Dual functionalized graphene oxide incorporated with sulfonated polyolefin proton exchange membrane for fuel cell application

Abstract

This study presented a strategy of incorporating hydrocarbon-based proton exchange membrane (PEM) with dual-functionalized GO attached phosphonic and sulfonic functional groups to improve proton conductivity, ion exchange capacity (IEC) and methanol permeability for direct methanol fuel cell application. It was found that the proton conductivity, IEC of PEM and fuel cell power density enhanced remarkably through doping functionalized GO. The PEM doped with 8% PS-MGO exhibited the IEC value of 2.06 mmol g−1, proton conductivity of 0.084 S cm−1, and power density of 78 mW cm−2 at 25 °C. The methanol permeability of doped PEM was constrained effectively, reduced to 18.42 10−7 cm2 S−1. In addition, the results suggested the properties improvements were proportional to the functionalized GO contents and the improving effects of dual-functionalized GO on PEM were superior to the single functionalized GO. These improvements were attributed to the additional acidic sites offered by functionalized GO construct consecutive proton conduction pathways for facilitating protons transportation and the potential differences between phosphonic and sulfonic groups provided extra energy to drag water-connected protons through the membrane under the vehicular mechanism. This study proposed a promising strategy to use dual functionalized GO preparing PEM with excellent proton conductivity, IEC, power density and methanol permeability properties for fuel cell application.