Graduate Student Zahed Ghelichkhah

"Mechanistic Modelling of Electrochemical Processes on Gold using Electrochemical Impedance Spectroscopy"

Electrochemical impedance spectroscopy is one of the most powerful techniques in electrochemistry. It is a nondestructive method that can be utilized in a variety of applications, including sensors, electrodeposition, corrosion, fuel cells, batteries, and modeling of electrochemical reactions.[1] For many years, researchers have studied the electrochemistry of gold as a model system in acidic and basic solutions, and its behavior in various regimes of applied potential —double-layer region, adsorption of ions and oxygen in the pre-oxide region, and formation of oxide at higher potentials— have been the subject of disagreement among scientists in the area. We have developed mechanistic impedance-based models to explore the electrochemistry of gold in sulfuric acid and potassium hydroxide solutions in these potential regions, and also at cathodic potentials where the hydrogen evolution reaction occurs. We used Point Defect Model to describe the mechanism of the formation of gold oxide.[2] The Anion-Catalyzed Active Dissolution Model was used to describe the potential dependent adsorption of bisulfate, sulfate and oxygen on the gold surface.[3] And lastly, an impedance-based model based on the Volmer-Heyrovsky-Tafel mechanism was developed and optimized on experimental potentiodynamic polarization and impedance data to describe the hydrogen-evolution region. [4]

[1]. R. Srinivasan, F. Fasmin, An Introduction to Electrochemical impedance Spectroscopy
CRC Press, Boca Raton, FL (2021), 10.1201/9781003127932.
[2]. Z. Ghelichkhah, G. S. Ferguson, D. D. Macdonald, S. Sharifi-Asl, Point Defect Model Description of the Formation of Anodic Gold Oxide in H 2 SO 4 Solution, J. Electrochem. Soc.168
(2021) 041506.
[3]. Z. Ghelichkhah, R. Srinivasan, D. D. Macdonald, G. S. Ferguson, Anion-catalyzed active dissolution model for the electrochemical adsorption of bisulfate, sulfate, and oxygen on gold in H2SO4 solution, Electrochim. Acta, 439 (2023)141515.
[4]. Z. Ghelichkhah, D. D. Macdonald, G. S. Ferguson, Mechanistic Analysis of Hydrogen Evolution Reaction on Stationary Gold Polycrystalline Electrodes in H2SO4 Solutions, J. Electrochem. Soc. (Under review)