Di-ureasil hybrid electrolytes incorporating a new proton ionic liquid

Abstract

The protic ionic liquid (PIL) N-butylimidazolium trifluoromethanesulfonate ([BIm][TfO]) was obtained for the first time and incorporated into a sol–gel-derived di-ureasil matrix with a concentration of X=5, 10, and 30 %, where X is the ratio of the mass of PIL per mass of poly(oxyethylene). Four years after their synthesis, the resulting quasi-anhydrous electrolytes remained amorphous, homogeneous, flexible, and thermally stable below 200 °C. SEM/EDS data revealed the presence of the PIL at the surface of the xerogels with X>5 %, demonstrating that this type of morphological characterization is mandatory to avoid misleading ionic conductivity values. The highest ionic conductivity was produced in the washed sample with X=30 % (3.5×10−5 and 2.1×10−3 S cm−1 at 25 and 170 °C, respectively). The present family of electrolytes yielded higher conductivities than the N-ethylimidazolium trifluoromethanesulfonate-based analogues introduced earlier by our group and may thus be considered as promising candidates for applications in fuel cells.