Nafion chains have been reacted onto graphene oxide (GO) through atom transfer radical addition (ATRA) reaction between the C-F groups of Nafion and the C=C groups of GO. The obtained nanohybrids of GO and Nafion (GO-Nafion) are characterized with Fourier transform Infrared spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy to support the performance of the ATRA reaction between GO and Nafion and the chemical structure of GO-Nafion. Morphological observation on GO-Nafion with transmission electron microscopy and atomic force microscopy further demonstrates the organic inorganic hybrid nanosheet structure of GO-Nafion. GO-Nafion has been used as a nanoadditive for fabrication of Nafion-based nanocomposite proton exchange membranes for fuel cells. Compared to the neat recast Nafion membrane, addition of GO-Nafion results in a 1.6-folds of proton conductivity to the corresponding nanocomposite PEM. The single cell tests on the nanocomposite PEM also exhibit an about 35-40% increase in the fuel cell performance. (C) 2016 Elsevier B.V. All rights reserved.