فهرست مطالب

  • Volume:6 Issue:1, 2019
  • تاریخ انتشار: 1398/03/11
  • تعداد عناوین: 6
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  • Masoud Majidi, Ahmad Gholizade, Nesa Rafia, Ali Akbar Babaluo *, Mohammad Vaezi Pages 1-9

    Palladium doped silica membranes were synthesized by the sol-gel method using two different procedures. The first palladium-doped silica membrane (M1) was synthesized with a coating of four layers of silica-palladium sol. The second membrane (M2) was synthesized with a coating of two silica layers followed by a coating of two silica-palladium layers. Scanning electron microscopy (SEM) proved the formation of uniform γ-alumina interlayers on the supports. SEM results for M1 showed that  synthesis of a membrane with this procedure leads to the formation of crack on the membrane selective layer. Single gas permeation measurements of H2 and N2 were carried out at room temperature, 100 °C and 550 °C. Gas permeation results revealed that Knudsen diffusion was dominant in permeation of these gases through membrane M1 while the dominant mechanism in permeation of gases through  membrane M2 was activated transport which has exhibited different behavior in comparison with M1. This result is due to the activated sublayers of membrane M2. In this case, H2 permeance increases and N2 permeance decreases with increasing temperature, leading to better separation perforamce of membrane M2 over M1 in separation of H2. Therefore, using the activated silica sublayer in the synthesis of M2 can be used as a high potential method to synthesize a selective palladium-doped silica membrane.

    Keywords: Hydrogen Separation, Silica membrane, Palladium-doped, Nanostructured silica sublayers, Activated transport
  • MOSTAFA FARNAK, Shahriar Bozorgmehri, Javad Abolfazli * Pages 11-22

    Catalytic partial oxidation (CPOX) has recently received particular attention because it is one of the most attractive technologies for the production of syngas and hydrogen in small to medium scales. Current study subjected to partial oxidation reforming which have simultaneously studied the effect of the fuel composition and flow rates of methane-oxygen mixed gas on the SOFCs performances. In this regard, the Reynolds number at the fuel channel inlet represents the mixture of methane and air mass flow rate. Moreover, the amount of oxygen ratio indicates the fuel composition. The results showed that the peak of power density (PPD) strongly depends upon both the Reynolds number at the fuel channel inlet and oxygen ratio. However, with the changes in Reynolds number or oxygen ratio, the oscillating behavior of PPD was observed. A dimensionless parameter can be introduced to take into account simultaneously the effect of oxygen ratio and Reynolds number of fuel on the PPD value. Considering the risk of carbon deposition as a constraint for selecting of oxygen ratio, the highest PPD corresponds to the methane/oxygen flow rates of 100/20 ccm for the applied methane/oxygen flow rates. The electrochemical experimental testing showed a stable performance of the SOFC in this condition and confirmed its durability after 120 hours testing.

    Keywords: Solid Oxide Fuel Cells (SOFCs), Catalytic Partial Oxidation (CPOX), Methane, Direct reforming, Reynolds number
  • Asrin Ghanbarian, Mohammad Jafar Kermani *, Joachim Scholta Pages 23-37
    Qualitatively, it is known that the reactants content within the catalyst layer (CL) is the driving moments for the kinetics of reaction within the CL. This paper aimed to quantitatively express the level of enhancement in electrical power due to enrichment in the oxygen content. For a given MEA, a flow field (FF) designer is always willing to design a FF to maximize the content of oxygen in all regions of the CL. Using the guidelines provided in this paper, FF-designers can predict the enhancement in electrical power achieved due to 1% enrichment in oxygen content within the CL without cumbrous CFD computations. A three dimensional CFD tool has been used to answer to this question. It simulates a steady, single-phase flow of the reactant-product, a moist air mixture, in the air side electrode of a proton exchange membrane fuel cell (PEMFC). The task was performed for different channel geometries, all   parallel straight flow fields (FF), and a relationship between the oxygen content at the face of the CL and the cell net power was developed. It is observed that at V=0.35 V, for 1% enrichment in oxygen content within the CL, the net power was enhanced by 3.5%.
    Keywords: Fuel Cells, Flow Field Design, Performance Prediction, CFD
  • Maryam Yaldagard * Pages 39-58
    In this study nanocomposite films of PtW nanoparticles deposited on a poly ethylen dioxy thiophene/graphene nanoplates/gas diffusion layer (PEDOT/GNP/GDL) electrode are fabricated via an electrochemical route involving a series of electrochemical process. GNPs are in situ reduced on carbon paper covered with 3, 4 ethylen dioxy thiophene during the in situ polymerization of EDOT. PtW nanoparticles 18.57nm in average size are prepared by electrodeposition on the surface of PEDOT/GNP/GDL. Field emission scanning electronic microscopy (FESEM) images showed spongy aggregates of PEDOT densely cover the surface and edges of the GNP layers, implying the existence of a strong interaction between PEDOT and GNP. Based on electrochemical characterization, it was found that the as prepared electrode exhibited comparable activity for the methanol oxidation (MEOH) reaction with respect to commercial Pt/C/GDL based on the traditional sprayed method. A significant reduction in the potential of the CO electro-oxidation peak from 0.92V for Pt/C to 0.75V for the PtW/PEDOT/GNP/GDL electrode indicates that an increase in the activity for CO electro-oxidation is achieved by replacing Pt with PtW. This may be attributed to structural changes caused by alloying and the increased conductivity and high specific surface area of PEDOT and GNPs catalyst support, respectively. CV scanning results showed that the PtW/PEDOT/GNP/GDL electrode has greater stability than the Pt/C/GDL electrode.
    Keywords: Direct Methanol Fuel Cell (DMFC), Galvanostatic Electrodeposition, graphene nanoplates, Platinum-Tungsten (PtW) Nanoparticles, fuel cell, Poly Ethylen Dioxy Thiophene (PEDOT)
  • Abbas Aghaeinejad *, Kamran Ghasemzadeh, Angelo Basile Pages 59-70

    The aim of this work is a theoretical study of multistage silica membrane configurations for hydrogen purification by methanol steam reforming (MSR) products.  Four membrane schemes including single permeator, CMC (continuous membrane column), ISMC ("in series" membrane cascade), and CRC (countercurrent recycle membrane cascade) were considered for this purpose. The modeling results showed that silica membranes have a high potential for high purity (more than 99.9%) hydrogen production. The lowest amounts of compressor duty and the required total membrane area were considered as the objective functions to select the optimal design and amount of hydrogen purification.  A comparison of our simulation results of the different multistage membrane schemes showed the CRC configuration was more efficient than the other configurations. The modeling results show that that increasing the retentate side pressure from 2 to 5 bar reduced the total silica membrane area for the CRC scheme by almost 13 times (30.67 and 2.37 cm2 silica membrane area for a retentate side pressure of 2 and 5 bar, respectively).

    Keywords: Silica membrane, Hydrogen Separation, Modeling, multistage membrane schemes
  • Shaker Kheradmandinia, Nahid Khandan *, Mohammad Hasan Eikani Pages 71-81
    The most important challenge in Proton Exchange Membrane (PEM) fuel cells is poisoning of the anode catalyst in the presence of impurities, especially carbon monoxide (CO) in the hydrogen feed. So, synthesis of catalysts with high CO tolerance is important for the commercialization of PEM fuel cells. In this study, a common borohydride reduction method was modified to synthesize a carbon supported Platinum Nanocatalyst (Pt/C) with a higher stability in the presences of CO impurity compared to a commercial Pt/C catalyst. The catalysts were characterized by X-ray diffraction and Scanning Electron Microscopy (SEM). The electrochemical cyclic voltammetry (CV) test procedure was used to evaluate the catalyst’s resistance to long-term CO exposure. The results showed that the synthesized catalyst’s electrochemical activity for CO electro-oxidation was comparable to commercial Pt/C under the same conditions. Moreover, the endurance of our catalyst for CO electro-oxidation after 100 CV with continuous CO gas bubbling is remarkable compared to the commercial catalyst performance, which dropped about 88 percent from its initial amounts.
    Keywords: fuel cell, Cyclic voltammetry, supported nano Platinum, CO electro-oxidation