Electrocatalytic activity of multi-walled carbon nanotubes for VO2+/VO2+ of a vanadium redox flow battery

Graphite powder (GP) and multi-walled carbon nanotubes (CNT) composite electrodes were prepared at various ratios for all-vanadium redox flow battery. The surface morphologies of the composite electrodes were characterized by scanning electron microscope (SEM), and electrochemical behaviors were investigated by cyclic voltammetry, chronoamperometry and impedance spectroscope. It is found from the observation of SEM that the surface roughness of GP-CNT composite electrodes increases after adding CNT to GP. Through Chronoamperometry we can obtain that the real superficial area of CNT electrode is about 8 times greater than that of GP electrode. The results of cyclic voltammograms indicate that the electrochemical performances of the composites were improved greatly with increasing the amount of CNT. The pure CNT electrode has the best electrochemical performance; the enhanced electrochemical activity may be ascribed to the high electrical conductivity and large specific surface area of CNT.