In-situ synthesis of fluorine-free MXene/TiO2 composite for high-performance supercapacitor

MXene (Ti3C2Tx) is a promising electrode material for supercapacitors. However, the current MXene material preparation process often requires hydrofluoric acid, and the etched MXene is easily oxidized and stacked, which is not conducive to the transfer of electrons and ions. In this study, we proposed a high concentration of sodium hydroxide solution mixed with sodium hypochlorite solution as an etchant for the preparation of fluorine-free MXene (Ti3C2Tx). Based on the alkali-assisted hydrothermal method, Ti3AlC2 was used as the raw material, and 10 % NaClO aqueous solution was added as the oxidant during the etching process to accelerate the etching and in-situ generate TiO2 with excellent conductivity. When the oxidation time is 12 h and the amount of NaClO is 0.2 mL, the TiO2 particles in-situ generated by the oxidation of Ti element in MXene are evenly distributed on the surface and interlayer of the material, which effectively curbs the stacking problem between the Ti3C2Tx layers and improves the specific surface area of the material. The prepared MXene/TiO2 electrode in 1 M H2SO4 electrolyte, − 0.5-0.2 V voltage window, the highest mass specific capacity can reach 321 F/g, and after 10000 charge-discharge cycles, the capacitance retention rate can still reach 86.4 %, which is higher than the capacitance retention rate of Ti3C2Tx material (81.7 %).