Preparation of chloromethylated/quaternized poly(phthalazinone ether ketone) anion exchange membrane materials for vanadium redox flow battery applications

Chloromethylated poly(phthalazinone ether ketone) (CMPPEK) was prepared from poly(phthalazinone ether ketone), with chloromethyl methyl ether (CME) as the chlromethylating reagent and concentrated sulfuric acid as the solvent. The effects of CME quantity, reaction temperature, and reaction time on degree of chloromethylation (DCM) were investigated. CMPPEK with DCM ranging from 0.73 to 2.32 mmol g−1 were obtained. CMPPEK were characterized with 1H NMR and TGA. CMPPEK membranes were prepared from CMPPEK/N-methyl-2-pyrrolidinone casting solutions. Quaternized poly(phthalazinone ether ketone) (QAPPEK) anion exchange membranes were prepared from CMPPEK membranes with different DCM. The ion exchange capacity (IEC) and water content (Wc) of QAPPEK membranes were studied. QAPPEK membranes exhibited IEC ranging from 0.70 to 2.04 mmol g−1 and Wc ranging from 12.9 to 52.3%. IEC and Wc of QAPPEK increased with an increase in DCM of CMPPEK. The vanadium ion permeability of QAPPEK membranes was much lower than that of Nafion117 membrane. The performance of vanadium redox flow battery (VRB) single cell with QAPPEK membranes was investigated. Compare to VRB cell with Nafion117 membrane, the VRB single cell with QAPPEK membranes exhibited higher columbic efficiency. The results show that QAPPEK membranes could be promising anion exchange membranes for VRB applications.