Facilitated belt for ion transport by comb-shape Poly(terphenyl piperidone) carried with macrocyclic crown ether as anchor in anion exchange membrane

Abstract

To ensure efficient ion transport in anion exchange membranes (AEMs) for hydrogen production, it is essential to develop efficient ion transport pathways. Utilization of intermolecular interactions induced by embedded macrocycles is an attemptable approach. Self-aggregated channels can be constructed with this force serving as a driving force for stepped-up ion transport. Herein, we present a delicate strategy to polymerize the macro crown ether in the backbone and graft flexible alkyl long chains to prepare comb-type copolymers as AEMs. The macrocycle dynamically traps ammonium ions as an anchor which accelerates the aggregation of ionic phases. The resulting AEMs show favorable membrane-forming ability and tensile strength. As the side chain length increases, the microphase-separated morphology develops well and formed ‘belt’-like channels in the poly(terphenyl piperidone)-5-bis-quaternary ammonium (PTCP-5-bisQA) membrane, exhibiting a hydroxide conductivity of 78.1 mS/cm at 80 °C. The alkaline durability of PTCP-5-bisQA AEM is explored by nuclear magnetic hydrogen spectrum (1H NMR) investigation at 80 °C for 720 h. Furthermore, the PTCP-5-bisQA based electrolyzer reaches a current density of 330 mA/cm2 at 1.85V by 1 wt% potassium hydroxide solution circulation. A life endurance observation is carried out on this electrolyzer for a 100h operation with performance degradation rate of 40.1 mV/h.