An efficient and scalable method combining ball-milling and liquid-phase exfoliation was used to prepare MoS2 nanosheets. Ammonium bicarbonate as an exfoliation aid could accelerate the delamination and pulverization of bulk MoS2 during preparation. The ballmilled MoS2 was further exfoliated by sonication (S-MoS2NS) or high-speed shear-exfoliation (H-MoS2NS) to obtain MoS2 nanosheets dispersion with high concentration. Moreover, MoS2 quantum dots were also obtained by prolonging sonication time (S-MoS(2)QS). Most of S-MoS2NS and H-MoS2NS have lateral dimensions less than 150 nm. The S-MoS(2)QS size concentrates at around 5 nm. The H-MoS2NS mixed with aminated multiwalled carbon nanotubes (MWCNT) could form H-MoS2NS/MWCNT composites with a good conductive network, and was used as a hydrogen evolution reaction (HER) catalyst. The H-MoS2NS/MWCNT composites containing 56 wt% H-MoS2NS exhibited a favorable HER activity with a low overpotential of 284 mV at 10 mA/cm(2), a Tafel slope of 97 mV/dec and good stability in acid medium. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.