.68 Impact Factor
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    ABSTRACT: In this paper we demonstrate that the Kubas interaction, a nondissociative form of weak hydrogen chemisorption with binding enthalpies in the ideal 20-30 kJ/mol range for room-temperature hydrogen storage, can be exploited in the design of a new class of hydrogen storage materials which avoid the shortcomings of hydrides and physisorpion materials. This was accomplished through the synthesis of novel vanadium hydrazide gels that use low-coordinate V centers as the principal Kubas H(2) binding sites with only a negligible contribution from physisorption. Materials were synthesized at vanadium-to-hydrazine ratios of 4:3, 1:1, 1:1.5, and 1:2 and characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, nitrogen adsorption, elemental analysis, infrared spectroscopy, and electron paramagnetic resonance spectroscopy. The material with the highest capacity possesses an excess reversible storage of 4.04 wt % at 77 K and 85 bar, corresponding to a true volumetric adsorption of 80 kg H(2)/m(3) and an excess volumetric adsorption of 60.01 kg/m(3). These values are in the range of the ultimate U.S. Department of Energy goal for volumetric density (70 kg/m(3)) as well as the best physisorption material studied to date (49 kg H(2)/m(3) for MOF-177). This material also displays a surprisingly high volumetric density of 23.2 kg H(2)/m(3) at room temperature and 85 bar--roughly 3 times higher than that of compressed gas and approaching the DOE 2010 goal of 28 kg H(2)/m(3). These materials possess linear isotherms and enthalpies that rise on coverage and have little or no kinetic barrier to adsorption or desorption. In a practical system these materials would use pressure instead of temperature as a toggle and can thus be used in compressed gas tanks, currently employed in many hydrogen test vehicles, to dramatically increase the amount of hydrogen stored and therefore the range of any vehicle.
    Journal of the American Chemical Society 08/2010; 132(33):11792-8. · 10.68 Impact Factor
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    ABSTRACT: Cyclopentadienyl chromium hydrazide gels were synthesized from the protonolysis reaction between bis(cyclopentadienyl) chromium and hydrazine. The amorphous products containing low valent chromium species are exploited as substrates for Kubas-type hydrogen storage. These materials demonstrate enthalpies that rise from 10 to 45 kJ mol(-1) and show a retention of 49% of the adsorption capacity at 298 K relative to 77 K, compared to values of 10-15% for most MOFs and amorphous carbons.
    Chemical Communications 05/2010; 46(18):3206-8. · 6.38 Impact Factor
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    ABSTRACT: Hexagonally packed mesoporous silica (HMS) grafted with titanium, vanadium, and chromium organometallic fragments possessing metal oxidation states between (II) and (IV) were synthesized and characterized by XRD, nitrogen adsorption, XPS, and elemental analysis. These materials were then tested for their excess hydrogen storage capacity, with the purpose in mind of subtracting out the physisorption component and establishing which transition metal fragments and oxidation states functioned as the most effective binding sites for hydrogen. By varying the metal type and the metal oxidation state, as well as the ligand environment by exchanging the alkyl group with hydride via hydrogenolysis, the effects of these variations on the H2 adsorption capacity of the metal center as well as on the binding enthalpies of these systems were investigated. This study demonstrated that titanium is more effective at hydrogen binding than vanadium and chromium. Hence, HMS silica grafted with benzyl titanium(III) fragments can accommodate up to 4.85 H2 per Ti center and 4.74 H2 per Ti center in the case of HMS grafted with bis(naphthalene) titanium. This compares to 2.74 H2 per vanadium center in the case of HMS grafted with tris(mesityl) vanadium, and to 1.82 H2 and 2.20 H2 per chromium center as in the HMS treated with tris[bis(trimethylsilyl)methyl] chromium and bis[(trimethylsilyl)methyl] chromium, respectively. The hydrogenation of the metal centers had no effect on the adsorption capacity of the titanium centers and only a slight effect on the vanadium centers; however, a far more pronounced effect was observed in the case of chromium as the adsorption capacity increased from 1.82 H2 to 3.2 H2 per chromium in the case of HMS treated with tris[bis(trimethylsilyl)methyl] chromium, and from 2.20 H2 to 3.5 H2 per chromium in the case of HMS treated with bis[(trimethylsilyl)methyl] chromium. The differences in binding capacity and the effect of hydrogenation were attributed to ligand environment, the availability of open binding sites, and the ability of the metal center to back-bond to the antibonding orbital of the chemisorbed H2 ligands.
    The Journal of Physical Chemistry C. 04/2010; 114(18).
  • M. Vettraino, B. Ye, X. He, D. M. Antonelli
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    ABSTRACT: Manuscript received: 9 October 2000.
    ChemInform 01/2010; 32(42).
  • ChemInform 01/2010; 33(45).

Publication Stats

291 Citations
375.05 Total Impact Points

Institutions

  • 2014
    • University of South Wales
      • Sustainable Environment Research Centre
      Понтиприте, Wales, United Kingdom
  • 1999–2013
    • University of Windsor
      • Department of Chemistry and Biochemistry
      Windsor, Ontario, Canada
  • 2012
    • University College London
      • Department of Chemistry
      London, ENG, United Kingdom
  • 2004
    • Max Planck Institute for Coal Research
      Mülheim-on-Ruhr, North Rhine-Westphalia, Germany