Ion Transporting Composite Membranes. I. Nafion Impregnated Gore-Tex

摘要

Ion transporting membranes are required in a variety of electrochemical processes and devices including chlorine-caustic production, batteries, fuel cell, electrolyzers, etc. Nafion, a perfluorosulfonate ionomer marketed by Du Pont has proved useful for a number of these applications. Nafion has a number of attractive features including good chemical and mechanical stability and high perselectivity. In addition, however, it has two potentially significant disadvantages - it is a cation transporting membrane (i.e., there is no anion transporting equivalent) and it is rather expensive. These difficulties have prompted efforts to develop anion and cation transporting materials which have Nafion's desirable chemical and mechanical features but which can be produced more cheaply. It occurred to us that a cheaper and more versatile membrane material might be prepared by doping an inexpensive, nonconductive material with a small amount of an ion transporting polymer. In an effort to demonstrate the feasibility of this approach, we have impregnated commericially available porous polytetrafluoroethylene membranes (Gore-Tex) with small quantities of Nafion, to make cation transporting composites. Electrode surfaces were covered with these composite membranes electrochemical techniques were used to study the membranes transport properties. We have shown that the Nafion-doped Gore-Tex does, indeed, transport cations and that the rate of transport can be much higher than the transport rate in a pure Nafion membrane.