Crosslinked quaternary phosphonium-functionalized poly(ether ether ketone) polymer-based anion-exchange membranes

A series of mechanically robust and highly conducting crosslinked anion-exchange membranes are synthesized by using quaternary phosphonium-functionalized poly(ether ether ketone) (QPPEEK) as base polymer and poly (ethylene glycol) (PEG) as the crosslinker. The crosslinked membrane containing both rigid and flexible polymer constituents (QPPEEK-PEG) revealed better flexibility and mechanical strength, and higher conductivity than the pristine QPPEEK membrane. The mechanical properties and ionic conductivity of the crosslinked membranes are tuned by the mass fractions of the QPPEEK and PEG components. Among the different QPPEEK and PEG compositions, the QPPEEK-PEG 20 (QPPEEK:PEG 80:20) membrane has the best properties, reaching a hydroxide conductivity of 102 mS cm(-1) at 80 degrees C, a tensile strength of 13.7 MPa, and 48% of elongation. The membrane is chemically stable in alkaline environment, retaining 85% of its initial conductivity and mechanical strength after being exposed to 1 M KOH at 80 degrees C for 400 h. Finally, in the operando anion-exchange membrane fuel cell the QPPEEK-PEG 20 crosslinked membrane performs well, displaying an open-circuit voltage of 1.05 V and a maximum power density of 154 mW cm(-2) measured at 0.55 V, showing the potential of PEEK-based membranes for fuel cell applications.

Automated summary

A series of mechanically robust and highly conducting crosslinked anion-exchange membranes were synthesized using quaternary phosphonium-functionalized poly(ether ether ketone) (QPPEEK) as the base polymer and poly(ethylene glycol) (PEG) as the crosslinker. Among different compositions, the QPPEEK-PEG 20 membrane showed the best properties with high hydroxide conductivity, good mechanical strength, and flexibility. This crosslinked membrane was chemically stable in alkaline environment and performed well in anion-exchange membrane fuel cell applications, indicating the potential of PEEK-based membranes for such applications.