Preparation Of Self-Assembled Ti₃C₂T_x/ Polypyrrole Composite And Supercapacitor Performance

With the increasing demand for sustainable energy,the development of new high-performance electrochemical materials has become the focus of attention.Ti₃C₂T_x,as one of the most widely studied MXenes two-dimensional nanomaterials has broad research significance in energy storage.In this paper,the distribution of functional groups on the surface of Ti₃C₂T_xis adjusted.First,the introduction of oxygen-containing functional groups on the surface is improved to reduce the self-stacking of Ti₃C₂T_xsheets,improve solution dispersion performance,and increase the attraction to positive charges.Then,the Ti₃C₂T_x/PPy composite material was prepared by self-assembly method,and PPy was embedded in the Ti₃C₂T_xframe by the electrostatic attraction effect of the two to prevent Ti₃C₂T_xfrom being oxidized by the oxidizing agent,thereby improving the structural stability and the dynamic activity in the chemical reaction process.This article mainly includes the following aspects:The surface structure of Ti₃C₂T_xis modified by an acid-base two-step etching method.In an alkaline solution,partly of the Al element in Ti₃Al C₂be dissolved,absenting of F ions,O molecules in water preferentially occupy the structural defects of Ti and C in the two-dimensional structure.Subsequently,the remaining Al element is removed by further etching in the acid solution.The preferential occupation of oxygen atoms effectively prevents the introduction of F atoms and improves the dispersion performance and surface charge density of Ti₃C₂T_xin the solution.Ti₃C₂T_x(KN-Ti₃C₂T_x)obtained by two-step etching method is compared with Ti₃C₂T_x(N3-Ti₃C₂T_x)obtained by one-step etching method.The proportion of oxygen-containing functional groups on the surface is increased from 71.54%to 82%,and the specific surface area is greatly increased from254.4 m²/g to 317.4 m²/g.Electrochemical measurements show that the specific capacitance of KN-Ti₃C₂T_xcan reach 188.4 F/g at a scanning speed of 2 m V/s,and it can maintain 93.5%of the initial specific capacitance after 5000 cycles.In this paper,NSA is used to modify PPy,and the weak polar group in the NSA structure is beneficial to reduce the polarity of PPy and improve its solubility and dispersion performance in NMP to form a stable and controllable sol.Electrochemical measurements show that at current density of 1 A/g,the specific capacitance of PPy can basically reach 161.83 F/g,and after 5000 cycles of 5 A/g current density,it still maintains71%of the initial specific capacitance.The composite materials KN-Ti₃C₂T_x/PPy(KNP)and N3-Ti₃C₂T_x/PPy(NP)are prepared by electrostatic attraction between the negatively charged Ti₃C₂T_xand the positively charged PPy macromolecular chains in the mixed solution.The nanosheets are evenly embedded in the interval of the Ti₃C₂T_xlayer,and the PPy nanosheets play a space barrier effect to a certain extent,effectively preventing the re-stacking of Ti₃C₂T_xmaterials.The result is conducive to the formation of a stable multi-level slice structure,thereby increasing the specific surface area of Ti₃C₂T_xand enhancing the contact between the electrolyte and the active sites on the surface.Electrochemical measurements show that at current density of 1 A/g,the weight-specific capacitances of KNP,NP and PPy can reach 238.6,204.3,and 161.83 F/g.Respectivly,compared with NP and PPy,the specific capacitance of KNP is significantly changed and improved.Moreover,the capacitance retention of KNP can still be higher than 71.55%after 5000 cycles.