Cation effects in electrochemical CO₂ reduction

Electrochemical CO₂ reduction (CO₂R) provides a pathway toward the sustainable production of chemicals. Recent catalyst- and system-level innovations have enabled electrosynthesis of multi-carbon products at practical productivities (>200 mA cm⁻²) and single-pass CO₂ conversion efficiencies (>80 %). However, practical CO₂R requires high single product selectivity (>85 %) without compromising readily-achieved metrics. Coupling these metrics in a single system warrants clear understanding of the electrical double layer at the catalyst–electrolyte interface. Combining selective catalysts with cation effects can effectively tune CO₂R kinetics at the catalyst–electrolyte interface. Here we overview recent progress and current understanding on the sophisticated nature of the cation effects and underscore critical parameters that influence cation distributions in the electrical double layer. We highlight the emerging characterization and computational approaches to elucidate cation effects on CO₂R. Finally, we emphasize research directions through which cation effects could be coupled with other micro-reaction environment tuning strategies for further selectivity and efficiency improvements.