Water-dispersible Ti3C2Tz MXene nanosheets by molten salt etching

Molten-salt etching of Ti₃AlC₂ MAX phase offers a promising route to produce 2D Ti₃C₂T_z (MXene) nanosheets without hazardous HF. However, molten-salt etching results in MXene clays that are not water dispersible, thus preventing further processing. This occurs because molten-salt etching results in a lack of -OH terminal groups rendering the MXene clay hydrophobic. Here, we demonstrate a method that produces water-dispersible Ti₃C₂T_z nanosheets using molten salt (SnF₂) to etch. In molten salt etching, SnF₂ diffuses between the layers to form AlF₃ and Sn as byproducts, separating the layers. The stable, aqueous Ti₃C₂T_z dispersion yields a ζ potential of -31.7 mV, because of -OH terminal groups introduced by KOH washing. X-ray diffraction and electron microscopy confirm the formation of Ti₃C₂T_z etched clay with substantial d-spacing as compared with clay etched with HF. This work is the first to use molten salt etching to successfully prepare colloidally stable aqueous dispersions of Ti₃C₂T_z nanosheets.