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    A COMPARATIVE STUDY FOR SODIUM BOROHYDRIDE DEHYDROGENATION AND ELECTROOXIDATION ON CERIUM AND COBALT CATALYSTS
    (Health & Environment Assoc, 2020) Hansu, Tulin Avci; Caglar, Aykut; Sahin, Omer; Kivrak, Hilal
    In the present study, Co/CNT and Ce/CNT catalysts are prepared via sodium borohydride (NaBH4) reduction method. Co/CNT and Ce/CNT catalysts are examined to the dehydrogenation and electrooxidation of NaBH4. NaBH4 dehydrogenation activities of these Co/CNT and Ce/CNT catalysts are performed in alkaline environment. 5% Co/CNT catalyst exhibits superior hydrogen evolution compared with other catalysts. Activation energy is calculated using Arrhenius equation. Initial rate for this catalyst is found as 1700 ml H-2 g(cat)(-1) min(-1). As a result of the kinetic calculations, the activation energy of the catalyst is calculated as 44,68775 kj/mol. The degree of reaction (n) is found to be 0.5 by trial and error. In conclusion, 5% Co/CNT catalyst is a promising catalyst for hydrogen production from NaBH4. Cyclic voltammetry (CV) analysis is utilized to examine the electrochemical activity of the catalysts for NaBH4 electrooxidation. 0.1% Co/CNT catalyst has 0.38 mA cm(-2) (3181 mA mg(-1) Co) specific activity.
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    A novel hazelnutt bagasse based activated carbon as sodium borohydride methanolysis and electrooxidation catalyst
    (Pergamon-Elsevier Science Ltd, 2023) Saka, Ceren; Yildiz, Derya; Kaya, Sefika; Caglar, Aykut; Elitok, Dilarasu; Yayli, Elif; Kaya, Mustafa
    In this study, activated carbon is produced from defatted hazelnut bagasse at different activation conditions. The catalytic activities of activated carbons are evaluated for NaBH4 methanolysis and electrooxidation. These materials are characterized by N2 adsorption -desorption, FTIR, SEM-EDS and XPS and results show that these materials are prepared successfully. N2 adsorption-desorption results reveal that activated carbon (FH3-500) has the highest BET surface area as 548 m2/g, total pore volume as 0.367 cm3/g and micropore volume as 0.205 cm3/g. On the orher hand, as a result of hydrogen production studies, FH3-500 activated carbon catalyst has the highest initial hydrogen production rate compared to other materials. At 50 & DEG;C, this metal-free activated carbon catalyst has a high initial hydrogen production rate of 13591.20 mL/min.gcat, which is higher than literature values. Sodium borohydride electrooxidation measurements reveal that FH2-500 also has the highest electrocatalytic activity and stability. Hazelnut pulp-based activated carbons are firstly used as a metal-free catalyst in the methanolysis and electrooxidation of sodium borohydride, and its catalytic activity is good as a metal-free catalyst. The results show that the hazelnut pulp-based activated carbon catalyst is promising as a metal-free catalyst for the methanolysis and electrooxidation of sodium borohydride.& COPY; 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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    A remarkable Mo doped Ru catalyst for hydrogen generation from sodium borohydride: the effect of Mo addition and estimation of kinetic parameters
    (Springer, 2020) Hansu, Tulin Avci; Sahin, Omer; Caglar, Aykut; Kivrak, Hilal
    At present, carbon nanotube supported monometallic Ru at 3 wt% Ru loading (3% Ru/CNT) per gram support and bimetallic RuMo at 3 wt% Ru loading per gram support (3% Ru-Mo/CNT) at varying Ru:Mo atomic ratios are synthesized via sodium borohydride (NaBH4) reduction method to investigate their performance towards NaBH4 hydrolysis. These monometallic Ru/CNT and bimetallic Ru:Mo/CNT catalysts prepared at varying Ru:Mo atomic ratios are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX), and transmission electron microscopy (TEM). Characterization results reveal that Mo addition to Ru alters the electronic state of the catalysts. The NaOH concentration, the amount of catalyst, the NaBH4 concentration and the temperature parameters that affect the hydrolysis rate of this synthesized and developed catalyst were examined. The kinetic calculations of these parameters related to the order of the reaction were determined. Under optimum conditions catalyst hydrogen production rate was found to be 82,758.43 ml H-2 g(cat)(-1) min(-1). The reaction order (n) and activation energy (E-a) are determined as 0.42 and 35.11 kJ mol(-1). Ru:Mo/CNT catalyst is a novel and promising catalyst for hydrogen generation from NaBH4.
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    Enhanced catalytic performance of Pd/PMAc-g-CNT composite for water splitting and supercapacitor applications
    (Springer Heidelberg, 2024) Hansu, Tulin Avci; Kaya, Sefika; Caglar, Aykut; Akdemir, Murat; Kivrak, Hilal Demir; Orak, Ceren; Horoz, Sabit
    In this study, we explore the multifaceted applications of poly(methyl acrylate) (PMAc)-based composites, specifically focusing on their use as an efficient electrocatalyst for water splitting and a high-capacity supercapacitor. After a synthesis step, a characterization study (SEM, TEM, XRD, and Raman spectroscopy) was performed, and based on TEM results, a consistent pattern of small, uniform, and narrowly distributed Pd NPs within the range of 5-10 nm was observed. Also, other analyses confirmed the successful synthesis of PMAc-based composites. Through meticulous experimentation, the electrocatalytic performance of Pd/PMAc-graphene-carbon nanotube (Pd/PMAc-g-CNT) composites was evaluated against that of traditional Pd/PMAc catalysts. Tafel slope analysis was conducted to assess the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) efficiencies, where Pd/PMAc-g-CNT composites demonstrated significantly lower Tafel slopes of 274.53 mV dec(-1) for OER and 389.91 mV dec(-1) for HER. This indicates a superior electrocatalytic activity, enhancing the water splitting process. Furthermore, the same composite showcased an impressive specific capacitance of 132.3 F g(-1) at a current density of 0.5 A/g, markedly surpassing the performance of the Pd/PMAc catalyst. This exceptional capacitance underlines its potential as a high-efficiency energy storage material. The novelty of this research lies in the synergistic integration of PMAc with graphene and carbon nanotubes to fabricate a dual-functional material. This composite not only excels in electrochemical catalysis for energy conversion but also demonstrates remarkable energy storage capabilities. The Pd/PMAc-g-CNT composite, therefore, emerges as a promising candidate for advancing supercapacitor technology and the electrocatalytic efficiency of water splitting, highlighting its dual utility in renewable energy systems.
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    Enhanced Photocatalytic Hydrogen Production on Cd-, Te-, Se-, and S-Doped Titanium Dioxide Catalysts
    (Springer, 2023) Kaya, Sefika; Saka, Ceren; Caglar, Aykut; Kaya, Mustafa; Kivrak, Hilal
    Herein, cadmium (Cd)-, tellurium (Te)-, selenium (Se)-, and sulfur (S)-doped titanium dioxide (TiO2) support material catalysts are prepared via incipient wetness impregnation. Hydrogen generation performances of the prepared catalysts from sodium borohydride (NaBH4) by methanolysis are investigated. Experimental studies are carried out under ultraviolet (UV) illumination and in the dark. The highest initial hydrogen generation rate is reached on 0.1% Cd/TiO2 catalyst under UV illumination. The optimum catalyst, sodium borohydride, and methanol amounts and temperature parameters affecting the initial hydrogen generation rate are investigated and obtained as 0.025 g, 0.150 g, 2 mL, and 60 degrees C, respectively. The initial hydrogen generation rate of 0.1% Cd/TiO2 catalyst is 16130.64 mL/min.gcat in optimum conditions. The activation energy of the reaction with the 0.1% Cd/TiO2 catalyst is calculated by carrying out kinetic studies. The activation energy is 22.48 kJ/mol. X-ray diffraction (XRD), electron microscopy with energy-dispersive x-ray spectroscopy (SEM-EDX), inductively coupled plasma mass spectrometry (ICP-MS), x-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM) analytical techniques are performed to characterize the catalysts. The results show that TiO2 catalysts doped with Cd, Te, Se, and S, which are cheaper than noble metals, are promising for the production of hydrogen from NaBH4 by methanolysis under UV illumination.
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    Exploring the Triple Applications of Ag/PMAc-g-CNT Nanocomposites in Enhancing HER, OER and Supercapacitor Performance
    (Springer, 2024) Kaya, Sefika; Caglar, Aykut; Akdemir, Murat; Kivrak, Hilal Demir; Horoz, Sabit; Kaya, Mustafa
    The research aims to investigate the potential of using Ag/PMAc-g-CNT as a high-efficient catalyst for overall water splitting and supercapacitor applications. The results of Tafel slope measurements for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) showed that the Ag/PMAc-g-CNT catalyst had a lower Tafel slope of 22.62 mV dec-1 and 62.74 mV dec-1, respectively, compared to the other electrocatalysts. Additionally, the capacitance value of the Ag/PMAc-g-CNT catalyst was found to be 41.87 F at 0.5 A/g current density which is much higher than that of the Ag/PMAc catalyst. These results demonstrate that the Ag/PMAc-g-CNT catalyst has superior properties in terms of electrochemical activity, stability and energy storage capacity, making it a promising material for both water splitting and supercapacitor applications.
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    Fabrication of novel palladium-platinum based graphene/ITO electrodes and third metal addition effect through the glucose electrooxidation
    (Elsevier Science Sa, 2022) Caglar, Aykut; Hansu, Tulin Avci; Sahin, Ozlem; Kivrak, Hilal
    Graphene was coated on Cu foil by chemical vapor deposition (CVD) method. The graphene on the Cu foil was modified by doping N. Then, N-doped graphene (G) was coated on several layers of indium tin oxide (ITO) electrodes. In addition, Pd, Pt, and M (Ag, V, Ni, Zn) metals were electroprecipitated on the graphene/indium tin oxide electrode by electrochemical technique. In this way, the glucose (C6H12O6) electrooxidation activities of these electrodes obtained from PdMPt-N doped graphane/indium tin oxide were investigated by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) measurements. The obtained materials were characterized by SEM-EDX. Results revealed that the network of Pd, Pt, Ag, V, Ni, Zn and graphene was clearly visible from the SEM results. As a consequence, PdZnPt-N doped G/ITO showed the most effective C6H12O6 electrooxidation activity with a specific activity of 14.5 mA cm(-2), considerably above the literature's published values. In all electrochemical measurements, PdZnPt-N doped G/ITO exhibited the best electrocatalytic activity, stability, and resistance. PdZnPt-N doped G/ITO electrode is promising electrode for glucose electrooxidation.
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    High-efficiency catalyst for water splitting and supercapacitor applications: the promising role of Ni/PMAc-g-CNT
    (Springer Heidelberg, 2023) Caglar, Aykut; Kaya, Sefika; Avci Hansu, Tuelin; Akdemir, Murat; Demir Kivrak, Hilal; Horoz, Sabit; Kaya, Mustafa
    In this study, we investigated the use of electrocatalysts, PMAc, PMAc-g-CNT, Ni/PMAc, and Ni/PMAc-g-CNT for water splitting and supercapacitor applications. Our results showed that the Ni/PMAc-g-CNT catalyst exhibited superior properties in terms of electrochemical activity, stability, and energy storage capacity. The Tafel slope for OER was found to be 471.25 mV dec(-1), which was lower than other catalysts studied. The capacitance value of the Ni/PMAc-g-CNT catalyst was 35.23 F/g at 0.5 A/g current density, which was higher than the Ni/PMAc catalyst. These findings provide a novel and detailed insight into the performance of these catalysts and suggest that the Ni/PMAc-g-CNT catalyst is a promising material for both water splitting and supercapacitor applications.
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    Hydrolysis and electrooxidation of sodium borohydride on novel CNT supported CoBi fuel cell catalyst
    (Elsevier Science Sa, 2020) Hansu, Tulin Avci; Caglar, Aykut; Sahin, Omer; Kivrak, Hilal
    At present, Co, Bi, CoBi, and CoBi/CNT catalysts are prepared via co-precipitation method and sodium borohydride (NaBH4) reduction method for NaBH4 electrooxidation and hydrolysis. These Co, Bi, and CoBi catalysts are characterized by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), N-2 adsorption-desorption, Inductively Coupled Plasma Mass Spectrometry (ICP-MS), and Temperature Programmed Reduction (TPA). These catalysts are employed for NaBH4 hydrolysis and further measurements are performed to investigate their NaBH4 electrooxidation activity. For NaBH4 hydrolysis, NaOH concentration, reaction temperature, NaBH4 concentration, and catalyst amount are optimized for CoBi and CoBi/CNT catalysts. Furthermore, the rate constants (k) are found between 20 and 50 degrees C and the activation energy is calculated from the Arrhenius equation. The hydrogen generation rates on CoBi (95-5) and % 10 CoBi (95-5)/CNT catalysts are found as 2605.6ml H-2 g(-1)cat min(-1) and 12996 ml H-2 g(-1)cat min(-1), respectively. NaBH4 electrooxidation is investigated with cyclic voltammetry (CV), chronoampemmetry (CA), and electrochemical impedance spectroscopy (EIS) measurements. Maximum mass activities are obtained as 5.86 mA mg(-1) Co for CoBi and 25.7 mA mg(-1) Co for CoBi/CNT catalysts. EIS and CA results are also in a good agreement with CV results in terms of stability and electrocatalytic activity of CoBi/CNT catalyst. The CoBi/CNT catalyst is believed to be a promising anode catalyst for the direct borohydride fuel cell (DBFC).
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    Metal-free catalysts for hydrogen production
    (Elsevier, 2022) Caglar, Aykut; Hansu, Tulin Avci; Demir-Kivrak, Hilal
    Catalysts are vital for speeding up the reaction during hydrogen production. Both metal-based and metal-free catalysts are used. Metal-free catalysts are less expensive than metal-based catalysts and do not have the disadvantages of oxidation and poisoning. Metal-free catalysts doped with heteroatoms, carbon materials, and polymers have been investigated for their high catalytic activity in hydrogen production. Carbon materials are typically high-surface-area carbon forms such as activated carbon, carbon nanotubes, fullerene, graphite, and graphene. In addition, heteroatoms are obtained by adding atoms to carbon materials, such as replacing carbon atoms with heteroatoms such as N, P, or B or bonding heteroatoms such as S, CI, Br, or O to the carbon surface. Hydrogen is produced from boron-based chemical hybrids, water, and other sources. Sodium borohydride (NaBH4), ammonium borane (NH3BH3), and hydrazine borane (N2H4BH3) are boron-based hybrid chemical sources. Examining the different production methods of these hydrogen sources is important for achieving cheaper and more efficient hydrogen production. Water splitting is examined in three categories: electrolysis, thermolysis, and photoelectrolysis. Furthermore, catalyst characterization is a technique that must be studied to relate catalytic activities with their properties. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric and differential thermal analysis techniques are examined to determine the composition and structure of metal-free catalyst surfaces. © 2022 Elsevier Inc. All rights reserved.
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    Ruthenium modified defatted spent coffee catalysts for supercapacitor and methanolysis application
    (Wiley, 2021) Akdemir, Murat; Hansu, Tulin Avci; Caglar, Aykut; Kaya, Mustafa; Kivrak, Hilal Demir
    Currently, a novel green material, defatted spent coffee ground (DSCG), is employed as a support to prepare DSCG supported Ru (DSCG-Ru) material. DSCG and DSCG-Ru materials are characterized by advanced surface analytical techniques such as N-2 adsorption-desorption, X-ray diffraction, X-ray photoelectron spectroscopy, and H-2-temperature-programmed reduction. Characterization results revealed that DSCG-Ru was prepared successfully. First, DSCG-Ru is prepared at varying Ru contents on deoiled coffee waste and hydrogen production experiments are performed by the methanolysis of sodium borohydride on the DSCG-Ru catalysts. It is observed that optimum conditions for the catalyst preparation are examined on the 10% Ru containing DSCG-Ru catalysts and found as 10% Ru, 300 degrees C, and 60 minutes. DSCG catalyst containing 10% Ru completed the methanolysis reaction in 1.5 minutes. Capacitive measurements to investigate the supercapacitor property of DSCG-Ru catalysts prepared at optimum conditions 10% Ru, 300 degrees C, and 60 minutes is investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge measurements. Results revealed that gravimetric capacitance of the electrode at a current density is found as of 0.5 A/g and 43 F/g, greater than the literature values. DSCG-Ru, green novel supported Ru catalyst, has a dual promising performance in hydrogen production and supercapacitor measurements.
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    Structure of ruthenium nanocatalysts of bismuth, investigation of its effect on hydrolysis performance and kinetic studies
    (Wiley, 2021) Avci Hansu, Tulin; Caglar, Aykut; Demir Kivrak, Hilal; Sahin, Omer
    In this study, a new nanocatalyst, RuBi/carbon nanotube, was synthesized to be used in the hydrolysis reaction of sodium boron hydride. The sodium boron hydride hydrolysis performance was investigated by adding bismuth to the structure of ruthenium nanocatalysts. Hydrolysis experiments were carried out by adding bismuth at different atomic proportions to ruthenium. The best atomic ratio was determined to be 90:10. These catalysts are characterized by scanning electron microscopy with energy-dispersive X-ray analysis, X-ray diffraction, and transmission electron microscopy. The parameters affecting hydrolysis such as temperature, catalyst amount, sodium hydroxide concentration, and sodium borohydride concentration were examined. The reusability of the catalyst was tested five times. In the calculations, the reaction order was calculated as n, 0.73, and activation energy E-a, 49657 kJ/mol.
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    The characterization and sodium borohydride electrooxidation of novel carbon nanotube supported copromoted Pd as anode catalyst for fuel cell
    (Wiley, 2022) Caglar, Aykut; Hansu, Tulin A.; Sahin, Omer; Kivrak, Hilal
    In the present study, the effect of Co addition on Pd is investigated. Pd/CNT and PdCo/CNT catalysts are prepared via the sodium borohydride (SBH, NaBH4) reduction method. The X-ray diffraction, transmission electron microscope, and inductively coupled plasma-mass spectrometry analyses are performed to characterize the PdCo(70-30)/CNT catalyst. These characterization results reveal that Pd/CNT and PdCo/CNT catalysts are prepared successfully. NaBH4 electrooxidation activities of PdCo/CNT catalysts are examined with electrochemical methods such as cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. PdCo(70-30)/CNT catalyst has 11.52 mA/cm(2) specific activity, 477.18 m(2)/g electrochemical active surface area, and the best electrochemical stability. Pd is a promising catalyst for NaBH4 electrooxidation reaction.