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Catalyst layers of proton exchange membrane fuel cells (PEMFC) are formed by electrospray deposition (ESD) method. The cathode catalyst layers are formed and characterized by varying the settings of the system, such as flow rate, applied voltage and the distance between the capillary and the substrate. The dryness of the aggregates during deposition is evaluated using the Damkhöler number (Da), and the structure of the catalyst layer is observed using SEM, which shows that the catalyst layer is porous when dry and non-porous when insufficiently dry. In the case of insufficient drying, the structure changed significantly depending on the position. Single cell tests show that the maximum power density varies from 105 to 253 mWcm−2 depending on the settings, even with the same catalyst ink and the same amount of platinum. Electrochemical impedance spectroscopy shows that the charge transfer and mass transport resistances tend to decrease with increase in Da. 相似文献
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The effect of low frequency power ultrasound on Nafion® ionomer used for fabricating proton exchange membrane fuel cell (PEMFC) and water electrolyzer (PEMWE) catalyst inks was investigated. In this study, a series of Nafion® dispersions having three concentrations (10, 5, and 2.5% w/v) were studied under various irradiation durations (tus), at fixed ultrasonic frequency (f = 42 kHz) and ultrasonic power (P > 2 W), under either controlled or unregulated bulk solution temperature conditions using a laboratory ultrasonic cleaning bath. Viscosity (η), thermal degradation, and glass transition temperature (Tg) for all Nafion® dispersion samples was measured and compared to untreated Nafion® samples. In our conditions, it was found that power ultrasound lowered the viscosity of all tested Nafion® dispersion samples; whilst thermogravimetric and differential scanning calorimetry analyses showed that for all ultrasonically irradiated samples, a negligible overall polymer degradation and no obvious change in Tg was observed under controlled and unregulated bulk temperature conditions. It was found that it is possible that acoustic cavitation causes depolymerisation followed by a polymerisation initiation step during ultrasonication. By comparing the ultrasonically treated and high-shear mixed samples, it was also observed that acoustic and hydrodynamic cavitation played an important role in the reduction of dispersion viscosity. 相似文献
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The performance of a polymer electrolyte membrane fuel cell is contingent on the focal property of the protonic conductivity to accelerate the electrochemical reaction based on the membrane activity or on the uniform and even distribution of the reactants. For the even distribution, novel Flow Fields (FF) of the electrode pattern are obligatory to maintain the distribution for a long period for the conversion of protons from the anode reactant. In this study, a novel X Flow Field (XFF) electrode pattern is developed and compared with the conventional serpentine Flow Field (SFF) electrode pattern numerically and experimentally. The performance of the cell through the XFF electrode pattern has shown an improvement of 14.89% numerically and 14.61% experimentally as it distributes the reactants evenly to accelerate the electrochemical reaction, and induce a lower pressure drop and lower water saturation. The effect of pressure and Mass Flow Rate (MFR) of the reactants on the cell performance is discussed and it is found that the increment in Power Density (PD) of the cell is proportional to the increment of the MFR and the pressure because of the even distribution of the reactants, better membrane protonic conductivity, enhancement of the electrode kinetics and improvement in the mass transfer. 相似文献
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Rungsima Yeetsorn Michael Fowler Costas Tzoganakis Wang Yuhua Mali Taylor 《Macromolecular Symposia》2008,264(1):34-43
The polymer electrolyte membrane fuel cell (PEMFC) holds tremendous promise for a variety of mobile and stationary power generation applications and is the cornerstone of the anticipated hydrogen economy. One of the major factors limiting fuel cell commercialization is the development of bipolar plates since bipolar plates account for approximately 70% of the PEMFC weight, and 60% of the stack manufacturing and materials cost. The objective of this research is to investigate a feasibility of a conductive composite family to be used as bipolar plates in a PEMFC, in order to get the highly conductive, light weight, and low cost bipolar plates. This work utilized a combination of a polypropylene and low cost conductive filler materials: graphite, conductive carbon black, and carbon fibers. The components were combined in a batch mixer and injection molded into samples for testing with loadings up to 65%wt of fillers. The novel blends were tested for electrical conductivity, hydrophobicity, rheology, and actual plates (16 cm2) were tested in fuel cell testing trials. The impact of different types of fillers on the composite properties was evaluated, as well as the synergetic effect of mixtures of fill types within a polypropylene matrix. From the results, the highest conductivity, 1900 S/m (in-plane) and 156 S/m (through plane), was obtained with the 65% composite. Moreover, the effects of additives such as coupling agents, and intrinsically conductive polymer (polypyrrole) were observed in this work. The electrical conductivity was influenced by polypyrrole added to the polypropylene composite. 相似文献
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本文对实验室自制的自增湿空冷型PEMFC电堆进行了自适应特性研究,并分析了各单电池的性能以及各电池的电压分布情况. 实验中设定操作条件为:阳极工作压力为2 bar,阴极风扇功率0.3 W,氢气室每隔10 s排水1 s. 从实验结果可以看出,空冷型PEMFC的电压分布与负载电流的大小具有一定的联系,大电流负载下电池的电压分布会出现明显的不均匀现象,根据分析结果可以看出,电堆的单体电压波动率与负载电流之间存在近似的指数关系分布,且各单片电池间内阻的差异与大电流下过高的电堆温度都会造成电压分布不均匀的现象. 相似文献
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Antonio Rodolfo dos Santos Marcelo Carmo Almir Oliveira-Neto Estevam V. Spinacé João G. Rocha Poço Christina Roth Hartmut Fuess Marcelo Linardi 《Ionics》2008,14(1):43-51
This works report results of the structural and the electrochemical characterization of membrane electrode assemblies (MEA) for proton exchange membrane fuel cells (PEMFC) under various cell conditions using different MEA production processes. Electrochemical impedance spectroscopy (EIS) was applied “on-line” (in situ) as a tool for diagnosis concerning the cell performance. MEA with a 25-cm2 surface area were prepared using Pt/C and Pt–Ru/C commercial electrocatalysts from E-TEK and Pt–Ru/C electrocatalysts produced by the alcohol reduction process. The catalytic ink was applied directly onto the carbon cloth or, alternatively, onto the Nafion® membrane. Two carbon cloth thicknesses were tested as diffusion layers in the MEA: 0.346 mm (common) and 0.424 mm (ELAT). An increase of the electrocatalytic activity can be obtained by pH control in the alcohol reduction process, possibly due to the better particle dispersion and the smaller particle sizes observed. In addition, a slower current decay in the ohmic region was observed using the thinner carbon cloth. This can be related to a lower resistance of the gas flow through the cloth to the catalytic active layer. Different types of methanol feed were employed in the experiments: by humidification and by evaporation. The results showed that the choice of suitable methods for catalyst preparation as well as for MEA production enhance PEMFC performance. 相似文献
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PEMFC催化层中PTFE和Nafion对催化剂利用率的影响 总被引:3,自引:0,他引:3
本文利用循环伏安法,结合透射电镜和扫描电镜研究了质子膜燃料电池催化层中加入的聚四氟乙烯(PTFE)和全氟磺酸枝脂对催化剂利用率的影响。PTFE对催化剂利用率的影响很小。但在亲水型电极中,催化剂颗粒之间的电子导通会受到Nafion的阻碍,并导致催化剂利用率降低,由于Nafion分子很小,因此与Pt/C中Pt颗粒的接触没有大问题。 相似文献