In this study, amorphous MoSx catalysts are fabricated on carbon paper using a simple one-step electrodeposition. Varying the deposition potential and time enables the simple control of the morphology and composition of MoSx catalysts, which affects their catalytic activity for hydrogen evolution reaction. The intrinsic activity based on their electrochemical surface area shows a significant relation with S atoms with higher binding energy. The lowest hydrogen evolving overpotential among the electrodeposited MoSx catalysts is - 159.8 mV at a current density of -10 mA cm(-2) with a Tafel slope of 42.3 mV dec(-1). The MoSx formed on carbon paper is directly implemented as a cathode in a proton exchange membrane water electrolyzer, and it displays acceptable cell performance. The following results demonstrate the potential for the use of amorphous MoSx catalysts as an alternative to noble metals in cathode of proton exchange membrane water electrolyzer.