Preparation of the graphene oxide (GO)/Nafion composite membrane for the vanadium redox flow battery (VRB) system

Graphene oxide (GO) nano-plate was applied to the vanadium redox flow battery (VRB) system as the ion-exchange membrane to reduce the vanadium permeation and enhance the VRB system performance. The GO/Nafion membranes were prepared with the GO composition from 0.001 wt% to 1 wt%. The prepared composite membranes were analyzed by SEM to investigate the microstructure of the membranes. Water uptake, proton conductivity, thickness and vanadium ion permeability of the membrane were observed to evaluate the membrane properties. X-ray diffraction (XRD) analysis was conducted to observe the inter-planar microstructure of the membranes. The prepared membranes had a lower value of the inter-planar space dimension than that of the Nafion 117 membrane and because of this fact the prepared composite membrane had a lower value of the water uptake, vanadium permeability and proton conductivity than that of the Nafion 117. The value of the proton conductivity and the vanadium permeability were decreased when increasing the GO composition in the composite membrane. The optimum composition of the GO in the composite membranes for the application of the ion-exchange membrane of the VRB system ranged from 0.01 wt% to 0.1 wt%. The highest EE value of the VRB single cell was obtained by using the 0.01 wt% GO composite membrane and the value was 82.5%. We could suggest that the GO/Nafion composite membrane can be one of the promising candidates for the VRB membrane electrolyte.