Low-swelling proton-conducting multi-layer composite membranes containing polyarylene ether nitrile and sulfonated carbon nanotubes for fuel cells

• The multi-layer composite membrane was prepared via facile step-by-step solution casting technique.
• The intermolecular interactions between each layer can make the membrane more compact.
• The compact multi-layer structure leaded to lower dimensional swelling.
• The multi-layer composite membrane showed high proton conductivity.

To overcome the difficulties of excessively swollen or dissolve of sulfonated polyarylene ether nitrile in high temperature, the multi-layer proton exchange composite membranes based on sulfonated polyarylene ether nitrile (SPEN) and sulfonated carbon nanotubes (S-CNTs) were designed via facile step-by-step solution casting technique. The multi-layer structure of membranes can make the membrane more compact and reached the aim of low-swelling. The multi-layer structure of composite membrane was confirmed through scanning electron microscope, exhibiting improved dimensional stability, larger tensile strength and elongation at break than pure SPEN with a certain content of S-CNTs in the wet state. The proton conductivity of composite membranes with 3 wt% S-CNTs achieved 0.094 and 0.275 S/cm at 20 °C and 80 °C, respectively, which is higher than that of Nafion 117. Besides, the methanol permeability of SPEN/S-CNTs/SPEN composite membranes is lower than that of the commercial Nafion 117 membrane. All the data prove that the multi-layer composite membranes may be potential proton exchange membrane for fuel cells applications.