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

Amorphous molybdenum sulfide (MoS_x) is a highly active noble-metal-free electrocatalysts for the hydrogen evolution reaction (HER). The MoS_x 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 MoS_x 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 MoS_x 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 MoS_x film catalyst.