Preprint For: Unraveling the Potential of MXenes in Electrochemical Sensing: Mechanistic Insight, Design Principles, and Analytical Applications

MXenes, a rapidly expanding class of two-dimensional transition metal carbides, nitrides, and carbonitrides, have emerged as promising materials for electrochemical sensing due to their metallic conductivity, hydrophilic surfaces, and tunable surface terminations. These features enable efficient electron transfer, strong interfacial interactions, and versatile functionalization. However, despite extensive reports, a clear understanding of how MXene properties govern sensing performance remains limited. Herein, a mechanistic perspective on MXene-based electrochemical sensors is presented, emphasizing the relationship between composition, surface chemistry, structural organization, and analytical performance. Key material features, including surface terminations, interlayer interactions, and synthesis strategies, are discussed in terms of their roles in charge transfer, catalytic activity, and analyte adsorption. A unified framework is proposed to describe MXenes as conductive scaffolds, electrocatalytic interfaces, and adsorption-driven platforms. Recent advances are analyzed across major application domains, including small molecules, environmental pollutants, biomolecules, and pharmaceuticals, highlighting common design strategies and synergistic effects in hybrid systems. Current challenges related to stability, reproducibility, and standardization are also addressed. This work provides design insights for the development of next-generation MXene-based electrochemical sensors and supports their translation into practical applications.