Fabrication of Dual-Functional Bacterial-Cellulose-Based Composite Anion Exchange Membranes with High Dimensional Stability and Ionic Conductivity
Fei Wang, Ting Qu, Huiyu Yang, Haiyang Yang, Ying Ou, Quanyuan Zhang, Fan Cheng, Fuqiang Hu, Hai Liu, Zushun Xu, Chunli Gong
Abstract
Anion exchange membranes (AEMs) are increasingly becoming a popular research area due to their ability to function with nonprecious metals in electrochemical devices. Nevertheless, there is a challenge to simultaneously optimize the dimensional stability and ionic conductivity of AEMs due to the “trade-off” effect. Herein, we adopted a novel strategy of combining filling and cross-linking using functionalized bacterial cellulose (PBC) as a dual-functional porous support and brominated poly(phenylene oxide) (Br-PPO) as the cross-linking agent and filler. The PBC nanofiber framework together with cross-linking can provide a reliable mechanical support for the subsequent filled polymer, thus improving the mechanical properties and effectively limiting the size change of the final quaternized-PPO (QPPO)-filled PBC composite membrane. The composite membrane showed a very low swelling ratio of only 10.35%, even at a high water uptake (81.83% at 20 °C). Moreover, the existence of multiple −NR 3 + groups in the cross-link bonds between BC and Br-PPO can provide extra OH– ion transport sites, contributing to the increase in ionic conductivity. The final membrane demonstrated a hydroxide ion conductivity of 62.58 mS cm –1, which was remarkably higher than that of the pure QPPO membrane by up to 235.93% (80 °C). The successful preparation of the PBC 3 /QPPO membrane provides an effective avenue to tackle the trade-off effect through a dual-functional strategy.