Anion Exchange Membranes with an Extended Planar Conjugated Structure Enabled by π–π Stacking for Fuel Cells

Currently, main strategies for constructing microphase separation in anion exchange membranes (AEMs) include remote grafting, comb grafting, and blending cross-linking. The above strategies achieve the microphase separation effect by changing the size and ratio of hydrophilic and hydrophobic phases, which will cause a loss of mechanical properties and dimensional stability of membranes. In this study, we introduced π-π stacking interaction into the fluorinated poly(aryl-piperidine) backbone and constructed efficient ion transport channels in membranes through self-assembly effect induction, resulting in higher ion conductivity and alkaline stability. The rigid 1,6-stilbenepyrene (1,6-PyE) molecule with π-π stacking interaction was designed and synthesized, and serial QPEmTP<i>-x</i>/QPEpTP<i>-x</i> AEMs with wide-area planar conjugated structure were prepared. Among them, QPEpTP-15% AEMs have excellent overall performance (OH^- conductivity of 131.8 mS·cm^-1, water uptake of 53.7%, and swelling ratio of 15.8%) and tensile properties (36.85 MPa). This is due to the extended polymer backbone of QPEpTP-15% AEMs, which enables it to have a larger free volume and a higher degree of polymerization. After immersion in 2 mol·L^-1 NaOH for 1100 h, the conductivity of serial membranes remained above 94%. Furthermore, the above experimental data were verified by DFT and molecular dynamics simulation. Finally, H₂/O₂ fuel cell yields the peak power density of 483 mW·cm^-2 at 80 °C, and the fuel cell can operate at a constant current over 100 h without much voltage decay. This study shows that the AEMs with π-π stacking interaction have great potential in achieving excellent energy efficiency and multiple stability of fuel cells.