Improvement in properties of nanocrystalline cellulose/poly (vinylidene fluoride) nanocomposite membrane for direct methanol fuel cell application

Abstract

Improving methanol resistance and dimensional stability are the main challenges in polymer electrolyte membranes for direct methanol fuel cell application. In this study, nanocrystalline cellulose (NCC) was initially synthesized and then blended together with poly (vinylidene fluoride) (NCC/PVDF) and the resultant dope solution was used for the fabrication of membranes via solution casting method. The physical characteristics of the membranes were evaluated using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR). Crystallinity differences between all the membranes were confirmed by x-ray diffraction (XRD). Results revealed that the swelling ratio at 80° C and methanol permeability of NCC-3/PVDF were as low as 15.19% and 2.69 × 10-9 cm2/s, respectively compared to Nafion 117 (18.25% and 2.74 ×10-6 cm2/s). It was found that blending hydrophilic NCC with hydrophobic PVDF could profoundly influence the physical properties of the membrane. High crystallinity structure of NCC/PVDF membrane significantly improved the dimensional stability and reduce methanol permeation rate. Although the proton conductivity of NCC-3/PVDF (7.57 ×10-2 mS cm-1) is low, its selectivity (28.141 ×103 Scm-3s) was higher than that of Nafion 117 (0.074 ×103 Scm-3s) due to improvements in methanol barrier. The alternative membrane prepared from NCC and PVDF successfully overcame the weaknesses of Nafion 117, hence exhibiting its potential for DMFC application.