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

Abstract

Advanced materials for electrocatalytic and photoelectrochemical water splitting are central to the area of renewable energy. In this work, we developed a selective solvothermal synthesis of MoS₂ nanoparticles on reduced graphene oxide (RGO) sheets suspended in solution. The resulting MoS₂/RGO hybrid material possessed nanoscopic few-layer MoS₂ structures with an abundance of 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) relative to other MoS₂ catalysts. A Tafel slope of ∼41 mV/decade was measured for MoS₂ catalysts in the HER for the first time; this exceeds by far the activity of previous MoS₂ catalysts and results from the abundance of catalytic edge sites on the MoS₂ nanoparticles and the excellent electrical coupling to the underlying graphene network. The ∼41 mV/decade Tafel slope suggested the Volmer–Heyrovsky mechanism for the MoS₂-catalyzed HER, with electrochemical desorption of hydrogen as the rate-limiting step.