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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: 22Citation - Scopus: 23Complete Dehydrogenation of Hydrazine Borane on Manganese Oxide Nanorod-Supported Ni@ir Core-Shell Nanoparticles(Amer Chemical Soc, 2020) Yurderi, Mehmet; Top, Tuba; Bulut, Ahmet; Kanberoglu, Gulsah Saydan; Kaya, Murat; Zahmakiran, MehmetHydrazine borane (HB; N2H4BH3) has been considered to be one of the most promising solid chemical hydrogen storage materials owing to its high hydrogen capacity and stability under ambient conditions. Despite that, the high purity of hydrogen production from the complete dehydrogenation of HB stands as a major problem that needs to be solved for the convenient use of HB in on-demand hydrogen production systems. In this study, we describe the development of a new catalytic material comprised of bimetallic Ni@Ir core-shell nanoparticles (NPs) supported on OMS-2-type manganese oxide octahedral molecular sieve nanorods (Ni@Ir/OMS-2), which can reproducibly be prepared by following a synthesis protocol including (i) the oleylamine-mediated preparation of colloidal Ni@Ir NPs and (ii) wet impregnation of these ex situ synthesized Ni@Ir NPs onto the OMS-2 surface. The characterization of Ni@Ir/OMS-2 has been done by using various spectroscopic and visualization techniques, and their results have revealed the formation of well-dispersed Ni@Ir core-shell NPs on the surface of OMS-2. The catalytic employment of Ni@Ir/OMS-2 in the dehydrogenation of HB showed that Ni-0.22@Ir-0.78/OMS-2 exhibited high dehydrogenation selectivity (>99%) at complete conversion with a turnover frequency (TOF) value of 2590 h(-1) at 323 K, which is the highest activity value among all reported catalysts for the complete dehydrogenation of HB. Furthermore, the Ni-0.22@Ir-0.78/OMS-2 catalyst enables facile recovery and high stability against agglomeration and leaching, which make it a reusable catalyst in the complete dehydrogenation of HB. The studies reported herein also include the collection of wealthy kinetic data to determine the activation parameters for Ni-0.22@Ir-0.78/OMS-2-catalyzed dehydrogenation of HB.Article Citation - WoS: 150Citation - Scopus: 152Pd-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.Correction Citation - WoS: 1Citation - Scopus: 2Supported Copper-Copper Oxide Nanoparticles as Active, Stable and Low-Cost Catalyst in the Methanolysis of Ammonia-Borane for Chemical Hydrogen Storage (vol 165, Pg 169, 2015)(Elsevier, 2016) Yurderi, Mehmet; Bulut, Ahmet; Ertas, Ilknur Efecan; Zahmakiran, Mehmet; Kaya, Murat[No Abstract Available]Article Citation - WoS: 141Citation - Scopus: 147Carbon Dispersed Copper-Cobalt Alloy Nanoparticles: a Cost-Effective Heterogeneous Catalyst With Exceptional Performance in the Hydrolytic Dehydrogenation of Ammonia-Borane(Elsevier, 2016) Bulut, Ahmet; Yurderi, Mehmet; Ertas, Ilknur Efecan; Celebi, Metin; Kaya, Murat; Zahmakiran, MehmetHerein, we report the development of a new and cost-effective nanocatalyst for the hydrolytic dehydrogenation of ammonia-borane (NH3BH3), which is considered to be one of the most promising solid hydrogen carriers due to its high gravimetric hydrogen storage capacity (19.6 wt%) and low molecular weight. The new catalyst system consisting of bimetallic copper-cobalt alloy nanoparticles supported on activated carbon was simply and reproducibly prepared by surfactant-free deposition-reduction technique at room temperature. The characterization of this new catalytic material was done by the combination of multi-pronged techniques including ICP-MS, XRD, XPS, BFTEM, HR-TEM, STEM and HAADF-STEM-line analysis. The sum of their results revealed that the formation of copper-cobalt alloy nanoparticles (d(mean) =1.8 nm) on the surface of activated carbon (CuCo/C). These new carbon supported copper-cobalt alloy nanoparticles act as highly active catalyst in the hydrolytic dehydrogenation of ammonia-borane, providing an initial turnover frequency of TOF = 2700 h(-1) at 298 K, which is not only higher than all the non-noble metal catalysts but also higher than the majority of the noble metal based homogeneous and heterogeneous catalysts employed in the same reaction. More importantly, easy recovery and high durability of these supported CuCo nanoparticles make CuCo/C recyclable heterogeneous catalyst for the hydrolytic dehydrogenation of ammonia-borane. They retain almost their inherent activity even at 10th catalytic reuse in the hydrolytic dehydrogenation of ammonia-borane at 298K. (C) 2015 Elsevier B.V. All rights reserved.Article Citation - WoS: 125Citation - Scopus: 130Pdau-mnox< Nanoparticles Supported on Amine-Functionalized Sio2 for the Room Temperature Dehydrogenation of Formic Acid in the Absence of Additives(Elsevier Science Bv, 2016) Karatas, Yasar; Bulut, Ahmet; Yurderi, Mehmet; Ertas, Ilknur Efecan; Alal, Orhan; Gulcan, Mehmet; Zahmakiran, MehmetFormic acid (HCOOH) has recently been suggested as a promising hydrogen carrier for fuel cell applications. However efficient hydrogen production through the decomposition of formic acid in the absence of additives under mild thermodynamic conditions constitutes a major challenge because of the ease poisoning of active metals with CO formed as intermediate during formic acid decomposition. Recently, we have reported (App. Catal. B: Env. 164 (2015) 324) our discovery that the separately nucleated MnOx nanoparticles act as CO-sponge around catalytically active Pd nanoparticles exist on the same support and enhances both the activity and CO-resistivity of Pd nanoparticles. Using this important finding, herein, we present a new catalyst system consists of the physical mixture of PdAu alloy and MnOx nanoparticles supported on amine-grafted silica (PdAu-MnOx/N-SiO2) for the room temperature dehydrogenation of formic acid in the absence of any additives. PdAu-MnOx/N-SiO2 catalyst was simply prepared by deposition-reduction technique in water at room temperature with high reproducibility and characterized by the combination of various spectroscopic tools including ICP-OES, P-XRD, DR/UV-vis, XPS, BFTEM, STEM-EDX, STEM-line analysis and CO-stripping voltammetry techniques. The sum of their results shows that the formation of physical mixture of PdAu alloy and MnOx (dmean=2.2 nm) nanoparticles on the surface of support material. This new catalytic material facilitates the hydrogen liberation through the additive-free formic acid dehydrogenation at room temperature with previously unprecedented activity (TOF=785 mol H-2 mol catalyst(-1) h(-1)), converging to that of the existing state of the art homogenous catalysts. This new superior catalytic system enables facile catalyst recovery and very high stability against agglomeration, leaching and CO poisoning, which make it highly reusable catalyst (retains >92% activity and 85% conversion at the 5th catalytic reuse) in the additive-free formic acid dehydrogenation at room temperature. (C) 2015 Elsevier B.V. All rights reserved.Article Citation - WoS: 128Mnox< 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, MehmetFormic 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.Article Citation - WoS: 125Citation - Scopus: 133Supported 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: 148Citation - Scopus: 152Carbon 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.Article Citation - WoS: 19Citation - Scopus: 20Synthesis, Characterization, and Enhanced Formic Acid Electrooxidation Activity of Carbon Supported Mnox Promoted Pd Nanoparticles(Elsevier, 2018) Bulut, Ahmet; Yurderi, Mehmet; Alal, Orhan; Kivrak, Hilal; Kaya, Murat; Zahmakiran, MehmetFormic acid (HCOOH) is one of the promising fuels for direct liquid fed fuel cells. However, CO poisoning is a major challenge for the development of effective catalytic system for formic acid electrooxidation (FAEO). Herein, a novel CO-resistive activated carbon supported Pd-MnOx bimetallic catalyst (Pd-MnOx/C) was presented for FAEO. Pd-MnOx/C catalyst was prepared via simple and reproducible surfactant-free deposition-reduction technique. The characterization of this novel Pd-MnOx/C catalyst was performed by inductively coupled plasma-optical emission spectroscopy (ICP-OES), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), bright field transmission electron microscopy (BFTEM), high resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy (STEM), and scanning transmission electron microscope-energy dispersive X-ray spectroscopy (STEM-EDX). The characterization results revealed that Pd and MnOx nanoparticles (NPs) were well dispersed and separately nucleated with a mean diameter of 2.9 nm on the surface of active carbon. FAEO studies were performed on both Pd-MnOx/C and Pd/C catalysts to comprehend the effect of separately formed MnOx on the electrocatalytic activity of Pd NPs. The electrochemical measurements were carried out by using Cyclic Voltammetry (CV) and Chronoamperometry (CA), CO-Strriping Voltammetry, Lineer Sweep Voltammetry (LSV), Electrochemical impedance spectroscopy (EIS) techniques. Electrochemical results revealed that FAEO was activated by the addition of MnOx. Pd-0.6-Mn-0.4 exhibited the optimum catalytic activity with 1.05 A/mg Pd current density. The sum of their results clearly points that the existence of MnOx NPs enhances the electrocatalytic activity of Pd NPs by increasing their CO-resistivity and durability throughout the FAEO. (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.
