Radiation-Grafted Polymer Electrolyte Membranes for Anhydrous Fuel Cell Operation

TL;DR

This paper introduces a new type of polymer membrane for fuel cells that can operate efficiently at high temperatures without needing water.

Contribution

The novel approach uses radiation-grafted heterocyclic amine monomers to create anhydrous proton-conductive membranes.

Findings

The developed membranes have proton conductivities above 10–2 S/cm at temperatures over 100 °C.

Proton conductivity increases with rising temperatures above 100 °C, independent of humidity.

The chemical structure of grafted monomers influences proton conduction and overall performance.

Abstract

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.

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