On the design of a comb-shaped, poly(phenylene oxide)-based anodic binder for anion-exchange membrane direct methanol fuel cell (AEM-DMFC)

In this study, we present the synthesis of a poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) based comb-like ionomer and the characterization of this ionomer. The ionomer consists of a PPO backbone and a partially fluorinated cationic sidechain. The comb-like ionomer showed high stability regarding ionic conductivity and ion exchange capacity in alkaline media. Besides this, a low swelling ratio for 4M methanol anodic fuel was found for the ionomer making it a suitable candidate for an application in the anodic catalyst layer in AEM-DMFCs. Evaluation of the methanol diffusion with a mass exchanger unit coupled to a mass spectrometer showed that the partially fluorinated sidechain lowers methanol diffusion compared to a non-fluorinated ionomer. Nevertheless, the comb-like ionomer was implemented in single cells as a catalyst binder and provided strong enhancement in single cell performance when the cell was run with KOH-free anodic fuel.