A Ring-Disk Study of the Competition between Anodic Oxygen-Transfer and Dioxygen-Evolution Reactions

Area of Science:

• Electrochemistry
• Surface Science
• Chemical Kinetics

Background:

• Dimethyl sulfoxide (DMSO) oxidation is a complex electrochemical process.
• Understanding competing reaction pathways is crucial for electrochemical applications.
• Anodic reactions involving water discharge and oxygen evolution require detailed investigation.

Purpose of the Study:

• To investigate the competition between anodic O-transfer and O(2)(aq)-evolution during DMSO oxidation.
• To identify the common reaction precursor for these competing pathways.
• To evaluate the reliability of voltammetric techniques for deconvoluting simultaneous electrode processes.

Main Methods:

• Utilized rotated ring-disk electrode voltammetry to study DMSO oxidation.
• Analyzed electrochemical data to determine reaction kinetics and mechanisms.
• Developed and tested a mathematical model for simultaneous electrochemical reactions.

Main Results:

• Evidence supports a common precursor, the adsorbed OH radical, for O-transfer and O(2)(aq)-evolution.
• Increased O-transfer reaction flux inversely correlates with the rate of O(2)(aq) evolution.
• Difference voltammetry and hydrodynamically modulated voltammetry show limitations in deconvoluting these concurrent reactions.

Conclusions:

• The adsorbed OH radical, formed by water discharge, is the key intermediate in competing DMSO oxidation pathways.
• The observed competition necessitates careful consideration when interpreting voltammetric data for similar systems.
• A developed mathematical model accurately describes the total current from these simultaneous processes, validated by experimental data.