Nafion/graphene oxide layered structure membrane for the vanadium redox flow battery

The graphene oxide (GO) layer is applied to the ion-exchange membrane of the vanadium redox flow battery (VRB) system to reduce the vanadium ion permeation through the membrane. The pristine Nafion 117 membrane (Nafion) is coated with the Nafion/GO emulsion solution to prepare the modified GO coated Nafion 117 membrane (GO-Nafion). The GO-Nafion and Nafion show nearly the same IEC and water uptake results. The SEM image shows that the GO/Nafion ionomer layer is coated uniformly on the surface of the Nafion membrane with the thickness of 4~5 μm. The vanadium ion permeation is reduced effectively by using the GO-Nafion instead of the Nafion for the VRB system. The permeability of the GO-Nafion is 6.1×10^-7 cm² min^-1 which is less than one third that of Nafion (20.5 × 10^-7 cm² min^-1). Higher coulombic efficiency (CE) and energy efficiency (EE) is obtained with the GO-Nafion in the VRB system. We can suggest that the GO application for the VRB system can be a promising strategy to reduce vanadium ion permeation and to successfully improve the VRB performance.