Nafion® phosphonic acid composite membranes for proton exchange membranes fuel cells

Abstract

The fuel cells are electrochemical devices that convert the chemical energy stored in a fuel, directly and efficiently into electrical energy. Among the fuel cells, the proton exchange membrane fuel cells (PEMFCs) are considered promising power sources, due to their high power density and high power-to-weight ratio and the proton exchange membranes are considered a key material for the operation of these cells. Usually, these membranes are made of organic polymers containing acidic functionalities, but their proton transport properties strongly depend on their water content, which limit their operation temperatures up to 90ºC. These limitations have fostered the interest in research and development of new alternative membranes [1,2]. In order to develop novel membranes for application in PEMFCs, we have synthesized and characterized mono- or 1,4-dissubstituted aryl derivatives with phosphonic (PAs) and bisphosphonic acids (BPs) groups (Fig. 1). The new Nafion® membranes, doped with PAs or BPs, were prepared and characterized. Their proton conductivity was evaluated by electrochemical impedance spectroscopy (EIS) to analyse the influence of the structure of dopants and the method of the preparation of the membranes.