Study on the effect of the degree of grafting on the performance of polyethylene-based anion exchange membrane for fuel cell application

Abstract

Alkaline anion exchange membranes (AAEM) are fabricated using polyethylene as the base polymer offering a low cost AAEM. This study focuses on the synthesis and characterisation of AAEM with controlled degree of grafting (DOG) and ion-exchange capacity (IEC) with the following parameters investigated: LDPE film thickness 30–130 μm, gamma radiation dose and monomer concentration. The corresponding IEC, water uptake (WU) and degree of swelling (DS) are reported. The performance of 74.6% DOG membrane in a hydrogen fuel cell shows high OCV of 1.06 V with peak power density of 608 mW cm−2 at 50 °C under oxygen. The use of membrane with high DOG does not impact fuel cross-over significantly and provides improved fuel cell performance due to better conductivity, water transport and resilience to dehydration. The AAEM shows long term stability at 80 °C exhibiting a conductivity of ca. 0.11 S cm−1 over a period of 7 months under nitrogen. The membrane shows a degradation rate of 4 and 17 mS month−1 under nitrogen and oxygen, respectively. The estimated life time of the membrane is 2 years under nitrogen and 5.5 months under oxygen operating at 80 °C.