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

The structure and morphology of titanium carbide (Ti 3 C 2 T x ) MXene, a new class of two dimensional (2D) materials, are investigated and reported. Ti 3 AlC 2 MAX, treated with a hydrofluoric acid etching process, is used as a promising electrode material for electrochemical supercapacitor studies. The electrochemical supercapacitor performance of Ti 3 C 2 T 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 Ti 3 C 2 T x //Ti 3 C 2 T 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. A natural seawater electrolyte-mediated MXene//MXene asymmetric supercapacitor demonstrates a 27.4 F cm −3 volumetric specific capacitance at 0.25 A g −1 , and 96.6% capacitance retention after 5000 cycles.