Synthesis and characterization of anion exchange multi-block copolymer membranes with a fluorine moiety as alkaline membrane fuel cells

Abstract Multi-block copolymers containing a partially fluorinated hydrophobic moiety (F-PE) are synthesized for application as alkaline membrane fuel cells (AMFCs). The partially fluorinated monomer is synthesized by palladium-catalyzed Suzuki coupling, and quaternary ammonium groups are introduced after selective chloromethylation of the hydrophilic blocks. TEM investigation of the block copolymers show well-defined hydrophilic-hydrophobic phase separation behavior, resulting in high anion conductivity. In particular, the partially fluorinated hydrophobic blocks are stable even after immersing into a 1 M KOH solution because the hydrophobicity of the fluorine moiety excludes hydrophilic nucleophiles, which are the main sources of chemical degradation of AEMs. Although the hydrophilic domains are slightly degraded under harsh alkaline conditions, the F-PE survives at room temperature in a 1 M KOH solution for 720 h. F-PE membranes result in an AMFC performance of 310 mA cm −2 at 0.6 V and 70 °C.