In Situ Electrosynthesis of Peroxydicarbonate Anion in Ionic Liquid Media Using Carbon Dioxide/Superoxide System

Abstract

Climate engineering solutions with emphasis on CO2 removal remain a global open challenge to balancing atmospheric CO2 equilibrium levels. As a result, warnings of impending climate disasters are growing every day in urgency. Beyond ordinary CO2 removal through natural CO2 sinks such as oceans and forest vegetation, direct CO2 conversion into valuable intermediaries is necessary. Here, a direct electrosynthesis of the peroxydicarbonate anion (C2O6 2–) was investigated by the reaction of CO2 with the superoxide ion (O2 · –), electrochemically generated from O2 reduction in bis­(trifluoromethylsulfonyl)­imide [TFSI–] anion derived ionic liquid (IL) media. This is the first time that the IL media were employed successfully for CO2 conversion into C2O6 2–. Moreover, the charge transfer coefficient for the O2 · – generation process in the ILs was less than 0.5, indicating that the process was irreversible. Voltammetry experiments coupled with global electrophilicity index analysis revealed that, when CO2/O2 was contacted simultaneously in the IL medium, O2 · – was generated in situ first at a potential of approximately −1.0 V. Also, CO2 was more susceptible to attack by O2 · – before any possible interaction with the IL except for [PMIm+]­[TFSI–]. This was because CO2 has a higher global electrophilicity index (ωCO2 = 0.489 eV) than those for the [EDMPAmm+]­[TFSI–] and [MOEMMor+]­[TFSI–]. By further COSMO-RS modeling, CO2 absorption was proven feasible at the COSMO-surface of the [TFSI–] IL-anion where the charge densities were σ = −1.100 and 1.1097 e/nm2. Therefore, the susceptible competitiveness of either IL cations or CO2 to the nucleophilic effects of O2 · – was a function of their positive character as estimated by their electrophilicity indices. As determined by experimental attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and DFT-FTIR computation, the reaction yielded C2O6 2– in the ILs. Consequently, the presence of O=O symmetric stretching FTIR vibrational mode at ∼844 cm–1 coupled with the disappearance of the oxidative cyclic voltammetry waves when sparging CO2 and O2 confirmed the presence of C2O6 2–. Moreover, based on DFT/B3LYP/6-31G, pure C2O6 2– has symmetric O=O stretching at ∼805 and ∼844 cm–1 when it is in association with the IL-cation. This was the first spectroscopic observation of C2O6 2– in ILs, and the O=O symmetric stretching vibration has peculiarity for identifying C2O6 2– in ILs. This will open new doors to utilize CO2 in industrial applications with the aid of reactive oxygen species.

Electroreduction of CO2 and Quantification in New Transition-Metal-Based Deep Eutectic Solvents Using Single-Atom Ag Electrocatalyst

“…Global carbon dioxide (CO 2 ) concentrations have reached ∼420 ppm, the highest level since precise measurements began 63 years ago. , As evidence of the link between high CO 2 emissions and global warming grows, it becomes important to develop simple and sustainable CO 2 sequestration strategies. − The need for long-term CO 2 sequestration cannot be overstated because it can provide CO 2 as a cheap C-1 feedstock for the production of low molecular weight hydrocarbons, platform chemicals, − sustainable energy through electroreduction, , and energy storage. , Therefore, the facile measurement of CO 2 concentration in green solvents is essential to support the mitigation of anthropogenic CO 2 emissions and industrial CO 2 utilization.…”

Bifunctional Ionic Deep Eutectic Electrolytes for CO2 Electroreduction

“…The viscosity of DEACl–DEA ionic DESs was determined using a DV-II + Pro Extra Brookfield viscometer at 25 °C for different mole ratios similar to the previous report . Typically, 10 mL of DEACl–DEA DES was poured into a cylindrical container immersed with the spindle.…”

“…Using the graphical user interface of the Turbomole program version 4.0., the cut-out plane of DEACl–DEA DESs was constructed and optimized based on the Hartree–Fock level of theory and a def-SV (P) basis set. Then, utilizing density functional theory/Beck-Perdew-86 functional and zeta valence potential (def-TZVP) basis set, a single-point calculation for the ionic DESs cut–off plane was carried out. Finally, to examine CO 2 interaction with the ionic DEACl–DEA DESs, a conductor-like screening model for realistic solvents (COSMO-RS) was employed based on BP-TZVP-C30-1401-CTD parameterization in COSMOthermX19 software. , To accurately characterize the ionic DESs, an electroneutral method was used in the COSMO-RS study.…”

“…The viscosity of DEACl–DEA ionic DESs was determined using a DV-II + Pro Extra Brookfield viscometer at 25 °C for different mole ratios similar to the previous report. 15 Typically, 10 mL of DEACl–DEA DES was poured into a cylindrical container immersed with the spindle. The spindle speed was set from the viscometer to different revolutions per minute (rpm) and corresponding shear rates (s –1 ).…”

“…The current level of CO 2 in the atmosphere is approximately 420.57 ppm, causing a rise in global temperature because CO 2 can absorb UV-radiation from the sun and emit heat, consequently causing significant climate change. − Therefore, sustainable CO 2 sequestration that leaves behind a low carbon footprint and low earth temperature is desired to ameliorate climate change issues . Previous suggestions involve technologies for capture and storage of CO 2 (CCS), but the cost of desorbing and compressing CO 2 from the capture solution to a potential CO 2 electrolyzer is a major challenge. , Instead of the CCS, electrochemical CO 2 capture and utilization emerge to eliminate storage costs and promote the generation of platform chemicals − and sustainable energy storage options. − …”