Probing dissolved CO(2)(aq) in aqueous solutions for CO(2) electroreduction and storage

CO(2) dissolved in aqueous solutions CO(2)(aq) is important to CO(2) capture, storage, photo-/electroreduction in the fight against global warming and to CO(2) analysis in drinks. Here, we developed microscale infrared (IR) spectroscopy for in situ dynamic quantitating CO(2)(aq). The quantized CO(2)(g) rotational state transitions were observed to quench for CO(2)(aq), accompanied by increased H(2)O IR absorption. An accurate CO(2) molar extinction coefficient ε was derived for in situ CO(2)(aq) quantification up to 58 atm. We directly measured CO(2)(aq) concentrations in electrolytes under CO(2)(g) bubbling and high-pressure conditions with high spectral and time resolutions. In KHCO(3) electrolytes with CO(2)(aq) > ~1 M, CO(2) electroreduction (CO(2)RR) to formate reached >98% Faradaic efficiencies on copper (Cu(2)O/Cu)–based electrocatalyst. Furthermore, CO(2) dissolution/desolvation kinetics showed large hysteresis and ultraslow reversal of CO(2)(aq) supersaturation in aqueous systems, with implications to CO(2) capture, storage, and supersaturation phenomena in natural water bodies.