Radiation-Grafted Polymer Electrolyte Membranes for Anhydrous Fuel Cell Operation

Herein, we describe the design, synthesis, and analysis of anhydrous fuel cell membranes that can operate at temperatures above 100 °C, in view of enhanced performance and stability. Traditional polymer electrolyte membrane fuel cells (PEMFCs) do not operate efficiently above 100 °C because water is used as a proton-conductive medium through the Grotthuss hopping mechanism. By substitution of water with heterocyclic amine monomers and use of ionizing radiation to graft them onto fluoropolymer films, proton-conductive network solid-state polymer electrolyte membranes (PEMs) were developed. PEMs were synthesized using indirect radiation grafting of the following heterocyclic amine monomers: 4-vinylpyridine and 5-vinylpyrimidine onto fluorocarbon substrates. The resulting PEMs have proton conductivities greater than 10^-2 S/cm above 100 °C and perform independent of humidity conditions. These PEMs also demonstrate a positive correlation of increased proton conductivity with increasing temperatures above 100 °C. The chemical properties and structures of the grafted monomers affect the proton-conductive mechanism and performance of the PEMs. The data generated through this research will further the development of anhydrous PEMs through radiation grafting to achieve higher proton conductivity, enhanced performance, and stability.