High capacitance of MXene (Ti3C2Tx) through Intercalation and Surface Modification in Molten Salt

MXenes (Ti3C2Tx) with -F surface terminations have a negative impact on electrochemical properties when used as potential electrodes in supercapacitors. In this study, Ti3C2Tx, with -F surface terminations was one-step treated in LiCl-KCl-K2CO3 molten salt at atmospheric pressure to replace -F by -O surface terminations and simultaneously introduce the intercalation of potassium. Various potassium oxygenated complexes were intercalated into the interlayer of the Ti3C2Tx resulting in the expansion of O-spacing from 0.96 to 1.05-1.21 nm, the decrease of F content from 11.23 to 3.43 at%, and the increase of O content from 0.79 to 24.18 at%. The modified Ti3C2Tx, electrode (KM-Ti3C2Tx) showed an improved specific capacity of 323.6 F g(-1) at 1 A g(-1) in 1 M H2SO4 solution and excellent capacitance retention (97% after 10,000 charging-discharging cycles at 10 A g(-1)). The storage mechanism is attributed to the reversible conversion of Ti3C2O2 / Ti3C2(OH)(2) during the insertion/extraction of hydronium (H+). Therefore, the removal of -F by -O surface terminations can form more Ti3C2O2, leading to an increase in conductivity and electrochemical active surface area. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

By replacing the -F surface terminations with -O surface terminations and introducing potassium intercalation in Ti3C2Tx electrodes, the specific capacity was significantly improved to 323.6 F g(-1) at 1 A g(-1) with a capacitance retention of 97% after 10,000 charging-discharging cycles at 10 A g(-1). The storage mechanism is attributed to the reversible conversion of Ti3C2O2 / Ti3C2(OH)2 during the insertion/extraction of hydronium (H+).