Guiding the self-assembly of hyperbranched anion exchange membranes utilized in alkaline fuel cells

Anion exchange membrane fuel cells (AEMFCs) can efficiently convert chemical energy into electricity at high pH. However, as the critical component, the existing anion exchange membranes (AEMs), cannot have both high stability and high conductivity, which is intrinsic to the conventional linear AEMs. To address this, here we report hyperbranched AEMs cross-linked by diamines and proposed a strategy to guide the self-assembly of hyperbranched AEMs, thereby regulating the membrane microphase morphology. We found that the chain length of the diamine cross-linking agents plays a significant role in guiding the formation of microphase separated morphology inside hyperbranched AEMs and influences eventually the membrane conductivity and stability. The hyperbranched membrane HBM-6C exhibits the most distinct microphase separated morphology, leading to high conductivity and improved alkaline stability. For instance, the hydroxide conductivity of HBM-6C membrane is 27.18 mS cm−1 at 30 °C, 2.7 times of the linear counterpart membrane [PTMVPMA][OH] (10 mS cm−1). A H2/O2 AEMFC assembled with HBM-6C membrane herein demonstrates a maximum power density of 97 mW cm−2 at a current density of 190 mA cm−2. Our results would pave the way towards AEMs with novel chain architecture and stimulate further improvement in AEMFC performance.