Architecting side chain grafted poly (vinylidene fluoride) based graphene oxide composite polyelectrolyte membranes for hydrogen and direct methanol fuel cells

Chemically modified poly (vinylidene fluoride) (PVDF) as polyelectrolyte has generated immense interest due to its high efficiency in electrochemical energy devices. Herein, the design of a polymer electrolyte membrane (PEM) is formulated by the synergistic fusion of graphene oxide (GO) into chemically grafted PVDF with 2-acrylamido-2-methylpropane sulfonic acid (AMPS) by solution phase intercalation producing GO@PVDF-g-PAMPS composite membranes. Ozone-induced graft copolymerization technique is employed to prepare PVDF-g-PAMPS with 18.2 % (w/w) degree of grafting. Incorporation of GO into the polymeric membrane generates appropriate hydrophilic-hydrophobic phase separation and constructs well-organized sub-nano slit-like pathways that elevate the proton conduction. PAG-0 membrane without any filler shows a proton conductivity (kappa) of 15.1 mS/ cm at 80 degrees C whereas PAG-2 membrane (with 2% w/w GO loading) shows a kappa of 25.9 mS/cm under similar conditions. The presence of a perfluorinated backbone furnishes excellent oxidative stability to the PEMs by retaining 95 % of total mass and 97.3 % of kappa after dipping in harsh Fenton's reagent at 60 degrees C for 6 h. Representative PAG-2 shows a peak power density of 152.9 mW/cm2 with a maximum current density of 480.6 mA/ cm2 (fuel cell operating conditions: 75 degrees C at 100 % RH) in hydrogen fuel cell and a peak power density of 37.7 mW/cm2 in direct methanol fuel cell. Moreover, PAG-2 retains 91 % of its initial OCV and exhibits a mere 5.2 % loss in peak power density after 50 h of the durability test.