Direct polymer electrolyte membrane

Ren, X. Springer, T. E. and Gottesfeld, S. (1998). Direct Methanol Fuel Cell Transport Properties of the Polymer Electrolyte Membrane and Cell Performance. Vol. 98-27. Proc. 2nd International Symposium on Proton Conducting Membrane Euel Cells. Pennington, NJ Electrochemical Society. 

The electrocatalytic oxidation of methanol has been widely investigated for exploitation in the so-called direct methanol fuel cell (DMFC). The most likely type of DMFC to be commercialized in the near future seems to be the polymer electrolyte membrane DMFC using proton exchange membrane, a special form of low-temperature fuel cell based on PEM technology. In this cell, methanol (a liquid fuel available at low cost, easily handled, stored, and transported) is dissolved in an acid electrolyte and burned directly by air to carbon dioxide. The prominence of the DMFCs with respect to safety, simple device fabrication, and low cost has rendered them promising candidates for applications ranging from portable power sources to secondary cells for prospective electric vehicles. Notwithstanding, DMFCs were... 

Mustain WE, Kepler K, Prakash J. 2007. CoPd, oxygen reduction electrocatalysts for polymer electrolyte membrane and direct methanol fuel cells. Electrochim Acta 52 2102-2108. Nagy Z, You H. 2002. Applications of surface X-ray scattering to electrochemistry problems. Electrochim Acta 47 3037-3055. 

Shen M, Roy S, Kuhlmann JW, Scott K, Lovell K, Horsfall JA. 2004. Grafted polymer electrolyte membrane for direct methanol fuel cells. J Memb Sci 251 121-130. 

In addition to these smaller applications, fuel cells can be used in portable generators, such as those used to provide electricity for portable equipment. Thousands of portable fuel cell systems have been developed and operated worldwide, ranging from 1 watt to 1.5 kilowatts in power. The two primary technologies for portable applications are polymer electrolyte membrane (PEM) and direct methanol fuel cell (DMFC) designs. 

N. T. Nguyen and S. H. Chan. Micromachined polymer electrolyte membrane and direct methanol fuel cells and mdash a review. Journal of Micromechanics and Microengineering 16 (2006) R1-R12. 

This section addresses the role of chemical surface bonding in the electrochemical oxidation of carbon monoxide, CO, formic acid, and methanol as examples of the electrocatalytic oxidation of small organics into C02 and water. The (electro)oxidation of these small Cl organic molecules, in particular CO, is one of the most thoroughly researched reactions to date. Especially formic acid and methanol [130,131] have attracted much interest due to their usefulness as fuels in Polymer Electrolyte Membrane direct liquid fuel cells [132] where liquid carbonaceous fuels are fed directly to the anode catalyst and are electrocatalytically oxidized in the anodic half-cell reaction to C02 and water according to... 

In PEMFC systems, water is transported in both transversal and lateral direction in the cells. A polymer electrolyte membrane (PEM) separates the anode and the cathode compartments, however water is inherently transported between these two electrodes by absorption, desorption and diffusion of water in the membrane.5,6 In operational fuel cells, water is also transported by an electro-osmotic effect and thus transversal water content distribution in the membrane is determined as a result of coupled water transport processes including diffusion, electro-osmosis, pressure-driven convection and interfacial mass transfer. To establish water management method in PEMFCs, it is strongly needed to obtain fundamental understandings on water transport in the cells. 

Note PAFC phosphoric acid fuel cell PEMFC proton exchange membrane fuel cell/polymer electrolyte membrane fuel cell MBFC microbiological fuel cell DMFC direct methanol conversion fuel cell AFC alkaline fuel cell MCFC molten carbonate fuel cell SOFC solid oxide fuel cell ZAFC zinc air fuel cell. 

Direct-methanol fuel cell (DMFC) — This type of -+fuel cell is similar to the - polymer-electrolyte-membrane fuel cell in what concerns the nature of the -> electrolyte -a proton conducting membrane, such as a perfluorosul-fonic acid polymer. In the DMFC the fuel is -> methanol (CH3OH) which is oxidized in the presence of water at the anode and the resulting protons migrate through the electrolyte to combine with the -> oxygen, usually from air, at the cathode to form water ... 

In this book the focus is on PEMFCs therefore, in the following sections we will only discuss several major types of PEMFCs, such as H2/air (02) fuel cells, direct liquid fuel cells, PAFCs, and alkaline fuel cells. PEMFCs, also called solid polymer electrolyte fuel cells, use a polymer electrolyte membrane as the electrolyte. They are low-temperature fuel cells, generally operating below 300°C. 

In the internal type, the reference electrode is in direct contact with the polymer electrolyte membrane of the MEA, as depicted in Figure 5.44. This configuration requires extra attention when assembling and disassembling the fuel cell. 

Dielectric hydration models serve as primitive theories against which more detailed molecular descriptions can be considered. Of particular interest are temperature and pressure variations of the hydration free energies, and this is specifically true also of hydrated polymer electrolyte membranes. The temperature and pressure variations of the free energies implied by dielectric models have been less well tested than the free energies close to standard conditions. Those temperature and pressure derivatives would give critical tests of this model (Pratt and Rempe, 1999 Tawa and Pratt, 1994). But we don t pursue those tests here because the straightforward evaluation of temperature and pressure derivatives should involve temperature and pressure variation of the assumed cavity radii about which we have little direct information (Pratt and Rempe, 1999 Tawa and Pratt, 1994). 

Fuel cells are classified primarily according to the nature of the electrolyte. Moreover, the nature of the electrolyte governs the choices of the electrodes and the operation temperatures. Shown in table 10.1 are the fuel cell technologies currently under development. "" Technologies attracting attention toward development and commercialization include direct methanol (DMFC), polymer electrolyte membrane (PEMFC), solid-acid (SAFC), phosphoric acid (PAFC), alkaline (AFC), molten carbonate (MCFC), and solid-oxide (SOFC) fuel cells. This chapter is aimed at the solid-oxide fuel cells (SOFCs) and related electrolytes used for the fabrication of cells. 

Yamaguchi T, Miyata F, and Nakao S. Pore-fiUing type polymer electrolyte membranes for a direct methanol fuel cell. Journal of Membrane Science 2003 214 283-292. 

H. Uchida, Y. Mizuno, and M. Watanabe. Suppression of methanol crossover in Pt-dispersed polymer electrolyte membrane for direct methanol fuel cells. Chemistry Letters 11, 1268-1269 2000. 

On the other hand, the largest disadvantage is that the protonic resistance of the Sr-Ce-Yb oxide was comparatively larger than that of a polymer-electrolyte-membrane fuel cell (PEM-FC) and was comparable with 0 ion conductivity of an yttria-stabilised zirconia (YSZ). Consequently, as seen in Figs. 4 and 5, the current density through the Sr-Ce-Yb oxide fuel cell was order of niA/cni and was much smaller than that of PEM-FC. This is because a thin ceramic is very difficult to manufacture. The protonic conductivity of the Sr-Ce-Yb oxide itself was around one-tenth smaller than that of PEM. Moreover, the conductivity was order of 10 " S/cm when a CH4 and HjO mixture was supplied directly to the cell without external reformer. The overall conductivity became around 10 -fold less than that of PEM, because the rate-controlling step was in the steam-reforming reaction. 

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