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.