Solubility and Diffusivity of Oxygen in Ionic Liquids

Abstract

The solubility of O 2 was measured gravimetrically in 16 ionic liquids (ILs) containing piperidinium, pyrrolidinium, ammonium, tetrahydrothiophenium, methyltriazabicyclodecene, or guanidinium cations paired with bis(trifluoromethanesulfonyl)imide, bis(perfluoroethylsulfonyl)imide, or perfluoropropanoyl(trifluoromethylsulfonyl)imide anions. The temperature dependence of the solubility was determined for eight of the ILs. Henry' law constants were determined from the solubility data as well as standard enthalpies and entropies of absorption for systems with temperature-dependent data. Knowledge of these thermodynamic properties is essential in guiding the structural design of ionic liquids for different applications involving O 2 . The O 2 solubility did not follow any obvious trend with regard to IL structure or molar volume; instead, the dipole−quadrupole interactions are the primary driving forces for O 2 dissolution in ionic liquids, as demonstrated by negative standard enthalpies of absorption for all of the ILs. In addition, diffusion coefficients of O 2 in the ILs as a function of temperature (293, 313, and 333 K) and applied O 2 pressure (1, 3, and 5 MPa) were obtained by fitting the time-dependent absorption data to a widely used mass diffusion model. The diffusion coefficients of O 2 in ionic liquids at 293 K and 1 MPa roughly correlate inversely with the pure IL viscosity, likely due to the relatively low and similar O 2 solubilities under these conditions. As expected, O 2 diffusivities increase with increasing temperature. However, they also increase with increasing pressure, likely due to decreasing solution viscosity with increasing gas solubility.

Mechanistic Understanding of Oxygen Electrodes in Rechargeable Multivalent Metal‐Oxygen Batteries

“…Under large current densities, the diffusion rate of O 2 from the electrolyte/gas interface to the cathode surface could be limiting and contributes to overpotential. The use of solvents and additives that display high O 2 solubilities and diffusivities, e. g. ionic liquids [13] and perfluorinated carbon liquids, [14] are worth exploring.…”

Engineering the Electrochemical Interface of Oxygen Reduction Electrocatalysts with Ionic Liquids: A Review

“…a) A comparison of literature data for oxygen solubility in ILs. Presented data were originally reported as follows (from left to right on the graph): [BMPyrr][NTF2], [ 90–98 ] [BMIm][PF6], [ 93,99,100–102 ] [BMIm][NTF2], [ 92,93,95,103 ] [BMIm][BF4], [ 93,100,102,104,105 ] , 0.1 m HClO 4 . [ 106 ] Detailed information about the experimental parameters and additional experimental results are shown in Table S8, Supporting Information.…”

Saturated Dissolved Oxygen Concentration in in situ Fragmentation Bioleaching of Copper Sulfide Ores

“…Oxygen concentration decreased when ionic solutes presented in solution due to salting-out effect ( Cui and Wu, 2013 ). Most researchers measured dissolved oxygen concentration in seawater or ionic liquids ( Weiss, 1970 ; Song et al, 2019 ). There is a lack of models to accurately predict the saturated dissolved oxygen concentration in solutions during the bioleaching process of copper sulfide ores.…”