Abstract

Chitin nanowhiskers (Chws) were prepared from shrimp shells and modified by imidazole groups, using 3-Glycidoxypropyltrimethoxysilane (GPTMS), as a coupling agent, for application in direct methanol fuel cell (DMFC) membranes. New nanocomposite membranes were fabricated by incorporating the ChWs or imidazole modified chitin nanowhiskers (Chw-Im) into chitosan (CS) and Nafion (a perfluorinated ionomer) matrices as representative polycationic and polyanionic polymers, respectively. The electrostatic and hydrogen bond interactions between the positively charged imidazole groups on the surface of the Chw-Im and the proton conducting sites on Nafion or CS chains can form new proton conducting pathways at the interface of the Chw-Im and the polymer matrix, which results in an improvement in the membrane performance. The characteristics of these nanocomposite membranes, as well as the Chws and Chw-Im, were investigated by Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), ion exchange capacity (IEC) and water uptake, as well as the proton conductivity method. The results showed that the incorporation of the modified nanowhiskers could conduct at a lower methanol permeability, in parallel to an enhancement in the selectivity parameter (the ratio of proton conductivity to the methanol permeability) in the nanocomposite membranes, compared to neat Nafion or pristine CS membranes, which shows that the nanocomposites based on Chw-Im can be utilized as an efficient polyelectrolyte membrane for application in DMFCs.

摘要

几丁质纳米晶须 (Chws) 由虾壳制备并通过咪唑基团改性，使用 3-环氧丙氧基丙基三甲氧基硅烷 (GPTMS) 作为偶联剂，用于直接甲醇燃料电池 (DMFC) 膜。通过将 ChWs 或咪唑改性的几丁质纳米晶须 (Chw-Im) 加入壳聚糖 (CS) 和 Nafion（一种全氟化离聚物）基质中，分别作为代表性的聚阳离子和聚阴离子聚合物，制备了新的纳米复合膜。Chw-Im 表面带正电荷的咪唑基团与 Nafion 或 CS 链上的质子传导位点之间的静电和氢键相互作用可以在 Chw-Im 和聚合物基体的界面处形成新的质子传导通路，从而导致膜性能的改善。通过傅里叶变换红外光谱 (FTIR)、透射电子显微镜 (TEM)、场发射扫描电子显微镜 (FESEM)、能量色散光谱 (EDS) 研究了这些纳米复合膜以及 Chws 和 Chw-Im 的特性。 )、X 射线衍射 (XRD)、离子交换容量 (IEC) 和吸水率，以及质子电导率方法。结果表明，与纯 Nafion 或原始 CS 相比，改性纳米晶须的掺入可以在较低的甲醇渗透率下进行，同时提高纳米复合膜中的选择性参数（质子电导率与甲醇渗透率的比率）膜，这表明基于 Chw-Im 的纳米复合材料可用作有效的聚电解质膜，用于 DMFC。