Comparative Electrocatalytic Performance of Single-Walled and Multiwalled Carbon Nanotubes for Zinc Bromine Redox Flow Batteries

Abstract

Carbon nanotubes (CNTs) have been employed as electrode materials in rechargeable zinc bromine redox flow batteries (ZBB) owing to their high electrocatalytic activity, remarkable electrical conductivity, and excellent mechanical strength with high Young’s modulus. The electrocatalytic effect of single-walled carbon nanotube (SWCNT) and multiwalled carbon nanotube (MWCNT) electrodes for the 2Br–/Br2 redox couple has been investigated for zinc bromine redox flow battery application. The anodic peak current density of SWCNT electrode is found to be about 16 mA cm–2, which is almost 50% higher than that of MWCNT, indicating the enhanced electrocatalytic effect of SWCNT perhaps due to a large amount of basal planes. The peak separation between the anodic and cathodic process at SWCNT and MWCNT electrodes is 201 and 126 mV, respectively, demonstrating the quasireversible nature of the 2Br–/Br2 redox reaction. Moreover, the peak separation for the MWCNT electrode is 37% less compared to that on the SWCNT electr...