Thermal Stability of Protic IL

Intrinsically, an acid-base equilibrium exists in PILs that are prepared by proton transfer reactions from Bronsted acids to Bronsted bases. The thermal stabihty of PILs is dominated by the amount of neutral species (i.e., free acids and bases) because neutral species evaporate more easily than ionic species. Angell et al. [12] suggested that the difference between the pK values (ApJCJ of an add and a base is a good indicator of the equilibrium. Dai et al. [13] reported that protic ILs based on phosphazene or bicyclic guanidine superbases exhibit high thermal stability comparable to that of aprotic ILs. Ishiguro et al. [14] explored the 

Hagiwara et al. [15] reported unique PILs based on a fluorohydrogenate anion ([FH] F ,x=l-3).It should be noted that these PILs exhibit high ionic conductivity ( 100mScm at 120 °C) owing to their very low viscosities. Additionally, the proton transport and fuel cell reactions in these PILs occur via self-diffusion and electrochemical reactions of the fiuorohydrogenate anions. This contrasts with the proton transport in Bronsted acid-base PILs where ammonium cations play the same role. 

Membrane Fabrication Including PIL and Fuel Cell Operation 

3) The composite membranes exhibit thermal decomposition temperatures greater than 250 °C, which is caused by the eHmination of sulfonic acid groups in SPI. This thermal stability is sufficient for intermediate fuel cell operations. 

4) In the composite membranes, the PILs function as plasticizers toward SPI thus, the mechanical strength decreases as the [demaJfTfO] content increases. 

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