With the shortage of fossil energy,the research of new energies which can be used as the substitutes for the fossil energy have become more and more urgent.Hydrogen energy is clean and considered to be one of the most promising candidates for replacing petroleum fules in the future.Currently,water splitting using electrochemistryor photoelectrochemistry cells has been widely investigated as valid ways for hydrogen evolution reaction(HER).Up to now,Pt-based catalysts is the most efficient electrocatalysts for water electrolysis.However,the high cost and low reserves of Pt-based metals severely hinder their use for widely commercialization.In our work amorphous MoSx nanoparticles grown on graphene oxide(MoSx/GO)are prepared using a simple chemical method-wet chemistry process.MoSx/GO as a highly active and stable electrocatalyst is developed based on the in situ formation of MoSx nanoparticles on graphene oxide(GO)sheets.We use GO with various degrees of oxidation as support in order to study the function of the oxgen-containing functional group on the surface of the GO sheet and find out which degree of oxidation is suitable for the composite to enhance the electrochemical activity in water electrolysis.Significantly,the MoSx/GO composite which the medium degree of oxidation of GO sheet was used as the carrier shows excellent catalytic activity for HER with a small onset overpotential of~lOOmV.A tafel slope of~50mV per decade is measured for a MoSx/GO composite modified electrode.Our work suggested that the composite of MoSxand graphene which is very easy to synthesize is a great promising alternative to Pt in water electrolysis.