Electronic structure engineering of molybdenum carbides for efficient water electrolysis

Electrocatalytic water splitting for hydrogen production is one of the most promising sustainable energy conversion technologies, yet its development is hampered by sluggish electrocatalytic reaction kinetics. Owing to the unique electronic structures and Pt-like properties, molybdenum carbide-based (Mo_xC) catalysts have exhibited exceptional catalytic activity and stability in the hydrogen evolution reaction (HER) and have emerged as a research hotspot in the field of energy materials. As a crucial factor regulating catalyst activity, electronic structure has been established as a core descriptor. However, the underlying mechanism governing the fine-tuning of electronic structures remains unclear; furthermore, existing studies on Mo_xC-based catalysts generally lack systematic decoupling of the multidimensional correlation mechanisms among synthetic methods, structural modulation, and catalytic performance optimization, which severely impedes their rational design and precise regulation. To clarify the structure and activity relationship between material geometric structure, electronic behavior and catalytic activity, this review comprehensively summarizes the innovative synthetic strategies and structure-performance correlation mechanisms of Mo_xC-based catalysts on the basis of an in-depth understanding of the HER catalytic mechanism and d-band center theory. Core design principles of high-efficiency Mo_xC-based catalysts are further proposed, offering a cross-scale design paradigm for the development of high-performance Mo_xC electrocatalysts toward the HER.