Nafion-functionalized electrospun poly(vinylidene fluoride) (PVDF) nanofibers for high performance proton exchange membranes in fuel cells

Abstract

Nafion-functionalized poly(vinylidene fluoride) electrospun nanofibers (PVDFNF-Nafion) have been prepared through a 3-step reaction route. The chemical structure of PVDFNF-Nafion is characterized with Fourier transform infrared and X-ray photoelectron spectroscopy. Functionalization with Nafion chains improves the interfacial compatibility between the PVDF-based nanofibers and Nafion matrix in formation of PVDFNF-Nafion reinforced Nafion composite membrane (Nafion-CM1). Aggregation of Nafion chains on the nanofiber surfaces induces the formation of proton-conducting channels so as to increase the proton conductivity of the Nafion-CM1 membrane. In the H₂/O₂ single cell test, Nafion-CM1 shows a maximum power density of 700 mW cm⁻² which is higher than the value of 500 mW cm⁻² recorded with commercial Nafion 212 membrane. The presence of PVDFNF-Nafion also depresses the methanol permeability of the Nafion-CM1 membrane with alteration of the crystalline domains of Nafion. In direct methanol fuel cell tests, the low methanol permeability of Nafion-CM1 means it could be operated with 5 M methanol as the fuel and exhibits a maximum power density of 122 mW cm⁻², which is larger than the value (60 mW cm⁻²) recorded with commercial Nafion 117 membrane and 2 M methanol fuel.