燃料电池用磺化聚苯乙烯膜降解机理及其复合膜的初步研究

Primary Study on Degradation Mechanism of Polystyrenesulfonic Acid Membrane and Its Composite Membrane in Fuel Cells

对用磺化聚苯乙烯 (PSSA)膜组装的质子交换膜燃料电池 (PEMFC)进行寿命实验 ,通过高效液相色谱分析 PSSA膜电池寿命实验期间阴极和阳极侧的排水量 ,能谱分析电池寿命实验前后 PSSA膜断面 S元素含量的分布 ,红外光谱分析 PSSA膜结构的变化 ,根据分析结果推断出 PSSA膜的降解机理 .O2 在阴极还原时产生 H2 O2 中间产物 ,H2 O2 又与电池中微量的金属离子反应产生 HO· 和 HO2 · 等氧化性自由基 ,这些自由基进攻 PSSA膜 α碳上的叔氢而导致膜降解 .膜降解主要发生在电池阴极侧 ,降解过程中苯环和磺酸根同时从 PSSA膜上脱离 .根据 PSSA膜的降解机理设计了 PSSA-Nafion复合膜作为 PEMFC电解质 ,2 5μm厚的 Nafion1 0 1膜位于电池阴极侧 ,该复合膜组装的 PEMFC稳定操作 80 0

The lifetime behavior of the proton exchange membrane fuel cell(PEMFC) fabricated with polystyenesulfonic acid(PSSA) membrane was investigated in order to present the degradation mechanism of the PSSA membrane. The water evacuated from the anode and the cathode of the cell during the lifetime experiment was analyzed by the method of high\|performance liquid chromatogram. The distribution of S concentration in the cross\|section of the PSSA membrane was measured by energy dispersive spectrograph. Infrared spectroscopic measurements were carried out to investigate the structure of the PSSA membrane before and after the fuel cell experiment. The degradation mechanism of the PSSA membrane is indicated as that: during the fuel cell operation, the reduction of O\-2 gas at the cathode proceeds through a peroxide intermediate. H\-2O\-2 reacts with the trace metal ions in the cell to form HO\+\5, HO\-2\+\5 and other oxidation radicals, which can chemically attack the tertiary hydrogen at the \%α\%\|carbon of the PSSA membrane. The degradation of the PSSA membrane mainly occurs from the cathode of the cell. The loss of the aromatic ring and the SO\+-\-3 group simultaneously occurs from the PSSA membrane. A PSSA\|Nafion composite membrane was prepared according to the above\|mentioned degradation mechanism of the PSSA membrane. The Nafion 101 membrane of 25 μm thickness is located at the cathode. The PEMFC with the PSSA\|Nafion composite membrane could be operated steadily for more than 800 hours without significant performance deterioration.