Enhanced supercapacitive performance of delaminated two-dimensional titanium carbide/carbon nanotube composites in alkaline electrolyte

MXenes, a new family of two-dimensional materials, are terminated by O, OH and F groups. The existence of the oxygen-containing functional groups indicates a potential application in supercapacitor based on a redox mechanism. However, the irreversible stacking of MXenes will lead to an insufficient utilization of these functional groups and thus a decrease in the supercapacitive performance. To solve the problem, we synthesized a composite material comprised of carbon nanotube (CNT) and Ti3C2 sheets (d-Ti3C2) delaminated from MXenes by ultrasonic stirring. The FTIR result suggests that the ultrasonication has no significant effect on the oxygen-containing functional groups. The resultant composites exhibit significantly higher volumetric capacitance and better capacitance retention (during 5-100 mv s−1) than d-Ti3C2. A highest volumetric capacitance of 393 F cm−3 at 5 mv s−1 in KOH electrolyte can be obtained when the weight ratio of d-Ti3C2 to CNT is 2:1. In addition, the volumetric capacitance has no significant degradation even after 10000 cycles in cycling stability test, showing an excellent cycling stability compared with metal oxides. These enhanced electrochemical performances can be ascribed to the introduction of CNTs, which impede the stacking of Ti3C2, enlarge the distance between Ti3C2 sheets and improve the electrical conductivity.