Solubility and diffusion coefficient of oxygen in 1-ethyl-1-methylpyrrolidinium fluorohydrogenate room temperature ionic liquid at 298–373 K

Solubility (C) and diffusion coefficient (D) of oxygen in 1-ethyl-1-methylpyrrolidinium fluorohydrogenate (EMPyr(FH)1.7F) room temperature ionic liquid (RTIL) have been determined at 298–373 K by the combination of linear-sweep voltammetry and hydrodynamic chronocoulometry with a rotating disc electrode (RDE). The solubility was 0.409 mmol dm−3 at 298 K and decreased with an increase in temperature. The solubility was compared with other RTILs and the difference was explained by the free volume estimated from the observed molar volume and the calculated molar volume. The diffusion coefficient was 1.59 × 10−5 cm2 s−1 at 298 K. The activation energy of diffusion was estimated to be 24.5 kJ mol−1 from the slope of the Arrhenius plot. The permeability of oxygen (C × D) was compared with those in other RTILs, 0.5 M H2SO4 aqueous solution and Nafion® in water to discuss the oxygen cross-over in fuel cell application.

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► EMPyr(FH)1.7F room temperature ionic liquid (RTIL) for non-humidified fuel cells.
► Hydrodynamic chronocoulometry with a rotating disc Pt electrode.
► Solubility and diffusion coefficient of oxygen were determined at 298–373 K.
► Comparison with other RTILs, 0.5 M H2SO4 aqueous solution and Nafion® in water.
► EMPyr(FH)1.7F is a promising ionic liquid for fuel cell application.