High frequency faradaic rectification voltammetry at microelectrodes

Area of Science:

• Electrochemistry
• Analytical Chemistry
• Physical Chemistry

Background:

• Faradaic rectification (FR) is a technique used to study electrochemical processes.
• Accurate determination of kinetic parameters like standard rate constants and electron-transfer coefficients is crucial for understanding charge transfer.
• Traditional methods often require knowledge of electrode impedance, which can be challenging for microelectrodes.

Purpose of the Study:

• To describe an experimental setup for faradaic rectification measurements at potential-controlled, micrometer-sized electrodes.
• To introduce a novel data analysis method for determining kinetic parameters of fast charge transfer processes.
• To validate the new method using well-characterized redox couples on different microelectrode systems.

Main Methods:

• Development of an experimental setup for potential-controlled faradaic rectification at microelectrodes.
• Proposal of a new data analysis method based on the frequency dependence of FR voltammogram shape (peak width and height ratios).
• Application of the method to determine heterogeneous electron transfer kinetics for Fe(CN)6(3-/4-), Ru(NH3)6(2+/3+), and ferrocene/ferrocinium redox couples.

Main Results:

• The proposed method successfully determines the standard rate constant and electron-transfer coefficient without prior knowledge of microelectrode impedance.
• The frequency dependence of FR voltammogram shape proved to be a reliable indicator of kinetic parameters.
• Accurate kinetic data were obtained for fast charge transfer processes at platinum and gold microelectrodes.

Conclusions:

• A robust and simplified method for analyzing faradaic rectification data at microelectrodes has been established.
• This technique facilitates the study of fast heterogeneous electron transfer kinetics, particularly for systems where impedance is difficult to measure.
• The findings contribute to advancements in electrochemical analysis and the characterization of interfacial charge transfer.