Frenkel-defected monolayer MoS 2 catalysts for efficient hydrogen evolution.

Defect engineering is an effective strategy to improve the activity of two-dimensional molybdenum disulfide base planes toward electrocatalytic hydrogen evolution reaction. Here, we report a Frenkel-defected monolayer MoS 2 catalyst, in which a fraction of Mo atoms in MoS 2 spontaneously leave their places in the lattice, creating vacancies and becoming interstitials by lodging in nearby locations. Unique charge distributions are introduced in the MoS 2 surface planes, and those interstitial Mo atoms are more conducive to H adsorption, thus greatly promoting the HER activity of monolayer MoS 2 base planes. At the current density of 10 mA cm -2 , the optimal Frenkel-defected monolayer MoS 2 exhibits a lower overpotential (164 mV) than either pristine monolayer MoS 2 surface plane (358 mV) or Pt-single-atom doped MoS 2 (211 mV). This work provides insights into the structure-property relationship of point-defected MoS 2 and highlights the advantages of Frenkel defects in tuning the catalytic performance of MoS 2 materials.