A POLYMER ELECTROLYTE FOR OPERATION AT TEMPERATURES UP TO 200-DEGREES-C

In developing advanced fuel cells and other electrochemical reactors, it is desirable to combine the advantages of solid polymer electrolyte s with the enhanced catalytic activity associated with temperatures ab ove 100-degrees-C. This will require polymer electrolytes which retain high ionic conductivity at temperatures above the boiling point of wa ter. One possibility is to equilibrate standard perfluorosulfonic acid polymer electrolytes such as Nafion(TM), with a high boiling point Br onsted base such as phosphoric acid. The Nafion/H3PO4 electrolyte has been evaluated with respect to water content, ionic conductivity and t ransport of oxygen, and methanol vapor. The results show that at eleva ted temperatures reasonably high conductivity (>0.05 OMEGA-1 cm-1) can be obtained. Methanol permeability is shown to be proportional to the methanol vapor activity and thus decreases with increasing temperatur e for a given methanol partial pressure. Comparisons and distinctions between this electrolyte and pure phosphoric acid are also considered.