Water-Soluble Defect-Rich MoS 2 Ultrathin Nanosheets for Enhanced Hydrogen Evolution.

In this work, we report a facile cryo-mediated liquid phase exfoliation method to synthesize water-soluble defect-rich MoS2 ultrathin nanosheets (d-MoS2 NSs) with the assistance of NaBH4 in the solvent. The as-prepared d-MoS2 NSs show enhanced electrocatalytic hydrogen evolution reaction (HER) performance in comparison to that of MoS2 NSs due to surface hydrophilicity and abundant active edge sites. The formation process of the d-MoS2 NSs with exposed edge sites is illustrated by investigating the influence of exfoliation time on their structural morphology. The optimal water-soluble d-MoS2 NSs display excellent HER activities, including a low overpotential of 71.5 mV at a current density of -10 mA cm(-2), a small Tafel slope of 58.3 mV dec(-1), and good cycling stability.