Nafion-MPMDMS nanocomposite membranes with low methanol permeability

In this work Nation nancomposite membranes have been synthesised using a directed sol-gel synthesis technique with (3-mercaptopropyl) methyldimethoxysilane as the silicon alkoxide precursor. The resulting membranes with 16.7 wt% inorganic content showed a 89% reduction in methanol permeability compared to Nafion 117 at 50 degrees C. Small angle X-ray scattering data profiles for the nanocomposite membranes were distinctly different to those of unmodified Nafion 117 and showed a distinct upturn at low q. The slope of the curves was approximately -3.5 over the range 0.01 < q < 0.015, suggesting the presence of scattering objects with a mass fractal structure in the range 40-60 nm. Such objects were directly observed by transmission electron microscopy, and indicate an interpenetrated network of inorganic agglomerates and the host Nafion polymer, which significantly decreases the methanol permeability. The membranes may be suitable candidates for use in direct methanol fuel cells. (c) 2006 Elsevier B.V. All rights reserved

Physical and electrochemical characterization of nanocomposite membranes of Nafion and functionalized silicon oxide

Nafion nanocomposite membranes were prepared from Nafion 117 and a systematic range of organically functionalized silicon alkoxide precursors using an in situ sol gel synthesis technique. The physical structure of the resulting nanocomposite membranes were characterized using small and wide-angle X-ray scattering, small angle neutron scattering, positron annihilation lifetime spectroscopy, and transmission electron microscopy. A structural model is proposed for three typical nanocomposite membranes (Nafion-TEOS, Nafion-MPTMS and Nafion-MPMDMS). The proton and methanol transport properties of the membranes included in the model were evaluated by impedance spectroscopy and pervaporation experiments, respectively, and correlated to their composite microstructure. In particular, this model explains the increased selectivity for transport over protons for nanocomposite membranes produced using (3-mercaptopropyl)methyldimethoxysilane as the silicon alkoxide precursor, which is more than six times higher than that of Nafion 117

Cost effective cation exchange membranes: A review

This paper will look at developments of new polymer electrolyte membranes to replace high cost ion exchange membranes such as Nafion , Flemion and Aciplex . These perfluorinated polymer electrolytes are currently the most commercially utilized electrolyte membranes for polymer electrolyte fuel cells, with high chemical stability, proton conductivity and strong mechanical properties. While perfluorinated polymer electrolytes have satisfactory properties for fuel cell applications, they limit commercial use due to significant high costs as well as reduced performance at high temperatures and low humidity. A promising alternative to obtain high performance proton-conducting polymer electrolyte membranes is through the use of hydrocarbon polymers. The need for inexpensive and efficient materials with high thermal and chemical stability, high ionic conductivity, miscibility with other polymers, and good mechanical strength is reviewed in this paper. Though it is difficult to evaluate the true cost of a product based on preliminary research, this paper will examine several of the more promising materials available as low cost alternatives to ion exchange membranes. These alternative membranes represent a new generation of cost effective electrolytes that can be used in various ion exchange systems. This review will cover recent and significant patents regarding low cost polymer electrolytes suitable for ion exchange membrane applications. Promising candidates for commercial applications will be discussed and the future prospects of cost effective membranes will be presented