4 research outputs found
Electrooxidation of C-4 polyols on platinum single- crystals: a computational and electrochemical study
Many polyols are abundant and cheap molecules highly spread in the biomass. These molecules have an enormous potential to be used in electrochemical devices to generate energy and/or value-added molecules. The electrooxidation of polyols can produce different substances of interest in the chemical industry concomitantly to high purity hydrogen in electrolyzers. The cost in the production of all these chemicals depends, among other factors, on the develop of more active and selective catalysts. However, in order to search for these materials using computational experiments, it is mandatory to have a better understanding of the fundamental aspect of the reactions, which permit to base the search on the adsorption energies of one or more key reaction intermediates. To contribute to this task, we performed (spectro)-electrochemical and computational experiments to study the electrooxidation of C-4 polyols. We show that the electrooxidation of polyols does not depend on the relative orientation of their OH groups. Besides, using Pt single crystals, we demonstrate that the trend for the oxidation of the primary carbon (relative to the secondary) increases in the order Pt(111) < Pt(100) < Pt(110) and that this result can be extended to polyols with longer carbon chains. Finally, computational experiments permit us to rationalize these trends looking at the relative stability of double dehydrogenated intermediates on the Pt basal planes.Catalysis and Surface Chemistr
1h Nmr Spectroscopy Study Of Water Adsorbed On The Surface Of Layered Ilerite
The hydrated layered alkaline silicate ilerite synthesized by a hydrothermal methodology was characterized by various techniques that confirmed a good structural quality of the resulted material. In an attempting to investigate the characteristics of water boundary layers in this hydrated powder sorbent, 1H NMR spectroscopy method was performed to measure the temperature dependence of the observed proton signal intensities in water sorbed, from 200.15 to 298.15 K. Gibbs energy of water molecules at the sorbent water interface decreased due to the sorption interactions, causing the water dosed to the sorbent surface freezes at T < 273.15 K. Due to a disturbing action of the sorbent surface and confined space, water occurs in the quasi-liquid state. As a result, it is observed in the 1H NMR spectra narrow signal relatively, but increase in peak broadening with the decrease of temperature. The presence of two types of hydrogen bonding was observed with the presence of signals around 3.9 and 16 ppm. The water at the interface freezes when the Gibbs energies of the sorbed water ice are identical. The variation of energy of ice observed in this material was 4.37 kJ mol-1 at 200.15 K with a decrease to null value at 298.15 K. © 2013 AIP Publishing LLC.153610711072Department of Science and Technology (DST, India),Department of Science and Technology (DST, Rajasthan),Council of Scientific and Industrial Research (CSIR)Pérez-Carvajal, J., Lalueza, P., Casado, C., Téllez, C., Coronas, J., (2012) Appl. Clay Sci., 56, pp. 30-35Pires, C.T.G.V.M.T., Da Costa, J.R., Airoldi, C., (2012) Micropor. Mesopor. Mater., 163, pp. 1-10Moscofian, A.S.O., Pires, C.T.G.V.M.T., Vieira, A.P., Airoldi, C., (2012) RSC Adv., 2, pp. 3502-3511Almond, G.G., Harris, R.K., Graham, P.J., (1994) Chem. Soc. Chem. Commun., pp. 851-852Turov, V.V., Brei, V.V., Khomenko, K.N., Leboda, R., (1998) Micropor. Mesopor. Mater., 23, pp. 189-196Gun'Ko, V.M., Turov, V.V., Zarko, V.I., Voronin, E.F., Tishchenko, V.A., Dudnik, V.V., Pakhlov, E.M., Chuiko, A.A., (1997) Langmuir, 13, pp. 1529-1544Turov, V.V., Bogillo, V.I., Chuiko, A.A., (1993) Ukr. Khim. Zh., 59, pp. 580-58
The Influence Of The Leaving Iodine Atom On Phyllosilicate Syntheses And Useful Application In Toxic Metal Removal With Favorable Energetic Effects
Novel nanostructured 2:1 hybrid cobalt and nickel phyllosilicates containing attached diethyl iminodiacetate moieties within the interlamellar spaces were synthesized using a mild non-hydrothermal sol-gel methodology. The organofunctionalization of these hybrids was achieved using silylating agents formed by the reaction of 3-chloropropyltriethoxysilane or 3-iodopropyltrietoxysilane with diethyl iminodiacetate, whereas 3-iodopropyltriethoxysilane was synthesized from the reaction of 3-chloropropyltriethoxysilane with NaI. The degrees of functionalization of the new materials are associated with the nucleophilic displacement of the halide atom by the nitrogen basic center of diethyl iminodiacetate during the silylating agents' syntheses. The incorporation of an iodine atom favored the introduction of bulky basic moieties in the pendant chain. For example, the degree of functionalization for the nickel phyllosilicate functionalized from 3-iodopropyltriethoxysilane, (1.83 ± 0.01) mmol g-1, was higher than that of the nickel phyllosilicate functionalized from 3-chloropropyltriethoxysilane, (0.59 ± 0.02) mmol g-1. Infrared spectroscopy combined with 13C and 29Si NMR spectroscopy confirmed the attachment of organic moieties covalently bonded to the silicon sheet network, and the lamellar 2:1 trioctahedral phyllosilicate structures were confirmed by XRD. Further characterization was provided by thermogravimetry, SEM and TEM, which exhibited thermally stable hybrids presenting well-formed particles with a homogeneous distribution of cobalt, nickel, and nitrogen. The attached basic centers have the ability to sorb lead and cadmium from aqueous solution. The sorption data fit the Langmuir model and indicated maximum lead sorption values of (2.11 ± 0.16) mmol g-1for the cobalt phyllosilicate functionalized from 3-iodopropyltriethoxysilane and (1.99 ± 0.11) mmol g-1for the hybrid prepared from 3-chloropropyltriethoxysilane, for example, reflecting the higher degree of functionalization of the former. All of the other hybrids exhibited the same tendency, even for cadmium sorption. The thermodynamic data obtained from calorimetric titration revealed the spontaneity of these chelating interactive processes, which are enthalpically and entropically favorable for the proposed cation-basic center interactions at the solid-liquid interface. This journal is4774102841038Tan, M.X., Sum, Y.N., Ying, J.Y., Zhang, Y., (2013) Energy Environ. Sci., 6, pp. 3254-3259Reddy, D.H.K., Lee, S.-M., (2013) Adv. Colloid Interface Sci., pp. 68-93Awual, M.R., Yaita, T., El-Safty, S.A., Shiwaku, H., Suzuki, S., Okamoto, Y., (2013) Chem. Eng. 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