Two-Dimensional MXene Modified Electrodes for Improved Anodic Performance in Vanadium Redox Flow Batteries
Ali Vala Mizrak, Simge Uzun, Bilen Aküzüm, Lutfi Agartan, Yury Gogotsi, Emin C. Kumbur
Abstract
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.