Regulation of Sulfur Atoms in MoS_x by Magneto-Electrodeposition for Hydrogen Evolution Reaction

Compared with crystalline molybdenum sulfide (MoS₂) employed as an efficient hydrogen evolution reaction (HER) catalyst, amorphous MoS_x exhibits better activity. To synthesize amorphous MoS_x, electrodeposition serving as a convenient and time-saving method is successfully applied. However, the loading mass is hindered by limited mass transfer efficiency and the available active sites require further improvement. Herein, magneto-electrodeposition is developed to synthesize MoS_x with magnetic fields up to 9 T to investigate the effects of a magnetic field in the electrodeposition processing, as well as the induced electrochemical performance. Owing to the magneto-hydrodynamic effect, the loading mass of MoS_x is obviously increased, and the terminal S^2- serving as the active site is enhanced. The optimized MoS_x catalyst delivers outstanding HER performance, achieving an overpotential of 50 mV at a current density of 10 mA cm^-2 and the corresponding Tafel slope of 59 mV dec^-1. The introduction of a magnetic field during the electrodeposition process will provide a novel route to prepare amorphous MoS_x with improved electrochemical performance.