Electroreduction of CO(2) and Quantification in New Transition-Metal-Based Deep Eutectic Solvents Using Single-Atom Ag Electrocatalyst

[Image: see text] Deep eutectic solvents (DESs) are efficient media for CO(2) 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 CO(2) were determined for the first time. The CO(2) has a minimum detection time of 300 s, whereas 500 s of continous ambient CO(2) saturation provided ZnCl(2)/ethanolamine (EA) (1:4) and CoCl(2)/EA (1:4) TDESs with a maximum CO(2) absorption capacity of 0.2259 and 0.1440 mmol/L, respectively. The results indicated that CO(2) coordination modes of η(1) (C) and η(2) (O, O) with Zn in ZnCl(2)/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 CO(2)(•–)/CO(2) reside in the diffuse layer. These findings are important because they provide reliable inferences about interfacial phenomena for facile screening of CO(2) capture capacity of DESs or other green solvents.