Surface-Modified MXenes: Simulation to Potential Applications

MXenes are promising two-dimensional materials with good electrical conductivity, layered structure, biocompatibility, hydrophilicity, chemical inertness, and high surface area. Since the discovery of MXenes, they have been used for multiple applications, including energy storage, sensors, electronics, and optical devices. Theoretically, various MXenes are predicted by multiple studies, but few have been synthesized experimentally. The synthesized MXenes can possess various terminating groups that provide a great avenue to modify the surface of MXenes to fine-tune their chemical and physical properties. Notably, the terminating group of MXenes can be adjusted using diverse modification strategies, including covalent and noncovalent approaches. To advance future applications, it is necessary to have a deeper understanding of both theoretical and experimental approaches of MXenes. Although there have been some reviews on MXenes, less attention has been paid to the essential principle involved in surface modification using covalent and noncovalent chemistry and the controllable design of various MXenes compositions based on the theoretical calculations. This review focuses on a detailed understanding of the synthesis process of MXenes, as well as theoretical and experimental approaches toward the determination of their physical and chemical properties. In effect, both synthetic methods and postsynthesis functionalization will be complemented by density functional theory calculations. Furthermore, various functionalization strategies of MXenes have been discussed. Finally, we have provided an overview of current trends of modified MXenes in energy storage devices, electrocatalysts, and sensors applications with a brief comparison of the current state-of-the-art methods. This review will help researchers understand the feasibility of MXenes at the fundamental level for potential use in large-scale practical applications.