Abstract
Protic ionic liquids (PILs) immobilised in an ionogene host polymer represent an intriguing alternative to the state-of-the-art commercial fluoropolymer-based membranes as proton conducting electrolytes for future intermediate-temperature fuel cells (T > 100 °C, IT-PEMFCs). In this study, two PILs, N, N-diethyl-3-sulfopropane-1-ammonium trifluoromethanesulfonate [DESPA][TfO] and diethyl-methylammonium trifluoromethanesulfonate [DEMA][TfO], were investigated for their suitability as proton conducting species in a sulfonated poly(ether-ether-ketone) membrane (sPEEK). Both PIL membrane casts exhibit good thermal stability until 200 °C and a high ionic conductivity of up to 5.28 mS.cm(-1)(120 °C, 40%RH). The polarisation curves showed a maximum power density of 3.5 mW.cm(-2) for [DESPA][TfO] membrane cast and 6.5 mW.cm(-2) for [DEMA][TfO] membrane cast, proving the suitability of the PIL membrane cast as a polymer electrolyte membrane (PEM) for the IT-PEMFCs.