Surface Modification Of Ti₃C₂T_x MXene And Application In Supercapacitors

Supercapacitors have shown great potential for a range of applications including electronics,mobile equipment,engineering machinery,auxiliary energy of transportation due to their fast charge–discharge ability,safe operation,long cycle life and high power density.Two-dimensional materials have attracted tremendous attention in the field of supercapacitors.MXenes,a new series of two-dimensional(2D)transition metal carbides,nitrides and carbonitrides,have unique physical and chemical properties and are supposed to be promising materials for high pseudocapacitive energy storage.In order to further improve the performance of MXenes in supercapacitor and solve the restacking problem during the electrode preparation process,we took Ti₃C₂T_x MXene as the main research object and carried out the following research.(1)A new Ti₃C₂T_x/Polyaniline(Ti₃C₂T_x/PANI)composite was fabricated by chemical oxidative polymerization of aniline monomers on Ti₃C₂T_x MXene layers under acidic conditions.It was found that PANI grows on the surface or between the layers of Ti₃C₂T_x,inhibiting the restacking of Ti₃C₂T_x films.Moreover,the addition of PANI can effectively improve the conductivity,interplanar spacing and specific surface area of Ti₃C₂T_x.The results show that the Ti₃C₂T_x/PANI electrode exhibits an attractive specific capacitance(333 F g^-1 at 1 A g^-1),impressive rate capability and excellent cycling stability maintaining 96.8%of the initial specific capacitance after 3000 cycles.(2)The controllable oxidation and surface modification of Ti₃C₂T_x was achieved by using weak oxidant ammonium persulfate under acid condition,in order to improve the performance of Ti₃C₂T_x in supercapacitor.It was found that many F terminations on Ti₃C₂T_x can be successfully replaced by O terminations by readily adjusting the loading of ammonium persulfate.The results of a series of electrochemical tests show that the partially oxidized Ti₃C₂T_x(0.5 g APS/50 ml 4 mg m L^-1 Ti₃C₂T_x)achieved a high capacitance of 303 F g^-1 at 2 m V s^-1,and 96.6%capacity can remain even after 9000cycles.