Conductive Molybdenum Sulfide for Efficient Electrocatalytic Hydrogen Evolution.

Molybdenum sulfide (MoS2 ) is a layered material with high activity for electrocatalytic hydrogen evolution reaction (HER). In conventional MoS2 , the high electrical resistance between the layers hampers the bulk charge transfer and therefore greatly limits its performance in electrolysis. Herein, ultrathin MoS2 nanosheets with bent layers on reduced graphene oxide (RGO) are reported. In sharp contrast to the bulk MoS2 , the resulting MoS2 has mostly 1 or 2 layers, and the layer distance is significantly expanded to ≈1 nm. From computational studies, the prepared MoS2 with limited layer numbers and expanded layer distances has similar physical and chemical features with single-layer MoS2 . Importantly, the bent single layer is electrically conductive and is intrinsically more active than a normal flat single layer. In addition, the unusual features of confined sizes and distorted lattices in the prepared MoS2 can bring about plentiful active sites and are beneficial for mass diffusion during electrocatalysis. The hybrid material exhibits high activity for electrocatalytic HER, affording a current density of 10 mA cm-2 at a low overpotential of 66 mV.