MoS2 has been one of a widely researched hydrogen evolution reaction (HER) catalyst materials in recent years. However, the basal plane of MoS2 is considered to be inactive to hinder its further development. Herein, a new mass-scalable and facile intercalation method for the fabrication of multiple products, including pore-rich monolayer MoS2 (PR MoS2) and MoS2 quantum dots (MoS2 QDs), has been developed via the gas phase etching of bulk MoS2 in an acetone vapor atmosphere. The obtained monolayer MoS2 QDs with a narrow lateral size distribution (average size: 2.5 nm) present excitation-independent photoluminescence emission. Furthermore, the PR MoS2 shows a significantly enhanced HER electrocatalytic activity and good stability in 0.5 M H2SO4 solution with a small overpotential of 241 mV at a current density of 10 mA cm(-2). These results demonstrate that the as-prepared PR MoS2 is very promising for the application in HER. (C) 2019 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.