Engineering of Interconnected Ionic Channels in Polybenzimidazole Anion-Exchange Membranes
Ruizhen Yang, Xuemei Wu, Wanting Chen, Xiaozhou Wang, Tiantian Li, Xiaoming Yan, Leilei Wang, Fujun Cui, Gaohong He
Abstract
To balance the ion conduction and stability of anion-exchange membranes (AEMs), the efficiency of OH – transfer needs to be improved. Here a series of polybenzimidazole-based AEMs (UTA-PBI- x ) with comb-shaped tricationic side chains containing two diethoxy spacers and one alkyl spacer were synthesized. It is found that in the low-IEC region, hydrogen-bond network is the dominant contribution to ion transport, while the hydrated ionic channels would gradually become more dominant with increasing ionic content. With an optimal IEC of 1.40 mmol/g, OH – ions could rapidly transfer in the desired hydrated cationic clusters and through the thin intercluster ether-containing hydrogen-bond network domains. Meanwhile, the ether domains guarantee a continuous nonionic phase for resisting water swelling. Consequently, the UTA-PBI-1.40 membrane simultaneously possesses a low swelling ratio of 17.2%, sufficient conductivity of 46.9 mS/cm at 20 °C, excellent mechanical strength (21.1 MPa), and good alkaline stability (∼90% remaining conductivity) in 1 M NaOH for ∼1400 h. A high efficiency of OH – transport (σ/IEC ∼ 103.2) was achieved, which is superior to those of the recently reported AEMs. In a H 2 /O 2 fuel cell, the ultrathin UTA-PBI-1.40 membrane achieves a peak power density of 861.6 mW/cm 2 at 80 °C. This work provides a theoretical and experimental guidance for the design of AEMs with high-efficient OH – transfer.