Browsing by Author "Karatas, Yasar"

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Amylamine Stabilized Platinum(0) Nanoparticles: Active and Reusable Nanocatalyst in the Room Temperature Dehydrogenation of Dimethylamine-Borane
(Royal Soc Chemistry, 2014) Sen, Fatih; Karatas, Yasar; Gulcan, Mehmet; Zahmakiran, Mehmet
Herein, we report the preparation and characterization of platinum(0) nanoparticles stabilized by amylamine (C5H11NH2) ligands plus their catalytic use in the room temperature dehydrocoupling of dimethylamine-borane ((CH3)(2)NHBH3), which has attracted recent attention as a promising solid hydrogen storage material. Amylamine stabilized platinum(0) nanoparticles were reproducibly generated by an ethanol-superhydride reduction method and their preliminary characterization was done by ICP-OES, XRD, ATR-IR, TEM, HRTEM, and XPS spectroscopies. The sum of their results shows the formation of highly crystalline and colloidally stable platinum(0) nanoparticles. The catalytic performance of these new platinum(0) nanoparticles in terms of activity, isolability and reusability was investigated in the catalytic dehydrocoupling of dimethylamine-borane, in which they were found to be active and reusable heterogeneous catalysts even at room temperature.
Carbon-Nanotube Rhodium Nanoparticles as Highly-Active Catalyst for Hydrolytic Dehydrogenation of Dimethylamineborane at Room Temperature
(Academic Press inc Elsevier Science, 2018) Gunbatar, Serdar; Aygun, Aysenur; Karatas, Yasar; Gulcan, Mehmet; Sen, Fatih
In this study, we present a carbon nanotube-based Rh nanomaterial as a highly active catalyst for the hydrolytic dehydrogenation of dimethylamine - borane (DMAB) at room temperature. The prepared multi-walled carbon nanotube based Rh nanoparticles, called Rh NPs@ MWCNT, was readily prepared, stabilized and effectively used for the hydrolytic dehydrogenation of DMAB under ambient conditions. Monodisperse Rh NPs@ MWCNT nanocatalyst was characterized by using advanced analytical methods such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM) etc. These analytical methods revealed that Rh nanoparticles on the surface of MWCNT were well dispersed and the average particle size was found to be 1.44 +/- 0.17 nm. The catalytic experiments revealed that the new Rh NPs@MWCNT nanocatalyst has a high catalytic effect to obtain hydrogen in 3.0 equation from DMAB, and the record catalytic TOF value for the catalytic reaction catalyzed by Rh NPs@MWCNT nanocatalyst was found to be 3010.47 h(-1) at room temperature. The current study presents the detailed kinetic studies of the hydrolytic dehydrogenation of DMAB catalyzed by Rh NPs@MWCNT, the results of catalytic experiments were performed at different temperatures, substrate and catalyst concentrations, the Rh NPs@MWCNT nanocatalyst was effectively used in the completion of the hydrolytic dehydrogenation of DMAB, and activation energy, enthalpy and entropy parameters. The experimental results showed that monodisperse Rh NPs@MWCNT nanocatalyst have record catalytic activity with TOF value of 3010.47 h(-1), and Rh(0) nanoparticles were well dispersed on the multi-walled carbon nanotubes. (C) 2018 Elsevier Inc. All rights reserved.
The Catalytic Activity of Halloysite-Supported Ru Nanoparticles in the Methanolysis of Sodium Borohydride for Hydrogen Production
(Pergamon-elsevier Science Ltd, 2023) Gozeten, Ibrahim; Karakas, Kadir; Karatas, Yasar; Tunc, Mehmet; Gulcan, Mehmet
Finding environmentally friendly new energy sources is very urgent for a sustainable and clean energy future. It is vital to reach clean energy sources such as hydrogen, which does not create a polluting by-product when burned with oxygen. In this study, for a livable clean universe, hydrogen production studies were carried out from sodium borohydride (NaBH4), which is a very good hydrogen storage material, in a methanolysis environment, over ruthenium nanoparticles (Ru (0) NPs) impregnated on halloysite (Hall) support ma-terial (Ru (0)@Hall) at room conditions. The catalytic performance of the newly synthesized Ru (0)@Hall nanocatalyst was tested in the NaBH4 methanolysis reaction for hydrogen production. It was determined that Ru (0)/Hall nanocatalyst showed excellent activity (initial turn-over frequency (TOFinitial) = 1882 h-1; 31.37 min-1) and reusability (at the end of the 5th cycle, it retained 90% of its initial activity) performance in the catalytic meth-anolysis of NaBH4. The analyzes of the Ru (0)@Hall nanocatalyst, both fresh and at the end of the 5th catalytic cycle, were made with advanced analytical methods (ICP-OES, XRD, XPS, SEM, HRTEM, TEM, TEM-EDX, BET) and the nature of the catalytic material was clarified. The results showed the homogeneous distribution of Ru (0) NPs on the Hall surface (mean size = 1.53 +/- 0.17 nm). Kinetic studies of hydrogen production from catalytic methanolysis reaction of NaBH4 were performed based on nanocatalyst [Ru (0)@Hall], substrate [NaBH4] concentrations, and temperature (298-318 K). From the kinetic data, the kinetic parameters (Ea, DH*, and DS*) were calculated and the rate equation was determined.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Catalytic Methanolysis and Hydrolysis of Hydrazine-Borane With Monodisperse Ru Nps@nano-Ceo2 Catalyst for Hydrogen Generation at Room Temperature
(Pergamon-elsevier Science Ltd, 2019) Karatas, Yasar; Gulcan, Mehmet; Sen, Fatih
Herein, we report metal catalyzed methanolysis and hydrolysis of hydrazine-borane as a fast hydrogen generation system under mild conditions. To the best of our knowledge, this is the first report that a monodisperse Ru NPs@nano-CeO2 catalyst can achieve a complete conversion of N2H4BH3 to H-2 with the assistance of both methanolysis and hydrolysis reactions. In order to achieve hydrolysis and methanolysis effectively, monodisperse Ru NPs@nano-CeO2 catalyst have been prepared by modifying the chemical reduction method which is a very simple and efficient method in room conditions. The synthesized Ru NPs@nano-CeO2 catalyst showed excellent catalytic activity, stability, and selectivity in the production of hydrogen by both hydrolysis and methanolysis of the hydrazine-borane. The results reported here also includes (i) identification of the prepared catalyst by using analytical techniques such as XRD, XPS, TEM, HR-TEM, (ii) determination of stoichiometry for methanolysis and hydrolysis reactions, (iii) determination of rate constants and laws for methanolysis and hydrolysis reactions, (iv) determination of kinetic parameters such as enthalpy, entropy and activation energy for methanolysis and hydrolysis reactions. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Enhancement of Adsorption Capacity of Reduced Graphene Oxide by Sulfonic Acid Functionalization: Malachite Green and Zn (Ii) Uptake
(Elsevier Science Sa, 2020) Sogut, Eda Gokirmak; Karatas, Yasar; Gulcan, Mehmet; Kilic, Necla Caliskan
Graphene oxide (GO) was synthesized according to the Hummers' method developed to remove some impurities such as malachite green dye and Zn (II) metal ion from aqueous solutions. However, due to the problem of dispersion in water, graphene oxide surface is generally functionalized or composites are prepared with different materials. For this reason, the produced graphene oxide is functionalized with sulfanilic acid to obtain reduced sulfonated graphene oxide (rGO-SO3H). For the characterization of materials, DR/UV-vis, Raman, FT-IR, SEM and SEM-EDX mapping techniques were used. Also, reduced graphene oxide (rGO) was evaluated as a comparative example in adsorption. Effect of parameters such as pH, initial concentration and temperature on the removal of metal ions and dye was studied. Equilibrium was achieved in 90 min. The highest percentage removal of rGO and rSGO was observed at pH = 7. Equilibrium isotherms are defined using nonlinear Langmuir, Freundlich, Dubinin - Radushkevich (D - R) and Sips adsorption isotherm equations. Maximum adsorption capacities were determined as 588.23 mg g 1 and 1111.11 mg g(-1) for malachite green, 166.66 mg g(-1) and 322.58 mg g(-1) for Zn (II), respectively for rGO and rGO-SO3H. Kinetic experimental results fit well with the pseudo-second order model for both dye and metal ion; coefficients of determination were close to 1. Thermodynamic studies showed that the adsorption was spontaneous and the adsorption processes were controlled by a physical mechanism.
Enhancing the Catalytic Activity of Pd Nanoparticles in the Hydrolysis of Ethylenediamine-Bisborane Through Sulfonation of Graphene Oxide as a Solid Support
(Pergamon-elsevier Science Ltd, 2024) Karatas, Yasar; Gulcan, Mehmet
Ethylenediamine-bisborane (EDB), with its high hydrogen storage capacity, has been in the limelight among researchers. In this study, a new catalytic hybrid material (Pd@rGO-SO3H), comprising sulfonated reduced graphene oxide (rGO-SO3H) and palladium (Pd), was developed. This material serves as a highly efficient and reusable catalyst in the hydrogen production from EDB hydrolysis. The synthesized EDB, rGO-SO3H, and Pd@rGO-SO3H were characterized using ICP-OES, PXRD, XPS, SEM, TEM, and TEM/EDX tools. The initial TOF value of the Pd@rGO-SO3H catalyst in hydrogen production from EDB hydrolysis was calculated as 136 min- 1. This TOF value was found to be remarkably high compared to related studies in the literature. The reusability performance of Pd@rGO-SO3H was observed to be quite stable. Finally, activation parameters, such as activation energy (Ea), activation enthalpy (Delta H#), and activation entropy (Delta S#) for the hydrolysis reaction, were calculated by conducting catalytic reactions at different temperatures using relevant equations.
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.
Fabrication and Characterization of Copper Nanoparticles Anchored on Sulfonated Reduced Graphene Oxide as Effective Catalyst for the Reduction of Thioflavine-T Cationic Dye in Aqueous Medium
(Elsevier Science Sa, 2022) Yildirim, Rahel; Karatas, Yasar; Demirci, Umit B.; Gulcan, Mehmet
The development of innovative methods for the effective removal of toxic organic pollutants from wastewater is of paramount importance. Removal of organic pollutants from aqueous media by chemical reduction using low cost metal-based nanocatalysts and in the presence of sodium borohydride (NaBH4), as a reducing agent, has become a very valuable approach in recent years. We report the advanced catalytic property of copper (0) nanoparticles (Cu NPs) supported on sulfonated reduced graphene oxide (Cu@rGO-SO3H) for the catalytic reduction of thioflavine-T (ThT) dye in the presence of NaBH4, at moderate conditions. Cu@rGO-SO3H catalyst was synthesized by the impregnation-reduction method and diverse characterization techniques were applied to explain the structure and morphology. The results show that the Cu NPs are perfectly dispersed on the surface of the rGO-SO3H support surface (d(mean) = 6.9 +/- 0.4 nm). The catalytic activity of the Cu@rGO-SO3H catalyst was tested in the reduction of ThT in water at 298 K in the presence of NaBH4 and the excellent activity of catalyst have been detected against ThT with 30.5 min(-1) initial turn-over frequency (TOFinitial) value. Another important point is that the catalyst has good reusability performance (at 5th reuse 68%) for the catalytic reduction of ThT. Our catalytic studies were also carried out at various temperatures in order to calculate the E-a, Delta H-not equal and Delta S-not equal.
Green and Efficient Oxidative Desulfurization of Refractory S-Compounds From Liquid Fuels Catalyzed by Chromium-Based Mil-101 Stabilized Moox Catalyst
(Elsevier, 2022) Gumus, Ilkay; Karatas, Yasar; Gulcan, Mehmet
In this work, MoOx/MIL-101(Cr) a new composite material, involving the collaboration of MoOx and MIL-101 (Cr) to remove the refractory S-compounds (RSCs) from fuels via oxidative desulfurization (ODS) process were successfully synthesized. The prepared catalyst was characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDX), powder X-ray diffraction (P-XRD), inductively coupled plasma optical emission spectroscopy (ICP-OES), fourier transform infrared spectroscopy (FT-IR), N-2 sorption measurement (BET) and X-ray photoelectron spectroscopy (XPS). The prepared MoOx/MIL-101(Cr) was applied for the ODS of model fuel oil and showed the remarkably catalytic activity for the removal of RSCs from model fuel oil via oxidation. In addition, the effect of Mo-loading amount, H2O2/sulfur (O/S) molar ratio, and reaction temperature on the ODS reactivity were investigated. To explore the specific reaction mechanism of ODS over the MoOx/MIL-101(Cr), the effect of radical scavengers on ODS activity was examined. The radical scavengers experiments showed that the present oxidation reaction occurred through a radical mechanism involving the formation of center dot OH and center dot O-2 species. In addition, it was found that the ODS efficiency is majorly related to the Mo5+ species forming with electron transfer to Mo6+ ion from Lewis acid sites of MIL-101(Cr). Furthermore, the MoOx/MIL-101(Cr) catalyst possesses recycling performance and remarkable stability, and even after five recycles, the removal of DBT was > 94.8%. Hence, it could be confirmed that MoOx/MIL-101(Cr) is very useful in the ODS to remove RSCs from fuels in the presence of H2O2.
High-Efficiency Hydrogen Production From Hydrazine Borane Using Cu/Mil-53(al) Nanocatalysts: Synthesis, Characterization, and Performance Evaluation Nanocatalysts Supported on Mil-53(al)
(Wiley-v C H verlag Gmbh, 2025) Karatas, Yasar
This work highlights the novelty of investigating hydrogen production from hydrazine borane (HB) using copper (Cu). This first-row transition metal is abundant yet underexplored as a catalyst compared to precious metals. We focus on The synthesis of Cu nanoparticles supported on MIL-53(Al) (Cu/MIL-53(Al)) through an impregnation-reduction method and evaluate their performance in HB hydrolysis. Advanced characterization techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and TEM-energy-dispersive X-ray spectroscopy (TEM-EDX), reveal an average Cu nanoparticle size of 3.94 +/- 0.32 nm. Notably, the turnover frequency (TOF) for hydrogen production with Cu/MIL-53(Al) at 298 K was 966 h(-)(1) (16.1 min(-)(1)), representing the highest TOF reported for Cu-based systems in HB hydrolysis. Furthermore, we calculated the activation energy (Ea#), activation enthalpy (Delta H#), and activation entropy (Delta S#) for the Cu/MIL-53(Al) catalyst as 83.77 kJ mol(-)(1), 81.15 kJ mol(-)(1), and 48.56 J mol(-)(1) K--(1), respectively, using the Arrhenius and Eyring-Polanyi equations. These findings underscore the potential of Cu/MIL-53(Al) as an efficient and cost-effective catalyst for hydrogen production, significantly advancing sustainable hydrogen energy technologies.
Highly Efficient and Selective One-Pot Tandem Imine Synthesis Via Amine-Alcohol Cross-Coupling Reaction Catalysed by Chromium-Based Mil-101 Supported Au Nanoparticles
(Elsevier, 2021) Gumus, Ilkay; Ruzgar, Adem; Karatas, Yasar; Gulcan, Mehmet
One-pot tandem synthesis of imines from alcohols and amines is regarded as an effective, economic and green approach under mild conditions. In this work, Au nanoparticles (NPs) dispersed on MIL-101 (Au/MIL-101) were demonstrated as highly active and selective bifunctional heterogeneous catalyst for production of various imine derivatives with excellent yields, via amine-alcohol cross-coupling reaction at 343 K in an open flask under an Ar atmosphere. Various physicochemical techniques, including inductively coupled plasma optical emission spectroscopy (ICP-OES), powder X-ray diffraction (P-XRD), X-ray photoelectron spectroscopy (XPS) transmission electron microscopy (TEM) and N2 adsorption-desorption, were used to characterize of the Au/MIL-101 catalyst. The obtained bifunctional catalyst is highly active and selective towards one-pot imine formation and exhibited the highest TOF (30.15-51.47 h(-1)) among all the ever-reported MOF-supported Au catalysts. The reaction mechanism of the imine formation from alcohol and amine over Au/MIL-101 catalyst was proposed. Mechanism experiment results demonstrate that Au NPs highly effective in activating oxidation of benzyl alcohol to benzaldehyde while the Lewis acid sites on MIL-101 catalyzed the second condensation step without interfering with the oxidation step. As a result, the excellent catalytic performance of Au/MIL-101 can be ascribed to the synergistic effect between Au NPs with Lewis acid sites in MIL-101.
Improved Efficiency in Dye Sensitized Solar Cell (Dssc) by Nano-Mil Impregnated Photoanode
(Walter de Gruyter Gmbh, 2022) Ugur, Ali; Imer, Arife Gencer; Kaya, Esra; Karatas, Yasar; Gulcan, Mehmet
In the present work, MIL-101 nanoparticles (nano-MIL-101(Cr)) metal-organic framework (MOF) structure was synthesized by hydrothermal method, and characterized via Fourier transform infrared, X-ray diffraction, and scanning electron microscopy techniques. The optoelectronic application of MOFs was investigated for the first time. For this purpose, the dye-sensitized solar cells (DSSCs) consisting of the synthesized nano-MIL-101(Cr) impregnated photoanode (PA) was fabricated, and photovoltaic, photoelectric properties of them were investigated under different illumination intensities, and the obtained results were compared with reference one. The DSSC fabricated by impregnated PA showed better photovoltaic properties than reference one. It is obtained the power conversion efficiency (PCE) of about 0.828 and fill factor (ff) of 0.656 for the fabricated DSSC based on nano-MIL-101(Cr) impregnated PA under illumination power of 100 mW/cm(2) by AM1.5 G solar simulator. For the reference DSSC, PCE, and ff is about 0.468 and 0.28, respectively. The PCE of the fabricated device based on nano-MIL-101(Cr) is similar to 77% greater than the reference one. The improvement in the efficiency is because of good electrocatalytic activity, large pores, and high surface area of nano-MIL-101(Cr). The nano-MIL-101(Cr) can be used in organo-optoelectronic device fabrication to obtain better performance.
In Situ Formed Ruthenium(0) Nanoparticles Supported on Tio2 Catalyzed Hydrogen Generation From Aqueous Ammonia-Borane Solution at Room Temperature Under Air
(Taylor & Francis inc, 2016) Konus, Nihayet; Karatas, Yasar; Gulcan, Mehmet
Herein, the authors report that TiO2 supported ruthenium nanoparticles (Ru(0)/TiO2) during hydrolysis starting with RuCl3/TiO2 precatalyst act as highly active, long-lived, and reusable nanocatalyst in the hydrogen generation from the hydrolysis of ammonia-borane (NH3BH3) at room temperature. The resulting Ru(0)/TiO2 catalyze hydrogen generation from the hydrolysis of ammonia-borane with an initial turnover frequency value of 200min(-1) at 25 +/- 0.1 degrees C. More importantly, Ru(0)/TiO2 are stable enough to be isolated and bottled as solid material, which can be reused as active catalyst under the identical conditions of the first run.
Manganese Oxide Octahedral Molecular Sieves Stabilized Rh Nanoparticles for the Hydrogen Production From the Ethylenediamine-Bisborane Hydrolysis
(Pergamon-elsevier Science Ltd, 2022) Celebi, Metin; Ruzgar, Adem; Karatas, Yasar; Gulcan, Mehmet
Ethylenediamine-bisborane (C2H14B2N2, BH3NH2CH2CH2NH2BH3, EDB), an important carbon derivative of ammonia-borane (AB), has come to the fore in recent years due to some disadvantages that limit the practical use of AB for the applications of hydrogen storage. EDB is a very promising chemical hydrogen storage material in the solid crystal form at room temperature, with a hydrogen content of 16.3% by weight, which decomposes rapidly at temperatures above 363 K. Despite all these superior features, studies on catalytic systems that catalyze the hydrogen production from the EDB are very few. In the present study, we report the synthesis, characterization, and application of manganese oxide octahedral molecular sieves (OMS-2) stabilized Rh nanoparticles (Rh@OMS-2) as highly efficient and reusable catalysts for the hydrogen production from the hydrolysis of EDB. The results of characterization using P-XRD, XPS, FT-IR, SEM, SEM-elemental mapping, TEM, HR-TEM, and ICP-OES disclose that Rh (0) nanoparticles were well spread on the surface of OMS-2 nanorods. Rh@OMS-2 showed a record catalytic activity in EDB hydrolysis with an initial turn-over frequency of 102.95 min(-1) (6177 h(-1)) at 25 +/- 0.1 degrees C, the highest value ever reported for the hydrolysis of EDB. In addition, the fact that the Rh@OMS-2 catalyst kept its initial activity at the end of the 7th cycle in the hydrolysis of EDB showed that the Rh@OMS-2 was reusable and stable heterogeneous catalyst in this catalytic transformation. (c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Mnox-Promoted Pdag Alloy Nanoparticles for the Additive-Free Dehydrogenation of Formic Acid at Room Temperature
(Amer Chemical Soc, 2015) Bulut, Ahmet; Yurderi, Mehmet; Karatas, Yasar; Say, Zafer; Kivrak, Hilal; Kaya, Murat; Zahmakiran, Mehmet
Formic acid (HCOOH) has a great potential as a safe and a convenient hydrogen carrier for fuel cell applications. However, efficient and CO-free hydrogen production through the decomposition of formic acid at low temperatures (<363 K) in the absence of additives constitutes a major challenge. Herein, we present a new heterogeneous catalyst system composed of bimetallic PdAg alloy and MnOx nanoparticles supported on amine-grafted silica facilitating the liberation of hydrogen at room temperature through the dehydrogenation of formic acid in the absence of any additives with remarkable activity (330 mol H-2 center dot mol catalyst(-1)center dot h(-1)) and selectivity (>99%) at complete conversion (>99%). Moreover this new catalytic system enables facile catalyst recovery and very high stability against agglomeration, leaching, and CO poisoning. Through a comprehensive set of structural and functional characterization experiments, mechanistic origins of the unusually high catalytic activity, selectivity, and stability of this unique catalytic system are elucidated. Current heterogeneous catalytic architecture presents itself as an excellent contender for clean hydrogen production via room-temperature additive-free dehydrogenation of formic acid for on-board hydrogen fuel cell applications.
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.
A New Highly Active Polymer Supported Ruthenium Nanocatalyst for the Hydrolytic Dehydrogenation of Dimethylamine-Borane
(Elsevier Science Bv, 2019) Karatas, Yasar; Aygun, Aysenur; Gulcan, Mehmet; Sen, Fatih
Herein, we report a highly active Ru@PVP nanocatalyst for the hydrolytic dehydrogenation of dimethylamine-borane under room conditions. The Ru@PVP nanocatalyst was readily prepared, stabilized and used effectively in the catalytic dehydrogenation reaction of dimethylamine-borane in water at room conditions. The prepared Ru@PVP nanocatalyst was characterized using advanced analytical methods such as XPS, XRD, HR-TEM, etc. The characterization analyzes shown that Ru metals are uniformly distributed on the PVP support surface; the mean particle of catalyst size was found to be 2.78 +/- 0.16 nm. The catalytic test showed that DMAB had a high catalytic activity with Ru@PVP in aqueous solutions, and TOF value was found to be 2500.52 h(-1) for hydrolytic dehydrogenation of DMAB at room conditions. The study also included kinetic data such as activation parameters for different temperatures, catalyst concentration, and substrate concentration experiments. (C) 2019 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
Palladium (0) Nanoparticles Distributed on Lanthanum (Iii) Oxide as an Effective Catalyst for the Methanolysis of Hydrazine-Borane To Produce Hydrogen
(Tubitak Scientific & Technological Research Council Turkey, 2024) Ruzgar, Adem; Sener, Lokman; Karatas, Yasar; Gulcan, Mehmet
Pd (0) nanoparticles (NPs) distributed on lanthanum (III) oxide were ex situ generated from the reduction of Pd2+ ions using NaBH4 as reducing agent. The Pd/La2O3 displayed good catalytic activity in H2(g) releasing from the hydrazine-borane (HB) methanolysis reaction and it was identified by advanced techniques. Pd/La2O3 was found to be an active catalyst procuring three equiv. H2(g) per mole of HB. The results from TEM images represent the formation of Pd (0) NPs with an average particle size of 1.94 +/- 0.1 nm on the surface of La2O3. Moreover, Pd/La2O3 with various Pd loadings were prepared and tested as catalyst in the methanolysis reaction to find the optimum metal loading on La2O3 support. The highest H2 formation rate was achieved with 3.0 wt% Pd. Pd/La2O3 catalyst exhibited a turnover frequency (TOF) value of 24.4 mol H2 mol Pd-1 min-1 in the reaction conditions. Additionally, the effect of different catalyst concentrations and temperatures on the reaction kinetics for the methanolysis of HB catalyzed by Pd/La2O3.
Palladium Nanoparticles Decorated on Amine Functionalized Graphene Nanosheets as Excellent Nanocatalyst for the Hydrogenation of Nitrophenols To Aminophenol Counterparts
(Elsevier Science Bv, 2019) Sogukomerogullari, Hatice Gamze; Karatas, Yasar; Celebi, Metin; Gulcan, Mehmet; Sonmez, Mehmet; Zahmakiran, Mehmet
We reported the improved catalytic property of Pd (0) nanoparticles decorated on amine-functionalized graphene nanosheets (Pd/GNS-NH2) for the hydrogenation of nitrophenol derivatives in the presence of NaBH4 at moderate conditions. Pd/GNS-NH2 nanocatalyst was synthesized by the deposition-reduction method. Sundry techniques such as ICP-OES, P-XRD, XPS, TEM, HR-TEM and EDX have been applied to explain the structure and morphology of the Pd/GNS-NH2 nanocatalyst. The results show that the Pd (0) nanoparticles are perfectly dispersed on the surface of the GNS-NH2 support material (d(mean) = 1.38-2.63 nm). The catalytic activity of the Pd/GNS-NH2 nanocatalyst was tested in the hydrogenation of nitrophenol derivatives in water in the presence of NaBH4 as reductant and the excellent activity of nanocatalyst have been detected against 2-nitrophenol, 4nitrophenol, 2,4-dinitrophenol and 2,4,6-trinitrophenol derivatives with 116.8, 65.9, 42.8 and 11.4 min(-1) initial TOF values, respectively. Another important point is that the nanocatalyst has very high reusability performance (at 5th reuse between 71.5 and 91.5%) for the hydrogenation of nitrophenols. Finally, catalytic studies have been carried out at various temperatures to calculate the E-a, Delta H-not equal and Delta S-not equal.
Palladium(0) Nanoparticles Supported on Hydroxyapatite Nanospheres: Active, Long-Lived, and Reusable Nanocatalyst for Hydrogen Generation From the Dehydrogenation of Aqueous Ammonia-Borane Solution
(Springer, 2014) Karatas, Yasar; Yurderi, Mehmet; Gulcan, Mehmet; Zahmakiran, Mehmet; Kaya, Murat
Among the solidmaterials considered in the chemical hydrogen storage, ammonia-borane (NH3-BH3) appears to be one of the promising candidates as it can release hydrogen throughout hydrolysis in the presence of suitable catalyst under mild conditions. Herein we report, for the first time, the preparation and characterization of palladium(0) nanoparticles supported on nanohydroxyapatite and their catalytic use in the hydrolysis of ammonia-borane under air at room temperature. These new palladium(0) nanoparticles were generated in situ during the catalytic hydrolysis of ammonia-borane starting with palladium(II) immobilized nanohydroxyapatite. The preliminary characterization of the palladium(0) nanoparticles supported on nanohydroxyapatite was done by the combination of complimentary techniques, which reveals that the formation of well-dispersed Pd(0)NPs nanoparticles (1.41 +/- 0.52 nm) on the surface of hydroxyapatite nanospheres (60-150 nm). The resulting palladium nanocatalyst achieves hydrogen generation from the hydrolysis of ammonia-borane with an initial turnover frequency value (TOF) of 11 mol H-2 mol(-1) Pd x min at room temperature under air. In addition to their high activity, the catalytic lifetime experiment showed that they can also act as a long-lived heterogeneous catalyst for this reaction (TTON = 14,200 mol H-2 mol(-1) Pd) at room temperature under air. More importantly, nanohydroxyapatite- supported palladium(0) nanoparticles were found to be highly stable against to leaching and sintering throughout the catalytic runs that make them isolable, bottleable, and reusable heterogeneous catalyst for the hydrolysis of ammonia-borane.