Transition from Diffusion-Controlled Intercalation into Extrinsically Pseudocapacitive Charge Storage of MoS₂ by Nanoscale Heterostructuring

2D nanomaterials have been found to show surface-dominant phenomena and understanding this behavior is crucial for establishing a relationship between a material's structure and its properties. Here, the transition of molybdenum disulfide (MoS₂) from a diffusion-controlled intercalation to an emergent surface redox capacitive behavior is demonstrated. The ultrafast pseudocapacitive behavior of MoS₂ becomes more prominent when the layered MoS₂ is downscaled into nanometric sheets and hybridized with reduced graphene oxide (RGO). This extrinsic behavior of the 2D hybrid is promoted by the fast Faradaic charge-transfer kinetics at the interface. The heterostructure of the 2D hybrid, as observed via high-angle annular dark field-scanning transmission electron microscopy and Raman mapping, with a 1T MoS₂ phase at the interface and a 2H phase in the bulk is associated with the synergizing capacitive performance. This 1T phase is stabilized by the interactions with the RGO. These results provide fundamental insights into the surface effects of 2D hetero-nanosheets on emergent electrochemical properties.