Seawater electrolyte-mediated high volumetric MXene-based electrochemical symmetric supercapacitors

Abstract

The structure and morphology of titanium carbide (Ti₃C₂T_x) MXene, a new class of two dimensional (2D) materials, are investigated and reported. Ti₃AlC₂ MAX, treated with a hydrofluoric acid etching process, is used as a promising electrode material for electrochemical supercapacitor studies. The electrochemical supercapacitor performance of Ti₃C₂T_x as a negatrode in a natural seawater electrolyte solution, tested in a three-electrode system, demonstrated a specific capacitance of 67.7 F g⁻¹ at a current density of 1 A g⁻¹ which is in accordance with the volumetric specific capacitance of 121.8 F cm⁻³. A symmetric supercapacitor assembled with a Ti₃C₂T_x//Ti₃C₂T_x electrode configuration revealed a volumetric specific capacitance of 27.4 F cm⁻³ at 0.25 A g⁻¹, and 96.6% capacitance retention even after 5000 cycles, which is superior to those reported previously in similar systems, suggesting the importance of abundant and cost-effective seawater as a natural electrolyte in developing energy storage devices.