Identification of Active Edge Sites for Electrochemical H 2 Evolution from MoS 2 Nanocatalysts

The identification of the active sites in heterogeneous catalysis requires a combination of surface sensitive methods and reactivity studies. We determined the active site for hydrogen evolution, a reaction catalyzed by precious metals, on nanoparticulate molybdenum disulfide (MoS 2 ) by atomically resolving the surface of this catalyst before measuring electrochemical activity in solution. By preparing MoS 2 nanoparticles of different sizes, we systematically varied the distribution of surface sites on MoS 2 nanoparticles on Au(111), which we quantified with scanning tunneling microscopy. Electrocatalytic activity measurements for hydrogen evolution correlate linearly with the number of edge sites on the MoS 2 catalyst.