High Performance Carbon Nanotube Based Electrodes for Zinc Bromine Redox Flow Batteries

Abstract

Carbon nanotubes (CNTs) have been utilized as positive electrodes in rechargeable zinc bromine redox flow battery (ZBB) due to their high electrocatalytic activity, enhanced electrical conductivity and unusual mechanical strength with high Young's modulus. The electrochemical behavior of 2Br−/Br2 at pristine glassy carbon electrode (GCE) and CNT modified GCE studied by cyclic voltammetry (CV) in 0.05 M aqueous zinc bromide solution shows clear evidence for enhanced electrocatalytic activity for CNT based electrodes. The voltammetric peak current density at CNT is 16 mA cm−2 (2.5 times higher than that at GCE) presumably due to more active sites, demonstrating high electrocatalytic effect of CNT toward 2Br−/Br2 redox reaction. Composition and morphological changes have been further investigated using FTIR, Raman spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Zinc bromine flow cell with CNT coated carbon felt (CF) as bromine electrode reveals improved the electrochemical performance in terms of voltage (VE), columbic (CE) and energy efficiencies (EE). The VE, CE and EE of a zinc bromine flow cell with CNT (90%) modified bromine electrode are 87%, 77% and 67% respectively.