Preparation And Electrochemical Properties Of Ti₃C₂T_x MXene-based Composites

MXene,as the newly discovered two-dimensional transition metal carbide/nitride,is considered as a promising energy storage material.In recent years,researchers have combined a variety of active materials with MXene to prepare new MXene-based composites.Among them,MXene can provide high electrical conductivity,promote rapid electron transfer,and increase the surface area and active sites of the material.Therefore,MXene-based composites tend to have better electrochemical performance.In this paper,Ti₃C₂T_x MXene nanosheets were successfully prepared,and three MXene-based composite electrode materials with excellent performance were prepared by combining Ti3C2Tx MXene with carbon cloths of different improved methods for electrochemical capacitors.(1)A quinone-rich carbon cloth substrate(EOCC)was prepared by electrochemically oxidizing a commercial carbon cloth with mixed acid,and a new Ti3C2Tx/EOCC composite electrode material was prepared by self-assembling Ti3C2Tx MXene nanosheets on the surface.The results show that Ti3C2Tx MXene is well dispersed on the surface of EOCC carbon cloth,and the two are closely combined by hydrogen bonds,showing good electrochemical performance.The material provides an area specific capacitance of 887.76m F cm^-2 at a current density of 1 m A cm^-2.When the current density is increased by 5 times,the capacitance retention rate is 73.68%,which has good rate performance.The material was assembled into a symmetric capacitor,and at a current density of 10 m A cm^-2,the capacitance lost only 6.8%after 10,000 cycles,showing good cycling stability.(2)Ti₃C₂T_x(EPD)/EOCC composite electrode material with a novel nanosheet structure was formed on the surface of EOCC carbon cloth by electrophoresis.The material can provide a high areal specific capacitance of 1065.6 m F cm^-2 at a current density of 1 m A cm^-2 with good rate capability,with a capacitance retention of 65.59%when the current density is increased by a factor of 10.When this material was assembled into a symmetric capacitor,the capacitance retained 98.4%of its initial value after 10,000 consecutive cycles at a current density of 12 m A cm^-2.Therefore,using the electrophoresis method to modify the Ti₃C₂T_x MXene nanosheets on the surface of carbon cloth greatly increases the active sites on the surface of the electrode material,making the material have higher area specific capacitance and cycle stability.(3)The surface of carbon cloth was coated with PDA particles,and the nitrogen-doped superhydrophilic carbon cloth(ENCC)was obtained by carbonization and mixed acid electrochemical oxidation.Ti₃C₂T_x(EPD)/ENCC composite electrodes were obtained by depositing Ti₃C₂T_x MXene nanosheets on the surface of nitrogen-doped carbon cloth by electrophoresis.The composite electrode material exhibits a high areal specific capacitance of 2080.1 m F cm^-2 at a current density of 1 m A cm^-2.After being assembled into a symmetric capacitor,the capacitance still had 91%of its original value after 10,000 cycles at a current density of 20 m A cm^-2.After screening the best experimental conditions,it is found that the nitrogen-doped carbon layer on the surface of the carbon cloth protects the original mechanical flexibility of the commercial carbon cloth and improves the capacitance performance of the base material.Using a smaller electrophoretic deposition voltage,it is easier to combine with Ti₃C₂T_x MXene nanosheets to obtain materials with better performance.