Nafion

About: Nafion is a research topic. Over the lifetime, 9110 publications have been published within this topic receiving 320865 citations.

Microelectrode Investigation of Oxygen Permeation in Perfluorinated Proton Exchange Membranes with Different Equivalent Weights

Abstract: Oxygen concentrations (C{sub b}) and diffusion coefficients (D) in various proton exchange membranes were measured using chronoamperometry at microelectrodes. These measurements were made under conditions similar to those prevailing in proton-exchange-membrane fuel cells. Knowledge of the D and C{sub b} parameters is essential for the determination of oxygen permeation in the catalytic layers of gas diffusion electrodes, which could be rate limiting in these low-temperature fuel cells. Furthermore, the D and C{sub b} values also provide the permeation rates of oxygen through the bulk of the proton conducting membrane. it was found that the concentration of oxygen increased and the diffusion coefficient decreased with increasing equivalent weight of the membranes. These results were interpreted using a model based on the microstructure of the swollen membranes separated into two phases, one hydrophobic and the other hydrophilic, with distinctly different O{sub 2}-permeation properties. According to this model the relative amounts of the two phases in the membranes, caused by the different water contents, determine the O{sub 2} solubility and diffusion coefficient in the different membrane materials.

SiO2/sulfonated poly ether ether ketone (SPEEK) composite nanofiber mat supported proton exchange membranes for fuel cells

Abstract: A composite membrane of silica (SiO2)/sulfonated poly (ether ether ketone) (SPEEK) nanofiber mat impregnated with Nafion was fabricated and evaluated for its potential use as a proton conductor for high temperature polymer electrolyte membrane fuel cells. The supporting SiO2/SPEEK composite nanofibrous skeleton was prepared via electrospinning of a mixture of SPEEK solution and silica sol prepared from tetraethyl orthosilicate (TEOS). The control of hydrolysis and condensation of TEOS enabled to form entangled SiO2 networks miscible to SPEEK solution. The prepared SiO2/SPEEK nanofiber mat was impregnated with Nafion® to completely fill the inter-fiber voids to prepare a dense membrane. The morphology of the nanofiber mat and the composite membrane were observed by scanning electron microscopy and the presence of SiO2 and SPEEK in the prepared nanofibers was confirmed by FTIR spectroscopy. Proton conductivity and swelling of the membrane were measured. The H2/O2 single cell test using the composite membrane as a PEM was performed. At a high temperature and low humidity condition (120 °C and 40 % RH), the maximum power density was 170 mW/cm2 for the Nafion-impregnated SiO2/SPEEK (40/60 w/w) composite nanofiber membrane that was 2.4 times higher than recast Nafion (71 mW/cm2) while SPEEK film failed.

Proton Transfer and Proton Concentrations in Protonated Nafion Fuel Cell Membranes

Abstract: Proton transfer in protonated Nafion fuel cell membranes is studied using several pyrene derivative photoacids. Proton transfer in the center of the Nafion nanoscopic water channels is probed with the highly charged photoacid 8-hydroxypyrene-1,3,6-trisulfonate (HPTS). At high hydration levels, both the time-integrated fluorescence spectrum and the fluorescence kinetics of HPTS permit the determination of hydronium concentration of the interior of the water pools in Nafion. The proton transfer kinetics of HPTS in protonated Nafion at maximum hydration are identical to the kinetics displayed by HPTS in a 0.5 M HCl solution. The hydronium concentration near the water interface in Nafion is estimated with rhodamine-6G to be 1.4 M. Excited state proton transfer (ESPT) is followed in the nonpolar side chain regions of Nafion with the photoacid 8-hydroxy-N,N,N′,N′,N′′,N′′-hexamethylpyrene-1,3,6-trisulfonamide (HPTA). Excited state proton transfer of HPTA is possible in protonated Nafion only at the highest hydra...