Electrochemical performance of self-assembled two-dimensional Ti₃C₂T_x(MXene) thin films

With the rapid growth in the demand for portable/wearable electronic products, the demand for high-performance, flexible, and lightweight power is becoming stronger. Given the excellent cyclic stability, high rate of charge/discharge, and high power density of supercapacitors, they have become ideal devices to meet the power requirements of portable/wearable electronic products. The most effective method to enhance supercapacitor performance is to improve the electrode materials. Lately, researchers have concentrated on exploring and developing excellent-performance electrode materials. Two-dimensional (2D) materials are the most prospective supercapacitor materials owing to their outstanding properties. Transition-metal carbides and nitrides (MXene), a novel family of 2D materials, have been found to exhibit relatively better chemical stability, higher surface area and active surface sites, excellent hydrophilicity, and higher electrical conductivity. The earliest explored and the most widely applied MXene is Ti₃C₂T_x. In several types of energy-storage systems, such as electrochemical hydrogen storage, supercapacitors, and lithium-ion batteries, Ti₃C₂T_x has shown exceptional performance as potential electrode material. In this work, Ti₃C₂T_x colloidal solution was prepared by etching Ti₃AlC₂ with a LiF–HCl mixed solution and a flexible MXene film was obtained via vacuum filtration. The physical structures and morphologies of graphene and chemical elements were characterized via X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The capacitance properties of the MXene film electrode were studied via cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. The research shows that in H₂SO₄ electrolyte, the MXene film thickness is 6.6 μm, and the mass-specific capacitance can reach 228 F·g⁻¹ at 5 mV·s⁻¹. When the scanning speed increases to 100 mV·s⁻¹, the capacitance retention rate can reach 51%, which is three times that of the 40.2 μm MXene film electrode. The research shows that acidic electrolyte and thin film are beneficial to improve the performance of MXene supercapacitors.