Water Free Operated Phosphoric Acid Doped Radiation-Grafted Proton Conducting Membranes for High Temperature Polymer Electrolyte Membrane Fuel Cells

The present study uses the radiation-induced grafting method and applies it onto poly(ethylene-alt-tetratluorethylene) (ETFE) for the synthesis of proton-exchange membranes by using monomers 4-vinyl pyridine (4VP), 2-vinyl pyridine (2VP) N-vinyl-2-pyrrolidone (NVP) followed by phosphoric acid doping. Phosphoric acid that provides Grotthuss mechanism in proton mobilization is used to transform the graft copolymers to a high temperature membrane state. Resultant proton-exchange membranes are verified with their proton conductivity, water uptake, mechanical and thermal properties, and phosphorous distribution as ex situ characterization. Our most important finding as a novelty in literature is that ETFE-g-P4VP phosphoric acid doped proton-exchange membranes exhibit proton conductivities as 66 mS cm(-1) at 130 degrees C, 53 mS cm(-1) at 120 degrees C, 45 mS cm(-1) at 80 degrees C. at RH 100% and 55 mS cm(-1) at 130 degrees C., 40 mS cm(-1) at 120 degrees C. 35 mS cm(-1) at 80 degrees C at dry conditions. Moreover, ETFE-g-P4VP membranes still conserves the mechanical properties, i.e., tensile strength up to 48 MPa. ETFE-g-P4VP membranes were tested in PEMFC at 80, 100, and 120 degrees C and RH <2% and exhibit promising performance as an alternative to commercial Nafion (R) membranes. The single cell testing performance of ETFE-g-P4VP membranes is presented for the first time in literature in our study.