ZIF-67 Derived Porous Carbon Microstructures Modified Electrodes for High-performance Vanadium Redox Flow Batteries

Abstract

Graphite felts (GF) has been used as electrode material for VRFBs, yet surface modification is necessary to improve electrochemical activity and hydrophilia. Herein, a porous carbon modified electrode ZIF-67-GF@450-A was prepared by a ZIF-67 combination, calcination at 450 o C and subsequent acid etching. It was shown that the uniformly distributed carbon microstructures introduced to the microfilaments of graphite felt enhanced the electrodes performance, and promoted VO2+/VO2 + redox reaction. As a result, the all-vanadium redox flow battery (VRFB) assembled with ZIF-67-GF@450-A as the electrode could maintain energy efficiency (EE) of 82.09% and 71.33% at current densities of 200 mA cm-2 and 400 mA cm-2, respectively, with a discharge capacity of 477.5 mAh at 400 mA cm-2. This electrode modification method provides valuable insights for the further improvement of high-performance VRFB.