In–situ growth of carbon nanotubes on two–dimensional titanium carbide for enhanced electrochemical performance

Highlights: •A controllable preparation method was obtained to synthesize Ti₃C₂T_x@CNTs 3D composites. •The integrity of Ti₃C₂T_x structure is essential for the preparation of Ti₃C₂T_x@CNTs composites. •The areal capacitance of Ti₃C₂T_x@CNTs_6.0 is as high as 924.9 mF cm^-2 at 2 mV s^-1. -- Abstract: A novel two–step method has been proposed to synthesize Ti₃C₂T_x@CNTs three–dimensional composites. At the outset, the thin layer of polydopamine (PDA) was coated on Ti₃C₂T_x and served as protective cover to achieve the structural stability and integrity of Ti₃C₂T_x. CNTs were then in situ grown on Ti₃C₂T_x layers via a simple pyrolysis process using urea as carbon source, and the length and density of the grown CNTs can be effectively controlled by altering the amount of urea in the synthesis process. The vertically−aligned CNTs not only provided channels for electrolyte transport, but also greatly expanded the interlayer space of Ti₃C₂T_x sheets. When applied as electrode materials for supercapacitor energy storage, the Ti₃C₂T_x@CNTs_6.0 composites revealed a high areal capacity of 924.9 mF cm^-2 at 2 mV s^-1 and an advantageous retentive capacity of 78.1% at 1 A g^-1 after 10,000 cycles.