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)(2)MoS4, in a continuous flow reactor. The syntheses have been monitored with a mass spectrometer. After the precursor decomposition, an annealing treatment in N-2 to improve MoS2 order, and in few percent of O-2 in N-2 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.