Quasi-anhydrous proton conducting di-ureasil hybrid electrolytes incorporating a protic ionic liquid

• Quasi-anhydrous proton conducting sol-gel derived hybrid electrolytes were developed.
• The electrolytes synthesized contain N-ethylimidazolium trifluoromethanesulfonate.
• The proton conductivity of the materials suggests applications in fuel cells.

A wide range of concentrations of the [EIm][TfO] proton ionic liquid (PIL) were for the first time incorporated into a poly(oxyethyelene) (POE)/siloxane hybrid host matrix (d-U(2000)) belonging to the di-ureasil family. The synthesis procedure adopted, involving the lowest amount of water possible, resulted in the formation of essentially anhydrous electrolytes at certain PIL levels. The optimized sample d-U(2000)/[EIm][TfO]50 (where 50 represents the ratio in % of the mass of [EIm][TfO] per mass of POE precursor) is amorphous, thermally stable up to 200 °C, displays good mechanical properties and exhibits an ionic conductivity of 3.2×10-4 and 4.3×10-3 S cm-1 at 20 and 186 °C, respectively. These features have persisted for more than three years. These new electrolytes appear quite attractive for applications in fuel cells operating under non-humidified conditions.