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Browsing by Author "Demirkan, Buse"

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    Ex Situ Synthesis and Characterization of a Polymer-Carbon Nanotube-Based Hybrid Nanocatalyst With One of the Highest Catalytic Activities and Stabilities for the Hydrolytic Dehydrogenation of Hydrazine-Borane at Room Temperature Conditions
    (Academic Press inc Elsevier Science, 2019) Demirkan, Buse; Kuyuldar, Esra; Karatas, Yasar; Gulcan, Mehmet; Sen, Fatih
    In this study, a facile ex situ synthesis of a polyaniline-multiwalled carbon nanotube-based Pt nanocatalyst (Pt@PANI-MWCNT) with an average particle size of 3.18 +/- 0.12 nm was performed successfully. The obtained Pt@PANI-MWCNT nanocatalysts were isolated from the solution medium by centrifugation and then were characterized by spectroscopy and microscopy methods. The characterization studies showed that the prepared Pt nanoparticles were formed on PANI-MWCNT surface, and H-2 evolution was obtained by the dehydrogenation of hydrazine-borane in water as a model reaction under room temperature conditions, with the help of the synthesized nanocatalyst. It was observed that the Pt@PANI-MWCNT nanocatalyst had a very high catalytic activity for the hydrolytic dehydrogenation of hydrazine-borane and generated 2.95 mol of H-2 for 1 mol of hydrazine-borane. The initial turn-over frequency (TOFinitial) value of the prepared nanocatalyst for the model reaction at room temperature conditions was found to be 168.5 min(-1). The calculations for the kinetics of the hydrolytic dehydrogenation reaction showed that the hydrazine-borane catalytic reaction kinetics are first order, with respect to the catalyst concentration; several activation parameters, such as entropy (Delta S-#, (app) = -72.11 +/- 3 J/mol K), enthalpy (Delta S-#, (app) = 43.5 +/- 2 kJ/mol) and activation energy (E-a,E- app = 45.5 +/- 2 kJ/mol), of the catalytic reaction with the Pt@PANI-MWCNT nanocatalyst were calculated using these kinetic data. (C) 2019 Elsevier Inc. All rights reserved.
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    Monodisperse Ru-Rh Bimetallic Nanocatalyst as Highly Efficient Catalysts for Hydrogen Generation From Hydrolytic Dehydrogenation of Methylamine-Borane
    (Elsevier Science Bv, 2019) Tacyildiz, Suat; Demirkan, Buse; Karatas, Yasar; Gulcan, Mehmet; Sen, Fatih
    In this study, the polyvinylpyrrolidone (PVP) stabilized Ru and Rh (Ru-Rh@PVP) nanocatalyst was prepared using the precursor materials of Ru, Rh and also PVP as a polymeric material, characterized and its catalytic activity was investigated by using in the hydrolytic dehydrogenation of methylamine-borane (MeAB) at room temperature. The structural and morphological properties of the Ru-Rh@PVP nanocatalyst was examined by using analytical techniques such as TEM/EELS, HRTEM, XPS, P-XRD and UV-Vis spectra. These analytical techniques revealed that Ru-Rh based nanoparticles were well distributed on the PVP with a particle size of 3.42 +/- 0.33 nm. The preparation of catalyst was done according to alcohol reduction technique and then prepared Ru-Rh@PVP nanocatalyst was tested in the hydrolytic dehydrogenation of methylamine-borane at various MeAB-Ru-Rh@PVP concentrations, temperatures and reusability performance at room temperature. The one of the best TOF (initial turnover frequency) and E-a (activation energy) values were found to be 206.2 min(-1) and 43.5 kJ/mol, respectively. (C) 2019 Elsevier B.V. All rights reserved.