Characterization of an AX Compound Derived from Ti ₂ SC MAX Phase

Extraction of M elements from MAX phases results in “AX” compounds in contrast to the well-defined two-dimensional (2D) materials known as MXene, which are prepared by the selective etching of A elements. Despite the extensive studies on MXene from both experimental and computational aspects, the nature of the AX compounds still remains elusive, because the electrochemical etching of M atoms from MAX significantly spoils the crystal structure, predominantly resulting in amorphous AX products. Here, we demonstrate the characterization of an S/C complex prepared by the electrochemical etching of Ti ₂ SC. The spark plasma sintering (SPS) technique affords a well-sintered Ti ₂ SC disk with high purity, which can be directly utilized as a binder-free Ti ₂ SC electrode. It is found that the electrochemically extracted Ti elements in NH ₄ F electrolyte are partially crystallized into the monoclinic titanium oxynitride, TiO _0.34 N _0.74 . The formed amorphous S/C compound is classified into three components: acetone-soluble volatiles including elemental sulfur, acetone-insoluble volatiles, and non-volatile species carbonizable into S-doped carbon.