Boron-Doped Graphene as Efficient Electrocatalyst for Zinc-Bromine Redox Flow Batteries

It is well-known that boron-doped graphene (BDG) is a promising electrode material for various applications owing to its outstanding properties, such as high electrocatalytic activity, electrical conductivity, large surface area, and cycle stability. In the present study, BDG is synthesized and used as an electrocatalyst for improving the bromine reversibility in Zn-Br2 redox flow battery applications. BDG showed a highly improved peak separation potential (145 mV) for the 2Br(-)/Br-2 redox reaction compared to reduced graphene oxide (264 mV). Furthermore, the flow cell showed a low potential drop of 265 mV for the BDG-based cell, which is lower than those of the other flow cells tested herein (for CF: 434 mV; r-GO: 363 mV). The synthesized materials were also subjected to various physicochemical characterizations such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The durability of the flow-cell system employing BDG/CF was analyzed at 20 mA/cm(2) and the cell showed a maximum Coulombic efficiency of 86% at the 100th cycle.