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

Abstract

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 ZnÀ Br2 redox flow battery applications. BDG showed a highly improved peak separation potential (145 mV) for the 2Br À /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.

A TiN Nanorod Array 3D Hierarchical Composite Electrode for Ultrahigh‐Power‐Density Bromine‐Based Flow Batteries

“…However, some common challenges exist for such bromine‐based flow batteries. In particular, the high electrochemical polarization caused by the mismatch of the positive and negative redox couple kinetics leads to a low operating current density (40 mA cm −2 for zinc–bromine and viologen–bromine batteries) and lower power density, which seriously hampers the development of bromine‐based flow batteries . Thus, the development of high activity electrode materials for Br 2 /Br − is necessary to reduce electrochemical polarization and improve power density, which is truly significant for realizing the commercialization of bromine‐based flow batteries.…”

Progress and Perspective of the Cathode Materials towards Bromine-Based Flow Batteries

“…Moreover, N-doping was also carried out by a simple pyrolytic urea method [22] or a nanocasting method [89], both of which improved the electrocatalytic activity of electrodes. Apart from doping N element into electrodes, B-doping is also adopted to enhance Br 2 /Brredox reactions by inducing defect sites and destruction in the carbon lattice [90].…”

“…Thus, ZBFBs were able to reach an EE of 84.2% at 80 mA cm -2 (original CF: 71.8%). Boron-doped graphene (BDG) with high surface area and high electrocatalytic activity was used as the electrocatalyst in ZBFBs as well [90]. The introduction of B element in the graphene matrix greatly increased the peak current and reduced the double-layer charge storage due to defect sites and destruction in the carbon lattice (Figure 8(e)).…”

Carbon Materials as Positive Electrodes in Bromine‐Based Flow Batteries

“…Venkatesan et al . reported boron‐doped reduced graphene oxide (B‐rGO) as bromine electrode catalyst in zinc bromine flow battery to alleviate the sluggish Br 2 /Br − kinetics [97] . B‐rGO supported on CF substrate showed improved performance due to high electrical conductivity and electrocatalytic behavior of B‐rGO but at a relatively low operating current density of 20 mA cm −2 .…”