Direct high-resolution mapping of electrocatalytic activity of semi-two-dimensional catalysts with single-edge sensitivity

Significance A major challenge in electrocatalysis is pinpointing active sites on the surface, particularly when they are at the atomic scale. Direct electrochemical measurements of individual materials’ edges have not yet been reported. Here we use the scanning electrochemical microscope (SECM) to independently image topography and local catalytic activity. The 15-nm spatial resolution and high sensitivity allowed us to distinguish the higher activities of the materials’ edges from that of the fully coordinated surfaces in operando . The spatially resolved electrochemical information combined with state-of-the-art electron tomography that unravels the three-dimensional complexity of the edges and ab initio calculations revealed the intricate coordination-dependent catalytic activity of the Ni oxide nanosheet edge that is not accessible by other methods.