Measurement and prediction of CO2 solubility in organic electrolytes for high pressure CO2 reduction.

The electrochemical CO 2 reduction reaction (CO2RR) to organic products is becoming increasingly important. Here, organic electrolytes play a crucial role, since adding salt to organic solvent allows an increase in the current density, and together with supercritical CO 2 organic electrolytes suppress hydrogen evolution during the CO2RR. Since the selectivity to organic products depends on the CO 2 content, CO 2 solubility was investigated in organic electrolytes at different salt concentrations, pressures (up to 150 bar), and temperatures (25 °C and 70 °C). These organic electrolytes included the mixtures NaI-methanol, KSCN-methanol, (C 2 H 5) 4 NBF 4 -acetonitrile, and (C 4 H 9) 4 NBF 4 -acetonitrile. Afterwards, electrolyte Perturbed-Chain Statistical Associating Fluid Theory (ePC-SAFT) was applied to predict the CO 2 solubility in these organic electrolytes. The results showed that i) CO 2 solubility decreased with increasing temperature and salt concentration, ii) dissolving CO 2 may cause a precipitation of salts, and that iii) ePC-SAFT allowed to qualitatively model the CO 2 solubility in organic electrolytes [Display omitted] • CO 2 solubility decreases with increasing temperature and salt concentration in the electrolyte. • CO 2 dissolution in the organic electrolyte may cause salt precipitation. • Organic salts have less influence on CO 2 solubility than inorganic salts. • ePC-SAFT allows qualitatively predicting the CO 2 solubility in organic electrolytes over a broad range of conditions. [ABSTRACT FROM AUTHOR]