Arrhenius plots ionic liquid diffusion

Figure 5.3 depicts the Arrhenius plots of the apparent self-diffusion coefficient of the cation (Dcation) and anion (Oanion) for EMIBF4 and EMITFSI (Figure 5.3a) and for BPBF4 and BPTFSI (Figure 5.3b). The Arrhenius plots of the summation (Dcation + f anion) of the cationic and anionic diffusion coefficients are also shown in Figure 5.4. The fact that the temperature dependency of each set of the self-diffusion coefficients shows convex curved profiles implies that the ionic liquids of interest to us deviate from ideal Arrhenius behavior. Each result of the self-diffusion coefficient has therefore been fitted with VFT equation [6].

Viscosities of the ionic liquids at different temperature have been depicted in Figure 5.6 as Arrhenius plots. Resembling the self-diffusion behavior, the temperature dependence of viscosity follows the VFT equation ... 

Fig. 3 Arrhenius plot showing the temperature dependence of the surface diffusion coefficients for the three ionic liquids investigated. 

The effects of halides, carbon dioxide and water on the physical properties of Emim+[(CF3SQ3)2N] have been extensively studied by Barrosse-Antle et al., 2009. The system was studied using cyclic voltammetry, chronoamperometiy, and EPR spectroscopy. Diffusion coefficients in the pure and CC>2-saturated ionic liquid revealed a decrease in activation energy E ir of translational diffusion from 29.0 to 14.7 kj/ mol, suggesting a reduction in the viscosity of the RTIL with addition of C02. EPR spectroscopy was used to calculate Tc coefficients of a spin probe R H. Arrhenius plots of Tc in the pntre and C02-saturated RTIL resulted in a similar drop in E ot from 28.7 to 18.2 kj/mol. It was concluded that the voltammetric respense of the electroactive species in RTILs is not independent of other solutes. 

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