Comprehensive synthesis of Ti₃C₂T_x from MAX phase to MXene

MXenes are a large family of two-dimensional materials that have attracted attention across many fields due to their desirable optoelectronic, biological, mechanical and chemical properties. There currently exist many synthesis procedures that lead to differences in flake size, defects and surface chemistry, which in turn affect their properties. Herein, we describe the steps to synthesize Ti₃C₂T_x-the most important and widely used MXene, from a Ti₃AlC₂ MAX phase precursor. The procedure contains three main sections: synthesis of Ti₃AlC₂ MAX, wet chemical etching of the MAX in hydrofluoric acid/HCl solution to yield multilayer Ti₃C₂T_x and its delamination into single-layer flakes. Three delamination options are described; these use LiCl, tertiary amines (tetramethyl ammonium hydroxide/ tetrabutyl ammonium hydroxide) and dimethylsulfoxide respectively. These procedures can be adapted for the synthesis of MXenes beyond Ti₃C₂T_x. The MAX phase synthesis takes about 1 week, with the etching and delamination each requiring 2 d. This protocol requires users to have experience working with hydrofluoric acid, and it is recommended that users have experience with wet chemistry and centrifugation; characterization techniques such as X-ray diffraction and particle size analysis are also essential for the success of the protocol. While alternative synthesis methods, such as minimally intensive layer delamination, are desirable for certain MXenes (such as Ti₂CT_x) or specific applications, this protocol aims to standardize the more commonly used hydrofluoric acid/HCl etching method, which produces Ti₃C₂T_x with minimal concentration of defects and the highest conductivity and serves as a guideline for those working with MXenes for the first time.