New triazine-phosphonate dopants for proton exchange membranes (PEM)

Abstract

g their operating temperature range. Our previous studies have demonstrated that the incorporation of aryl or heterocyclic phosphonic acid dopants into Nafion, by casting, results in an enhancement of the proton conductivity1-4 and stability5 of the Nafion doped membranes. This work reports the synthesis and characterization of a new series of triazine-phosphonate derivatives for use as dopants in the preparation of Nafion modified membranes. Several arylphosphonate compounds were prepared bearing an amino or a hydroxy functional group at the para-position of the aryl ring. These compounds react with 2,4,5-trichloro-1,3,5-triazine through a nucleophilic substitution reaction to obtain the 2,4,6-(p-substituted)phosphonate-1,3,5-triazine dopants (Figure 1). The new compounds were characterized by NMR, IR spectroscopy and mass spectrometry, allowing the assignment of their structure. In the anticipation that these synthesized phosphonates can act both as a source of protons and proton acceptors, facilitating the intermolecular proton conduction throughout the modified membranes, new Nafion modified membranes were prepared by casting, through the incorporation of these synthesized 1,3,5- triazine-phosphonate derivatives. The new membranes were characterized, and their proton conduction properties were evaluated by electrochemical impedance spectroscopy (EIS), at different temperature and relative humidity (RH) conditions.