MoS2 Nanoparticles Grown on Graphene: An Advanced Catalyst for Hydrogen Evolution Reaction

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Advanced materials for electrocatalytic and photoelectrochemical water splitting are central to the area of renewable energy. Here, we developed a solvothermal synthesis of MoS2 nanoparticles selectively on reduced graphene oxide (RGO) sheets suspended in solution. The resulting MoS2/RGO hybrid material possessed nanoscopic few-layer MoS2 structures with abundant exposed edges stacked onto graphene, in strong contrast to large aggregated MoS2 particles grown freely in solution without GO. The MoS2/RGO hybrid exhibited superior electrocatalytic activity in the hydrogen evolution reaction (HER) to other MoS2 catalysts. A Tafel slope of 41 mV/decade was measured for MoS2 catalysts in HER for the first time, far exceeding the activity of previous MoS2 owing to the abundant catalytic edge sites of MoS2 nanoparticles and excellent electrical coupling to the underlying graphene network. The 41 mV/decade Tafel slope suggested the Volmer-Heyrovsky mechanism for MoS2 catalyzed HER, with electrochemical desorption of hydrogen as the rate-limiting step.