Crown ether bridged anion exchange membranes with robust alkaline durability

Abstract

A series of highly alkaline durable crosslinked anion exchange membranes (AEMs) is prepared via elimination reaction using a sodium salt of 4,4′(5′)-di(hydroxybenzo)-18-crown-6 as the crosslinker, and quaternary ammonium (QA) as the cation group. The ionic conductivity, ionic exchange capacity (IEC) and mechanical property of the AEMs are investigated. The highest ionic conductivity (about 117 mS cm−1) of the PPO-CE0.10-QA0.90 membranes is obtained at 80 °C and 100% relative humidity. The alkaline stability of the AEMs is determined by inspecting the decline in ionic conductivity, mechanical property and the change in chemical structure after the alkaline stability test. The ionic conductivity has only a 6.0% decrease, the tensile strength has an 11.8 MPa reduction and the elongation at break has a 2.7% depression after 480 h test in 2 M KOH at 80 °C. 13C NMR spectra confirm a negligible change in chemical structure of the AEMs after the alkaline resistance test. The peak power density (about 195 mW cm−2) is achieved under a current density of 350 mA cm−2 at 80 °C. Additionally, the AEMs with a novel crosslinked structure decompose above 230 °C and exhibit decent thermal stability.