Scanning Electrochemical Microscopy

Learn more about how the Leonard Lab is leading advancements in the capabilities of SECM and utilizing it for characterization information in other research endeavors.

Objectives

The Leonard group utilizes scanning electrochemical microscopy (SECM) in the development and characterization of electrocatalysts. SECM is a “non-contact” scanning probe technique capable of providing chemical and/or topographic information about surfaces immersed in a solution. It is a powerful in situ and operando tool for obtaining insights into electrocatalytic rates and mechanisms. Moreover, in situ and operando techniques are needed to (1) better understand adsorption mechanisms and structure effects to identify bottle-necks in catalytic processes and (2) bridge the gap between the conditions at which catalyst characterization measurements are taken and the conditions at which the catalysts need to operate. Using SECM, one is able to very accurately determine the kinetics of electrochemical reactions, as well as mechanistic information can be obtained by the investigation of reaction intermediates.

Principle Project

Catalyst characterization

The scanning electrochemical microscopy (SECM) instrument has vast capabilities. We can learn more about a catalyst surface and activity by utilizing SECM to gather chemical information. The goal is to gather data in situ and operando to determine how composition and structure correlate to catalyst activity. This data includes quantifying the activity site densities of catalysts, accurately determining electron-transfer kinetic rate contents of catalytic active sites, and quantifying rate constants of different active sites on a catalyst surface to discern between fast and slow sites. By analyzing this data, we can design catalysts with specific properties that yield high activity and efficiency. 

 

Visual for gathering kinetic data for catalysts¹

Artists representation of the function of SECM and experimental data from a catalyst sample.

 

Visual for topography experiments and corrections²

Before and after tilt correction where one graph shows illegible text and the other clearly displays the letters KU

 

Visual for the diffusion profile during an SECM experiment³

A snapshot at four different times showing the initial generation of the redox species, increase in redox, then the transition back to oxidize species

 

SECM holds the potential to be a unique instrument that could benefit the entire catalysis community by uncovering new insights into catalytic mechanisms and intermediates. Even though the reactions that occur on the tip electrode are electrochemical, the reactions that occur on the substrate electrode need not be electrochemical, as long as the liquid phase has enough conductivity to support the tip reactions. Thus, we envision that the imaging, generation/collection, surface-interrogation, and multireactional modes of SECM could be adopted by researchers studying chemocatalytic mechanisms in the liquid phase.

 

  1. Barforoush, J.M.; Jantz. D.T.; Seuferling, T.E.; Song, K.R.; Cummings, L.C. and Leonard, K.C. “Microwave-Assisted Synthesis of a Nanoamorphous (Ni₀.₈,Fe₀.₂) oxide oxygen-evolving electrocatalyst containing only ‘fast’ sites.” Journal of Materials Chemistry A Vol. 5, Issue 23, pp. 11661-11670 (2017). -  https://doi.org/10.1039/C7TA00151G
  2. Barforoush, J.M.; McDonald, T.D.; Desai, T.; Widrig, D.; Bayer, C.; Brown, M. K.; Cummings, L.C. and Leonard, K.C. “Intelligent Scanning Electrochemical Microscopy Tip and Substrate Control Utilizing Fuzzy Logic.” Electrochimica Acta Vol. 190, pp.713-719 (2016). - https://doi.org/10.1016/j.electacta.2015.12.112
  3. Jantz. D.T. and Leonard, K.C. “Characterizing Electrocatalysts with Scanning Electrochemical Microscopy.” Industrial & Engineering Chemistry Research Vol. 57, Issue 22, pp. 7431-7440 (2018). - https://doi.org/10.1021/acs.iecr.8b00922