Reduction of oxygen transport resistance in PEFC cathode through blending a high oxygen permeable polymer

Polymer electrolyte fuel cells (PEFCs) have been commercialized as fuel cell vehicles, but high oxygen transport resistance (OTR) needs to be improved for the operation at high current density. OTR is deeply related to oxygen transport to the Pt catalyst through the proton conduction ionomer. In this study, reduction of OTR has simply demonstrated by mixing a high oxygen permeable polymer, poly[1-phenyl-2[p(trimethylsilyl)phenyl]acetylene] (PTMSDPA), and a commercial Nafion® ionomer. Although the resulting blend ionomers have lower proton conductivity than Nafion® itself, they have contributed to increase in PEFC performance in the higher current density region. With small addition of PTMSDPA like 2.5%, local OTR around the Pt catalyst (R_Pt), is found to decrease as the amount of PTMSDA increases owing to high oxygen permeability of PTMSDPA. However, OTR inside the pore of the catalyst layer (R_pore) rather keeps increasing because of a hydrophilic character of PTMSDPA, leading to oxygen blockage by trapped water. Therefore, only the small amount of addition like 2.5% of PTMSDPA results in the best, and R_pore and R_pt are significantly lowered compared those of Nafion® ionomer by 29% and 43%, respectively, suggesting that utilizing high oxygen permeable polymer is effective for reducing OTR in PEFC.