A recast Nafion/graphene oxide composite membrane for advanced vanadium redox flow batteries

A graphene oxide (GO) nanosheet incorporated recast Nafion membrane (rNafion/GO) is applied to a vanadium redox flow battery (VRFB) as a promising ion-exchange membrane to reduce the vanadium permeation. Randomly embedded GO nanosheets in the composite membrane can serve as effective barriers to block the transport of vanadium ions, resulting in significant decrease of vanadium ion permeability. The rNafion/GO composite membrane exhibits a dense and homogeneous cross-section morphology as shown by SEM images. The hydrogen-bonding interaction between GO nanosheet filler and Nafion matrix is beneficial for the improvement of mechanical stability. Owing to the good balance of proton conductivity and vanadium ion permeability, the VRFB single cell performance of the rNafion/GO membrane shows higher coulombic efficiency (96% vs. 91%) and energy efficiency (85% vs. 80%) than the pure rNafion membrane at a current density of 80 mA cm(-2). A long cycling test confirms that the rNafion/GO membrane has superior chemical and mechanical stability and can be repeatedly used in a VRFB without any damage, revealing the advancement for practical VRFB application.