(392g) Resolving the Role of the Interfacial Electrolyte Environment in Electrochemical CO2 Reduction

To allay the impacts of climate change, the decarbonization of the global economy is a scientific challenge of great urgency. Electrochemical CO₂ reduction technologies, which use renewable electricity to power the conversion of abundant feedstocks (i.e.,water, air, and carbon dioxide (CO₂)) to value added products, present a promising pathway to decarbonize chemical manufacturing. Unfortunately, these devices are often challenged by poor efficiency and selectivity when operating at industrially relevant rates. Recent experimental studies from our group have demonstrated the capability to tailor and control the interfacial electrolyte environment (electrolyte cation, local pH, CO₂ availability, and water activity) to enhance the activity, selectivity, and durability of CO₂ electrolyzers towards value-added products. However, the fundamental physics that drive these enhancements have been poorly understood.

In this talk, I will explore how multi-scale continuum theory can be used to rationalize and guide the design of tailored electrolyte environments for CO₂ reduction. I will discuss our group’s recent efforts to bridge mesoscale mass transport, nanoscale double layer structure, and quantum-mechanical electron transfer to reveal the origin through which the local electrolyte environment dictates CO₂ reduction performance both in flow-cells and membrane-electrode assemblies. Our model quantitatively predicts enhancements in CO₂ reduction performance with differing electrolyte cations by coupling modified Poisson-Nernst-Planck approaches with coupled-ion-electron transfer theory. Furthermore, I will discuss how a complete understanding of electron tunneling and CO₂transport across multiple scales is required to accurately determine the rate of CO₂ reduction. While applied here for CO₂ reduction, the developed theory presents a significant advance in understanding the role of the double layer in electrocatalysis and is relevant for the myriad of electrochemical reactions where control of the interfacial electrolyte is useful.