Frenkel-defected monolayer MoS 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 catalyst, in which a fraction of Mo atoms in MoS 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 surface planes, and those interstitial Mo atoms are more conducive to H adsorption, thus greatly promoting the HER activity of monolayer MoS base planes. At the current density of 10 mA cm, the optimal Frenkel-defected monolayer MoS exhibits a lower overpotential (164 mV) than either pristine monolayer MoS surface plane (358 mV) or Pt-single-atom doped MoS (211 mV). This work provides insights into the structure-property relationship of point-defected MoS and highlights the advantages of Frenkel defects in tuning the catalytic performance of MoS materials.