Electrocatalysis

Electrocatalysis


An electrocatalyst is a material which is used to catalyze an electrochemical reaction (i.e., an electron transfer oxidation or reduction reaction). Electrocatalysis is a crucial component to many different energy and industrial applications. In artificial photosynthesis (a process in which sunlight, water, and CO2 are converted to fuels or chemicals) electrocatalysts are used to improve the efficiency of the hydrogen evolution reaction, the oxygen evolution reaction, and/or CO2 reduction. In addition, electrocatalysts are used in fuel cells and metal-air batteries to catalyze the oxygen reduction reaction. Industrially, electrocatalysts are used in electrowinning (the process of extracting metals from their ores), electroplating (the process of coating a material usually with a thin layer of metal), and electrogalvanizing (a corrosion protection method  usually applied to stainless steel).


The research goals of the Leonard laboratory include developing new electrocatalysts based on earth-abundant materials for all of the above applications. This encompasses investigating new materials as well as novel reaction media. In addition, the aim is to improve the understanding of the mechanisms of electrochemical reactions and how they are affected by electrocatalyst properties.


Example of novel reaction media, Carbon-dioxide eXpanded Electrolyte (CXE), which increases the rate of reaction by over one order of magnitude.






Electrochemical current response as a function of potential and pressure in CXE media. (a–c) Cyclic voltammetry conducted under varying pressures of CO2; red: 0.3 MPa; blue: 3.2 MPa; black: 5.2 MPa; gray: control under 0.3 MPa of Ar gas. Conditions : Au disk microelectrode ; A = 0.031 mm2 ; scan rate: 100 mVs􏰵1. (d) Steady-state currents with the same electrode at 􏰵2.5 V as a function of CO2 pressure. Following initial agitation to achieve equilibrium CO2 dissolution in the electrolyte phase, the solution was quies- cent during the cyclic voltammetry experiments. The gray line is parabolic and intended only to guide the eye.


[Shaughnessy, C.I.; Sconyers, D.; Kerr, T.; Lee, H-J.; Subramaniam, B.*; Leonard, K.C.* and Blakemore, J.D* “Intensified Electrocatalytic CO2 Conversion in Pressure‐Tunable CO2‐Expanded Electrolytes.” ChemSusChem Vol. 12, Issue 16, pp. 3761-3768 (2019).



      Example of electrocatalyst characterization for the Hydrogen Evolution Reaction








Electrochemical characterization of FeS2 discs, wires, and cubes in 0.1 M pH 7 phosphate buffer solution (PBS) for the hydrogen evolution reaction. (a) Experimental linear sweep voltammograms at 1 mV/s (solid lines) for the champion FeS2 discs, wires, cubes coated on glassy carbon along with a bare Pt electrode, and a bare glassy carbon electrode. Also shown are the corresponding best-fit single-electron Butler−Volmer equations (dashed lines) for each electrode.

[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)]



Example of electrocatalyst characterization for the Oxygen Evolution Reaction







Rotating disk cyclic voltammograms of microwave-assisted electrodeposited (MW-E) and drop-cast (MW-D) nanoamorphous Ni0.8:Fe0.2 oxide on a glassy carbon electrode at 10 mV s-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).]