Active electrospun nanofibers as an effective reinforcement for highly conducting and durable proton exchange membranes

Abstract

Mechanical reinforcement of proton exchange membranes is a great challenge allowing the reduction of their thickness, with the advantages of lower resistance, improved water transport, decreased fuel crossover and high durability, which are crucial for fuel cells. We describe herein a new class of reinforced membranes based on nanofibers of polysulfone (PSU) functionalized with 4-heptyl-1,2,3-triazole (PSUT) likely interacting via hydrogen bonds or ionic cross-linking with a short-side-chain type perfluorosulfonic acid (Aquivion®) matrix. PSUT with two functionalization degrees was electrospun into webs which were impregnated with Aquivion® to afford composite membranes that presented higher dimensional stability in water, increased mechanical strength and Young modulus in comparison to reinforced membranes of non-functionalized PSU and pristine ionomer membrane, without any decrease in proton conductivity. Membrane-electrode assemblies incorporating an Aquivion® membrane reinforced with PSUT exhibited 5 times superior durability than those with a pristine Aquivion® membrane without any radical scavenger. These features may be ascribed to the specific interaction between basic fibers and acidic ionomer. The incorporation of webs of active fibers in ionomer membranes is an effective strategy of reinforcement leading to high performance and increased durability, which can be extended to other kinds of ion exchange membranes and devices.