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

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.