Anhydrous proton exchange membranes at elevated temperatures: effect of protic ionic liquids and crosslinker on proton conductivity

Abstract

A series of novel anhydrous proton exchange membranes (poly(vinyl alcohol)–citric acid–ionic liquid (PVA–CA–IL)) were prepared using the low cost ionic liquids ethylammonium nitrate (EAN), diethylammonium nitrate (DEAN), and triethylammonium nitrate (TEAN) as conductive fillers in PVA support membrane. The properties of the PVA–CA–IL membranes can be controlled by changing the molar ratio of the PVA, ILs and CA. The thermal stability of PVA–CA–IL membrane was measured by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), and the microstructure was investigated using scanning electron microscopy (SEM) and the Anton-paar SAX Sess mc2 system (SAXS). The effects of temperature, ILs and crosslinker dosage on proton conductivity were also systematically investigated. The results showed that the PVA–CA–IL membranes had excellent performance. The proton conductivity of PVA–CA–EAN (mole ratio = 1 : 0.05 : 0.4) could reach up to 7.8 mS cm⁻¹ at 140 °C. The introduction of ionic liquid into PVA membrane constituted a new and efficient kind of anhydrous proton exchange membrane.