Mass‐Transport‐Corrected Transfer Coefficients: A Fully General Approach

Abstract

The transfer coefficient (or, equivalently, the Tafel slope) is an experimentally measurable parameter defined as the change in the logarithm of the current density as a function of the applied potential, where the current density has been corrected (j corr) for changes in the concentration of the reagent at the interface. For some electrode geometries (such as the rotating disc or a micro hemispherical electrode) where the electroactive interface is uniformly accessible and the mass-transport is at steadystate, these changes in concentration can be corrected for analytically. Correcting for the depletion of the reagent significantly increases the range over which Tafel analysis can be used to accurately yield information regarding the electrontransfer process. The important question arises, therefore, for non-uniformly accessible electrodes or for a system not at steady state, such as often encountered with disc electrodes, how can the experimentally measured electrochemical flux be rigorously corrected for to account for the changes in the surface concentration of the reagent? This work presents a simple simulation technique that allows the voltammetry of a disc to be "mass-transport"-corrected without recourse to the use of analytical approximations.

A simple and effective method for the accurate extraction of kinetic parameters using differential Tafel plots

“…Although advantageous, this approach is adopted by very few research teams 17 , 33 – 35 . The sensitivity of DTP towards different electrode geometry, non-uniformly accessible electrodes and unsteady processes have been extensively studied 4 , 33 , 36 . In this article we focus on two critical ratios, the ratio of exchange current to limiting current ( ) and ratio of exchange current to double layer charging current ( ).…”

Mass Transport Influence in the SO2 Oxidation Reaction on Au Electrodes

“…Tafel analysis can be influenced by mass transport, [60–62] since the reactant species concentration is normally different on the electrode surface and in the solution bulk. When the kinetically‐controlled currents from Figure 4A are at least 19 % of the j l im in Figure 1, some significant deviation can be observed [60,61] . If the kinetic current is around 10 %, the deviation is expected to be around 1.4 %, as suggested by Compton's group [61] .…”

“…When the kinetically-controlled currents from Figure 4A are at least 19 % of the j lim in Figure 1, some significant deviation can be observed. [60,61] If the kinetic current is around 10 %, the deviation is expected to be around 1.4 %, as suggested by Compton's group. [61] In the present case, the mass-transport corrected and the non-corrected Tafel plots were compared (Figure S5), however, the differences in the Tafel-slope were below 0.5 %, so it can be considered experimental deviation.…”

“…[60,61] If the kinetic current is around 10 %, the deviation is expected to be around 1.4 %, as suggested by Compton's group. [61] In the present case, the mass-transport corrected and the non-corrected Tafel plots were compared (Figure S5), however, the differences in the Tafel-slope were below 0.5 %, so it can be considered experimental deviation. As such, Tafel analysis were conducted without these corrections.…”

Discovering Electrochemistry with an Electrochemistry‐Informed Neural Network (ECINN)

“…The novel contribution of these experiments and analysis is threefold. First, ECINN‐BV is the first method, to the best of the authors’ knowledge, to seamlessly incorporate mass transport with the BV equation to automate the discovery of the global optimal $${\alpha }$$ and/or $${\beta }$$ from the whole voltammograms, such that the elaborate electrochemical practice of mass‐transport corrected fluxes, [20] identifying parts of voltammograms least affected by mass transport, [21] linear transformation [22] or Taylor expansion of the BV equation [23] and differentiating the current‐potential curves [24] are relatively inefficient and even unnecessary. Second, it allows accurate estimation of the electrochemical rate constant without assumptions about transfer coefficients [25] or electrochemical reversibility [26] .…”