Cyclic voltammetric preparation of graphene-coated electrodes for positive electrode materials of vanadium redox flow battery

In this work, a one-step procedure for preparing graphene pencil graphite electrodes is developed by using cyclic voltammetry (CV). The potential is scanned from -1.0 to +1.90V (vs. Ag/AgCl) in a sulfuric acid solution in this system. The in situ electrochemical oxidation of graphite to graphene oxide (GO) and then the electrochemical reduction of GO to graphene are observed in the cyclic voltammograms. The electrochemical behaviors of GO and graphene electrode are investigated by CV and electrochemical impedance spectroscopy. The morphological and physical properties of the graphene layers are elucidated by Raman spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. The prepared graphene-coated electrodes are as the positive electrode component of a vanadium redox battery (VRB). The electrodes show excellent electrochemical performance and high cyclic stability (more than 500cycles) in a VRB system. The presented processing route is faster, easier, less expensive, and more environmentally friendly than other electrochemical and chemical methods to obtain graphene electrodes.