Browsing by Author "Kuyuldar, Esra"

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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.
Polypyrrole-Multi Walled Carbon Nanotube Hybrid Material Supported Pt Nps for Hydrogen Evolution From the Hydrolysis of Meab at Mild Conditions
(Nature Portfolio, 2019) Karatas, Yasar; Kuyuldar, Esra; Acidereli, Hilal; Gulcan, Mehmet; Sen, Fatih
Herein, we report a facile method for the preparation of polypyrrole-multi walled carbon nanotube hybrid material including Pt nanoparticles (Pt@PPy-MWCNT NPs) and the use in methylamine borane (MeAB) for hydrolysis reaction at mild conditions. The prepared catalyst of Pt@PPy-MWCNT NPs was characterized by some advanced analytical methods. The catalytic experiments showed the Pt@PPy-MWCNT NPs can catalyze MeAB in aquatic solution with high catalytical performance at mild conditions. The reaction rate of catalytic hydrolysis with Pt@PPy-MWCNT NPs was found to be -d[CH3NH2BH3]/dt = + d[H-2]/3dt = kobs[Pt@PPy-MWCNT](1.19) [MeAB](0.88). The TOF value for the hydrolysis of MeAB catalyzed with Pt@PPy-MWCNT NPs was detected to be 10234.2 1/h (170.57 1/min) which is very high compared with TOF values found for other catalysts. Enthalpy, entropy and activation energy for the hydrolysis of MeAB were calculated to be 31.57 kJ mol(-1), -119.97 J mol(-1) K and 34.27 kJ mol(-1), respectively.
Single-Walled Carbon Nanotube Supported Pt-Ru Bimetallic Superb Nanocatalyst for the Hydrogen Generation From the Methanolysis of Methylamine-Borane at Mild Conditions
(Nature Portfolio, 2019) Sogut, Eda Gokirmak; Acidereli, Hilal; Kuyuldar, Esra; Karatas, Yasar; Gulcan, Mehmet; Sen, Fatih
Several metal nanoparticle based catalysts have been synthesized for catalyzing the hydrogen production process by hydrolysis of methylamine-borane (MeAB). However, there was only one study that catalyzes the producing of hydrogen via the methanolysis of MeAB, and it was carried out by our research group. For this reason, in this work, a new catalyst system entitled by single-walled carbon nanotube (SWCNT) supported bimetallic platinum-ruthenium nanoparticles were developed and called as PtRu@SWCNT. These NPs were characterized by several techniques (XRD, XPS, Raman, and TEM), and they were performed for the methanolysis of MeAB with high catalytic activity. The prepared PtRu@SWCNT NPs were also tested in the methanolysis of MeAB at different parameters including different temperatures, catalyst and substrate concentrations, and reusability performance. Experimental results revealed that the new PtRu@SWCNT NPs had excellent catalytic activity and reusability for removing of hydrogen from the methanolysis of MeAB at ambient conditions. According to the obtained data, the turnover frequency is 136.25 mole H-2/mole PtRu x min, and the activation energy (Ea) is 17.29 kJ/mole. More than 99% of conversion was observed at room temperature.