Investigation of the electrolyte properties for the vanadium redox flow battery (VI): Measurement and prediction of surface tension of aqueous VOSO4 at 283.15 to 313.15 K

Surface tension and density for aqueous VOSO4 solution have been measured at different temperatures from T=(283.15 to 313.15) K. The values of average molar volume, V, were calculated. Based on Li's theory, a new definition of molar surface Gibbs free energy has been proposed and was used to predict the surface tension of the aqueous VOSO4. The results show that the predicted values of the surface tension of the aqueous VOSO4 were in the consistency with the corresponding experimental ones. According to the relationship between the proposed molar surface Gibbs free energy and temperatures, a semi-empirical equation derived from the Eötvös equation with a more explicit physical meaning was subsequently presented, from which the molar surface enthalpy and entropy could be evaluated directly. Furthermore, the proposed semi-empirical approach also gave an opportunity to apply the molar surface Gibbs free energy to other types of solutions so as to assist in the prediction of the surface tension with satisfactory results.