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PEM-DEFC

The principle of PEM-DEFC (proton exchange membrane direct ethanol fuel cell) operation is illustrated in Eigure 15.1. The anode consists of an ethanol solution, while the cathode is composed by humidified air or oxygen, so that good conductivity is maintained in the PEM. [Pg.429]

The majority of the elements in the periodic table have been assessed as possible metals for an ideal nanoparticle distribution that could modify the structure of Pt. However, the metals described above exert a more significant effect when it comes to ethanol electrooxidation. Table 15.1 summarizes some results from PEM-DEFC. [Pg.436]

As described before in this chapter, conventional DEFCs can be divided into two types as a function of fhe employed membrane, namely proton exchange membrane DEFCs (PEM-DEFCs) and anion exchange membrane DEFCs (AEM-DEFCs), used in acidic and alkaline medium, respectively. As previously reported, Pt-based catalysts undergo rapid poisoning of the catalytic sites, which compromises cell performance. On the other hand, the kinetics of both ethanol oxidation (OER) and the oxygen reduction reaction (ORR) in alkaline medium are much faster than the corresponding kinetics in acidic medium, which substantially improves cell performance. The main limitation to the cell performance in AEM-DEFCs is the physical and chemical stability of the AEM [71]. Another problem encountered with the AEM is that its ionic conductivity is about one order of magnitude lower than that of Nafion membranes. [Pg.440]

The total voltage of fhis fype of cell can reach a value of 2.52V. Compared with 1.14V and 1.24 V obtained for the conventional PEM-DEFC and the AEM-DEFC, respectively, the theoretical voltage increases significantly. The authors claimed that a simple modification to the Nation 117 membrane must be made in other to stabilize the membrane in both supports... [Pg.441]

Colmati and co-workers [106] have examined how experimental conditions affect Pt75Sn2s/C catalysts prepared by the formic acid method. Prior to heat treatment, particle sizes of 4.5 nm and experimental compositions close to the nominal one were achieved, but these particles presented low power density, i.e., 20 mW cm" for ethanol oxidation in a PEM-DEFC. Antolini et al. [24] have looked into the effect of introducing ruthenium into PtSn/C catalysts. Again, the desired catalytic composition and homogeneously distribution small particles (3.5 nm) on the carbon support were obtained, but the power density reported for DEFC was relatively low (28mWcm ) for a PEM-DEFC. [Pg.442]

To date, AEM-DEFCs have exhibited higher performance than PEM-DEFCs [5]. [Pg.103]

DMFCs and direct ethanol fuel cells (DEFCs) are based on the proton exchange membrane fuel cell (PEM FC), where hydrogen is replaced by the alcohol, so that both the principles of the PEMFC and the direct alcohol fuel cell (DAFC), in which the alcohol reacts directly at the fuel cell anode without any reforming process, will be discussed in this chapter. Then, because of the low operating temperatures of these fuel cells working in an acidic environment (due to the protonic membrane), the activation of the alcohol oxidation by convenient catalysts (usually containing platinum) is still a severe problem, which will be discussed in the context of electrocatalysis. One way to overcome this problem is to use an alkaline membrane (conducting, e.g., by the hydroxyl anion, OH ), in which medium the kinetics of the electrochemical reactions involved are faster than in an acidic medium, and then to develop the solid alkaline membrane fuel cell (SAMFC). [Pg.5]

The rate of oxidation of alcohols [41] and reduction of oxygen [41, 42] is higher in alkaline than acidic media, so that the use of an AEM instead of a PEM brings new opportunities to develop DEFC with the concept of a SAMFC. For that purpose, in addition to the choice of an AEM with sufficiently good conductivity and stability, the investigation of electrode reaction catalysts, particularly non-noble metals, is challenging. [Pg.30]

The growth of interest in DMFC and DEFC seems to have reached a steady state during the last years with almost a factor 5 more works on methanol respect to ethanol. It can be also observed an incipient interest for ethylene glycol and propanol as a direct fuel in PEM fuel cell since 2000, and a small but raising number of studies exploring glycerol as a new liquid fuel since 5 years ago. [Pg.8]

Nafion, a sulfonated perfluorinated polymer developed by Dupont, which triggered the development of PEM fuel cells fed with hydrogen was also the PEM used in all the first generation of DMFC and DEFC. Very early in the development of DAFC it was recognized that alcohol crossover due to the relatively large permeability of Nafion to alcohols was a severe limitation to be overcome. In the case of methanol the high permeability can be understood by the preference of Nafion for sorbing methanol instead of water in the binary mixtures. [Pg.21]

Methanol and some other liquid foels can be fed to a PEM fuel cell directly without being reformed, thus forming a direct methanol fuel cell (DMFC), direct ethanol fuel cell (DEFC), direct formic acid fuel cell (DFAFC), and so on. [Pg.10]

Two subcategories of PEM fuel cells are currently being widely studied, for allowing the use of other fuels other than hydrogen directly into the cell direct methanol (DMFC) and direct ethanol (DEFC). [Pg.140]

As to the fabrication of PEMs, PVDF was usually used as a copolymer with hexafluoropropylene, indicated as PVDF-HFP. Kumar et al. have done much work on PVDF-HFP-based PEMs [29-33]. Since then, the copolymer was blended with other polymers or inorganic materials for ion introduction like Naflon, montmoril-lonite (MMT), and A10[0H]. Besides, PVDF has been grafted with PSSA or vinyl-imidazole (Vim) in some research works [34,35], and AI2O3, poly(ethylene glycol) (PEG), or poly(2-acrylamido-2-methyl-l-propanesulfonic acid) (PAMPS) have been used to blend with PVDF system [35,36]. In these researches, PVDF-based PEMs are designed mainly for DMFC application as well as DEFC. [Pg.453]


See other pages where PEM-DEFC is mentioned: [Pg.435]    [Pg.437]    [Pg.440]    [Pg.441]    [Pg.443]    [Pg.100]    [Pg.103]    [Pg.435]    [Pg.437]    [Pg.440]    [Pg.441]    [Pg.443]    [Pg.100]    [Pg.103]    [Pg.356]    [Pg.200]    [Pg.272]    [Pg.296]    [Pg.8]    [Pg.318]    [Pg.43]    [Pg.427]   


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