Rotating ring-disc electrode method: Assessing transient chemical interaction of redox intermediate with electrode surface.

[Display omitted] The collection efficiency (N eff) of rotating ring-disc electrode is diffusion- and reaction-dependent. The collection process at ring electrode can be used to assess the transient binding of redox intermediate with electrode surface, more specifically, the intermediate-electrode interaction within the double layer. The ability to capture the behavior of redox intermediate will facilitate understanding of electrocatalytic process on electrode surface • Revealed the fundamental dependence of the collection efficiency on diffusion. • Established a new affinity index for redox intermediate-electrode interaction. • Formulated an analytical solution to surface kinetics with practical application. • Benefits and limitations of the steady-state analytical model discussed in depth. The interaction of redox intermediate with electrode surface is a seldom explored realm yet an interesting facet in electrocatalysis. This work demonstrates, for the first time, the analytical use of rotating ring-disc electrode to measure the intermediate-electrode interaction in a double-layer model. Our solution to the electro-kinetics reveals the intrinsic dependence of the collection efficiency on the extent of intermediate-electrode interaction, as validated by two redox couples typical of 'outer-sphere' (Fe(CN) 6 3–/Fe(CN) 6 4–) and 'inner-sphere' (dopamine/ dopaminoquinone) nature on Pt and Au electrodes. The experiment with the model systems validates the applicability of the theory, allowing semi-quantitative comparison of the transient binding with different electrode surfaces, while the limitations of the method are also discussed at insightful depth. As a proxy to better understand redox intermediates, the method is set to provide a practical tool and an inspiration to expand the analytical toolset for materials research. [ABSTRACT FROM AUTHOR]