Auto-oxidation of exfoliated MoS2 in N-methyl-2-pyrrolidone: from 2D nanosheets to 3D nanorods

Abstract

There has been a great deal of interest in the electrochemical intercalation of two-dimensional materials in recent years, with studies of transition metal dichalcogenides (TMDs), a so-called “beyond graphene” material, coming to the fore in the context of energy storage devices. However, the electrochemical intercalation properties of these materials are restricted, especially in an aqueous environment, because of the limit of interlayer spacing between adjacent TMD (here, MoS₂) layers. We have therefore introduced a novel preparation route for MoO₃ nanorods from exfoliated 2H-MoS₂via the auto-oxidation of a mixture of N-methyl-2-pyrrolidone and water via the sonication-assisted exfoliation of MoS₂. It is found that the MoO₃·MoS₂ free-standing electrode displays a larger interlayer spacing than the MoS₂ electrode, which exhibits a capacitance roughly ten times higher than that of traditional 2H-MoS₂. This study expands on the behaviour of ion intercalation in aqueous media of transition metal dichalcogenides (TMDs) and transition metal oxide (TMOs) materials, which can be of use in various electrochemical applications such as energy storage devices.