SECM

Scanning Electrochemical Microscopy (SECM) 


The Leonard group utilizes scanning electrochemical microscopy (SECM) in the development and characterization of electrocatalysts and photoelectrocatalysts. Using SECM, one is able to very accurately determine the kinetics of electrochemical and photoelectrochemical reactions. In addition, mechanistic information can be obtained by the investigation of reaction intermediates. SECM is also used in electrocatalyst and photoelectrocatalyst screening


SECM Tip Schematic




Schematic comparing (A) the traditional tip generation/ substrate collection (TG/SC) mode of SECM to (B) the multireactional TG/SC mode of SECM. In the multireactional TG/SC mode, two reactions occur on the tip electrode while only one product is collected on the substrate electrode. This allows for separation of simultaneous reactions occurring on the tip electrode. [Leonard, K. C.; Bard, A. J. J. Am. Chem. Soc. 2013, 135, 15890–15896]


COMSOL Simulations




COMSOL Multiphysics simulations showing H+ concentration at three different tip/substrate distances (700, 140, and 60 μm) for the 3D approach curve simulations. [Leonard, K. C.; Bard, A. J. J. Am. Chem. Soc. 2013, 135, 15890–15896]


Simulated and Experimental Current Data





Three-dimensional COMSOL Multiphysics simulations of (A) the tip current and (B) the substrate current along with the experimental data for the approach curve using the Mn tip electrode and Pt substrate electrode. Using the simulation, it was determined that the final tip/substrate distance was 65 μm.. [Leonard, K. C.; Bard, A. J. J. Am. Chem. Soc. 2013, 135, 15890–15896]


Example of Chemical Reactivity Maps Obtained Via SECM

























Hydrogen evolution electrochemical reactivity maps obtained via scanning electrochemical microscopy (SECM). (a) Schematic of the SECM experiment showing hydrogen collection on the SECM tip electrode. (b) The reactivity map for a bare glassy carbon electrode. (c, d) Electrochemical reactivity maps for the HER on Pt and FeS2 discs on glassy carbon, respectively. [Jaison, D.; Barforoush, J.M.; Qiao, Q.; Zhu, Y.; Ren, S. and Leonard, K.C. "Low-Dimensional Hyperthin FeS2 Nanostructures for Efficient and Stable Hydrogen Evolution Electrocatalysis.” ACS Catalysis Vol. 5, pp. 6653 - 6657 (2015)]






SECM positive feedback image of the letters “KU” printed in gold on a glass slide using a 200 mm Pt tip electrode at +0.4 V vs Ag/AgCl in 0.5 mM FcMeOH. (A) Positive feedback image before the automated substrate tilt algorithm was performed. (B) Positive feedback image after the automated substrate tilt algorithm was performed.  [Barforoush, J.M.; McDonald, T.D.; Desai, T.; Widrig, D.; Bayer, C.; Brown, M. K.; Cumming, 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)]