Electrocatalysis at Nanoelectrode Ensembles of Ultramicroelectrode Dimensions

Electrocatalysis studies at nanoelectrode ensembles (NEEs) of ultramicroelectrode dimensions (UME-NEEs) have a number of advantages that are related to the ability to access kinetics under high mass transport, steady-state diffusion which is difficult to achieve at macro-NEEs where convection is traditionally used. Of particular interest is the use of UME-NEEs as platforms for nanoparticle (NP) deposition in forming UME-NPEs. The use of NP electrodes in the study of electrocatalysis is of fundamental interest, ranging from nanoparticle ensembles (NPEs) to single NP electrodes and single NP collision experiments.  Electrocatalysis at UME-NPEs permit direct investigation of  NP interaction under high mass transport, steady-state diffusion  that is comparable in magnitude to a single NP, thereby bridging the gap between classical ensemble studies on large platforms and isolated single NP investigations.   Applications  of  UME-NEEs, UME-NPEs, and NP collision experiments to oxygen reduction (ORR) and hydrogen evolution (HER) electrocatalysis in acidic solution will be described.