Effects of organic solvents on the structure and performance of catalyst coated membrane used in PEM fuel cells
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摘要: 采用直接喷涂法将催化剂涂覆在质子交换膜上形成CCM（catalyst coated membrane），CCM与碳纸扩散层组成膜电极用于质子交换膜燃料电池。制备CCM的混合液由质量分数20%的Pt/C催化剂、质量分数5%的Nafion溶液、有机溶剂和水组成。不同的有机溶剂（乙醇、异丙醇和叔丁醇）、有机溶剂的含量、溶剂的挥发速率直接影响所制备的CCM孔结构，进而影响膜电极的电化学性能。采用扫描电镜（SEM）表征了膜电极的表面形貌和孔结构；采用单体质子交换膜燃料电池（PEMFC）的电流密度-电压曲线评价了膜电极的极化特性。实验结果表明，以异丙醇为溶剂，异丙醇与Nafion溶液的质量比为4.28，在 50℃~75℃制备的CCM具有良好的孔结构和膜电极性能。Abstract: Catalyst coated membrane (CCM) was prepared by direct spraying deposition of the catalyst on the surface of proton exchange membrane, which was then assembled with carbon paper diffusion layers to form a membrane electrode assembly (MEA) for the proton exchange membrane fuel cell (PEMFC). The mixture solution for preparing CCM was composed of 20%(mass ratio) Pt/C catalyst, 5%(mass ratio) Nafion solution, organic solvent and de-ionized water. The surface morphology and pore structure were characterized by the environmental scanning electron microscopy (SEM) and the polarization characteristics of MEA were evaluated by the current-voltage curves of a single PEMFC. The results indicated that the selection of solvent (ethanol, isopropyl alcohol and tert-butyl alcohol) as well as its content and volatility exhibit direct impact on the pore structure of catalyst layers of CCM, which affects the electrochemical performances of MEA. CCM fabricated with isopropyl alcohol solvent and a mass ratio of 4.28 to Nafion solution under 50℃~75℃ exhibits an improved pore structure and I-V characteristic of MEA obtained.
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