Rapid and highly efficient chemical exfoliation of layered MoS 2 and WS 2

An efficient nitrate/HCl chemical exfoliation system for rapid production of MoS2 and WS2 nanosheets were presented here. After exfoliation in the NaNO3/HCl solution with the assistant of ultrasonication, MoS2 and WS2 nanosheets were produced with yields of 58% and 52%, respectively. The morphologies and crystallinity of MoS2 and WS2 nanosheets were characterized by transmission electron microscopy, atomic force microscopy and X-ray diffraction spectroscopy. This efficient exfoliation method is based on the synergy effects of surface etching, insertion of ions and eruption of gas bubbles. The MoS2 and WS2 nanosheets exhibited improved catalytic activity toward the oxygen-reduction reaction.