Coupling of single-layered $WS_2$ nanoplates with carbon nanofibers exhibiting extraordinary electrochemical performance as anodes for lithium ion batteries and electrocatalysts for hydrogen evolution

Abstract

Transition metal dichalcogenides (TMDs) such as $WS_2$ have drawn tremendous attention due to their fascinating physicochemical properties when they are single-layered or few-layered. Such attention can be ascribed to an interesting phenomenon that dimension reduction from three-dimensional to two-dimensional TMDs leads to the emergence of extraordinary physicochemical properties that are different from those of their bulk material counterparts. Unfortunately, their poor intrinsic conductivities hamper their use in energy storage and conversion applications. In this regard, it is an efficient strategy to make a composite, combining single-layered TMDs with highly conductive materials. In this study, it is demonstrated that single layers of $WS_2$ nanoplates can be uniformly embedded in nitrogen-doped carbon nanofibers ($WS_2@NCNFs$), and also can be anchored to hollow nitrogen-doped carbon nanofibers ($WS_2@HNCNFs$) via electrospinning. Crystallization of the single-layer $WS_2$ nanoplates and in situ nitrogen doping into the carbon nanofibers are simultaneously accomplished during a two-step heat treatment. These rationally designed materials were electrochemically tested as anode materials for lithium ion batteries and electrocatalysts for hydrogen evolution. The distinctive design of the materials enables outstanding electrochemical performances.