Morphology Regulation of MoSe ₂ via Salt-Assisted CVD for Enhanced Hydrogen Evolution Catalysis

Precise regulation of the morphology and layer number of molybdenum diselenide (MoSe 2 ) is crucial for unlocking its full potential in energy catalysis as these features directly determine the exposure of active edge atoms and electron transport efficiency. Herein, we develop a salt-assisted chemical vapor deposition (CVD) strategy to synthesize high-quality MoSe 2 flakes with controllable morphologies. By systematically adjusting salt dosage and growth temperature, we achieve reliable fabrication of MoSe 2 with diverse morphologies (triangular, dendritic, etc.) and tunable layers (monolayer to tetralayer). Mechanistic investigations reveal that salt dosage modulates the nucleation and growth kinetics of MoSe 2 to govern its morphology, while the growth temperature serves as a key parameter for layer number tuning. On-chip electrochemical tests for the hydrogen evolution reaction (HER) demonstrate that dendritic MoSe 2 exhibits optimal catalytic performance, delivering an overpotential of 228 mV at −10 mA cm –2 and a Tafel slope of 117 mV dec –1 . This superiority originates from the intricate branched structure, which maximizes the exposure of highly reactive edge atoms─validating the structure–activity relationship where morphological regulation dominates HER performance enhancement over layer number adjustment. This study provides a viable strategy for the controlled synthesis of transition metal dichalcogenides with tailored structures, offering valuable insights for the development of high-efficiency electrocatalysts in clean energy conversion.