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-x/QPEpTP-x 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.