Probing Single-Particle Electrocatalytic Activity at Facet-Controlled Gold Nanocrystals

Electrocatalytic reduction reactions (i.e. the hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR)) at individual, faceted Au nanocubes (NCs) and nano-octahedra (ODs) expressing predominantly {100} and {111} crystal planes on the surface, respectively, were studied by nanoscale voltammetric mapping. Cyclic voltammograms were collected at individual nanoparticles (NPs) with scanning electrochemical cell microscopy (SECCM) and correlated with particle morphology imaged by electron microscopy. Nanoscale measurements from a statistically informative set of individual NPs revealed that Au NCs have superior HER electrocatalytic activity compared with Au ODs, in good agreement with macroscale cyclic voltammetry (CV) measurements. Au NCs exhibited more particle-to-particle variation in catalytic activity compared to Au ODs. Our approach of single-particle SECCM imaging coupled with macroscale CV on well-defined NPs provides a powerful toolset for the design and activity assessment of nanoscale e...