In order to develop a non-precious metal cathode for PEFCs, we have tried to improving oxygen reduction activity of Zr oxide-based cathodes. We succeeded to prepare Zr oxide-based cathodes with fine primary particles using zirconium oxy-phthalocyanine as a starting material. However, secondary particle size was very large, resulting that the activity was insufficient. Therefore, we performed ball mill to crack secondary particles for increasing the actual surface area. In addition, nitridation of oxide-based compounds was performed to increase the active sites for oxygen reduction reaction such as oxygen defects and/or nitrogen atoms including oxide lattice.
Platinum, which is used as cathode electrocatalysts for polymer electrolyte fuel cell, have many problems such as its high cost, small amount of resource, insufficient activity for oxygen reduction reaction (ORR) and stability. In this study, we focused on titanium, which had large amount of resources, and tried to prepare higher active catalysts by pyrolysis or combination of pyrolysis and partial oxidation of oxytitanium phthalocyanine which had both C and N. It was revealed that the partial oxidation of catalyst during heat treatment was efficient to obtain high activity of ORR. The maximum current density at 0.8V vs. RHE was about 108 mA g-cat./C-1. This result indicated that the titanium oxide-based compounds had great potential as alternative cathodes for platinum.
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