Modification of Nafion membranes with ternary composite materials for direct methanol fuel cells

Composite membranes for direct methanol fuel cells (DMFCs) were prepared by using Nafion115 membrane modification with polyvinyl alcohol (PVA), polyimide (PI) and 8-trimethoxysilylpropyl glycerin ether-1,3,6-pyrenetrisulfonic acid (TSPS). The performance of the composite membranes was evaluated in terms of water sorption, dimensional stability, thermal stability, proton conductivity, methanol permeability and cell performance. The proton conductivity was slightly decreased by 1-3% compared with Nafion115, which still kept the high proton conduction of Nafion115. The methanol permeability of Nafion/PI-PVA-TSPS composite membranes was remarkably reduced by 35-55% compared with Nafion115. The power density of DMFCs with Nafion/PI-PVA-TSPS composite membranes reached to 100 mW/cm², exceeding that with Nafion115 (68m W/cm²).     

Decreasing resistances of membrane-electrode assemblies containing hydrocarbon-based ionomers for improving their anodic performances

To improve methanol-oxidation performances of membrane-electrode assemblies composed of a hydrocarbon-based ionomers, the resistances involved in the reaction were decreased. Electrochemical impedance spectroscopy revealed that the proton-conductive resistance (R_i) in the anode was decreased from 0.54 to 0.40 Ω cm² by increasing a loading ratio of platinum-ruthenium to carbon support of anode catalyst from 54 to 73 wt.%. In addition, R_i was decreased to be 0.25 Ω cm² by increasing ion-exchange capacity (IEC) of the ionomer from 1.4 to 2.9 mequiv. g⁻¹. Consequently, the polarization resistance of the anode was significantly decreased, in turn, increasing current density of methanol oxidation at the potential of 0.45 V from 0.110 to 0.244 A cm⁻².     

Glassy carbon electrode modified with Nafion-Au colloids for clenbuterol electroanalysis

Stable Nafion-Au colloids were immobilized on a glassy carbon electrode (GCE) for detection of β-agonist clenbuterol by electroanalysis. The Au colloids were prepared by a one-step electrodeposition onto GCE, with obvious electrocatalytic activity present. The negatively charged Nafion film was an efficient barrier to negatively charged interfering compounds, resulting in accumulation of positively charged clenbuterol at the Nafion film. The electrochemical characters of the electrode during various modified steps in a redox probe system of K₄[Fe(CN)₆]/K₃[Fe(CN)₆] were confirmed by cyclic voltammetry (CV) and AC-impedance. In Britton-Robinson (B-R) buffer solution (pH = 2.0) and the potential range of −0.2 to 1.2 V, the Nafion-Au colloid modified electrode, compared to a bare GCE, exhibits obvious electrocatalytic activity towards the redox of clenbuterol by greatly enhancing the peak current with a linear calibration curve from 8.0 × 10⁻⁷ to 1.0 × 10⁻⁵ mol/L and a detection limit of (1.0 × 10⁻⁷ mol/L) (R = 0.996). The modified electrode shows high sensitivity, selectivity and reproducibility. The recovery for detecting clenbuterol (∼10⁻⁶ mol/L) in human serum is up to 98.19%.     

Effect of polymer binders in anode catalyst layer on performance of alkaline direct ethanol fuel cells

In preparing low-temperature fuel cell electrodes, a polymer binder is essential to bind discrete catalyst particles to form a porous catalyst layer that simultaneously facilitates the transfer of ions, electrons, and reactants/products. For two types of polymer binder, namely, an A3-an anion conducting ionomer and a PTFE-a neutral polymer, an investigation is made of the effect of the content of each binder in the anode catalyst layer on the performance of an alkaline direct ethanol fuel cell (DEFC) with an anion-exchange membrane and non-platinum (non-Pt) catalysts. Experiments are performed by feeding either ethanol (C₂H₅OH) solution or ethanol–potassium hydroxide (C₂H₅OH–KOH) solution. The experimental results for the case of feeding C₂H₅OH solution without added KOH indicate that the cell performance varies with the A3 ionomer content in the anode catalyst layer, and a content of 10 wt.% exhibits the best performance. When feeding C₂H₅OH–KOH solution, the results show that: (i) in the region of low current density, the best performance is achieved for a membrane electrode assembly without any binder in the anode catalyst layer; (ii) in the region of high current density, the performance is improved with incorporation of PTFE binder in the anode catalyst layer; (iii) the PTFE binder yields better performance than does the A3 binder.     

燃料电池用新型质子交换膜的研究进展

质子交换膜燃料电池(PEMFC)以其高效、清洁、高能量密度和高功率密度等诸多优点正引起人们越来越多的关注和研究．目前,质子交换膜是制约PEMFC技术应用的一个主要问题．为此,开发性能良好、成本经济的新型质子交换膜是一项很有意义的工作、综述了近几年国内外在新型质子交换膜(包括全氟磺酸膜、部分含氟磺酸膜、非氟质子交换膜)方面的研究进展．     

Degradation mechanism study of PTFE/Nafion membrane in MEA utilizing an accelerated degradation technique

Nafion membranes are widely used for commercial membrane electrode assemblies (MEAs) in proton exchange fuel cells (PEMFCs). The polytetrafluoroethylene (PTFE)/Nafion (PN) composite membrane has the advantages of being low in cost, high in mechanical strength, and does not swell excessively. This study focuses on the properties of PTFE/Nafion membranes and PTFE/Nafion MEAs by comparing the durability and performance of the PN MEAs to commercial Nafion 211 MEAs. In an accelerated degradation test (ADT), the characterization of PTFE/Nafion and Nafion MEAs were analyzed using in-situ electrochemical methods such as polarization curves, AC impedance, cyclic voltammetry (CV), and linear sweep voltammetry (LSV). The results demonstrate an increase in the internal resistance on the PTFE/Nafion MEA only. The three mechanisms behind this unique result were proposed to be: (a) Separation of the catalyst layer from the membrane due to creep deformation; (b) Separation of the outer Nafion layer film from the core PTFE/Nafion membrane due to creep deformation; (c) Degradation of the Nafion plane (or Nafion dissolution) from the PTFE surface.     

温度和湿度对Nafion膜氢传感器性能的影响

系统研究了以Nafion112膜为电解质的氢传感器在不同工作环境下的氢敏感性能.结果表明,以Nafion112膜为电解质的氢传感器对氢具有很好的敏感性,可以实现微量氢气泄漏的快速检测.该传感器在氢气体积分数为(500～3000)×10^-6时的响应电压与氢气体积分数的对数呈线性关系,为标定不同环境下氢气含量与传感器响应电压的对应关系提供了依据.在相同湿度条件下,传感器响应电压随温度的升高而下降.湿度对传感器响应电压的影响与温度相关:温度较低时,响应电压随湿度的增加而下降;温度较高时,响应电压随湿度的增加而升高.     

离聚物对PET／LDPE共混物的结构与性能研究

用双螺杆挤出机反应性挤出的方法合成了低密度聚乙烯接枝马来酸镧（ＬＤＰＥ－ｇ－ＭＡＬａ）离聚物。与其它方法相比，该法具有工艺简单，易于工业化生产的特点。我们将离聚物与ＰＥＴ，ＬＤＰＥ在双螺杆挤出机上熔融共混挤出，并用注射成型机制备标准样条，对共混物力学性能进行了测试，发现离聚物有显著的增韧效果，另外，通过ＩＲ，ＤＳＣ，溶解性实验，分子量的测定等还考察了离聚物对ＰＥＴ／ＬＤＰＥ共混体系的结构影响。     

镁表面Nafion/聚吡咯与Nafion/二甲基亚砜有机涂层耐蚀性能的研究

采用浸镀法在镁基体表面制备了Nafion/聚吡咯和Nafion/二甲基亚砜(DMSO)有机涂层,利用光学显微镜和电化学测量系统研究了有机涂层的形貌及其耐蚀性能.结果表明,Nafion/聚吡咯有机涂层的厚度随着浸镀次数的增加几乎不变,且Nafion/聚吡咯有机涂层降低了镁的耐蚀性能;而Nafion/DMSO有机涂层的厚度则随着浸镀次数的增加而线性增加,并且Nafion/DMSO有机涂层能有效地改善镁的耐蚀性能,耐蚀性能随着涂层厚度的增加而提高.与无涂层的试样相比,耐蚀性能最高提高18倍.     

Nafion改性多级孔径石墨烯气凝胶制备与性能研究

通过溶胶-凝胶法制备了孔径小于1 μm的多级孔径新型石墨烯气凝胶。制备过程中, 首先通过Nafion对氧化石墨烯(GO)表面进行化学修饰, 并利用乙二胺还原制备石墨烯水凝胶, 最终通过冷冻干燥形成石墨烯气凝胶。实验发现Nafion可以有效减少制备过程中氧化石墨烯的团聚, 使石墨烯气凝胶形成多级孔径形貌。所得石墨烯气凝胶的孔径可控制在1 μm以内, 远小于传统石墨烯气凝胶材料的孔径(20~100 μm)。这种具有独特结构的石墨烯气凝胶表现出优异的性能, 例如高比表面积, 高孔隙率, 其电化学电容性能相对传统气凝胶提高了约40%。