Electro-spraying process is chosen for direct deposition of catalyst electrodes on proton exchange membrane. Catalyst ink is composed of J&M 40wt.% Pt/C, Nafion ionomer, and isopropyl alcohol. After depositing catalyst electrode on both sides of membrane, MEA was heat treated in different temperature and environment and then linear polarization and electrochemical impedance spectroscopy were conducted. I-V polarization behaviors are dependent on the heat treatment condition: improvements in the activation polarization and ohmic loss but deterioration of concentration polarization. It may be due to the change of pore structure according to heat treatment. Besides the heat treatment, functional layer is designed to facilitate transfer reactions. Ionomer rich thin layer is inserted between membrane and electrode while thin film having lower ionomer content than electrode is deposited between electrode and gas diffusion layer. By inserting functional layer, concentration polarization resistance can be markedly reduced.
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