Effect of catalytic ink on sub-freezing endurance of PEMFCs

Effect of catalytic ink on sub-freezing endurance of proton exchange membrane fuel cells (PEMFCs) was investigated in this paper. By direct spraying method, a catalyst-coated membrane (CCM) was fabricated with isopropyl alcohol as organic solvent (CCM-A), and CCM-B was fabricated with isopropyl alcohol and butyl acetate. The hydrophobicity of the two CCMs was similar proved by contact angle tests, and CCM-B showed larger pore volume demonstrated by mercury intrusion tests. Initial cell performance and relevant electrochemical characteristics of the two CCMs were measured and compared. CCM-B showed better performance and larger electrochemical active surface area (ECA). By analyzing the electrochemical impedance spectra (EIS) at low current densities, the ionic resistances of the catalyst layers were calculated. Results indicated that adding butyl acetate to the catalytic ink benefited the ionic resistance. Then, the fuel cells with the two CCMs were subzero stored at -20 degrees C with saturated residual water. After 20 freeze thaw cycles, the CCM prepared with isopropyl alcohol and butyl acetate showed less degradation in terms of polarization curves and EIS. And the ionic resistances of the both CCMs decreased to a certain extent. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.