(671h) Hydrodynamics Change Tafel Slopes in Electrochemical CO2 Reduction on Copper

As we continue to explore electrochemical routes for a variety of reactions, most lab-scale systems are variations on the same cell design, namely an “H-cell”, which is functionally two beakers connected via a separator or membrane. While this serves well for preliminary exploration of electrochemical reactions, it remains impractical for both industrial scale-up as well as automated screening of reaction conditions. In particular, the electrolyte hydrodynamics in electrochemical CO2 reduction (CO2R) systems is an insufficiently investigated area of research that has broad implications on catalyst activity and selectivity. In this talk, I will focus on the chemical mechanism implications that result from a range of electrolyte hydrodynamics controlled via electrolyte recirculation systems. We find that increased convection 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 CO2R 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.