Phase-dependent growth of Pt on MoS 2 for highly efficient H 2 evolution

Crystal phase is a key factor determining the properties, and hence functions, of two-dimensional transition-metal dichalcogenides (TMDs) 1 , 2 . The TMD materials, explored for diverse applications 3 – 8 , commonly serve as templates for constructing nanomaterials 3 , 9 and supported metal catalysts 4 , 6 – 8 . However, how the TMD crystal phase affects the growth of the secondary material is poorly understood, although relevant, particularly for catalyst development. In the case of Pt nanoparticles on two-dimensional MoS 2 nanosheets used as electrocatalysts for the hydrogen evolution reaction 7 , only about two thirds of Pt nanoparticles were epitaxially grown on the MoS 2 template composed of the metallic/semimetallic 1T/1T′ phase but with thermodynamically stable and poorly conducting 2H phase mixed in. Here we report the production of MoS 2 nanosheets with high phase purity and show that the 2H-phase templates facilitate the epitaxial growth of Pt nanoparticles, whereas the 1T′ phase supports single-atomically dispersed Pt (s-Pt) atoms with Pt loading up to 10 wt