Probing dissolved CO2(aq) in aqueous solutions for CO2 electro-reduction and storage

Abstract

CO2 dissolved in aqueous solutions is of wide ranging importance from CO2 capture, storage and photo-/electro-reduction in the fight against global warming, to CO2 analysis in various liquids including natural waterbodies and consumer drinking products. Here we developed micro-scale infrared (IR) spectroscopy for in-situ dynamic monitoring and quantitating CO2(aq) in aqueous solutions with high time resolutions under various conditions including CO2 gas bubbling and high pressures. The quantized CO2(g) rotational state transitions were observed to quench when dissolved in water to form CO2(aq) solvated by water molecules, accompanied by increased H2O IR absorption. An accurate CO2 molar extinction coefficient ε was derived for in-situ CO2(aq) quantification up to 58 atm. For the first time, we directly measured CO2(aq) concentrations in electrolytes under CO2(g) bubbling and high pressure conditions. In KHCO3 electrolytes with CO2(aq) > ~ 1 M, CO2 electroreduction (CO2RR) to formate reaches > 98% Faradaic efficiencies on copper (Cu2O/Cu) based electrocatalyst. Further, we probed CO2 dissolution/desolvation kinetics important to energy and environmental applications dynamically, revealing large hysteresis and ultra-slow reversal of CO2(aq) supersaturation in water, with implications to CO2 capture, storage and supersaturation phenomena in natural water bodies.

Addressing the Effectiveness and Molecular Mechanism of the Catalytic CO2 Hydration in Aqueous Solutions by Nickel Nanoparticles

“…), 57,58 our plateau value (∼1000 ppm) is in the range of those reported in literature at the same pH values. 58 The initial boost in the dissolved CO 2 (Figure 3) with NiNPs, together with the variation of hydronium concentration (Figure 2b) suggest the co-presence of multiple mechanisms when NiNPs are present in the solution, which are discussed below.…”

Unlocking direct CO2 electrolysis to C3 products via electrolyte supersaturation

“…4e, Supplementary Note 22). 26 Importantly, we identified that [CO2] ≥ 0.2 mol L -1 unlocks the C1-C2 coupling reaction to form C3 products, which emphasizes the benefit of performing the CO2RR in the supersaturated electrolyte. 33 To discriminate the role of CO2, we systematically examined the CO2RR performance of CO2-10-Cu94Ag6 with and without supersaturation as well as the influence of the current density for the codeposition of the alloy (Supplementary Fig.…”

“…18, Supplementary Note 16). 26 Electrochemical activation was carried out before the reaction to remove the surface oxides (Supplementary Fig. 19, Supplementary Note 17).…”