(Invited) Fullerene and Fullerene Nanocomposites for an Enhanced All-Vanadium Redox Flow Battery

The dependence on fossil fuels to meet the world energy demand caused several social, economical, and environmental problems. An immediate switch to sustainable, clean, and renewable sources of energy is a necessity. To achieve this switch, developing efficient technologies to convert renewable energy sources into electricity is a necessity but not enough due to the intermittent behavior of renewable sources. The incorporation of energy storage systems as regulators allows for the sustainable integration of renewable energy resources into the electrical grid. Vanadium redox flow batteries (VRFBs) are the most promising candidates of the currently available energy storage technologies, as they have an unlimited capacity (theoretically) and design flexibility. Enhancing the kinetics of the VRFBs electrochemical reactions will enhance their energy efficiency, and hence decrease the kWh cost of VRFBs. Currently, carbon-based electrodes are employed due to their suitable stability and conductivity, but with no treatment, they suffer from sluggish kinetics, hydrophobicity, and parasitic reactions catalyzation.1 Modifying these carbon-based electrodes with carbon nanostructures2 and metal oxides(MOx)3 was found to enhance the kinetics at the VRFB electrodes. Even though fullerenes have very unique structural and chemical properties they were rarely explored for the VRFBs application.4 In this work, fullerene C76 showed superior electrocatalytic activity towards VO2+/VO2 + redox reaction in G1 and G3 VRFBs and eliminated the necessity for thermal treatment of the carbon cloth support while inhibiting the chlorine evolution in G3 VRFB. A composite of C76 and hydrated WOx that reduces the fullerene content to half further inhibited the chance for chlorine evolution while maintaining the catalytic activity. References: Y. Gao et al., Carbon, 148, 9–15 (2019). D. O. Opar, R. Nankya, J. Lee, and H. Jung, Electrochimica Acta, 330, 135276 (2020). M. Faraji, R. Khalilzadeh Soltanahmadi, S. Seyfi, B. Mostafavi Bavani, and H. Mohammadzadeh Aydisheh, J Solid State Electrochem, 24, 2315–2324 (2020). F. A. E. Diwany, B. A. Ali, E. N. E. Sawy, and N. K. Allam, Chem. Commun., 56, 7569–7572 (2020).