Proton exchange membrane conductors

Figure 29. Conductivity of some intermediate-temperature proton conductors, compared to the conductivity of Nafion and the oxide ion conductivity of YSZ (yttria-stabilized zirconia), the standard electrolyte materials for low- and high-temperature fuel cells, proton exchange membrane fuel cells (PEMFCs), and solid oxide fuel cells (SOFCs).

The principles of the fuel cell are illustrated in Figure 1.1. The electrochemical cell consists of two electrodes, an anode and a cathode, which are electron conductors, separated by an electrolyte [e.g. a proton exchange membrane (PEM) in a PEMFC or in a DAFC], which is an ion conductor (as the result of proton migration and diffusion inside the PEM). An elementary electrochemical cell converts directly the chemical... 

Proton exchange membrane fuel cell (PEMFC) working at around 70 °C with a polymer membrane electrolyte, such as Nafion, which is a solid proton conductor (conducting by the H + cation). 

In general, because PAFCs are proton conductors like the proton exchange membrane (PEM) and the subcategory direct methanol fuel cells (sections 3.5 and 3.6), there is a continuous conceptual transition between them. The polymers used in PEM cells usually contain weakly acidic components such as HSO3, but may be reinforced with a stronger acid in order to increase conductivity or allow operation at higher temperatures. 

PEMFCs are characterized by the use of proton exchange membranes as electrolytes, which are good electronic insulators and very good proton conductors in the presence of water. 

So SY, Yoon YJ, Kim TH, Yoon K, Hong YT. Sulfonated poly(arylene ether sulfone)/functionalized silicate hybrid proton conductors for high-temperature proton exchange membrane fuel cells. J Membr Sci 2011 381(l-2) 204-10. 

M. B. Herath, S. E. Creager, A. Kitaygorodskiy, D. D. DesMarteau, ChemPhysChem 2010, 11, 2871-2878. Perfluoroalkyl phosphonic and phosphinic acids as proton conductors for anhydrous proton-exchange membranes. 

Nation sulfonated tetrafluoroethylene (tetrafluoroethylene and perfluorovinyl ether groups terminated with sulfonate groups) Nation is used as proton conductor for proton exchange membrane fuel cells. 

Cation- or anion-conducting polymer membrane that separates the two electrodes in a fuel cell. In most PEM fuel cells, the polymer is a cation (proton) conductor and in this case PEM can stand for proton exchange membrane. 

A variant of the enhanced reaction zone concept is to utilize as catalyst support various porous three-dimensional electrodes with thickness between 200 to 2,000 pm. Thus, the electric contact resistance between the individual layers is eliminated. The three-dimensional matrix (such as various graphite felts, reticulated vitreous carbon, metal mesh, felt, and foam) supporting uniformly dispersed electrocatalysts (nanoparticles or thin mesoporous coating) could assure an extended reaction zone for fuel (methanol, ethanol, and formie aeid) electrooxidation, providing an ionic conductor network is established to link the catalytically active sites and the proton exchange membrane. The patent by Wilkinson et al. also suggests such electrode configurations (e.g., carbon foam, expended metal and reticulated metal) but experimental results were not provided [303]. 

The membrane electrode assembly (MEA) in a proton exchange membrane (PEM) fuel cell has been identified as the key component that is probably most affected by the contamination process [1]. An MEA consists of anode and cathode catalyst layers (CLs), gas diffusion layers (GDLs), as well as a proton exchange membrane, among which the CLs present the most important challenges due to their complexity and heterogeneity. The CL is several micrometers thick and either covers the surface of the carbon base layer of the GDL or is coated on the surface of the membrane. The CL consists of (1) an ionic conductor (ionomer) to provide a passage for proton transport ... 

CindreUa, L., Kannan, A. M., Lin, J. F. et al. 2009. Gas diffusion layer for proton exchange membrane fuel ceUs—A review. Xlth PoUsh Conference on Fast Ionic Conductors. Journal of Power Sources 194 146-160. 

The proton exchange membrane (PEM) is a key component of PEM fuel cells. It separates the anodic and cathodic compartments and at the same time acts as a proton conductor by transporting protons generated at the anode to the cathode. The protons in the membrane are the main charge carriers. Hence, the conductivity induced by this proton transport is called proton conductivity. Because protons can get transported in two directions, both across and through the membrane, there are two types of conductivity in-plane and through-plane conductivities. The two types are theoretically different unless the membrane is isotopic in these two dimensions. In reality, the PEM is not an absolute electronic isolator. The electronic conductivity, normally much smaller than the... 

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