Editorial Overview: Nanoscale Electrochemistry

A central challenge in electrochemical sciences is that the electrochemical response of an electrode is dominated by nanoscale features on the surface, yet our traditional electrochemical techniques operate on a millimeter or greater length scales. For instance, when we make a cyclic voltammetry measurement on a millimeter-scale electrode, the signal we obtain is based on the average response of all the active sites across the surface while details such as the activities of each site, their spatial distribution, and dynamics cannot be revealed. Nanoscale electrochemistry raises this challenge and has developed a range of techniques to effectively “zoom in” to the micro or nanoscale and, ultimately, to single molecules and atoms, enabling precise measurement of dynamic electrochemical process. This special edition highlights the cutting edge of nanoscale electrochemical research, spanning nanoparticle structure-activity relationships to DNA sequencing and 3D printing.

A mainstay of modern nanoscale electrochemistry is the scanning droplet approach known as scanning electrochemical microscopy (SECCM). SECCM simply and effectively restricts an electrochemical measurement to micro or nanoscale region of a large sample surface. In this special edition (Table 1), Schuhmann and co-workers use SECCM to investigate the structure-activity relationships in a high entropy alloy and reveal that active site-specific activities can be detected with probes of dimensions below a micrometer.^[1] Takahashi and coworkers use SECCM to investigate the capacitive response of carbon surfaces with 100-nanometer resolution and evaluate the difference in degradation of HOPG occurring at the edge and basal planes.^[2] Caleb and co-workers apply a targeted electrochemical cell microscopy (TECCM) approach to isolate the electrocatalytic response of individual shape-controlled nanoparticles toward borohydride oxidation and reveal the significant variations in reactivity and stability for individual nanoparticles.^[3] In the review by Bentley, the author summarizes how SECCM has been used to study (nano)particle electrochemistry, often isolated single nanoparticles dispersed on inert supports, and sometimes at sub-particles level.^[4] Finally, Momotenko and coworkers review how scanning probe approaches, including but not limited to SECCM, can be utilized for micro and nanoscale electrochemical 3D printing, an innovative strategy for precise fabrication of micro and nanoscale structures.^[5]

A different approach of electrochemical measurements at nanointerfaces is nano-collision or nano-impact electrochemistry. Shen and Wang demonstrate three different configurations to investigate the size, surface charge, dielectric properties, and electrochemical features of individual graphene oxide sheets.^[6]

Another approach towards nanoscale electrochemistry is the advanced optical microscopy, where electrochemical processes at nanointerfaces can be imaged with high spatial and temporal resolution by detecting local optical properties. Willets and Bohn investigate the potential-dependent luminescence emission from three different electrofluorogenic probes an indium-tin oxide (ITO) surface.^[7] A counterintuitive spectroelectrochemical observation at high irradiance or at low concentration is reported, highlighting the largely ignored importance of interaction between electrofluorogenic probes and ITO surfaces.

Finally, we have two opinions that highlight how conductometric electrochemical sensors that make use of nanopores can effectively enable accurate measurements to single molecules. Tan and Ming review how biological nanopores can be used to detect nucleobase modifications in DNA,^[8] while Johnson and co-workers elaborate how this approach can be used to sequence double-stranded DNA.^[9]

To summarize, nanoscale electrochemistry will continue to advance at space and time, revealing the intrinsic features that are often buried and gaining more complete understanding of intricate electrochemical process. Finally, we would like to express our thanks to the Publisher Dr. Brian P. Johnson and Editorial Manager Dr. Jing Tang for their kind supports during the preparation of this special edition.

The authors declare no conflict of interest.