In this work, we report the concept of synthesizing graphene nanoribbon-graphene quantum dot (GNR-GQD) hybrids with even grafting of GQD on GNR sheet in a facile single step process under ultra-sonication in chlorosulfonic acid. Further, diazotization route is followed for the preparation of 4-benzenediazonium sulfonate precursor to sulfonate both GNR and GQD to form sulfonated graphene nanoribbons-sulfonated graphene quantum dots (sGNR-sGQD) nanohybrids. Synergistic and structure dependent effect of nanohybrids is seen via its dispersion in sulfonated poly(ether ether ketone) (sPEEK) to form nanocomposite membrane. sPEEK/sGNR-sGQD (1.5 wt %) nanocomposite membrane shows remarkable direct methanol fuel cell (DMFC) performance compared to pristine sPEEK and Nafion 117 with 40% increment in peak power density along with higher durability up to 100 h due to better physicochemical properties like water uptake, ion exchange capacity, proton conductivity, and reduced methanol crossover to suggest its potential which includes diverse membrane applications. (C) 2018 Elsevier Ltd. All rights reserved.