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)
2
MoS
4
and avoid the poison gas (H
2
S) to generate or employ. The (MoO
2
S
2
)
2−
, (MoOS
3
)
2−
and (MoS
4
)
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 (MoO
2
S
2
)
2−
ion and (MoOS
3
)
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.
Electronic supplementary material
The online version of this article (10.1186/s13065-019-0600-0) contains supplementary material, which is available to authorized users.