Surface Terminations of MXene: Synthesis, Characterization, and Properties

MXene, 2D transition metal carbides, nitrides, and carbonitrides with a unique 2D structure, inspired a series of function applications related to energy storage and conversion, biometrics and sensing, lighting, purification, and separation. Its surface terminations are confined by the adjacent MXene layers, and form the 2D planar space with symmetrical surfaces, which is similar to a 2D nanoreactor that can be utilized and determined MXene’s function. Based on the working principle, surface and interface play critical roles in the ion intercalation, physical/chemical adsorption, and chemical reaction process, and show significant effects on MXene’s properties and functions. Although there have been some reviews on MXene, less attention has been paid to the underlying principle of the involved surface chemistry, controllable design, and resultant properties. Herein, the regulation methods, characterization techniques, and the effects on properties of MXene surface terminations were summarized to understand the surface effects, and the relationship between the terminations and properties. We expected this review can offer the route for a series of ongoing studies to address the MXene surface environment and the guidelines for MXene’s application.