In Situ Synthesis of MXene with Tunable Morphology by Electrochemical Etching of MAX Phase Prepared in Molten Salt

Abstract MXenes, a rapidly growing family of 2D transition metal carbides, carbonitrides, and nitrides, are one of the most promising high‐rate electrode materials for energy storage. Despite the significant progress achieved, the MXene synthesis process is still burdensome, involving several procedures including preparation of MAX, etching of MAX to MXene, and delamination. Here, a one‐pot molten salt electrochemical etching (E) method is proposed to achieve Ti 2 C MXene directly from elemental substances (Ti, Al, and C), which greatly simplifies the preparation process. In this work, different carbon sources, such as carbon nanotubes (CNT) and reduced graphene oxide (rGO), are reacted with Ti and Al micro‐powders to prepare Ti 2 AlC MAX with 1D and 2D tuned morphology followed by in situ electrochemical etching from Ti 2 AlC MAX to Ti 2 CT x MXene in low‐cost LiCl‐KCl. The introduction of the O surface group via further ammonium persulfate (APS) treatment can act in concert with Cl termination to activate the pseudocapacitive redox reaction of Ti 2 CCl y O z in the non‐aqueous electrolyte, resulting in a Li + storage capacity of up to 857 C g −1 (240 mAh g −1 ) with a high rate (86 mAh g −1 at 120 C) capability, which makes it promising for use as an anode material for fast‐charging batteries or hybrid devices in a non‐aqueous energy storage application.