Application of a novel PUB enhanced semi‐interpenetrating chitosan‐based anion exchange membrane

Abstract

A novel OH− conducting membrane containing chitosan (CS), poly-(acrylamide-co-diallyldimethylammonium chloride) (PAADDA) and linear structured poly-bis (2-chloroethyl) ether-1,3-bis [3-(dimethylamino)propyl] urea copolymer (PUB) was synthesized via a solution-casting method and subsequently modified by hot treatment and chemical cross-linking. The structural characterizations of scanning electron microscope (SEM), atomic force microscope (AFM), Fourier transform infrared spectra (FT-IR), and X-ray photoelectron spectroscopy (XPS) were carried out, showing that CS, PAADDA, and PUB formed a compact interpenetrating polymer network structure without apparent phase separation phenomenon under the help of cross-linking. By changing the content of PUB in the membrane, the application performance such as mechanical properties, thermal gravimetric (TG) analysis, water uptake (WU), OH− conductivity ( ) and ion exchange capacity (IEC) were investigated to evaluate the feasibility for alkaline membrane fuel cells. The maximum OH− conductivity could be reached up to 3.12 × 10−2 S cm−1 at 80°C in a mass ratio of CS/PAADDA/PUB (1:0.5:0.5) while a good tensile strength of 22.73 MPa and an excellent elongation at break of 23.55% could be obtained in a mass ratio of CS/PAADDA/PUB (1:0.5:0.25). Furthermore, the membrane also exhibited relatively high oxidative stability as well as excellent alkaline resistance stability, when conditioned in 30% H2O2 solution at ambient temperature for 120 hours and 8 M KOH solution at 60°C for 320 hours, respectively. Membrane electrode assemblies (MEAs) achieved a peak power density of 38.1 mW cm−2 at the maximum current density of 73.2 mA cm−2 in a H2/O2 system at room temperature. PUB was successfully introduced into the CS-based membrane to improve the conductivity. Maximum OH− conductivity reached 0.016 S cm−1 at room temperature. Tensile strength of the prepared membrane could reach up to 22.73 MPa. The prepared membrane exhibited an excellent elongation at break of 23.55%. The membrane showed good oxidative stability and excellent alkaline resistance stability.