A Review on MXene Terminations

Abstract In the present review, available MXene surface‐terminating species are explored in view of current synthesis protocols. Their chemical properties are also considered in view of stoichiometry and coordination, which govern the stability of both terminations and MXene sheets. Furthermore, available post‐processing methods are discussed in relation to how the termination chemistry can be further tuned, enabling bare MXene sheets as well as terminations that are not native to the MXene synthesis. Finally, this review explores the properties enabled by the MXene surface chemistry and the emerging applications they facilitate. In the conversion of three‐dimensional (3D) MAX phases to two‐dimensional (2D) MXene sheets, the freshly exposed and highly reactive surfaces are terminated by species that originate from the ambient environment. Accordingly, these are known as surface terminations. The MXene sheets inherit properties such as composition and structure from the parent MAX phase; however, given the reduced dimensionality of MXenes, the surface terminations decisively influence their chemistry, which ultimately governs the MXene properties.