Real-time monitoring of electrochemical reactions on single nanoparticles by dark-field and Raman microscopy.

Nanoparticles (NPs) play a central role in a wide range of electrochemical applications. One of the ultimate goals for nano-electrochemistry is to establish the structure-activity relationship (SAR) of NPs, so that they can be rationally designed and synthesized. However, it has remained a critical challenge until now, despite the tremendous efforts that have been made. This is largely because most ensemble characterization methods cannot resolve the significant static and dynamic disorder among the individual NPs and their respective active sites. The recently developed single NP electrochemical methods, including both collision and immobilization, opened up a radically new and effective way to uncover such heterogeneity. More importantly, it has also been increasingly recognized that coupling electrochemistry with operando optical microscopy is of great benefit to elucidate the dynamic SAR as well as the underlying reaction mechanisms. Herein, this frontier article aims to provide a timely update on the recent progress of using dark-field and Raman microscopy to probe the single NP electrochemistry in real time.