BACKGROUND Proton-exchange membrane (PEM) has a significant effect on the performance and overall cost of microbial fuel cells (MFCs). In this study, a novel composite PEM is fabricated by compositing sulfonated graphene oxide (SGO) with the Poly(vinylidene fluoride)-g-Poly(styrene sulfonic acid) (PVDF-g-PSSA) copolymer. The performance of MFCs with these newly prepared composite PEMs as separators was evaluated. A Quartz crystal microbalance with dissipation (QCM-D) combined with membrane-coated sensor crystals was used to investigate the biofouling mechanism of PEMs in MFCs at a micro-perspective. RESULTS The successful sulfonation of GO was confirmed by Fourier transform infrared spectrometry and X-ray photoelectron spectroscopy. When the SGO loading was 1.0 wt%, the SGO/PVDF-g-PSSA membrane had higher water uptake (32.56%), proton conductivity (0.083 S cm(-1)) and excellent hydrophilicity (contact angle 70.78 degrees) than that of Nafion 117. QCM-D results further confirmed its better anti-fouling property vs that of the PVDF-g-PSSA, GO/PVDF-g-PSSA, and Nafion 117 membranes. Moreover, the MFC working with the SGO/PVDF-g-PSSA membrane exhibited the highest maximum power density and best stability of power production after 3 months of operation. CONCLUSION The SGO/PVDF-g-PSSA-1.0 composite PEM can be used as an alternative material to Nafion in MFCs and is conducive to the long-term stable operation of MFCs. (c) 2018 Society of Chemical Industry