Electroreduction of CO₂ and Quantification in New Transition-Metal-Based Deep Eutectic Solvents Using Single-Atom Ag...

Deep eutectic solvents (DESs) are efficient media for CO₂ capture, and an electroreduction process using the deterministic surface of single-atom electrocatalysts is a facile way to screen gas absorption capacities of novel DESs. Using newly prepared transition-metal-based DESs indexed as TDESs, the interfacial mechanism, detection, quantification, and coordination modes of CO₂ were determined for the first time. The CO₂ has a minimum detection time of 300 s, whereas 500 s of continous ambient CO₂ saturation provided ZnCl₂/ethanolamine (EA) (1:4) and CoCl₂/EA (1:4) TDESs with a maximum CO₂ absorption capacity of 0.2259 and 0.1440 mmol/L, respectively. The results indicated that CO₂ coordination modes of η¹ (C) and η² (O, O) with Zn in ZnCl₂/EA (1:4) TDESs are conceivable. We found that the transition metals in TDESs form an interface at the compact layer of the electrocatalyst, while CO₂ ^•-/CO₂ reside in the diffuse layer. These findings are important because they provide reliable inferences about interfacial phenomena for facile screening of CO₂ capture capacity of DESs or other green solvents.