Understanding Correlation between Magnetism and Electrocatalytic Hydrogen Evolution Based on Intrinsic Properties of Single MoS2 Entity

Few-layered molybdenum chalcogenide (MoS2) has attracted considerable attention due to its defect-rich structure and active edge sites, triggering distinctive electrocatalysis and magnetism properties. Quantifying the intrinsic properties of a single entity is of paramount importance for clarifying the structure–activity correlation. Here, the intrinsic activities of single MoS2 flakes toward the hydrogen evolution reaction (HER) were investigated by single nanoparticle collision electrochemical measurements with and without a moderate magnetic field. Our results demonstrate that single bilayer MoS2 flakes show the highest HER performance and the greatest magnetic enhancement among bilayer-, trilayer-, and multilayer-MoS2 flakes. This is because bilayer MoS2 flakes possess abundantly exposed edge sites and sulfur vacancies, which simultaneously accelerate the reaction kinetics of HER and increase the ferromagnetism properties. This work gives new insight into providing specific guidance for the magnetic modulation of few-layered MoS2 and the design of highly effective MoS2-based electrocatalysts.