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Sigal A.,National University of Cordoba | Rojas M.I.,INFIQC | Leiva E.P.M.,INFIQC
International Journal of Hydrogen Energy | Year: 2011

In the present work, the decoration of a graphene sheet with nickel is considered as a hydrogen storage material by means of density functional theory calculations. A number of factors relevant for the handling and operation of this material were analyzed. This includes the interaction with potentially interfering chemicals, hydride formation and the hydrogen storage capacity. The present results show that unless the access of oxygen to the surface is restricted, its strong bond to the decorated systems will preclude the practical use for hydrogen storage. In the best case, the energy required to replace an adsorbed oxygen molecule by hydrogen is of the order of 1.7 eV, something that indicates the severe problem that the presence of oxygen represents for this type of systems. © 2010, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Source

(Figure presented) The synthesis of 6-substituted 2,4-dimethoxypyrimidines with different nucleophiles was accomplished with good to excellent yields (50-95%) through S RN1 reactions, starting from commercially available 6-chloro-2,4-dimethoxypyrimidine (1). Hydrolysis of these derivatives gave access to 6-substituted uracils with good yields and short times by the use of microwave irradiation. The preparation of uracils from 1 without the isolation of 2,4-dimethoxypyrimidine derivatives affords a rapid access to these compounds in good yields and excellent purity by avoiding an unnecessary step of purification. © 2010 American Chemical Society. Source

Vazquez C.I.,INFIQC | Lacconi G.I.,INFIQC
Journal of Electroanalytical Chemistry | Year: 2013

Silver electrodeposition onto HOPG electrodes in the presence of picolinic acid (PA) has been studied by cyclic voltammetry and chronoamperometry. Changes in the nucleation and growth mechanisms, which are dependent on the PA concentration and solution pH, have been observed. Formation of complexes with Ag+ ions and adsorption of the additive molecules on both, the substrate and the growing silver crystallites can be correlated with the potential dependence of the kinetic parameters, N0 and A. The amount, distribution (random or localized on the defects sites) and size of the crystallites on the substrate are influenced by the composition of the solution (PA concentration and pH) when the control of the nucleation and growth processes is regulated by application of a double potential program. © 2013 Elsevier B.V. All rights reserved. Source

Heredia A.A.,INFIQC | Penenory A.B.,INFIQC
European Journal of Organic Chemistry | Year: 2013

A new protocol for the one-pot synthesis of styryl alkyl sulfides was developed. This methodology involves the in situ generation of thiolate anions by nucleophilic substitution between potassium thioacetate and alkyl halides followed by fragmentation. Further reactions of these thiolate anions with substituted (E,Z)-β-styryl halides gave the corresponding sulfides with retention of stereochemistry in good to excellent yields. This procedure does not require a metal catalyst, it proceeds under mild conditions and in short times, and it is free from malodorous and air-sensitive alkyl thiols. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Sigal A.,National University of Cordoba | Rojas M.I.,INFIQC | Leiva E.P.M.,INFIQC
Physical Review Letters | Year: 2011

Density functional theory (DFT) calculations are performed for the adsorption energy of hydrogen and oxygen on graphene decorated with a wide set of metals (Li, Na, K, Al, Ti, V, Ni, Cu, Pd, Pt). It is found that oxygen interferes with hydrogen adsorption by either blocking the adsorption site or by the irreversible oxidation of the metal decoration. The most promising decorations are Ni, Pd, and Pt due to a reasonable relationship of adsorption energies which minimize the oxygen interference. The DFT results are used to parametrize a statistical mechanical model which allows evaluation of the effect of partial pressures in the gas phase during storage. According to this model, even in the most promising case, it is necessary to reduce the oxygen partial pressure close to ultrahigh vacuum conditions to allow hydrogen storage. © 2011 American Physical Society. Source

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