Solvent processible, high-performance partially fluorinated copoly(arylene ether) alkaline ionomers for alkaline electrodes

Abstract

A solvent processable, low water uptake, partially fluorinated copoly(arylene ether) functionalized with pendant quaternary ammonium groups (QAPAE) was synthesized and uses as the ionomer in alkaline electrodes on fuel cells. The quaternized polymers containing fluorinated biphenyl groups were synthesized via chloromethylation of copoly(arylene ether) followed by amination with trimethylamine. The resulting ionomers were very soluble in polar, aprotic solvents. Highly aminated ionomers had conductivities approaching 10mScm−1 at room temperature. Compared to previous ionomers based on quaternized poly(arylene ether sulfone) (QAPSF) with similar ion exchange capacity (IEC), the water uptake of QAPAE was significantly less due to the hydrophobic octafluoro-biphenyl groups in the backbone. The performance of the fuel cell electrodes made with the QAPAE ionomers was evaluated as the cathode on a hybrid AEM/PEM fuel cell. The QAPAE alkaline ionomer electrode with IEC=1.22meqg−1 had superior performance to the electrodes prepared with QAPSF, IEC=1.21meqg−1 at 25 and 60°C in a H2/O2 fuel cell. The peak power densities at 60°C were 315mWcm−2 for QAPAE electrodes and 215mWcm−2 for QAPSF electrodes.