物理化学学报 >> 2019, Vol. 35 >> Issue (5): 517-522.doi: 10.3866/PKU.WHXB201806011

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墨水溶剂对低铂含量质子交换膜燃料电池性能的影响

陈雯慧,陈胜利*()   

  • 收稿日期:2018-05-09 发布日期:2018-10-19
  • 通讯作者: 陈胜利 E-mail:slchen@whu.edu.cn
  • 基金资助:
    国家自然科学基金(21633008);国家自然科学基金(21673163)

Effect of Ink Solvents on Low-Pt Loading Proton Exchange Membrane Fuel Cell Performance

Wenhui CHEN,Shengli CHEN*()   

  • Received:2018-05-09 Published:2018-10-19
  • Contact: Shengli CHEN E-mail:slchen@whu.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(21633008);the National Natural Science Foundation of China(21673163)

摘要:

由于铂的资源稀缺,开发用于质子交换膜燃料电池(PEMFC)的低铂含量电极至关重要。与传统的高铂含量电极相比,低Pt膜电极(MEA)中电解质离聚物的分布状态和电极的表面形态对其性能有着更重要的影响。本工作研究了催化剂墨水溶剂对所制备的低Pt含量(0.1 mg·cm-2)燃料电池阴极性能的影响。单电池测试表明,与其他溶剂相比,以异丙醇-水混合物作为溶剂所得到的电极具有最好的性能。通过扫描电镜和透射电镜的测试发现,该电极表面形貌和催化剂与离聚物的分散性的均匀性都有所改善。其原因是由于加入的水增强了溶液内的氢键作用,使溶剂蒸发速率减慢,同时也使溶剂的介电常数增加而提高离聚物的分散性。动态光散射的结果表明,催化剂与离聚物的粒子尺寸也受到溶剂的影响,最佳尺寸范围为400–800 nm范围内。

关键词: 质子交换膜燃料电池, 膜电极, 溶剂, 氢键, 介电常数

Abstract:

Owing to the scarcity of platinum, it is of high importance to develop electrodes with low platinum metal loading and to thereby improve the utilization of Pt for the commercialization of proton-exchange membrane fuel cells (PEMFCs). In comparison to conventional high-platinum electrodes, the thickness of the catalyst layer (CL) is thinner and the interatomic Pt spacing is larger for the low-Pt loading electrodes. The distribution of electrolyte ionomer and the electrode morphology, which are strongly influenced by the solvents used in the fabrication process, are therefore increasingly important factors for achieving high performance in the membrane electrode assembly (MEA). In this work, different solvents with various dielectric constants and evaporation rates were used to prepare the inks for low-Pt loading cathode (0.1 mg·cm-2) fabrication. First, the inks were fabricated by dispersing the catalyst and ionomer in different solvents which were then coated onto carbon paper to prepare the gas diffusion electrodes. The anode and cathode electrodes were then hot-pressed together with the Nafion membrane to produce the MEAs. The results showed a mixture of isopropanol-water (4:1) yielded the best-performing MEA during the single-cell tests compared to the other solvents tested. In order to elucidate the relationship between the performance of MEAs and the solvents, the structure and the surface morphology of the CL and the distribution of Nafion ionomer in the CL was characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A comparison of the SEM and TEM images of representative samples indicated that the best performing electrode had a much improved homogeneity in the surface morphology as well as the dispersion of catalyst and ionomer. This was because of the moderate evaporation rate and better dispersion, caused by the increased hydrogen bonding and high dielectric constant, respectively. The results from dynamic light scattering (DLS) showed that the size of the catalyst and ionomer aggregates are influenced by the solvents. It is suggested that larger aggregates might help the formation of holes in the CL for gas diffusion and water removal, with the optimum size found to be around 400–800 nm. In conclusion, the MEA fabricated from the isopropanol-water solvent exhibited a significantly increased power density (1.79 W·cm-2), and the utilization of Pt was increased to approximately 0.047 mg·W-1, which is among the best-performing fuel cells reported to date.

Key words: Proton exchange membrane fuel cell, Membrane electrode assemble, Solvent, Hydrogen bond, Dielectric constant

MSC2000: 

  • O646