(622g) Effect of Cathodic Potential in Electrochemical CO2 Reduction

In this presentation, we will discuss the critical role of cathodic-potential in modulating the selectivity, activity and even stability of electroreduction of CO₂ (CO₂R). We will first introduce the potential-dependent selectivity in Cu-based CO₍₂₎R, originating from a combination of pH-effect, kinetics of different *CO activation pathways, local field effect, and CO coverage effects, etc. By carefully elucidating the intricate interplays among these effects, we could leverage cathodic potential as an effective lever to steer the CO₍₂₎R selectivity towards multi-carbon-products. Additionally, we will introduce how cathodic-potential plays affects the CO₂R stability, particularly in preventing the electrolyte flooding. Specifically, we observed that CO₂R kinetic-curves typically enter the mixed-control-region at approximately > 0.75 V, and then quickly transition to the CO₂ mass transport-limited-region, regardless of the type of GDE used or the current density achieved. This suggests that GDE flooding is closely associated with the cathodic-potential. Inspired by this understanding, we demonstrate that an intrinsically more active catalyst capable of sustaining a sufficient CO₂R current at a low cathodic potential before entering the mixed-controlled region can lead to significantly enhanced CO₂R stability and improved energy efficiency.

If time allows, we will also briefly introduce two non-Cu-based systems:

(1) The potential-dependent structural-evolution of Pd-based catalysts during CO₂R to formate. We found that by manipulating the valence state of Pd, one could substantially extend the cathodic-potential window for stabilizing the desired a-Pd phase, achieving robust and efficient CO₂-to-formate conversion on Pd-catalysts.

(2) The potential-dependent CO₂-to-methanol production on Co-Phthalocyanine. Here, the cathodic-potential is critical in inducing the structural-distortion of the Co-N₄ plane, influencing the *CO binding mode and strength, which leads to the selectivity change from CO to methanol on Co-Phthalocyanine.

Overall, we wish to underscore the importance of considering cathodic potential as a crucial parameter in the design and optimization of electrochemical CO₂R systems.