Studies of performance degradation of a high temperature PEMFC based on H₃PO₄-doped PBI

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• 作者：Gang Liu ; Huamin Zhang ; Jingwei Hu ; Yunfeng Zhai ; Dongyan Xu and Zhi-gang Shao
• 刊名：Journal of Power Sources
• 出版年：2006
• 出版时间：8 November 2006
• 年：2006
• 卷：162
• 期：1
• 页码：547-552
• 全文大小：856 K

文摘

In this paper, a 600 h life test of a high temperature PEMFC based on phosphoric acid (H₃PO₄)-doped polybenzimidazole (PBI) (H₃PO₄/PBI HT-PEMFC) at a current density of 714 mA cm⁻² (the beginning 510 h continuous test) and 300 mA cm⁻² (the last 90 h intermittent test) was carried out. After the life test, degradation of the MEA occurred. The H₂ crossover rate through the PBI membrane and the open circuit voltage (OCV) of the cell were tested with time. The results showed that, at the beginning of 510 h continuous test, the PBI membrane did not show much physical degradation, but during the last 90 h test there was a remarkable physical degradation which resulted in a higher H₂ crossover. The catalysts, PBI membranes and the membrane electrode assemblies (MEAs) before and after the life test were comprehensively examined by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). TEM results showed that the particle size of the Pt/C catalysts in the anode and cathode increased from 3.72 to 7.40 and 8.39 nm, respectively. SEM images of MEA in cross-section revealed that the PBI membrane became thin after the life test. EDS analysis implied the leaching of H₃PO₄ from the PBI membrane had occurred. Therefore, we conclude that physical degradation of PBI membrane, agglomeration of the electrocatalysts (both anode and cathode) and the leaching of H₃PO₄ from the PBI membrane were responsible for the performance degradation of the H₃PO₄/PBI HT-PEMFC.