The polyvinylidene fluoride (PVDF) drew great attention over time amongst the hydrocarbon polymer membranes because of its high C-F chemical bond strength. In this work is to increase the proton conductivity of the PVDF polymer by doping phosphonated graphene oxide to its structure and investigate the improvement of the membrane. Different amounts of phosphonated graphene oxide additive (0.5%, 1% and 1.5% w/w) were doped to PVDF polymer on the purpose of synthesizing proton exchange composite membranes. Characterization tests, i.e, water uptake, swelling properties, ion exchange capacity, and proton conductivity of the synthesized membranes were investigated. The electrochemical impedance analysis results of synthesized membranes vary between 0.0224 S cm(-1) for 0.5% graphene oxide doped PVDF (PVDF/0.5PGO) and 0.0867 S cm(-1) for PVDF/1.5GO membrane. The power density values of PVDF/1.5PGO and PVDF/0.5GO are 48 mW cm(-2) and 28 mW cm(-2) at 0.6 V and 100% relative humidity at 80 degrees C. The experimental results demonstrate the importance of phosphonated graphene oxide doping into the PVDF composite membrane. (c) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.