(537d) High-Throughput Electrochemical Tool to Study CO2 Solubility in Ionic Liquids: Synergism of Void Fractions and Ionic Interactions

The continuous anthropogenic emission and accumulation of CO₂ significantly contribute to climate variation associated with global warming and the greenhouse effect. Therefore, mitigating the relentless rise and accumulation of CO₂ emissions becomes a paramount global challenge. The imperative need for efficient CO₂ capture and utilization technologies to mitigate climate change has sparked interest in room-temperature ionic liquids (RTILs) as promising solvents for CO₂ capture and utilization. Most CO₂ capture processes function under pressures substantially higher than atmospheric levels, leading to increased process costs and reduced feasibility for large-scale CO₂ capture and conversion. The electrochemical method is an ideal method for simple and accurate access to CO₂ solubility values in RTILs under standard conditions. To streamline the CO₂ solubility measurement process, an automated high throughput electrochemical system utilizing the 96-wells of a microtiter plate as micro-electrolysis cells is developed, enabling quick, accurate, and sustainable assessment. This system only requires a significantly less amount (in the microliter range) of RTILs for CO₂ solubility studies. The electrocatalytic properties of electrodes and RTILs allow cyclic voltammetry (CV) to be turned into an ideal tool to determine the CO₂ solubility in RTILs with the help of a high throughput three-electrode electrochemical cell. The Cottrell analysis of the CO₂ reduction CV peak provides a direct measurement of CO₂ permeance in RTILs, which yields Henry’s constant from the estimated diffusion coefficient of CO₂. Henry’s constants thus obtained are in very good agreement with those reported earlier. The measured CO₂ permeance and Henry’s constant of all RTILs seem to follow a first-order dependence on void fraction and a second-order dependence on electrostatic interaction between anion and cation of IL, with some synergistic dependence on the product of a void fraction and electrostatic interaction. Henry’s constant decreases with increasing void fraction or decreasing electrostatic interaction. For ILs with lower void fractions, Henry’s constant first increases and then decreases with increasing electrostatic interaction. Therefore, this study explores the application of CV in electrochemical measurement in a high throughput manner to determine the CO₂ solubility in RTILs. In addition, we also highlight that the influence of structural and compositional changes in RTILs on CO₂ solubility can be accurately represented by considering void fraction and electrostatic interaction and their synergistic effect, making them two significant parameters to design novel ILs.