Effect of CO2 dissolution on electrical conductivity and self-diffusion coefficients of 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid

We have determined the electrical conductivity in CO2-saturated 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]) at 298.1, 313.1 and 333.1 K as a function of CO2 pressure. Moreover, self-diffusion coefficients of cation and anion in CO2-saturated [C4mim][PF6] have been measured at high pressures up to ∼15 MPa and at a fixed temperature of 333.2 K by 1H and 19F NMR using the pulsed field gradient spin-echo method. As CO2 dissolves in [C4mim][PF6], marked increases in all the three transport quantities were observed at lower pressure, and then they showed very slight changes at higher pressure. The correlation between the conductivity and the ionic diffusion coefficients has been discussed.