Effect of Vinyl Phosphonic Acid Addition with Different Binders on Performance of MEA for High Temperature Polymer Electrolyte Membrane Fuel Cell

Abstract

The high-temperature polymer electrolyte membrane fuel cell (HT-PEMFC) is operated between 120°C and 180°C, so that the Nafion® as an ionomer for electrodes cannot be applied because proton conductivity of the Nafion® is very low without water at above 100. The polymers like polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE) is adopted as a binder to maintain the electrode structure and phosphoric acid is used as a proton conductive material in the HT-PEMFC. In this study, to enhance the performance of membrane electrode assembly (MEA) for HT-PEMFC, the vinyl phosphonic acid (VPA) incorporated on cathodes that have different binders, such as PPO-MPA and PPO-HPA, which are new polymers having phosphate group on the side chain to increase the proton conductivity in the electrode. The electrode using PPOMPA showed low contact angles than that of the electrode with PPO-HPA. However, after adding the VPA, the electrode of PPO-MPA became more hydrophobic while the electrode with PPO-HPA became hydrophilic. At 0.2A/cm2 , and 150°C, the performance of MEA using PPO-MPA electrode increased from 0.55V to 0.59V by addition of VPA, while that of the MEA using PPO-HPA electrode decreased from 0.61V to 0.57V, which might be attributed to the change of hydrophilicity by VPA. From the FT-IR spectrum, the peak of the P=O bond was changed, which implies the phosphate group is changed. Therefore, the change of MEA performance is accounted for hydrophobicity change and formation of new bonding .