MXene-Based Electrocatalysts for Water Splitting: Material Design, Surface Modulation, and Catalytic Performance.

Developing efficient and sustainable hydrogen production technologies is critical for advancing the global clean energy transition. This review highlights recent progress in the design, synthesis, and electrocatalytic applications of MXene-based materials for electrochemical water splitting. It discusses the fundamental mechanisms of the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), and the structure-function relationships that govern electrocatalytic behavior. Emphasis is placed on the intrinsic structural and surface properties of MXenes, such as their layered architecture and tunable surface chemistry, which render them promising candidates for electrocatalysis. Despite these advantages, several practical limitations hinder their full potential, including oxidation susceptibility, restacking, and a limited number of active sites. Several studies have addressed these challenges using diverse engineering strategies, such as heteroatom doping; surface functionalization; and constructing MXene-based composites with metal chalcogenides, oxides, phosphides, and conductive polymers. These modifications have significantly improved catalytic activity, charge transfer kinetics, and long-term operational stability under various electrochemical conditions. Finally, this review outlines key knowledge gaps and emerging research directions, including defect engineering, single-atom integration, and system-level design, to accelerate the development of MXene-based electrocatalysts for sustainable hydrogen production.