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    Effect of microwave irradiation on PEMFCs anode and cathode catalysts
    (Springer, 2023) Sahin, Oemer; Yilmaz, Adem; Ekinci, Arzu
    This study explored the effects of PtCo/C catalysts modified by microwave radiation as anode and cathode catalysts in proton exchange membrane (PEM) fuel cells. The PtCo/C catalyst was synthesized using sodium borohydride and formic acid-reducing agents by a chemical reduction method. The structural properties of PtCo/C and modified PtCo/C catalysts were analyzed by XRD analysis. The composition and distribution of these alloys in Vulcan XC-72R carbon were determined by SEM techniques. The electrochemical properties of the catalysts were evaluated by CV studies. The tafel slope b values for PtCo/C and modified PtCo/C catalysts were calculated as 84 mV/dec and 43 mV/dec when used as cathode catalysts, and 54 mV/dec and 41 mV/dec when used as anode catalysts, respectively. The power density values were calculated as 52 mW/cm(2) and 58 mW/cm(2) when PtCo/C and modified PtCo/C were used as cathode catalysts, and 33.48 mW/cm(2) and 52.08 mW/cm(2) when used as anode catalysts, respectively. The power density rises by 12% when the modified PtCo/C catalyst is employed as the anode catalyst and by 56% when it is used as the cathode catalyst, as compared to PtCo/C catalysts.
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    Hydrogen production from sodium borohydride for fuel cells in presence of electrical field
    (Wiley, 2010) Sahin, Oemer; Dolas, Hacer; Kayal, Mustafa; Lzgi, Mehmet Sait; Demir, Halil
    Sodium borohydride (NaBH4) reacts with water to produce 4 mol of hydrogen per mol of compound at room temperature. Under certain conditions, it was found that 6 mol of hydrogen per mol of sodium borohydride was produced in the presence of electrical field created by DC voltages, whereas 4 mol of hydrogen was produced in the presence or catalyst per mole of sodium borohydride. Electrical field created by alternative current with three different waves (sin, square and triangle type) increases the hydrolysis of sodium borohydride. It was found that hydrogen produced from sodium borohydride by applying, an electrical field can be effectively used for both increasing the electrolysis of water and hydrolysis of sodium borohydride. The hydrolysis reaction was carried out at temperature of 20, 30, 40 and 60 degrees C in the presence of electrical field created by AC voltages square wave. The experimental data were fitted to the kinetic models of zero-order, first-order and nth-order. The results indicate that the first-order and nth-order model give a reasonable description of the hydrogen generation rate at the temperature higher than 30 degrees C. Reaction rate constant at different temperatures were determined from experimental data, and activation energy was found to be 50.20 and 52.28 kJ mol(-1) for first-order and nth-order, respectively. Copyright (C) 2009 John Wiley & Sons, Ltd.
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    Optimizing hydrogen production from alkali hydrides using supported metal catalysts
    (Springer Heidelberg, 2023) Karabulut, Abdurrahman; Izgi, M. Sait; Demir, Halil; Sahin, Oemer; Horoz, Sabit
    The present study aimed to investigate the effect of different parameters on the hydrogen production rate (HPR) during KBH4 hydrolysis using Co-B (pure) and Co-B@GO (supported) catalysts. The results showed that the HPR value for Co-B@GO catalyst was 2299.81 mL*gcat-1 min-1, which was approximately 2.3 times higher than that of the Co-B catalyst (1012.71 mLgcat-1 *min-1). The activation energy of Co-B@GO was also calculated to be 21.62 kJ/mol, lower than some reported values in the literature. This demonstrates the potential of Co-B@GO as a cost-effective and efficient catalyst for hydrogen production from alkali hydrides. The results of this study provide novel insights into the optimization of hydrogen production processes using supported metal catalysts.
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    Synthesis of Co-Cr(0) and Co-Cr-B catalysts from bean pods extract by the green synthesis method and their application in sodium borohydride hydrolysis
    (Springer, 2024) Baytar, Orhan; Sahin, Oemer; Canpolat, Gurbet; Ekinci, Arzu
    In this study, the effect of Co-Cr(0) and Co-Cr-B nanocatalysts on sodium borohydride hydrolysis was investigated. The extract obtained from the pods of the bean plant was produced using the environmentally friendly green synthesis method, along with the chemical reduction method as the production procedure for the catalysts. The analyses used to study the structure and surface morphology of catalysts are SEM, TEM, EDX, XRD, FTIR, and XPS. From the SEM and TEM pictures, the shape of the catalysts comprises of tiny spheres and has a porous nanostructure, and the particle size is 35-40 nm. The XRD investigation revealed that the catalysts had an amorphous structure. The catalysts' structure has been confirmed to include the components Co, Cr, and B using EDX and XPS analyses. It was examined how different amounts of catalyst, different NaBH4/NaOH concentrations, and different solution temperatures affected the hydrolysis of sodium borohydride. The n-th order kinetic model was utilized to determine the activation energies of Co-Cr(0) and Co-Cr-B nanocatalysts, which were found to be 24.39 kJ/mol and 43.09 kJ/mol, respectively. Also, the turnover frequency (TOF) values of synthesized nanocatalysts Co-Cr(0) and Co-Cr-B at 60 degrees C were calculated as 19,210 mLmin- 1g- 1 and 12,410 mLmin- 1g- 1, respectively. The repeatability of catalysts in NaBH4 hydrolysis showed high activity even after the fifth use.Graphical AbstractThe production scheme of Co-Cr(0) and Co-Cr-B nanocatalysts center dot Green synthesis provides an environmentally friendly, simple, economical and reproducible approach for faster metal nanoparticle production.center dot Green synthesis method increased the activity of Co-based catalysts center dot In kinetic studies, activation energies were calculated using the n-th order and Langmuir-Hinshelwood models.center dot Co-Cr(0) and Co-Cr-B nanocatalysts, the activation energies were calculated to be 24.39 kJ/mol and 43.09 kJ/mol, respectively.