Ternary Composite Nanosheets with MoS2/WS2/Graphene Heterostructures as High-Performance Cathode Materials for Supercapacitors

A new class of ternary heterostructures consisting of a reduced graphene oxide, molybdenum disulfide, and tungsten disulfide (rGO-MoS2-WS2) is prepared through a simple chemical method. According to Raman and X-ray photoelectron spectroscopy, a MoS2/WS2 heterostructure is uniformly formed on the conductive rGO support. Furthermore, rGO-MoS2-WS2 possesses s large surface area of 109m(2)g(-1) and a hierarchical pore architecture. When serving as the electrode for supercapacitors, rGO-MoS2-WS2 exhibits pseudocapacitive behavior in a KOH solution. It is found that rGO-MoS2-WS2 displays a specific capacitance (C-s) of 365 Fg(-1) at 1Ag(-1), which is much higher than those of single TMD (MoS2 or WS2)-based composites. The enhanced electrochemical performance of rGO-MoS2-WS2 is attributed to the lower internal resistance through heterostructure formation, the wide range of TMD oxidation states, and uniform distribution of the few-layered TMD nanosheets on the rGO surface. Furthermore, the optimal loading amount of MoS2/WS2 heterostructure in the composite is investigated. To demonstrate its practical application, rGO-MoS2-WS2 is used as a positive electrode for an asymmetric supercapacitor (ASC). The maximum energy density of the ASC device is 15Whkg(-1) at a power density of 373Wkg(-1). Furthermore, the device remains approximately 70% of the initial C-s value after 3000 cycles, which shows the excellent cycling stability.