Impact of side-chain-type poly(dibenzyl-co-terphenyl piperidinium) ionomers for anion exchange membrane fuel cells

Abstract

Anion exchange membrane fuel cells (AEMFCs) have experienced rapid advancement in the past few years due to the discovery of high-performance AEMs, while the ionomer effect has not been well elucidated. Here, we report a series of side-chain-type poly(diphenyl-co-terphenyl piperidinium) (s-PDTP) ionomers for AEMFC applications. The features of aryl ether-free polymer backbone and pendent ammonium groups endow both high alkaline stability and excellent micromorphology of s-PDTP ionomers. These ion-exchange-capacity (IEC)-controlled s-PDTP ionomers possess high OH− conductivity >120 mS cm-1 at 80 oC, reasonable molecular weight (Mw=200,000), and excellent ex-situ durability in 1 M NaOH at 80 oC for 1,000 h (~90% conductivity remaining). We found that s-PDTP ionomers with moderate IEC (~3.0 mmol g-1) and rational water uptake (~200%) are more suitable for AEMFCs compared to high IEC or low IEC s-PDTP ionomers (>3.4 mmol g-1 or <2.4 mmol g-1). Based on Pt/C, s-PDTP-based AEMFCs reach the peak power density (PPD) of 1.47 W cm-2 in H2-O2 and 1.04 W cm-2 in H2-air (CO2-free) at 80 oC. The present work contributes to elaborating the impact of side chain on ionomers.