Yazar "Kivrak, Hilal Demir" seçeneğine göre listele

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    A double-functional carbon material as a supercapacitor electrode and hydrogen production: Cu-doped tea factory waste catalyst
    (Springer, 2021) Ozarslan, S.; Atelge, M. R.; Kivrak, Hilal Demir; Horoz, Sabit; Yavuz, Cenk; Kaya, M.; Unalan, S.
    In the present study, our main aim is to show that the first synthesized metal-doped tea factory waste (TFW) catalyst can be used in both hydrogen production and supercapacitor application. In this context, TFW catalyst doped with copper (Cu) (TFW-Cu) was synthesized for methanolysis of NaBH4 and supercapacitor measurement. In the presence of four different parameters (metal type, metal amount, carbonization temperature, and carbonization time), methanolysis experiments of NaBH4 were performed and the catalyst with the maximum hydrogen production rate (HPR) was determined. As a result, it was determined that the 30% Cu-doped TFW (TFW-30%Cu) catalyst had a maximum HPR at a carbonization temperature of 300 degrees C and a carbonization time of 60 min compared to other substances. As a result of the methanolysis experiments performed in the presence of TFW-30%Cu catalyst, the maximum HPR and activation energy were determined as 9475 mL (min.g)(-1) and 13.02 kJ mol(-1), respectively. In supercapacitor application, the capacitance of the electrodes in the presence of TFW-30%Cu was calculated as 7-19.9 F.(g)(-1). Thus, it is expected that the synthesized catalyst will make a promising contribution in both energy storage and energy production areas-especially for distributed generation systems operating in national networks.
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    Biomass-based metal-free catalyst as a promising supercapacitor electrode for energy storage
    (Springer, 2022) Karakas, Duygu Elma; Akdemir, Murat; Imanova, Gunel T.; Kivrak, Hilal Demir; Horoz, Sabit; Kaya, Mustafa
    In present study, biomass doped H3PO4-Cat, named as STW-H3PO4-Cat, was used as a catalyst in the methanolysis of sodium borohydride (NaBH4). Spent tea waste (STW) was used for the first time in this study as biomass. The generated existing catalyst was also employed as an active supercapacitor material, demonstrating its dual function. To identify the most active catalyst in the methanolysis of sodium borohydride, the catalyst was functionalized in different H3PO4 concentrations (1-7 M), and different annealing temperatures (200-500 degrees C) and different annealing times (20-80 min). Optimum parameters were determined as 7 M H3PO4, 400 degrees C, and 40 min. The maximum hydrogen production (HPR) value and the activation energy (E-a) were determined as 76,640 mL min(-1) g cat(-1) and 12.03 kJ mol(-1). When the catalyst was investigated in terms of the supercapacitor, the electrode's capacitance at 1 A/g current intensity was found to be 158 F/g utilizing the charge-discharge curve. The catalyst with optimum conditions was structurally and morphologically characterized by Fourier Transform Infrared (FTIR), x-ray diffraction (XRD), and scanning electron microscope (SEM) measurements, respectively.
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    Boron-containing compounds as a new candidate for supercapacitor electrode: simplified synthesis and structural identification properties
    (Elsevier Science Inc, 2023) Akdemir, Murat; Kivrak, Hilal Demir; Kilic, Ahmet; Beyazsakal, Levent; Kaya, Mustafa; Horoz, Sabit
    In this study, the performance of two boron-containing compounds, C14H14BNO2 center dot HCl (BCC1) and C38H38B2Cl2N4O4 (BCC2), as electrodes in supercapacitor applications was investigated in the presence of Na2SO4 and KOH electrolyte solutions. The specific capacitance values of the compounds were compared, and the results showed that trivalent boron (BCC1) exhibited higher specific capacitance values than tetravalent boron (BCC2) in both electrolyte solutions. In the presence of Na2SO4 electrolyte solution, the specific capacitance values of the trivalent (BCC1) and tetravalent (BCC2) boron compounds at a current density of 0.75 A/g were 135.21 and 94.87 F/g, respectively, while in the presence of KOH electrolyte, the specific capacitance values of the trivalent (BCC1) and tetravalent (BCC2) boron compounds at a current density of 0.75 A/g capacitance values were determined as 106.62 and 88.25 F/g, respectively. The cycling stability of the electrodes was also studied, and it was found that the capacitance of BCC1 electrode increased gradually over the cycles, while the capacitance of BCC2 electrode decreased. The study suggests that trivalent boron can be a promising material for supercapacitor applications. However, further research is required to optimize the cycling stability of the electrodes and understand the underlying mechanism.
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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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    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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    Investigation of a novel Defatted Spent Coffee Ground (DSCG)-supported Ni catalyst for fuel cell and supercapacitor applications
    (Elsevier, 2024) Hansu, Tulin Avci; Al-Samaraae, R. R.; Atelge, M. R.; Kaya, Mustafa; Kivrak, Hilal Demir; Bogrekci, Ismail; Yildiz, Yalcin Sevki
    With the increase in energy demand, a material that can be used in fuel cell applications has been developed for both energy storage and the use of alternative energy sources to fossil fuels. In this study, a new Defatted Spent Coffee Ground (DSCG)-based electrode material was synthesized for two different application areas. A new electrocatalyst synthesis was carried out by subjecting DSCG to chemical activation and carbonization processes. The glycerol electrooxidation performances of the catalysts synthesized at 10-50 % Ni loading rates were investigated by CV measurements. 30 % Ni-DSCG catalyst exhibited the highest catalytic activity with 3.290 mA/ cm2.As 2 .As a result of the electrochemical measurements, 30 % Ni-DSCG catalyst with the best catalytic performance was used as the supercapacitor electrode material. The electrochemical performances of the produced super- capacitor electrodes were tested at room temperature using galvanostatic charge-discharge (GCD), Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques, and the capacity and stability of the electrodes were calculated as a result of the findings. In the calculations, the energy and power density of the 30 % Ni-DSCG supercapacitor electrode were calculated as 22.897 Wh kg(- 1) , 841.114 W kg(- 1) , respectively. The supercapacitor electrode capacitance was found to be 50.48 F/g. Its cyclic capacity was found to be 90 %. It showed that the DSCG-based synthesized electrocatalyst could be a good option for energy storage technology as EDLC electrode material and fuel cell applications as anode catalyst due to its good conductivity, superior cyclic stability, environmental friendliness and low cost.
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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.