(278c) Utilization of Metal Phthalocyanines as Cathode Catalysts of Proton Exchange Membrane Fuel Cells

In this study, phthalocyanines of cobalt, iron and nickel were synthesized via phthalic anhydride-urea method and used as cathode catalyst of proton exchange membrane fuel cells. Infrared spectrometry and X-Ray diffractometry were used for the verification of the synthesis. Thermal gravimetric analysis (TGA) revealed the decomposition behaviors of the different metal phthalocyanines. Catalyst materials were prepared by the impregnation method so that each one contains either cobalt (4%), iron (4% or 10%) or nickel (4%) phthalocyanines on carbon black (Vulcan XC72) matrix. The impregnated catalysts were pyrolyzed at 600^oC or 1000^oC and cathode electrodes were prepared by these catalysts as well as unpyrolyzed ones obtained by the spraying technique. The impregnated catalysts were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS) and pore structures were analyzed by means of a surface area analyzer. All of the anode electrodes were prepared by using Pt (20%) containing catalysts. Voltage-current density characteristics of the manufactured membrane electrode assemblies (MEA) were determined by means of a test station having a 5 cm² test cell.

The cobalt phthalocyanine based cathode catalysts were more active than iron phthalocyanine based catalysts. The increased pyrolysis temperature showed a positive effect on the performance of the fuel cell prepared with metal phthalocyanine catalytic cathodes. Whereas, unpyrolyzed cobalt phthalocyanine impregnated on carbon black exhibited low performance.The highest power attained was 0.04W/cm² which was obtained by using the MEA having a loading density of 0.28mg Co/cm², prepared from the CoPc/C catalyst pyrolyzed at 1000 ^oC. Increasing the impregnated catalyst amount did not result an increase in the performance. Contrarily, the performance of the iron phthalocyanine with 4% loading on the carbon black was higher than 10% loading . Nickel phthalocyanine based catalysts, either unpyrolyzed or pyrolyzed at 600 or 1000^oC did not exhibit a potential catalytic effect.