Enhanced Capacitive Performance Based on Diverse Layered Structure of Two-Dimensional Ti3C2MXene with Long Etching Time

Abstract

Two-dimensional Ti₃C₂ MXene nanosheets were synthesized by selective etching of Al layer from ternary carbides Ti₃AlC₂ MAX phase using HF solution for different etching times and then evaluated as working electrodes. The effects of the etching time on the morphology, structure, surface termination, and electrochemical properties of Ti₃C₂ MXene were investigated. With longer etching time, Ti₃C₂ nanosheets were gradually delaminated and more C was exposed. The electrochemical properties of Ti₃C₂ show a significant improvement at the reaction time of 216 h (Ti₃C₂-216), with no obvious changes with etching time from 2 to 168 h. Ti₃C₂-216 exhibited higher capacitive performance with the specific capacitance of 118 F g⁻¹ at the scan rate of 5 mV s⁻¹, excellent rate performance, and cycling stability. This improvement in the performance is attributed to higher carbon content for better conductivity and faster transportation of electrons, and the larger specific surface area for more access of aqueous electrolyte to the electrodes.