Polypyrrole nanowires as a cathode microporous layer for direct methanol fuel cell to enhance oxygen transport.

Summary: Microporous layers (MPLs) have a crucial effect on the performance of direct methanol fuel cells (DMFCs). High polytetrafluoroethylene (PTFE) loading is normally adopted to remove water in a conventional cathode MPL based on carbon black, which hinders oxygen transport and increases ohmic resistance. In this study, we report a novel cathode MPL based on polypyrrole nanowires, which were grown on hydrophobic carbon paper via in situ electropolymerization. Compared with carbon black, the unique structure of polypyrrole nanowires allows for less PTFE content to obtain similar hydrophobicity. The maximum power density of a DMFC based on the novel MPL (20 wt% PTFE) is 101.1 mW cm−2, which is about 1.3 times that based on a traditional MPL (40 wt% PTFE, 79.4 mW cm−2). This improvement can be ascribed to increased oxygen transfer and decreased ohmic resistance, which were evidenced by oxygen gain and electrochemical impedance spectroscopy. [ABSTRACT FROM AUTHOR]