Hydrodynamics Change Tafel Slopes in Electrochemical CO₂ Reduction on Copper

Abstract

The hydrodynamics of electrochemical CO 2 reduction (CO 2 R) systems is an insufficiently investigated area of research that has broad implications on catalyst activity and selectivity. While most previous reports are limited to laminar and CO 2 -sparged systems, herein we address a wide range of hydrodynamics via electrolyte recirculation systems. We find that increased hydrodynamics at the electrode surface results directly in changes to the ethylene and methane Tafel slopes, demonstrating that mass transport is on equal footing with catalyst active sites in determining reaction mechanisms and the ensuing product distribution. Mass transport is traditionally considered to be in the purview of systems-level engineering, yet the present work shows that CO 2 R mechanistic work must be considered in the context of the mass transport conditions. We extend our analysis to organic coatings, demonstrating that the films shield the active sites from variability in hydrodynamics and increase the residence time of CO so that it may be further reduced to desirable products.

Promoting CO2 Electroreduction to Multi‐Carbon Products by Hydrophobicity‐Induced Electro‐Kinetic Retardation

“…[ 9] For instance, using perfluorinated sulfonic acid (PFSA) ionomers can enhance the C 2 + product selectivity/activity. [ 9,18,19] However, with fast electro-kinetics, the C 2 + -formation-determining *CO intermediate would be rapidly formed and consumed, either by desorption or further reduction at the surface, [20] and its residence on the surface is likely to be shortened (Figure 1a). Without the presence of high alkalinity -a condition that brings unacceptable energy cost, [3,[21][22][23] this can greatly reduce the probability of CÀ C coupling.…”

Dynamic hydrogen bubbling templated AgSn@SnOx electrocatalyst for selective electrochemical CO2 reduction: adjusting the binding energy of the HCOO* intermediate

“…3d). 31,32 The results demonstrated the coincidence between the kinetic findings of Tafel analysis and the adsorption affinity of HO − anions on the different surfaces, indicating the better performance of AgSn@SnO x (30 s) relative to the other samples, with the lowest adsorption energy of 0.015 V. These findings are attributed to the in situ formation of oxygen vacancies under the used cathodic conditions ( i.e. , partial reduction of the oxide layer).…”

Tafel Slope Plot as a Tool to Analyze Electrocatalytic Reactions

“…The observed effect of loading could be due to the conductivity within the catalyst layer or pores that can result in local potential drops or to reactant and product mass transport limitations within the catalyst layer ,− resulting in apparent Tafel slope values. Moreover, differences in gas bubble coverage can exist, which is important for the accessible surface area during the measurement. , Therefore, it is advisable to use thin layers with relatively high reactant concentrations under high-mass-transport conditions. − An overview of the practical considerations for Tafel slope analysis with a Tafel slope plot is given in Figure .…”