Yazar "Akdag, Abdurrahman" seçeneğine göre listele

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    Effects of H2/O2 and H2/O3 gases on PtMo/C cathode PEMFCs performance operating at different temperatures
    (Pergamon-Elsevier Science Ltd, 2023) Sahin, Omer; Akdag, Abdurrahman; Horoz, Sabit; Ekinci, Arzu
    This study reported the activity of catalysts synthesized from platinum and molybdenum alloys in different atomic ratios and used as cathode electrocatalysts in the PEMFC. The structural properties of PtMo/C and Pt/C catalysts were analyzed by XRD analysis. The composition and distribution of these alloys in Vulcan XC-72R Carbon were determined by SEM and EDX techniques. CV studies assessed electrochemical properties such as ORR and ECSA activity. The performance of PEMFC cathodes that supplied pure hydrogen and ox-ygen was examined using polarization curves at different temperatures. Another way to improve the cathodic reaction is to use ozone as a potent oxidizing agent. It was measured that the OCV of the H-2/O-3 PEM fuel cell was 1.60 V, much greater than the open circuit voltage of the traditional H-2/O-2 PEM fuel cell. The PtMo/C catalyst achieved its highest power density of 137 mWcm(-2) at 70 degrees C, 128 mWcm(-2) at 60 degrees C, 101 mWcm-2 at 50 degrees C, and 85 mWcm(-2) at 40 degrees C when exposed to H-2/O-2. As the temperature of the cell was raised, it was seen that the catalyst's catalytic activity increased.
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    Improved catalytic activity in PdCo nanocatalysts synthesized via ultrasonic spray method for PEMFC applications
    (Pergamon-Elsevier Science Ltd, 2024) Ekinci, Arzu; Buyukkanber, Kaan; Akdag, Abdurrahman; Sahin, Ohmer
    The current emphasis of research on PEM fuel cells is the exploration of novel, resilient, and very efficient electrocatalysts that do not rely on platinum, while also ensuring long-term stability. This study aimed to enhance the catalytic activity as cathode electrocatalysts by synthesizing Palladium-cobalt alloy nanoparticles using the ultrasonic spraying (US) technique and then dispersing them over a carbon black substrate. The ultrasonic spray method produces crystalline catalysts in the liquid-vapor interface reaction without requiring additional energy. Analyses were performed using XRD, SEM, EDS, XPS and TEM to determine the structural and morphological properties of the nanocatalysts. XRD analysis determined the average particle size of USCo-Pd/C and US-CoPd/C nanocatalysts to 1.37 nm and 1.09 nm, respectively. CV measurements identified ECSA values for USCo-Pd/C and US-CoPd/C as 7.1 m(2)/gPd and 8.9 m(2)/gPd. The relative performance ranking of cathode electrocatalysts for PEM fuel cells was evaluated at a cell temperature of 70 C-degrees. The order of reactivity for the catalysts is as follows: US-CoPd/C > USCo-Pd/C > PdCo/C > Pd/C. The better electrochemical performance of USCo-Pd/C and US-CoPd/C nanocatalysts as cathode catalysts in PEM fuel cell applications, in comparison to Pd/C and PdCo/C catalysts, can be attributed to the modification of the electronic structure of palladium. This modification depends on the synthesis of cobalt and palladium metals together using the US method and the synergistic effect of the catalysts.
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    PEM fuel cell applications of doped (Ni, Zr) metal alloyed Pt/C cathode catalysts
    (Springer, 2024) Akdag, Abdurrahman; Horoz, Sabit; Sahin, Omer; Ekinci, Arzu
    This investigation reported the performance of PEMFC cathode electrocatalysts produced from platinum, zirconium, and nickel alloys with varying atomic ratios. XRD, SEM, and EDX analyses were performed to investigate the structural and morphological properties of the synthesized catalysts. The studies evaluated electrochemical properties, specifically the ORR and the ECSA activity. Based on XRD data, the average crystallite diameters of Pt/C, PtZr2/C, and PtZr2Ni/C catalysts were calculated to be 4.95 nm, 4.33 nm, and 3.35 nm, respectively. Pt/C, PtZr2/C, and PtZr2Ni/C catalysts were used as cathode electrocatalysts in a single cell, and polarization curves were generated for each catalyst at temperatures of 40 degrees C, 50 degrees C, 60 degrees C, and 70 degrees C, respectively. It was determined that the PtZr2Ni/C and PtZr2/C catalysts had better performance than the Pt/C catalyst. Ozone, a powerful oxidizing agent, is another strategy for enhancing the cathodic process. The activity of PtZr2Ni/C catalyst used as cathode electrocatalyst increased with increasing cell temperature in both H2/O2 and H2/O3 usage, and the power density values at 70 degrees C cell temperature were calculated as 165.87 mWcm-2 and 242.08 mWcm-2, respectively.
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    Physical and Electrochemical Effect of Bimetallic Pd-Mo Nanoalloys Supported on Vulcan XC-72R Carbon as Cathode Catalysts for Proton Exchange Membrane Fuel Cell
    (Springer, 2023) Sahin, Omer; Akdag, Abdurrahman; Horoz, Sabit; Ekinci, Arzu
    Synthesis of the bimetallic carbon-supported Pd and PdMo electrocatalysts via the chemical reduction with sodium borohydride as a reducing agent is presented. The Pd/C and PdMo/C electrocatalysts were used as cathode electrocatalysts in proton exchange membrane (PEM) fuel cells in order to examine their catalytic activity. The characterization of the prepared nanoparticles has been carried out using various methods, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy- dispersive X-ray analysis (EDX). Moreover, the activities of the produced catalysts have been determined using cyclic voltammetry (CV), chronoamperometry, electrochemical impedance spectroscopy (EIS), and single-cell PEM fuel cell. The findings reveal that the crystallite size of the electrocatalysts Pd and Pd-Mo is less than 5.5 nm and that the Pd-Mo/C catalyst exhibits high activity for the oxygen reduction process when used alone. Furthermore, catalysts outperform other temperatures at 70 degrees C under varied cell temperatures and Mo concentrations in a single-cell fuel cell. A single cell using Pd-Mo/C as the cathode achieves a maximum power density of 107 mW cm(-2) at its maximum current density. Maximum current densities of synthesized catalysts at 70 degrees C cell temperature were measured as 61, 116, 188, and 168 mA cm(-2) for Pd/C, PdMo/C, PdMo2/C, and PdMo3/C catalysts, respectively. The efficiency according to the current of the PdMo2/C cathode catalyst at 70 degrees C was 52%, and Pd/C, PdMo/C, and PdMo3/C cathode catalysts at the same temperature were calculated as 26%, 38%, and 50%, respectively. The evenly scattered nanoparticles and more crystalline lattice flaws in the Pd-Mo/C catalyst are thought to be responsible for the catalyst's superior performance.
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    Synthesized PdNi/C and PdNiZr/C catalysts for single cell PEM fuel cell cathode catalysts application
    (Elsevier Sci Ltd, 2023) Sahin, Omer; Akdag, Abdurrahman; Horoz, Sabit; Ekinci, Arzu
    In this study, Vulcan XC-72 R supported PdNix, and PdNiZr bimetallic catalysts were synthesized by using so-dium borohydride (NaBH4) and formic acid as reduction agents. The structural properties and morphological qualities of these nanocatalysts were evaluated by XRD, SEM, and TEM analysis. The XPS analysis spectra for Pd/ C, PdNi/C, and PdNiZr/C catalysts showed that Pd, Ni, Zr, and C elements successfully entered the structure. The weights in percent metals of the Pd/C, PdNi/C, and PdNiZr/C catalysts were determined by EDX analysis. In addition, these catalysts' electrochemical properties, activity, and stability, such as their electrochemically active surface area (ESA), were examined using cyclic voltammetry (CV) chronoamperometry, chronopotentiometry, and electrochemical impedance spectroscopy. Polarization curves were created for Pd/C, PdNi/C, and PdNiZr/C catalysts utilized as cathode electrocatalysts in a single cell at temperatures of 40 degrees C, 50 degrees C, 60 degrees C, and 70 degrees C. The PdNiZr/C and PdNi/C catalysts were determined to have higher performance than the Pd/C catalyst. Power densities of Pd/C, PdNi/C, and PdNiZr/C catalysts were measured to be 27.54 mWcm(-2), 114 mWcm(-2), and 188 mWcm(-2), at 70 degrees C, respectively.
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    The Use of NiFe2O4 and CoFe2O4 Nanoparticles Produced by Green Synthesis as Electrode Material for Supercapacitors
    (Wiley-V C H Verlag Gmbh, 2024) Baytar, Orhan; Ekinci, Arzu; Sahin, Omer; Akdag, Abdurrahman
    In this report, for the first time, we have applied green synthesized NiFe2O4 and CoFe2O4 nanoparticles as electrode materials for supercapacitors (SCs). Bean pods extracts were used for the green synthesis of NiFe2O4 and CoFe2O4 nanoparticles. The structure and morphology of the samples were characterized by fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). From XRD analysis, it was determined that NiFe2O4 and CoFe2O4 nanoparticles had a crystalline structure. EDX analysis confirms the presence of carbon and the stoichiometries of NiFe2O4 and CoFe2O4 . In TEM analyses, it was determined that the sizes of nanoparticles varied in the range of 5-20 nm. The FTIR spectra supported the presence of Fe-O, Ni-O, and Co-O bonds. Electrochemical measurements of active materials were performed using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy techniques in a 1 M H2SO4 solution. It was determined that the specific capacitance value of NiFe2O4 (129 F/g) was higher than that of CoFe2O4 (106 F/g). The cyclic stability of CoFe2O4 and NiFe2O4 was found to be 59 and 106 % retention at the end of 10000 cycles, respectively. The specific capacitance value and very good cyclic stability of NiFe2O4 showed that it is a good active substance that can be used in supercapacitor applications.