High-temperature proton exchange membranes from ionic liquid absorbed/doped superabsorbents

Abstract

The development of high-temperature proton exchange membranes (HTPEMs) operated over 120 °C under anhydrous conditions is pursued worldwide in order to solve some core problems of current PEM fuel cells based on Nafion (CO tolerance, improved kinetics, water management, etc.). In the current work, two classes of HTPEMs based on absorbing and doping of the protic ionic liquid, 1-methylimidazolium trifluoromethanesulfonate ([MIm][Tfo]), into a 3D framework of poly(acrylic acid)–poly(ethylene glycol) (PAA–PEG) superabsorbent are successfully synthesized. The resultant membranes show high proton conductivity, good thermal stability and excellent mechanical strength due to the unique absorption property and interpenetrated polymer network of PAA–PEG, and good conduction of [MIm][Tfo]. Proton conductivities as high as 40.4 and 19.4 mS cm⁻¹ at 200 °C under anhydrous conditions are obtained in [MIm][Tfo] doped and absorbed PAA–PEG membranes, respectively. The long-term stability of the superabsorbent-based membranes at high-temperatures, in combination with simple preparation, low cost, scalable host and proton conductor, demonstrates the potential use of these materials in HTPEMs.