Electrochemistry With Nanoelectrodes

Nanometer-sized electrodes have drawn considerable interest in recent years. One of the reasons is that with nanoelectrodes one can obtain a high rate of mass transport and study kinetics of fast heterogeneous electron transfer (ET) reactions. They can also be used for high-resolution chemical imaging of surfaces and interfaces and as microscopic chemical sensors.

We developed methodologies for preparation and characterization of electrochemical nanoprobes and their use as tips in the scanning electrochemical microscope (SECM). The applications range from studies of hydrogen adsorption and spillover to high-resolution imaging of surface topography and reactivity to nanofabrication. Finally, some unusual physicochemical phenomena can be observed at nanointerfaces but are not accessible by macroscopic electrochemical probes will be discussed.

Visualization of the nanoelectrode surface is challenging, and the interpretation of the electrochemical response often relies on assumptions about its shape and size. Recently, we obtained first AFM images of nanoelectrodes, which provide detailed and unambiguous information about the electrode geometry. In-situ AFM is also useful for monitoring surface reactions at nanoelectrodes. This approach was used to control electrodeposition of Pt black into an etched nanocavity and prepare well-shaped platinized nanoelectrodes for intracellular measurements of reactive oxygen and nitrogen species.

We have also used In-situ AFM to investigate surface layer morphology during potential cycling on (111) oriented terraces and octahedral facets of LiMn2O4 thin films. These studies as a function of time, potential, and cycling rate allowed us to determine the impact of local microstructure on surface layer nucleation and growth.