Effect of Nanostructure of the Electrocatalyst Based on Carbon Nanotube for the Activation Overpotential for PEFC
Polymer electrolyte fuel cells (PEFC) are considered as one of the promising power sources for automobile and house in near future due to their high energy conversion efficiency and compactness. Recently high temperature PEFC using the polymer membrane doped with liquid phosphoric acid (PA) is attracting strong interest since it shows higher power density, CO poisoning on platinum (Pt) can be avoided and no cooling and humidifying devices are required. However, it was pointed the high temperature PEFC has poor durability due to leaching of PA from the membrane, which causes the deterioration of PEFC performance during long-term operation. To overcome this issue, poly(vinylphosphonic acid) (PVPA) was used as the electrolyte instead of PA. We found the membrane doped with PVPA was free from the leaching of the electrolyte since PVPA is polymer and solid acid. Although this PEFC showed high durability, this catalyst had large overpotential in the area of low current density, probably because the poisoning of Pt by PVPA coating or the lack of electrolyte in catalyst layers. In this study, first we explored the new preparation method to avoid the Pt poisoning and investigated the catalytic performance by electrochemical techniques. And then, we increased the amount of acid in the electrolyte and compared the overpotential.
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