Abstract
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.