Cationic Hexagonal Boron Nitride, Graphene, and MoS₂ Nanosheets Heteroassembled with Their Anionic Counterparts for Photocatalysis and Sodium-Ion Battery Applications

Various layered materials, including hexagonal boron nitride (h-BN), graphite, and molybdenum disulfide (MoS2), have been successfully exfoliated to be cationic two-dimensional (2D) materials for the first time. The raw layered materials were exfoliated by a ball milling method with polycation solution as the medium, which can effectively stabilize the layered materials in the solution, mitigate the large ball momentum to destroy the layered materials, impede the oxidation of the layered materials, and functionalize the obtained 2D materials. These advantages lead to the preparation of various cationic 2D materials, such as h-BN, graphene, and MoS2, with high yield, good quality, and good solution processability. The prepared cationic 2D materials were heteroassembled with anionic ones because of the electrostatic interactions between them, showing much better performance than that obtained when using one single component alone. By using the 2D h-BN/rGO as a photocatalyst, the dye decomposed by 95% after 7 min of light illumination, which was much more efficient than using the rGO (54%) and 2D h-BN (38%) alone. By using the titania nanosheets/ball milled graphene composites as the anode for the sodium-ion battery application, the capacity was 353 mA h g–1 at a cycling speed of 100 mA g–1, ∼6 folds of pure titania nanosheets. This facile method to synthesize various cationic 2D materials may open up a new avenue to fabricate 2D heterostructures and study their properties.