فهرست مطالب

  • Volume:5 Issue:1, 2018
  • تاریخ انتشار: 1397/04/19
  • تعداد عناوین: 6
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  • Ali Reza Madram *, Mehdi Mohebbi, Mohammad Nasiri, Mohammad Reza Sovizi Pages 1-11

    In this study ternary Ni-P-CeO2 catalysts were first synthesized by the Co-electrodeposition method on a copper substrate and then characterized by means of microstructural and electrochemical techniques toward a hydrogen evolution reaction (HER). Also, for comparison other catalysts such as Ni-CeO2, Ni-P, and Ni were prepared and characterized by the same methods. The microstructure of the investigated catalysts was characterized by scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectrometry (EDX) and X-ray diffraction (XRD) methods. The electrochemical efficiency of all investigated catalysts was studied based on electrochemical data obtained from electrochemical impedance spectroscopy (EIS) and steady-state polarization Tafel curves in 1 M NaOH solution. The results showed that microstructural properties play an essential role in the high electrocatalytic activity of Ni-P-CeO2. Furthermore, it was observed that the HER mechanism for all investigated systems was Volmer-Heyrovsky with a Volmer step as the rate determining step (RDS). The Ni-P-CeO2 catalyst, as the most active catalyst in this work, was characterized by an exchange current density of j0=168.0 µAcm-2, a Tafel slope of b=-162.0 mV.dec-1, and overpotential at j0=250 mAcm-2; η250=-143.0 mV.

    Keywords: Hydrogen evolution reaction (HER), Ni-P-CeO2, electrocatalytic activity, Electrochemical Impedance Spectroscopy (EIS)
  • zeinab darabi, Ali Akbar Babaluo*, Sona Jamshidi Pages 13-19

    A palladium membrane was prepared using the electroless plating technique (ELP) for the separation and purification of hydrogen from a gas mixture. Depending on operating conditions, hydrogen flux from the membrane was in the range of 0.012-0.023 mol.m-2.s-1. The membrane performance in the presence of CO2 was investigated. The results of the GC analysis showed that at a feed concentration of 10% CO2 and a difference pressure of 1-2 bar, no traces of CO2 was observed in the permeate side. However, hydrogen permeation through the membrane decreased due to the occupation of the catalytic active sites by CO2.. At the concentration of 20% CO2 and a difference pressure of 1-2 bar, a peak of methane was detected in the permeate side by the GC analysis, this is related to the diffusion of carbon from the feed side to the permeation side. Study on the topography of the membrane surface showed short height hills and wide valleys on its surface. This topology of the surface conduced high chemical resistance of the membrane, so that the effect of CO2 poisoning was reversible without defect creation on the membrane. Recovery of the poisoned membrane was done by exposing it to hydrogen atmosphere at 500 °C for an hour. The obtained results show that the recovery of hydrogen permeation was up to 99%.

    Keywords: Palladium membrane, Electroless plating technique, Poisoning, Membrane recovery
  • Shima Sharifi, Rahbar Rahimi*, Davood Mohebbi, Kalhori, Can Ozgur Colpan Pages 21-33

    A two-dimensional, single-phase, isothermal model has been developed for a direct methanol fuel cell (DMFC). The model considers the anode and cathode electrochemical equations, continuity, momentum and species transport in the entire fuel cell. Then, the equations are coupled together and solved simultaneously using a commercial, finite element based, COMSOL Multiphysics software. The crossover of methanol is also investigated in the model. This model describes the electrochemical kinetics of methanol oxidation at the anode catalyst layer by non-Tafel kinetics. The concentration distribution of methanol, water, and oxygen was predicted by the model. In addition, the changes of methanol crossover and fuel utilization with current density were evaluated for different methanol concentrations (0.5 M, 1 M, 2 M, 4 M, and 6 M). Furthermore, it was also found that the crossover of methanol decreases at low methanol concentrations and high current densities. The results show that the polarization curve is in agreement with experimental data.

    Keywords: Direct methanol fuel cell, DMFC, Crossover, 2D model, Isothermal
  • biuck habibi* , Hamideh Emanzadeh Pages 35-47

    The electrocatalytic oxidation of ethanol was studied for the platinum nanoparticles/ functionalized carbon nanoparticles composites supported at the carbon-ceramic electrode (PtNPs/tosyl-CNPs/CCE) as an electrocatalyst in acidic medium. The PtNPs/tosyl-CNPs/CCE electrocatalyst was synthesized by electrodeposition of PtNPs on/in casted tosyl-CNPs at the CCE. The characterization of the fabricated nanocomposite was done by X-ray powder diffraction (XRD) spectroscopy, field emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray (EDX) spectroscopy. The obtained electrocatalytic oxidation of ethanol was studied by cyclic voltammetry and chronoamperometry techniques. The results showed that the PtNPs/tosyl-CNPs/CCE was electrocatalytically more active than PtNPs/CCE and had high anodic peak current densities, low onset potential, low poisoning and high stability. Hence, the proposed nanocomposite, PtNPs/tosyl-CNPs/CCE, can be extended as an attractive and promising electrocatalyst for the ethanol electrooxidation reaction in fuel cells.

    Keywords: Ethanol oxidation, Electrocatalyst, Pt nanoparticles, functionalized carbon nanoparticles, Carbon-ceramic electrode
  • Rasol abdullah mirzaie* , Azam Anaraki Firooz, Maliheh Bakhtiari Pages 49-55

    Recently, methanol fuel cell systems have been attracted research activities by improving electrocatalysts to investigate facilitating the methanol oxidation reaction. ZnO and ZnO doped with other metals or metal oxide can be used as an additive in carbon substrate of an electrocatalyst to improve electro catalytic properties of a platinum electrocatalyst. In this work, a simple low temperature hydrothermal method has been used for synthesis of different morphologies of 1% mol Ni, Cu and Co doped ZnO nanostructures. The prepared nanostructures were used in carbon substrate of a platinum electrocatalyst on carbon paper. Then platinum was electrodeposited by simple cyclic voltammetry on a modified carbon substrate of electrocatalyst. Prepared electrodes were investigated for methanol oxidation reaction in a three electrode half-cell system by the electrochemical methods like as linear sweep voltammetry. The results revealed that with using Ni doped ZnO in carbon substrate, the current density was increased. While, with using Cu doped ZnO in carbon substrate, a significant reduction in anodic over voltage was observed.

    Keywords: Methanol oxidation reaction, Platinum electrodeposition, Electrocatalyst, Doped zinc oxide, carbon substrate
  • Maryam Yaldagard* Pages 57-69

    Many researchers proposed the use of graphene nanoplates (GNPs), carbon nanofibers(CNFs) and metal oxide nanorods as an advanced metal catalyst support for electrocatalysis applications. In this research, Platinum (Pt) catalytic electrode was developed by using GNPs and CNFs containing ZrO2 nanorods (buckypaper) as supporting medium and electrodeposition method to deposit Pt catalyst. Special mixed buckypapers (BPs) was developed by layered microstructures with a large porous structures of CNFs networks at the surface, as well as dense and high-conducting GNP networks as back supports. This unique microstructure led to improve Pt catalyst accessibility and mass exchange properties. The topographical features, structure, morphology and composition of the prepared film samples are characterized by AFM, XRD, FESEM and EDX. The thickness of approximately 39micrometer and a porosity of 81%, were obtained by porometer using mercury prosimetry test. Catalytic properties of Pt/BPs electrodes and MEA performance evaluations were measured using potensiostat/galvanostat and fuel cell test station based on cyclic voltammetry and single cell polarization measurements. Pt particles of about 6.66nm were uniformly deposited in porous BPs. A promising electrochemical surface area of 31.66m2g-1 was obtained from these electrodes. The peak power density of the cell worked by BPs with ZrO2 nanorods was 0.288 kWcm-2, higher than 0.23kWcm-2 measured on the cell worked by the BPs without ZrO2 nanorods. A Pt utilization as high as 0.675gPtkW-1 was achieved for the cathode electrode at 80◦C. Pt utilization efficiency can be further improved by optimization of the electrodeposition condition in order to reduce the Pt particle size.

    Keywords: Buckypaper electrode, nanofiber, graphene nanoplates, ZrO2 nanorod, PEMFC