Preparation and characterization of composite membranes with Brønsted acidic ionic liquid

Poly-(vinyl alcohol) (PVA) proton-conducting composite membranes were prepared using succinic acid (SA) as a cross-linking agent and Brønsted acidic ionic liquid (BAIL) as a proton source. The incorporated BAILs resulted in a relatively high proton conductivity compared with PVA/SA membrane without BAILs. The proton conductivities of PVA/SA/BAIL composite membranes increased versus the BAIL content. In addition, the optimal resultant proton conductivity of PVA/SA/BAIL composite membrane under dry condition could reach 0.4 mS/cm at 140 °C, which was higher than that of PVA/sulfosuccinic acid (SSA) composite membrane (0.032 mS/cm), PVA/SSA/5-aminotetrazole membrane (0.022 mS/cm at 130 °C), and PVA/chlorosulfonic acid/glutaraldehyde membrane (0.0585 mS/cm at 90 °C) measured at the same condition. It was notable that the PVA/SA/BAIL composite membranes could reach high thermal stability up to 150 °C, which was higher than that of traditional PVA membranes (below 80 °C).