Low-dimensional nitrogen-doped carbon for Br2/Br- redox reaction in zinc-bromine flow battery

Abstract Nitrogen-doped ordered mesoporous carbon (NOMC) is developed for the Br2/Br- redox couple, and the effect of the characteristic dimension is investigated. The resultant carbon is extensively investigated by electron microscope, nitrogen adsorption/desorption isotherms, X-ray photoelectron spectroscopy and electrochemical methods. Salient findings are as follows. First, the template determines the morphology of the resultant carbon, which features high specific surface area. Second, the nitrogen-doped carbon, in which the heteroatom-activated carbon act as the active sites, yields a decent electrocatalytic activity towards the Br2/Br- redox couple. The standard reaction rate constant is calculated by using rotating disk electrode method. Third, as compared with NOMC-3D, the lamellar morphology of NOMC-2D favors the exposure of the active sites and mass transfer of the reactive species, yields a high energy efficiency of 84.3% in zinc-bromine flow battery at the current density of 80 mA cm-2. In addition, NOMC-2D shows negligible degradation after 200-cycle test at 80 mA cm-2, revealing its superior electrochemical stability in ZBFB.