The role of anions for phosphoric acid uptake behaviors and electrochemical performance of ion-pair type high-temperature polymer electrolyte membranes

Abstract

Quaternized ion-pair membranes have high phosphoric acid (PA) uptake and retention due to strong interaction energy between quaternary ammonium with PA. However, there is currently a lack of clear understanding of the role of anions on the PA uptake behaviors and mechanism of ion-pair type membranes. In this work, the PA uptake behaviors of quaternized poly (terphenyl piperidinium) (QAPTP-X, X represents anions) with four kinds of anions (Cl−, OH−, HCO3− and H2PO4−) were investigated. Due to the neutralization reaction between PA and OH−/HCO3−, QAPTP-OH− and QAPTP-HCO3− membranes show a faster PA adsorption rate (PA uptake for 2 min: 116 wt% of QAPTP-OH−≈109 wt% of QAPTP-HCO3− >95 wt% of QAPTP-H2PO4− ≫64 wt% of QAPTP-Cl−). Besides, the Pt catalyst is poisoned by strong adsorption anions Cl− migrated from the QAPTP-Cl− membrane, which leads to sluggish electrode reaction kinetics and lower peak density. Therefore, a new perspective is provided for studying the mechanism of PA uptake and electrochemical performance for ion-pair type membranes.