Phosphonic acid functionalized proton exchange membranes for PEM fuel cells

In recent years there has been a shift from sulfonic acid to phosphonic acid functionality as the preferred potential polymeric material for application in proton exchange membrane (PEM) fuel cells. This paper explores the synthesis of poly(trifluorostyrene)-based ionomers which contain as their ion exchange functionality the phosphonic acid grouping. The paper describes details of preparation, characteristics of the material and indications of fuel cell performance capabilities. Results show that while these materials do provide indication of demonstrable performance in experimental fuel cells, at their present stage of development they do not appear to be a serious threat to the more standard sulfonic acid-based ionomers for application in commercial fuel cell products. 14 refs., 5 figs.