Nafion

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

Evidence of elongated polymeric aggregates in Nafion

Abstract: Small-angle X-ray and neutron-scattering techniques have been used to probe the structure of swollen Nafion membranes in the range 10−10000 A. From analyzing the scattering data as a function of the polymer volume fraction and using a contrast variation method for the neutron experiments, we suggest a new structural model of Nafion in the hydrated state. It is based on the aggregation of the ionomer chains into elongated polymeric bundles with a diameter on the order of 40 A and a length larger than 1000 A, surrounded by the electrolyte solution.

Water-oxidation catalysis by manganese in a geochemical-like cycle

Abstract: Water oxidation in all oxygenic photosynthetic organisms is catalysed by the Mn₄CaO₄ cluster of Photosystem II. This cluster has inspired the development of synthetic manganese catalysts for solar energy production. A photoelectrochemical device, made by impregnating a synthetic tetranuclear-manganese cluster into a Nafion matrix, has been shown to achieve efficient water oxidation catalysis. We report here in situ X-ray absorption spectroscopy and transmission electron microscopy studies that demonstrate that this cluster dissociates into Mn(II) compounds in the Nafion, which are then reoxidized to form dispersed nanoparticles of a disordered Mn(III/IV)-oxide phase. Cycling between the photoreduced product and this mineral-like solid is responsible for the observed photochemical water-oxidation catalysis. The original manganese cluster serves only as a precursor to the catalytically active material. The behaviour of Mn in Nafion therefore parallels its broader biogeochemistry, which is also dominated by cycles of oxidation into solid Mn(III/IV) oxides followed by photoreduction to Mn²⁺.

High Performance Catalyzed Membranes of Ultra‐low Pt Loadings for Polymer Electrolyte Fuel Cells

Abstract: This paper reports on polymer electrolyte membranes that are catalyzed by the direct application of thin film catalyst layers cast from solutions of suspended Pt/C catalyst and solubilized Nafion ionomer. Both the ionomeric membrane and the solubilized ionmer are in the Na{sup +} form during casting to enable higher curing temperatures, which results in more robust catalyst layers. In addition to simplifying the fabrication process, the direct application apparently provides enhanced bonding at the interface between the membrane and the catalyst layer. Consequently, the performances of fuel cells utilizing these catalyzed membranes with ultra-low platinum loading are superior to those achieved with other approaches to polymer electrolyte membranes of low Pt loading.

Design and properties of functional hybrid organic–inorganic membranes for fuel cells

Abstract: This critical review presents a discussion on the major advances in the field of organic–inorganic hybrid membranes for fuel cells application. The hybrid organic–inorganic approach, when the organic part is not conductive, reproduces to some extent the behavior of Nafion where discrete hydrophilic and hydrophilic domains are homogeneously distributed. A large variety of proton conducting or non conducting polymers can be combined with various functionalized, inorganic mesostructured particles or an inorganic network in order to achieve high proton conductivity, and good mechanical and chemical properties. The tuning of the interface between these two components and the control over chemical and processing conditions are the key parameters in fabricating these hybrid organic–inorganic membranes with a high degree of reproducibility. This dynamic coupling between chemistry and processing requires the extensive use and development of complementary ex situ measurements with in situ characterization techniques, following in real time the molecular precursor solutions to the formation of the final hybrid organic–inorganic membranes. These membranes combine the intrinsic physical and chemical properties of both the inorganic and organic components. The development of the sol–gel chemistry allows a fine tuning of the inorganic network, which exhibits acid-based functionalized pores (–SO3H, –PO3H2, –COOH), tunable pore size and connectivity, high surface area and accessibility. As such, these hybrid membranes containing inorganic materials are a promising family for controlling conductivity, mechanical and chemical properties (349 references).