Halogen Ion-Mediated Hydrothermal Synthesis of Diverse MXenes with Tailored Heterostructures

Two-dimensional transition metal carbides and nitrides (MXenes) have attracted significant attention due to their exceptional physicochemical properties. Despite extensive studies, efficient methods for the production of MXenes with precise structural control still remain a challenge, thus hindering their potential in many specific applications. Herein, a halogen ion-mediated hydrothermal approach is proposed for the controllable preparation of diverse MXenes and their heterostructures with well-defined interfacial architectures, demonstrating its potential as a high-throughput synthesis strategy. As proof of concept, Mo₂C can be synthesized on a gram scale by employing NH₄F in the hydrothermal etching process of Mo₂Ga₂C. Subsequently, this approach is applied to various MXenes, including Ti₃C₂, V₂C, and Nb₄C₃. Moreover, NH₄X (X = Cl, Br, I) etchants combined with small-molecule intercalants enabled the targeted synthesis of MXene-based heterostructures, such as Mo₂CT_x@MoS₂ featuring ≈15 nm amorphous MoS₂ surface layers. Notable, the Mo₂CT_x(Br) heterostructure exhibited outstanding electrochemical stability, delivering a capacity of 465.5 mAh g⁻¹ after 300 cycles at 1 A g⁻¹, and achieving high coulombic efficiency of 99.8% during lithium-ion battery cycling. This work establishes a versatile and scalable platform for the synthesis of MXene-based materials, thus paving the way for accelerating their potential in various fields.