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

Abstract

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 cm 2 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 H 2SO 4 aqueous solution and Nafion ® in water to discuss the oxygen cross-over in fuel cell application.