System-Level Approaches for Intensifying the CO2 Electrolysis Process

Electroreduction of CO₂ (CO₂RR) is a potentially carbon-neutral method to utilize a fraction of the excess CO₂ emissions. CO₂RR can convert CO₂ into various carbon-based chemicals such as methanol, formic acid, ethylene, and carbon monoxide. Significant research efforts by academia and industry have resulted in various energy-efficient cell configurations and active/selective catalysts for CO₂RR, however, significant electrochemical performance improvements 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 on Ag nanoparticles (NPs). Insights obtained from polarization curves, Tafel slopes, Pourbaix diagrams, onset potentials, and electrochemical impedance spectroscopy will be used to explain the effects of electrolyte identity, concentration, and pH on the rate determining step.

Next, we cover the systematic process optimization of CO₂RR to CO on Ag NPs resulting in state-of-the-art electrochemical performance: CO partial current density (j_CO) exceeding 850 mA/cm² with a CO Faradaic efficiency (FE_CO) of 98% at a cell potential (V_cell) of -3 V corresponding to a full cell energy efficiency for CO production (EE_CO) exceeding 40% for a conversion per pass of CO₂ to CO exceeding 35%.

Finally, we discuss establishing quantitative/qualitative functional property relationships between system parameters (e.g.: pH, electrolyte flow rate) and system performance (e.g.: cathode overpotentials, j_CO) to help in rational system design for CO₂RR to CO on Ag NPs. We also briefly discuss the effect of electrolyte composition on performance stability over time for CO₂RR to CO on Ag NPs.