Electrodeposition of amorphous molybdenum sulfide thin film for electrochemical hydrogen evolution reaction

Amorphous molybdenum sulfide (MoSx) is a highly active noble-metal-free electrocatalysts for the hydrogen evolution reaction (HER). The MoSx was prepared by electrochemical deposition at room temperature. Low-cost precursors of Mo and S were adopted to synthesize thiomolybdates solution as the electrolyte. It replaces the expensive (NH)2MoS4 and avoid the poison gas (H2S) to generate or employ. The (MoO2S2)2-, (MoOS3)2- and (MoS4)2- ions were determined by UV-VIS spectroscopy. The electrodeposition of MoSx was confirmed with XRD, XPS and SEM. The electrocatalyst activity was measured by polarization curve. The electrolyte contained (MoO2S2)2- ion and (MoOS3)2- ion electrodeposit the MoSx thin film displays a relatively high activity for HER with low overpotential of 211 mV at a current density of 10 mA cm-2, a relatively high current density of 21.03 mA cm-2 at η = 250 mV, a small Tafel slope of 55 mV dec-1. The added sodium dodecyl sulfate (SDS) can efficient improve the stability of the MoSx film catalyst.