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Article Citation - WoS: 28Citation - Scopus: 30Functionalized Polysulfide Copolymers With 4-Vinylpyridine Via Inverse Vulcanization(Elsevier Science Bv, 2019) Berk, Hasan; Balci, Burcu; Ertan, Salih; Kaya, Murat; Cihaner, AtillaA new series of functional polysulfide copolymers called poly(sulfur-random-4-vinylpyridine) (poly(S-r-4VP)) was synthesized via inverse vulcanization technique by ring opening polymerization of elemental sulfur in the presence of 4-vinylpyridine (4VP). The corresponding copolymers can be post functionalized by using amine group in 4VP unit to get polymers bearing various properties. Elemental sulfur was heated up to 160 degrees C and 4VP was added slowly to a clear yellowish orange colored liquid at this temperature. The reaction mixture was vitrified to form a reddish-brown polymeric material at 180 degrees C in 1 h. The products were characterized by using FTIR, NMR, and Raman spectroscopic techniques. Poly(S-r-4VP) copolymers are soluble in common solvents like dichloromethane, chloroform and tetrahydrofuran. Weight-average molecular weights of poly(S-r-4VP) copolymers with different wt% 4VP were measured by using gel permeation chromatography technique. The polysulfide copolymers with different wt% 4VP have high weight-average molecular weights with polydispersity indeces (PDI) in a range from 1.88 to 4.06 measured by gel permeation chromatography. Post functionalization of the copolymer with 50 wt% 4VP as an example was performed successfully by using alkyl bromide to get N-alkyl quaternized 4VP in polymer backbone.Article Citation - WoS: 51Citation - Scopus: 54Atomic Layer Deposition-sio2 Layers Protected Pdconi Nanoparticles Supported on Tio2 Nanopowders: Exceptionally Stable Nanocatalyst for the Dehydrogenation of Formic Acid(Elsevier Science Bv, 2017) Caner, Nurdan; Bulut, Ahmet; Yurderi, Mehmet; Ertas, Ilknur Efecan; Kivrak, Hilal; Kaya, Murat; Zahmakiran, MehmetTiO2 nanopowders supported trimetallic PdCoNi alloy nanoparticles were simply and reproducibly prepared by wet-impregnation followed by simultaneous reduction method, then to enhance their stability against to sintering and leaching atomic layer deposition (ALD) technique was utilized to grow SiO2 layers amongst these surface bound PdCoNi alloy nanoparticles (PdCoNi/TiO2-ALD-SiO2). These new nanomaterials are characterized by the combination of complimentary techniques and sum of their results exhibited that the formation of ALD-SiO2 layers protected well-dispersed and highly crystalline PdCoNi alloy nanoparticles (ca. 3.52 nm) supported on TiO2 nanopowders. The catalytic performance of the resulting PdCoNi/TiO2-ALD-SiO2 in terms of activity, selectivity and stability was investigated in the dehydrogenation of aqueous formic acid (HCOOH), which has recently been suggested as a promising hydrogen storage material with a 4.4 wt% hydrogen capacity, solution under mild conditions. The results collected from our systematic studies revealed that PdCoNi/TiO2-ALD-SiO2 nanomaterial can act as highly active and selective nanocatalyst in the formic acid dehydrogenation at room temperature by providing an initial turnover frequency (TOF) value of 207 mol H-2/mol metal;: h and >99% of dehydrogenation selectivity at almost complete conversion. More importantly, the catalytic reusability experiments separately carried out with PdCoNi/TiO2-ALD-SiO2 and PdCoNi/TiO2 nanocatalysts in the dehydrogenation of formic acid under more forcing conditions pointed out that PdCoNi/TiO2-ALD-SiO2 nanocatalyst displays unprecedented catalytic stability against to leaching and sintering throughout the reusability experiments it retains almost its inherent activity, selectivity and conversion even at 20th reuse, whereas analogous PdCoNi/TiO2 completely lost its catalytic performance. (C) 2017 Elsevier B.V. All rights reserved.Article Citation - WoS: 153Citation - Scopus: 156Pd-mnox< Nanoparticles Dispersed on Amine-Grafted Silica: Highly Efficient Nanocatalyst for Hydrogen Production From Additive-Free Dehydrogenation of Formic Acid Under Mild Conditions(Elsevier Science Bv, 2015) Bulut, Ahmet; Yurderi, Mehmet; Karatas, Yasar; Zahmakiran, Mehmet; Kivrak, Hilal; Gulcan, Mehmet; Kaya, MuratHerein we report the development of a new highly active, selective and reusable nanocatalyst for additive-free dehydrogenation of formic acid (HCOOH), which has great potential as a safe and convenient hydrogen carrier for fuel cells, under mild conditions. The new catalyst system consisting of bimetallic Pd-MnOx nanoparticles supported on aminopropyl functionalized silica (Pd-MnOx/SiO2-NH2) was simply and reproducibly prepared by deposition-reduction technique in water at room temperature. The characterization of Pd-mnO(x)/SiO2-NH2 catalyst was done by the combination of multipronged techniques, which reveals that the existence of highly crystalline individually nucleated Pd(0) and MnOx nanoparticles (d(mean) = 4.6 +/- 1.2 nm) on the surface of aminopropyl functionalized silica. These supported Pd-MnOx nanoparticles can catalyze the additive-free dehydrogenation of formic acid with record activity (TOF = 1300 h(-1)) at high selectivity (>99%) and conversion (>99%) under mild conditions (at 50 degrees C and under air). Moreover, easy recovery plus high durability of these supported Pd-MnOx nanoparticles make them a reusable heterogeneous catalyst in the additive-free dehydrogenation of formic acid. (C) 2014 Elsevier B.V. All rights reserved.Article Citation - WoS: 203Citation - Scopus: 213Palladium Nanoparticles Supported on Amine-Functionalized Sio2 for the Catalytic Hexavalent Chromium Reduction(Elsevier Science Bv, 2016) Celebi, Metin; Yurderi, Mehmet; Bulut, Ahrnet; Kaya, Murat; Zahmakiran, MehmetHexavalent chromium (Cr(VI)) is commonly identified acutely toxic, a proven mutagen and carcinogen heavy metal pollutant in the aquatic environment, whereas Cr(III) is believed to be an essential element. In the present study, we show that palladium(0) nanoparticles supported on 3-aminopropyltriethoxysilane (APTS) functionalized silica (Pd@SiO2-NH2) effectively catalyze the reduction of Cr(VI) to Cr(III) by using formic acid (HCOOH) as reducing agent under mild conditions (at room temperature under air). Pd@SiO2-NH2 catalyst was reproducibly prepared by deposition-reduction technique and characterized by the combination of various spectroscopic tools including ICP-OES, P-XRD, DR/UV-vis, XPS, BFTEM, HRTEM and TEM-EDX techniques. The sum of their results is indicative of the formation of well-dispersed palladium(0) nanoparticles (d(mean) = 3.7 nm) on the surface of APTS-functionalized SiO2. The catalytic performance of the resulting palladium(0) nanoparticles in terms of activity and stability was evaluated by the catalytic reduction of Cr(VI) to Cr(III) in aqueous solution in the presence of formic acid as a reducing agent. Our results reveal that Pd@SiO2-NH2 catalyst displays unprecedented activity (TOF = 258 mol Cr2O72-/mol Pd min) and reusability (<85% at 5th reuse) for the reduction of Cr(VI) to Cr(III) at room temperature. The present study reported here also includes the compilation of wealthy kinetic data for Pd@SiO2-NH2 catalyzed the reduction of Cr(VI) to Cr(III) in aqueous formic acid (HCOOH)-sodium formate (HCOONa) solution depending on substrate [Cr2O72-], catalyst [Pd@SiO2-NH2], surface grafted amine [APTS], formic acid [HCOOH], sodium formate [HCOONa] concentrations, temperature and type of support material (Al2O3, C, unmodified SiO2) to understand the nature of the catalytic reaction and determine the rate expression and activation parameters. (C) 2015 Elsevier B.V. All rights reserved.Article Citation - WoS: 79Citation - Scopus: 84Methylene Blue Photocatalytic Degradation Under Visible Light Irradiation on Copper Phthalocyanine-Sensitized Tio2 Nanopowders(Elsevier Science Bv, 2017) Cabir, Beyza; Yurderi, Mehmet; Caner, Nurdan; Agirtas, Mehmet Salih; Zahmakiran, Mehmet; Kaya, MuratDescribed herein is a new photocatalytic material that shows remarkable catalytic performance in terms of activity and reusability in the photocatalytic degradation of methylene blue (MB) in water. The new catalyst system comprised of copper phthalocyanine modified titanium(IV) oxide (TiO2) nanopowders (CuPc-TiO2\) was prepared by the wet chemical impregnation method to improve the photocatalytic activity of TiO2 and characterized by the combination of various spectroscopic tools including ICP-OES, P-XRD, DR/UV-Vis, FTIR, FE-SEM, SEM-EDX, BFTEM, HRTEM and N-2-adsorption-desorption techniques. The photocatalytic performance of the resulting CuPc-TiO2 in terms of activity and stability was evaluated by the photocatalytic degradation of MB in aqueous solution under mild conditions. Our results revealed that CuPc-TiO2 photocatalyst displayed remarkable activity (TOF = 3.73 mol MB/(mol CuPc + mol TiO2) x h) in the complete (100%) photocatalytic degradation of MB under visible light irradiation (150 W). Moreover, CuPc-TiO2 photocatalyst showed excellent stability against to sintering and clumping throughout the reusability experiments and it retained >80% of its initial activity even at 5th reuse, which makes it reusable photocatalyst in the photocatalytic degradation of MB. (C) 2017 Elsevier B.V. All rights reserved.Article Citation - WoS: 126Citation - Scopus: 134Supported Copper-Copper Oxide Nanoparticles as Active, Stable and Low-Cost Catalyst in the Methanolysis of Ammonia-Borane for Chemical Hydrogen Storage(Elsevier Science Bv, 2015) Yurderi, Mehmet; Bulut, Ahmet; Ertas, Ilknur Efecan; Zahmakiran, Mehmet; Kaya, MuratThe physical mixture of copper (Cu) copper(I) oxide (Cu2O) and copper(II) oxide (CuO) nanoparticles supported on activated carbon (Cu-Cu2O-CuO/C) were reproducibly prepared by a simple deposition-reduction technique without using any stabilizer in water at room temperature. The characterization of the resulting material by ICP-OES, P-XRD, XPS, DR-UV/vis, BFTEM and HRTEM techniques reveals that the formation of well-dispersed highly crystalline 3.8 +/- 1.7 nm nanoparticles on the surface of activated carbon. These carbon supported Cu-Cu2O-CuO nanoparticles were employed as heterogeneous catalyst in the methanolysis of ammonia-borane (NH3BH3), which has been considered as one of the attractive materials for the efficient storage of hydrogen, under mild conditions. We found that only 3.0 mol % Cu-Cu2O-CuO/C catalyst is enough to catalyze the methanolysis of ammonia-borane with high activity (TOF = 24 min(-1)) and conversion (>99%) at room temperature. More importantly, the exceptional stability of supported Cu-Cu2O-CuO nanoparticles against to sintering and leaching make Cu-Cu2O-CuO/C recyclable catalyst for the methanolysis of ammonia-borane. Cu-Cu2O-CuO/C catalyst retains >76% of its initial activity with 94% of conversion even at 8th recycle in the methanolysis of ammonia-borane at complete conversion. The study reported here also includes the collection of kinetic data for Cu-Cu2O-CuO/C catalyzed methanolysis of ammonia-borane depending on catalyst [Cu], substrate [NH3BH3] concentrations and temperature to determine the rate expression and the activation parameters (E-a, Delta H-#, and Delta S-#) of the catalytic reaction. (C) 2014 Published by Elsevier B.V.Article Citation - WoS: 46Citation - Scopus: 51Ruthenium(0) Nanoparticles Supported on Magnetic Silica Coated Cobalt Ferrite: Reusable Catalyst in Hydrogen Generation From the Hydrolysis of Ammonia-Borane(Elsevier Science Bv, 2014) Akbayrak, Serdar; Kaya, Murat; Volkan, Murvet; Ozkar, SaimRuthenium(0) nanoparticles supported on magnetic silica-coated cobalt ferrite (Ru(0)/SiO2-CoFe2O4) were in situ generated from the reduction of Ru3+/SiO2-CoFe2O4 during the catalytic hydrolysis of ammonia-borane (AB). Ruthenium(III) ions were impregnated on SiO2-CoFe2O4 from the aqueous solution of ruthenium(III) chloride and then reduced by AB at room temperature yielding Ru(0)/SiO2-CoFe2O4 which were isolated from the reaction solution by using a permanent magnet and characterized by ICP-OES, XRD, TEM, TEM-EDX and XPS techniques. The resulting magnetically isolable Ru(0)/SiO2-CoFe2O4 were found to be highly reusable catalyst in hydrolysis of AB retaining 94% of their initial catalytic activity even after tenth run. Ru(0)/SiO2-CoFe2O4 provide the highest catalytic activity after the tenth use in hydrolysis of AB as compared to the other ruthenium catalysts. The work reported here also includes the formation kinetics of ruthenium(0) nanoparticles. The evaluation of rate constants for the nucleation and autocatalytic surface growth of ruthenium(0) nanoparticles at various temperatures provides the estimation of activation energy for both reactions; E-a = 116 +/- 7 kJ/mol for the nucleation and E-a = 51 +/- 2 kJ/mol for the autocatalytic surface growth of ruthenium(0) nanoparticles. The report also includes the activation energy of the catalytic hydrogen generation from the hydrolysis of AB (E-a = 45 +/- 2 kJ/mol) determined from the evaluation of temperature dependent kinetic data and the effect of catalyst concentration on the rate of hydrolysis of AB. (C) 2014 Elsevier B.V. All rights reserved.Article Citation - WoS: 149Citation - Scopus: 153Carbon Supported Trimetallic Pdniag Nanoparticles as Highly Active, Selective and Reusable Catalyst in the Formic Acid Decomposition(Elsevier Science Bv, 2014) Yurderi, Mehmet; Bulut, Ahmet; Zahmakiran, Mehmet; Kaya, MuratTrimetallic PdNiAg nanoparticles supported on activated carbon were simply and reproducibly prepared by wet-impregnation followed by simultaneous reduction method without using any stabilizer at room temperature. The characterization of the resulting material was done by the combination of complimentary techniques and the sum of their results shows that the formation of well-dispersed 5.6 +/- 2.2 nm PdNiAg nanoparticles in alloy form on the surface of activated carbon. These carbon supported PdNiAg nanoparticles were employed as heterogeneous catalyst in the catalytic decomposition of formic acid, which has great potential as a safe and convenient hydrogen carrier for fuel cells, under mild conditions. It was found that PdNiAg/C can catalyze the dehydrogenation of formic acid with high selectivity (similar to 100%) and activity (TOF = 85 h(-1)) at 50 degrees C. More importantly, the exceptional stability of PdNiAg nanoparticles against to agglomeration, leaching and CO poisoning make PdNiAg/C reusable catalyst in the formic acid dehydrogenation. PdNiAg/C catalyst retains almost its inherent activity (>94%) even at 5th reuse in the dehydrogenation of formic acid with high selectivity (similar to 100%) at complete conversion. The work reported here also includes the compilation of kinetic data for PdNiAg/C catalyzed dehydrogenation of formic acid depending on catalyst [PdNiAg], substrate [HCOOH], promoter [HCOONa] concentrations and temperature to determine the rate expression and the activation parameters (Ea, Delta H-#, and Delta S-#) of the catalytic reaction. (C) 2014 Elsevier B.V. All rights reserved.
