An Extension to the Analytical Evaluation of the Oxygen Reduction Reaction Based On the Electrokinetics On a Rotating Ring-Disk Electrode.

The use of rotating ring-disk electrodes has become a general practice for evaluating the activity of the oxygen reduction reaction (ORR) performed with electrocatalysts. This technique typically employs simple equations based on the charge/mass balance to calculate the average number of electrons transferred and the percentage of peroxide production. However, the underlying mechanistic assumptions of this analysis and the uncertainty involved when considering the catalytic decomposition of HO₂⁻ have not been well elucidated. This work demonstrates through electrokinetic derivations that the conventional formalism presumes a stepwise ORR pathway and four reaction parameters in total are provided for indexing ORR activity. Furthermore, we provide a method of current density deconvolution to separate the individual reaction components and exemplify its use for Tafel analysis. Finally, we provide analytical solutions to the reaction parameters for the ORR when heterogeneous HO₂⁻ decomposition is involved. [ABSTRACT FROM AUTHOR]