Two-Dimensional MXene Modified Electrodes for Improved Anodic Performance in Vanadium Redox Flow Batteries

In this work, Ti 3 C 2 T x MXene was investigated as electrocatalyst material for the anodic V 2+ /V 3+ reaction in vanadium redox flow batteries (VRFBs). A simple drop coating process was established using additive-free, aqueous MXene dispersions to fabricate MXene-coated carbon paper electrodes. The performance of Ti 3 C 2 T x as an anodic electrocatalyst was studied using cyclic voltammetry and electrochemical impedance spectroscopy in a three-electrode cell. Furthermore, flow battery testing was performed to determine the performance of the modified electrodes. At a current density of 50 mA cm −2 , the electrode with Ti 3 C 2 T x loading of 0.2 mg cm −2 enabled a 7% higher energy efficiency and 22% higher electrolyte utilization rate than the pristine electrode. At a higher current density (100 mA cm −2 ), the energy efficiency and electrolyte utilization were increased by 17% and 46%, respectively. At 50% SOC, the coated electrode was able to reach a limiting current density of 220 mA cm −2 while maintaining a voltaic efficiency above 80%, whereas the pristine electrode could only reach up to 160 mA cm −2 at the same voltaic efficiency. The improved performance was mainly attributed to the enhanced electrode kinetics, increased electrochemically active surface area, and improved wetting properties due to the addition of Ti 3 C 2 T x nanoflakes.