A facile and almost HF-free synthesis of Ti3C2@CuCl composite for supercapacitors

• CuCl 2 can be used as an effective etching agent for the aluminum (Al) layer in Ti 3 AlC 2 . • We successfully prepared Ti 3 C 2 @CuCl composite by a one-step process. • The composites exhibits enhanced specific capacitance of 508.72 F·g -1 at 1A·g -1 , much higher than that of the pure Ti 3 C 2 electrode. This work demonstrates a distinctive almost HF-free route of etching Ti 3 AlC 2 MAX phase by metal displacement reaction at room temperature. The Ti 3 AlC 2 particles are directly etched by CuCl 2 solutions in different concentrations instead of HF. The etchant is reduced to nano CuCl particles, adhering to the surface of Ti 3 C 2 layers to form the Ti 3 C 2 @CuCl composite which is evaluated as working electrodes for supercapacitors. Due to the synergistic effect between CuCl and Ti 3 C 2 matrix, the appropriate amount of CuCl enhances the specific capacitance to 508.7 F·g -1 at 1A·g -1 in 6 M KOH electrolyte solution, which is much higher than pure Ti 3 C 2 electrode. This work shows the possibility of synthesis of various Mxene-based frameworks by other metallic cations with lower metal activity.