MoS2/MoO2/Graphene Electrocatalyst for HER

MoS2 nanosheets have been successfully synthesized, on few layer graphene (FLG) obtained by physical exfoliation of graphite, by thermolysis of (NH4)2MoS4, in a continuous flow reactor. The syntheses have been monitored with a mass spectrometer. After the precursor decomposition, an annealing treatment in N2 to improve MoS2 order, and in few percent of O2 in N2 to promote also MoO2 nanocrystals formation, permits to obtain MoS2/FLG and MoS2/MoO2/FLG hybrid materials via a solvent free, easily controllable and scalable process. The samples were characterized by Raman Spectroscopy, Electron Microscopy, and X-ray diffraction, and tested for HER activity using a typical three-electrode setup. We obtained excellent HER activity, with a Tafel slope compatible with electrochemical desorption as rate limiting step, while the presence of MoO2 leads to a very low starting cathodic voltage of about 50 mV.