Comment on: Temperature-dependent conductivity in room temperature ionic liquids. The relative importance of diffusional and exchange mechanisms. [Simonis ED, Blanchard GJ (2026) J Solid State Electrochem. https://doi.org/10.1007/s10008-025–06512-w]

Simonis and Blanchard have reported tracer diffusion coefficients for the cationic chromophore rhodamine B in four ionic liquids (IL), using a Fluorescence Recovery After Photobleaching (FRAP) technique and employing a Stokesian hydrodynamic argument to deduce the self-diffusion coefficients of the constituent ions. The latter are used to calculate the Nernst-Einstein approximation to the conductivity which is compared to literature experimental data. Contrary to considerable experimental and computational evidence in the literature for the ILs examined, and statistical mechanics treatments of ion transport, they find that the conductivity exceeds the Nernst-Einstein estimate and suggest “exchange-mediated ion-transport” as a possible explanation for their observation. Examination of the data shows that their technique considerably underestimates the ion self-diffusion diffusion coefficients as conventionally measured by both steady and pulsed gradient spin-echo NMR and misestimates their temperature dependence. It is concluded that the FRAP technique and the Simonis-Blanchard treatment of the data give erroneous low estimates for ion self-diffusion in ionic liquids are the conclusion that additional mechanisms for charge transport beyond ionic vehicular motion is unwarranted.