Electroreduction of CO2 (CO2RR) is a potentially carbon-neutral method to convert a fraction of the excess CO2 emissions into carbon-based chemicals such as carbon monoxide and ethylene. Despite research breakthroughs, significant improvements in electrochemical performance are still needed for economic feasibility at scale. This talk will cover multiple system-level approaches that can be further explored to intensify the electrochemical performance of a flow electrolyzer for CO2RR. First, we focus on the role of electrolyte composition in the mechanism of CO2RR to CO. Insights obtained from electrochemical measurements and characterizations will be used to – (i) explain the effects of electrolyte identity, concentration, and pH on the rate-determining step, CO partial current density (jCO), and CO Faradaic Efficiency (FECO) and (ii) guide the choice/design of a rational electrolyte for CO2RR. Second, we cover the systematic process optimization of CO2RR to CO resulting in state-of-the-art electrochemical performance under ambient conditions: jCO exceeding 850 mA/cm2 with a FECO of 98% at a cell potential (Vcell) of -3 V for a full cell energy efficiency (EECO) exceeding 40% at a CO2 conversion per pass exceeding 35%. We will also discuss the process intensification of CO2RR to CO by – (i) operating at elevated temperatures and pressures or (ii) using magnetic fields to enhance mass transfer. Third, we discuss establishing system design rules (SDRs) in the form of quantitative/qualitative functional property relationships between system parameters (e.g.: pH, electrolyte flow rate) and system performance (e.g.: cathode overpotentials, jCO) to help in rational system design for CO2RR to CO. Kinetic modeling in combination with machine learning-based models will be used to provide theoretical insights into the SDRs. Finally, we evaluate the technoeconomic feasibility of operating the CO2RR process in a carbon-neutral manner and identify a range of operating conditions using a generalized system-level technoeconomic and life-cycle assessment framework. We will conclude this talk by discussing the outlook for CO2RR and how the approaches discussed here can be applied to various other electrochemical reactions/processes.

System-level approaches for intensifying the CO2 electrolysis process: From reaction chemistry to process development

ACS Fall 2021

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