Bayesian data analysis reveals no preference for cardinal Tafel slopes in CO2 reduction electrocatalysis

Abstract

The Tafel slope is a key parameter often quoted to characterize the efficacy of an electrochemical catalyst. In this paper, we develop a Bayesian data analysis approach to estimate the Tafel slope from experimentally-measured current-voltage data. Our approach obviates the human intervention required by current literature practice for Tafel estimation, and provides robust, distributional uncertainty estimates. Using synthetic data, we illustrate how data insufficiency can unknowingly influence current fitting approaches, and how our approach allays these concerns. We apply our approach to conduct a comprehensive re-analysis of data from the CO2 reduction literature. This analysis reveals no systematic preference for Tafel slopes to cluster around certain "cardinal values” (e.g. 60 or 120 mV/decade). We hypothesize several plausible physical explanations for this observation, and discuss the implications of our finding for mechanistic analysis in electrochemical kinetic investigations.

Using voltammetry augmented with physics-based modeling and Bayesian hypothesis testing to identify analytes in electrolyte solutions

“…35 With the voltammetric labeling presented in this work, the results for each compound can be combined to estimate the overall makeup, which, in turn, can be used to inform subsequent studies that may involve different techniques. Bayesian methods are also a powerful framework to evaluate physics-informed models across multiple disciplines, [35][36][37][38] including electrochemistry; [39][40][41][42][43] for example, researchers have shown that parameters for electrochemical reactions can be reliably estimated using sensitive voltammetric techniques, mathematical optimization, and Bayesian inference. 44 However, to the best of our knowledge, Bayesian inference has not been used for voltammetric labeling.…”

High Performance 3D Self‐Supporting Cu−Bi Aerogels for Electrocatalytic Reduction of CO2 to Formate

“…The relatively low Tafel value may be attributed to the catalyst exposing more of the specific index crystal plane. According to literature reports, the rate‐determining step of the CO 2 RR reaction is that CO 2 obtains the first electron to generate CO 2 * − anion radicals when the Tafel slope is 118 mV dec −1 [55] . It is worth noting that the Tafel value of the prepared Cu−Bi electrocatalyst in this study was higher than 118 mV dec −1 .…”

“…According to literature reports, the ratedetermining step of the CO 2 RR reaction is that CO 2 obtains the first electron to generate CO 2 * À anion radicals when the Tafel slope is 118 mV dec À 1 . [55] It is worth noting that the Tafel value of the prepared CuÀ Bi electrocatalyst in this study was higher than 118 mV dec À 1 . The specific mechanism for the reduction of CO 2 to HCOOH is described by Equations (5-9), which are depicted in Figure 5d.…”

Using pH dependence to understand mechanisms in electrochemical CO reduction

“…The three contributions to the effect of the overpotential on ∆𝐺 ‡ in equation 4 are captured by the transfer coefficient 𝛼 = 𝑁 H + 𝛾 + 𝛽. 𝛼, therefore, incorporates the net potential dependence and defines the measured Tafel slopes as While NH is an integer, both 𝛾 and 𝛽 can add up continuously along the reaction pathway. Hence, 𝛼 is a smooth function meaning that the resulting Tafel slopes are not limited to any characteristic ("cardinal") values such as 60 or 120mV/dec, as has also been highlighted in a recent statistical study on experimentally determined Tafel slopes 51 .…”