Fabrication of a low-cost functionalized poly(vinylidene fluoride) nanohybrid membrane for superior fuel cells

Abstract

Nanochannels were created in poly(vinylidene fluoride) and its nanohybrid films by bombarding with high-energy swift heavy ions. The nanochannel dimensions of the membranes varied from 80 to 100 nm using 5 × 107 ion fluence of SHIs. The walls of the nanochannels were grafted with the monomer 3-hexylthiophene using the free radicals generated by the swift heavy ions, which was followed by their sulphonation for better ion conduction. Organically modified nanoclay enhanced the electroactive β-phase in the polymer and its extent increased after irradiation, grafting and sulphonation, resulting in a better material for different electroactive applications. The semiconducting current-voltage characteristics of the functionalized nanochannels were studied through a parameter analyzer of the bulk film against the insulating behavior of the neat polymer. The current-voltage characteristic of the membrane exhibited strong dependency on functionalization and showed superior conduction in the functionalized nanohybrid membrane. The proton conductivity of the functionalized nanohybrid was 4.59 × 10-2 S cm-1 at 30 °C, while methanol permeability was drastically reduced as compared to that of standard Nafion 117; this indicated the higher values of the selectivity parameter, which is a key feature of the better performance of the fuel cell membrane: 1.02 × 105 S cm-3 s as opposed to the value of 0.73 × 105 S cm-3 s for Nafion 117. The membrane electrode assembly studies of the functionalized nanohybrid showed 0.76 V open circuit voltage, leading to power density of 92 mW cm-2 and current density of 252 mA cm-2, which were significantly higher than those of the functionalized pure polymer and standard Nafion 117 membrane, indicating its good potential for applications in fuel cells. © 2019 The Royal Society of Chemistry.