Electrode Modification for Better Kinetics in all Vanadium Redox Flow Battery (AVRFB): A Short Review

One critical component in a vanadium redox flow battery (VRFB) system is its electrode. The redox reactions between V +2 /V +3 and V +4 /V +5 take place on electrodes surfaces. Commonly used electrode material is the graphite felts (GFs); this material has good chemical and electrochemical stabilities, conductivity, and suitable surface area, with low price tag. However, its relatively poor kinetics and electrochemical activity often limit the VRFB operation at low current density. Many researchers have attempted to enhance VRFB performance by trying other carbon materials such as, carbon nanotubes, graphene, and composite materials. They also deposited noble metals on to these electrodes as catalysts, which are not very practical due to their high cost and susceptibility to hydrogen/oxygen evolution reactions. Low-cost metal oxides, such as Mn 3 O 4 , CeO 2 and WO 3 were also been explored as catalysts, but their performance is limited by their low conductivity and stability in concentrated sulfuric acid. Significant improvement in electrode performance are reported when different nanostructured metal catalysts were deposited. However, the performance of modified electrodes also depends on the size and uniform distribution of these nanoparticles. In this article, some important developments of this area are reviewed.