Surface Functional Group Engineering of MXenes: Mechanisms, Tailoring Strategies, and Performance‐Oriented Applications

MXenes, as an emerging 2D material, hold considerable energy storage potential. However, the intrinsic stochastic distribution and thermodynamic metastability of their surface functional groups impair key electrochemical properties, compromising their cyclability and rate capability. Regulating the type, density, and spatial arrangement of MXene surface functional groups is thus a pivotal strategy for optimizing the electrochemical performance. This review first focuses on the surface functional group modification mechanisms of MXenes leveraging ultrahigh conductivity, tunable interlayer spacing, and mechanical flexibility, including chemical etching thermodynamics and post‐synthetic modification chemistry. We then compare the distinct electrochemical effects of oxygen‐containing, halogen‐, and nitrogen/sulfur‐based functional groups on the ionic adsorption energetics, pseudocapacitive charge storage, and catalytic turnover frequency of MXenes. Subsequently, we detail the typical applications of MXenes surface functional group engineering in energy storage, extending from lithium‐sulfur batteries and supercapacitors to emerging frontiers including catalysis, sensing, water desalination, and biomedicine. This review attempts to establish a basic theoretical framework for optimizing MXene‐based energy storage materials, offering modest references for developing next‐generation high‐efficiency energy storage devices.