Nafion

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

Metallic Nanoparticle−Carbon Nanotube Composites for Electrochemical Determination of Explosive Nitroaromatic Compounds

Abstract: Metal nanoparticles (Pt, Au, or Cu) together with multiwalled and single-walled carbon nanotubes (MWCNT and SWCNT) solubilized in Nafion have been used to form nanocomposites for electrochemical detection of trinitrotoluene (TNT) and several other nitroaromatics. Electrochemical and surface characterization by cyclic voltammetry, AFM, TEM, SEM, and Raman spectroscopy confirmed the presence of metal nanoparticles on CNTs. Among various combinations tested, the most synergistic signal effect was observed for the nanocomposite modified glassy carbon electrode (GC) containing Cu nanoparticles and SWCNT solubilized in Nafion. This combination provided the best sensitivity for detecting TNT and other nitroaromatic compounds. Adsorptive stripping voltammetry for TNT resulted in a detection limit of 1 ppb, with linearity up to 3 orders of magnitude. Selectivity toward the number and position of the nitro groups in different nitroaromatics was very reproducible and distinct. Reproducibility of the TNT signal was w...

Ionic Conductivity of PEMFC Electrodes Effect of Nafion Loading

Abstract: The effect of Nafion loading in the cathode catalyst layer of proton exchange membrane fuel cell (PEMFC) electrodes was studied by impedance spectroscopy, cyclic voltammetry, and polarization experiments. Catalyst utilization. determined by cyclic voltammetry, peaked at 76% for a Nafion loading of ca. 30 mass %, and this coincides with the optimum performance obtained in H 2 /O 2 fuel cells. However, the small range of utilizations observed (55-76%) cannot explain the wide range of performances. The impedance results show that the ionic conductivity of the cathode increased greatly with increasing Nafion content, and this is the main factor responsible for the increase in performance up to 30% Nafion. The loss of performance at higher Nafion loadings must have been due to an increasing oxygen transport resistance, because the electronic resistance did not increase significantly. In fact, the highest electronic resistances were observed at low Nafion loadings, indicating that Nafion played a significant role as a binder.

Modeling of Conductive Transport in Proton-Exchange Membranes for Fuel Cells

Abstract: The proton-exchange membrane (PEM) fuel cell has lately emerged as a highly promising power source for a wide range of applications. The solid polymer electrolyte utilized in these fuel cells is typically a polyperfluorosulfonic acid (PFSA) membrane ( e.g., Nafion ® , manufactured by DuPont), that provides excellent performance in the presence of water by virtue of its strong acidity, low permeability of hydrogen and oxygen, and good electrochemical stability in the presence of electrocatalysts. This has allowed the development of low-temperature PEM fuel cells with impressive current densities. These membranes have also been widely utilized in the chlor-alkali industry. However, an understanding and modeling of the transport of ionic species through these ion-exchange membranes is not yet adequately developed, especially for proton transport, which is the focus of this paper. There are numerous studies on the nanostructural aspects of the

Diffusion and interfacial transport of water in Nafion.

Abstract: Water absorption, membrane swelling, and self-diffusivity of water in 1100 equivalent weight Nafion were measured as functions of temperature and water activity. Free volume per water at 80 °C, determined from water uptake and volume expansion data, decreases with water content in the membrane from 12 cm3/mol at λ = 0.5 H2O/SO3 to 1.5 cm3/mol at λ = 4. The change in free volume with water content displays a transition at λ = 4. Limiting water self-diffusivity in Nafion was determined by pulsed gradient spin echo NMR at long delay times. The limiting self-diffusivity increases exponentially with water activity; the rate of increase of diffusivity with water content shows a transition at λ = 4. The tortuosity of the hydrophilic domains in Nafion decreased from 20 at low membrane water activity to 3 at λ = 4. It suggested a change in the connectivity of the hydrophilic domains absorbed water occurs at λ ∼ 4. The diffusivity results were employed to separate the contributions of diffusional and interfacial re...