  Surface terminations for 2D MXene have dramatic impacts on physicochemical
properties. The commonly etching methods usually introduce -F surface
termination or metallic into MXene. Here, we present a new molten salt assisted
electrochemical etching (MS-E-etching) method to synthesize fluorine-free
Ti3C2Tx without metallics. Due to performing electrons as reaction agent, the
cathode reduction and anode etching can be spatially isolated, thus no metallic
presents in Ti3C2Tx product. Moreover, the Tx surface terminations can be
directly modified from -Cl to -O and/or -S in one pot process. The obtained -O
terminated MXenes exhibited capacitance of 225 and 205 F/g at 1 and 10 A/g,
confirming high reversibility of redox reactions. This one-pot process greatly
shortens the modification procedures as well as enriches the surface functional
terminations. More importantly, the recovered salt after synthesis can be
recycled and reused, which brands it as a green sustainable method.
