Browsing by Author "Tunc, Nihat"

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Hydrogen Generation From Hydrolytic Dehydrogenation of Hydrazine Borane by Poly(n-Vinyl Palladium Nanoparticles
(Elsevier Science Bv, 2015) Tunc, Nihat; Abay, Bayram; Rakap, Murat
Poly(N-vinyl-2-pyrrolidone)-stabilized palladium nanoparticles (3.5 +/- 1.0 nm) are efficient catalysts in the hydrolytic dehydrogenation of hydrazine borane to give hydrogen gas. The catalyst, prepared by reduction of palladium metal ion in ethanol/water mixture by an alcohol reduction method, is durable and efficient catalysts for hydrogen generation from the hydrolytic dehydrogenation of hydrazine borane even at very low concentrations and temperature, providing an average turnover frequency of 42.9 min(-1) with an activation energy of 54.5 +/- 2 kJ mol(-1) for the hydrolytic dehydrogenation of hydrazine borane. (C) 2015 Elsevier B.V. All rights reserved.
Hydrolysis of Ammonia Borane and Hydrazine Borane by Poly(n-Vinyl Copd Nanoparticles for Chemical Hydrogen Storage
(Tubitak Scientific & Technological Research Council Turkey, 2017) Rakap, Murat; Abay, Bayram; Tunc, Nihat
For the first time the synthesis of poly(N-vinyl-2-pyrrolidone)-stabilized cobalt-palladium nanoparticles by an easy method, their characterization, and their use as active catalysts for hydrogen release from hydrolysis of ammonia borane and hydrazine borane is reported here. The catalyst is prepared by simultaneous reduction of suitable cobalt and palladium ions by sodium borohydride in the presence of poly(N-vinyl-2-pyrrolidone) as a stabilizer. They are characterized by UV-Vis spectroscopy, TEM analysis, X-ray diffraction, and X-ray photoelectron spectroscopy. They provide average turnover frequencies of 30 min(-1) and 45 min(-1) in the hydrolysis of ammonia borane and hydrazine borane. They also provide activation energies of 48.6 +/- 2 and 50.6 +/- 2 kJ mol(-1) in the hydrolysis of ammonia borane and hydrazine borane.
Instant Hydrogen Release From Ethylenediamine Bisborane by Highly Efficacious Rh Catalysts Via Hydrolysis
(Elsevier, 2025) Tunc, Nihat; Rakap, Murat
This current study reports preparation, characterization, and first-time catalytic employment of rhodium nanoparticles (2.6 nm) stabilized by polyvinylpyrrolidone (PVP) in hydrolysis of ethylenediamine bisborane (EDAB) to release hydrogen gas needed for fuel cells. Rhodium nanoparticles stabilized by PVP are characterized by advanced analytical techniques like fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). They are identified as the most effective catalyst up to date for hydrogen gas evolution from EDAB hydrolysis with the highest turnover frequency (TOF) value of 1928.6 min- 1. They also provide 4821 total turnovers in the same hydrolysis reaction. Their energy (Ea), enthalpy (Delta H#), and entropy (Delta S#) of activation in EDAB hydrolysis are determined to be 65.5 kJmol-1, 63.1 kJmol-1, and -49.3 Jmol-1K-1.
Nanoceria-Supported Ru-Based Nanoparticles as Highly Efficient Catalysts for Hydrolysis of Ethane 1,2-Diamine Borane
(Wiley-v C H verlag Gmbh, 2022) Tunc, Nihat; Rakap, Murat
Here, the first ever preparation of some series of nanoceria-supported Ru-based nanoparticles with different compositions (RuxM100-x@NC, M: Co, Ni, Pd) and their use as highly active catalysts to liberate hydrogen gas from hydrolysis of ethane 1,2-diamine borane (EDAB) is reported. For the preparation of totally fifteen RuxM100-x@NC nanoparticles with different compositions, the related metal cations are first supported on nanoceria surfaces by wet impregnation method in aqueous solution. Then, Ru3+-M2+-exchanged nanoceria samples are synchronously reduced during hydrolysis reaction of EDAB to form corresponding RuxM100x@NC nanoparticles meanwhile the formed nanoparticles catalyze the same reaction. RuxM100x@NC nanoparticles are identified by inductively coupled plasma-optical emission spectroscopy (ICP-OES), powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and BET surface area techniques. They provide quiet high catalytic activities in the hydrolysis reaction of EDAB. Among them, Ru20Pd80@NC nanoparticles are by far the best one up to date with a TOF value of 608.49 min(-1) at 25 degrees C.
Nickel-Rhodium Nanoparticles as Active and Durable Catalysts for Hydrogen Liberation
(Taylor & Francis inc, 2020) Tunc, Nihat; Rakap, Murat
Herein, synthesis, characterization, and catalytic utilization of rather efficient carboxymethyl cellulose-stabilized nickel-rhodium nanoparticles (4.5 +/- 0.7 nm) in hydrogen liberation from ammonia borane and hydrazine borane by hydrolysis are reported. The catalysts are prepared by simultaneous reduction of appropriate nickel and rhodium salts in aqueous solution by sodium borohydride by using carboxymethyl cellulose as a stabilizer. Transmission electron microscopy, ultraviolet-visible spectroscopy, and X-ray photoelectron spectroscopy are used to characterize the catalysts. The catalysts are highly durable and effective to liberate hydrogen from ammonia borane and hydrazine borane in aqueous solution at lower concentrations and temperature. Among prepared catalysts, Ni0.50Rh0.50@CMC provides 200 min(-1) and 188 min(-1) of average turnover frequencies and 46.8 +/- 2 kJ/mol and 60.3 +/- 2 kJ/mol of activation energies for ammonia borane and hydrazine borane hydrolysis reactions, respectively.
Preparation and Characterization of Ni-M (M: Ru, Rh, Pd) Nanoclusters as Efficient Catalysts for Hydrogen Evolution From Ammonia Borane Methanolysis
(Pergamon-elsevier Science Ltd, 2020) Tunc, Nihat; Rakap, Murat
Here, first-time preparation, characterization, and catalytic use of hydroxyapatite-supported nickel-based Ni-M (NiRu@HAP, NiRh@HAP, NiPd@HAP) nanoclusters in hydrogen evolution from methanolysis of ammonia borane is reported. Ni-M nanoclusters have been in-situ formed by reduction of hydroxyapatite-supported corresponding metal ions during methanolysis reaction of ammonia borane. The hydroxyapatite-supported Ni-M nanoclusters are isolated as stable solid materials to be characterized by advanced analytical techniques of ICP-OES, TEM, XPS, and XRD. They are found to be isolable, highly redispersible and reusable nanocatalysts for hydrogen evolution from ammonia borane methanolysis under ambient conditions. Ni20Ru80@HAP, Ni38Rh62@HAP, and Ni20Pd80@HAP nanoclusters have TOF values of 58.9, 120.3, and 25.2 min(-1), respectively, in the methanolysis of ammonia borane at 25 +/- 0.1 degrees C. Their apparent activation energy (E-a) values for the same reaction are calculated to be 65.9, 66.8, and 58.1 kJ/mol, respectively, for Ni20Ru80@HAP, Ni38Rh62@HAP, and Ni20Pd80@HAP nanoclusters. (C) 2020 Elsevier Ltd. All rights reserved.
Surfactant-Aided Synthesis of Rhco Nanoclusters as Highly Effective and Recyclable Catalysts for the Hydrolysis of Methylamine Borane and Dimethylamine Borane
(Royal Soc Chemistry, 2020) Tunc, Nihat; Rakap, Murat
In the present study, the first ever and easy surfactant-aided synthesis of hexadecyltrimethyl ammonium bromide-stabilized RhCo nanoclusters (Rh0.63Co0.37@CTAB) and their employment as highly efficient, relatively cost-saving, and recyclable catalysts to generate hydrogen from the hydrolysis reactions of methylamine borane (MeAB) and dimethylamine borane (DMAB) are reported. The easy synthesis of Rh0.63Co0.37@CTAB nanoclusters is accomplished by synchronous reduction of appropriate rhodium and cobalt salts by sodium borohydride in the presence of CTAB as a surfactant in aqueous solution at room temperature. The Rh0.63Co0.37@CTAB nanoclusters are characterized by some techniques like ultraviolet-visible electronic absorption spectroscopy (UV-vis), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). They provide very remarkable turnover frequencies (TOFs) of 107.1 min(-1) and 142.9 min(-1) (8571.4 h(-1), best ever value) in the hydrolysis of MeAB and DMAB, respectively, even at very low temperatures. Their activation energies in the same reactions are calculated to be 55.3 kJ mol(-1) and 50.3 kJ mol(-1), respectively.
Surfactant-Aided Synthesis of Rhco Nanoclusters as Highly Effective and Recyclable Catalysts for the Hydrolysis of Methylamine Borane and Dimethylamine Borane (Vol 10, Pg 7865, 2020)
(Royal Soc Chemistry, 2021) Tunc, Nihat; Rakap, Murat