A graphene oxide polymer brush based cross-linked nanocomposite proton exchange membrane for direct methanol fuel cells

Abstract

Functional polymer brush modified graphene oxide (FPGO) with functional linear polysiloxane brushes was synthesized via surface precipitation polymerization (sol–gel) and chemical modification. Then, FPGO was covalently cross-linked to the sulfonated polysulfone (SPSU) matrix to obtain novel SPSU/FPGO cross-linked nanocomposite membranes. Meanwhile, SPSU/GO composite membranes and a pristine SPSU membrane were fabricated as control groups. Reduced agglomeration of the inorganic filler and better interfacial interaction, which are benefit to increase diffusion resistance of methanol and to generate continuous channels for fast proton transportation at elevated temperature, were observed in SPSU/FPGO cross-linked membranes. Moreover, the enhanced membrane stability (thermal, oxidative and dimensional stability) and good mechanical performance also guaranteed their proton conducting durability. It is noteworthy that the SPSU/FPGO-1 cross-linked membrane possesses the best comprehensive properties among all the prepared membranes and Nafion®117, it acquires the highest proton conductivity of 0.462 S cm⁻¹ at 90 °C under hydrated conditions together with a low methanol permeability of 1.71 × 10⁻⁶ cm² s⁻¹ at 30 °C. The resulting high membrane selectivity displays the great potential of the SPSU/FPGO cross-linked membrane for DMFCs application.