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

An efficient nitrate/HCl chemical exfoliation system for rapid production of MoS 2 and WS 2 nanosheets were presented here. After exfoliation in the NaNO 3 /HCl solution with the assistant of ultrasonication, MoS 2 and WS 2 nanosheets were produced with yields of 58% and 52%, respectively. The morphologies and crystallinity of MoS 2 and WS 2 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 MoS 2 and WS 2 nanosheets exhibited improved catalytic activity toward the oxygen-reduction reaction.