Browsing by Author "Karahan, Senem"

Now showing 1 - 3 of 3

Catalytic Methanolysis of Hydrazine Borane: a New and Efficient Hydrogen Generation System Under Mild Conditions
(Royal Soc Chemistry, 2012) Karahan, Senem; Zahmakiran, Mehmet; Ozkar, Saim
Safe and efficient hydrogen storage is a major obstacle for using hydrogen as an energy carrier. Therefore, intensive efforts have been focused on the development of new materials for chemical hydrogen storage. Of particular importance, hydrazine borane (N2H4BH3) is emerging as one of the most promising solid hydrogen carriers due to its high gravimetric hydrogen storage capacity (15.4 wt%) and low molecular weight. Herein, we report metal catalyzed methanolysis of hydrazine borane (N2H4BH3, HB) as a fast hydrogen generation system under mild conditions. When trace amounts of nickel(II) chloride (NiCl2) is added to the methanol solution of hydrazine borane ([HB]/[Ni] >= 200) the reaction solution releases 3 equiv. of H-2 with a rate of 24 mol H-2 (mol Ni min)(-1) at room temperature. The results reported here also includes (i) identification of the reaction products by using ATR-IR, DP-MS, H-1 and B-11 NMR spectroscopic techniques and the establishment of the reaction stoichiometry, (ii) investigation of the effect of substrate and catalyst concentrations on the hydrogen generation rate to determine the rate law for the catalytic methanolysis of hydrazine borane, (iii) determination of the activation parameters (E-a, Delta H-#, and Delta S-#) for the catalytic methanolysis of hydrazine borane by using the temperature dependent rate data of the hydrogen generation.
A Facile One-Step Synthesis of Polymer Supported Rhodium Nanoparticles in Organic Medium and Their Catalytic Performance in the Dehydrogenation of Ammonia-Borane
(Royal Soc Chemistry, 2012) Karahan, Senem; Zahmakiran, Mehmet; Ozkar, Saim
A new type of supported rhodium nanoparticles were reproducibly prepared from N2H4BH3 reduction of [Rh(mu-Cl)(1,5-cod)](2) without using any solid support and pre-treatment technique. Their characterization shows the formation of well dispersed rhodium(0) nanoparticles within the framework of a polyaminoborane based polymeric support. These new rhodium(0) nanoparticles were found to be the most active supported catalyst in the catalytic dehydrogenation of ammonia-borane in water at room temperature.
Hydrogen Generation From the Hydrolysis of Hydrazine-Borane Catalyzed by Rhodium(0) Nanoparticles Supported on Hydroxyapatite
(Pergamon-elsevier Science Ltd, 2012) Celik, Derya; Karahan, Senem; Zahmakiran, Mehmet; Ozkar, Saim
Herein, we report the preparation and characterization of rhodium(0) nanoparticles supported on hydroxyapatite (Ca-10(OH)(2)(PO4)(6), HAP) and their catalytic use in the hydrolysis of hydrazine-borane, which attracts recent attention as promising hydrogen storage materials. Hydroxyapatite supported rhodium(0) nanoparticles were readily prepared by the hydrazine-borane reduction of rhodium(III)-exchanged hydroxyapatite in situ during the hydrolysis of hydrazine-borane at room temperature. Characterization of the resulting material by ICP-OES, TEM, SEM, EDX, XRD, XPS spectroscopies and N-2 adsorption-desorption technique, which shows the formation of rhodium(0) nanoparticles well dispersed on hydroxyapatite support. The catalytic performance of these new supported rhodium(0) nanopaiticles in terms of activity, lifetime and reusability was tested in the hydrolysis of hydrazine-borane. They were found to be highly active, long-lived and reusable catalyst in this important catalytic reaction even at low temperatures and high initial [substrate]/[catalyst] conditions. This report also includes the detailed kinetic study of the hydrolysis of hydrazine-borane catalyzed by hydroxyapatite supported rhodium(0) nanoparticles depending on the catalyst concentration, substrate concentration, and temperature. Copyright (C) 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.