(670h) Resolving Local Microenvironments and Fluxes in Electrochemical CO2 Reduction Using Continuum Modeling

Electrochemical carbon dioxide reduction (CO₂R), which uses renewable electricity to power the conversion of abundant feedstocks (i.e., water, air, and CO₂) to value-added products, present a promising pathway to decarbonize the manufacturing of various chemical commodities. Unfortunately, these devices are challenged by poor efficiency and selectivity when operating at industrially relevant rates. Continuum modeling enables the simulation of transport and catalysis in these systems to resolve the effects of mass transfer and the local catalyst microenvironment on reaction kinetics. Accordingly, recent advances in multi-scale modeling have resolved variations in species activities and fluxes from the mesoscale (e.g., the mass transport boundary layer) to the nanoscale (e.g., the electrical double layer) to better understand and optimize selectivity in CO₂R systems. Unfortunately, many recent models are not well validated to experimental data, and there has yet to be a model capable of both reproducing partial current density experimental data and rationalizing experimentally observed reaction phenomena such as the effect of the electrolyte cation on CO₂R activity.

In this talk, I will explore how continuum modeling can be used to understand the performance of CO₂ electrolyzers. I will discuss our group’s efforts to determine how mass transport and double layer structure dictate activity and selectivity in CO₂R. We couple the developed model with covariance matrix adaptation to extract kinetic parameters that match experimentally observed partial current densities of CO₂R over an Ag catalyst with quantified uncertainty. This analysis demonstrates the extent to which mass transport impacts observed kinetic parameters. Through careful development of a multi-scale model, transport to the catalytic active site in electrochemical CO₂R is described and unexplained phenomena, such as the effect of electrolyte cations, can be rationalized. While applied here for electrochemical CO₂R, the developed techniques are relevant for all electrochemical reactions where an understanding of transport processes is critical.