Electrodeposition of Amorphous Molybdenum Chalcogenides from Ionic Liquids and Their Activity for the Hydrogen...

This work reports on the general electrodeposition mechanism of tetrachalcogenmetallates from 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Both tetrathio- and tetraselenomolybdate underwent anodic electrodeposition and cathodic corrosion reactions as determined by UV-vis spectroelectrochemistry. Electrodeposition was carried out by cycling the potential between the anodic and cathodic regimes. This resulted in a film of densely packed nanoparticles of amorphous MoS_x or MoSe_x as determined by SEM, Raman, and XPS. The films were shown to have high activity for the hydrogen evolution reaction. The onset potential (J = 1 mA/cm²) of the MoS_x film was E = -0.208 V vs RHE, and that of MoSe_x was E = -0.230 V vs RHE. The Tafel slope of MoS_x was 42 mV/decade, and that of MoSe_x was 59 mV/decade.