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 (MoSe2) 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 MoSe2 flakes with controllable morphologies. By systematically adjusting salt dosage and growth temperature, we achieve reliable fabrication of MoSe2 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 MoSe2 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 MoSe2 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.