Sulfonated PVDF nanocomposite membranes tailored with graphene oxide nanoparticles: Improved proton conductivity and membrane selectivity thereof

The nanocomposite membranes consisting of polyvinylidene fluoride (PVDF) and graphene oxide (GO) are prepared via solution casting method and the membranes are subsequently sulfonated by chlorosulfonic acid. A series of physicochemical properties such as, thermogravimetric analysis (TGA), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) are carried out to investigate the thermal and structural properties of the prepared sulfonated PVDF GO (SPG) nanocomposite membranes. The preliminary studies including ion exchange capacity (IEC), water and methanol absorption are conducted for evaluating the feasibility of the SPG membranes to perform as a proton exchange membrane (PEM). The results are quite encouraging and acceptable for further investigations on membrane performance evaluation. The proton conductivity of the membrane has been remarkably improved after the sulfonation and found to be 0.075 S cm at 25 °C which can be ascribed to the hydrophilic nature of incorporated graphene oxide nanoparticles as well as sulfonic groups attached to the PVDF chains which forms a suitable proton conduction channel and favors easy proton migration. Further, the blocking effect of GO provides an advantage for the methanol permeation rate thereby creating a torturous path and giving the methanol permeability value as 1.62 × 10 cms which is 76.62% less than Nafion 117 membrane. Finally, the higher selectivity of the SPG membranes makes them more competitive than Nafion 117 membranes to employ as a PEM for DMFC. Graphical Abstract: [Figure not available: see fulltext.]