质子交换膜燃料电池研究进展

由于质子交换膜燃料电池（PEMFC）具有能量转化效率高、寿命长、比功率和比能量高、以及对环境友好等优点,近年来得到迅速发展.笔者综述了PEMFC的特点,分析了PEMFC在国内外的最新研究进展,介绍了PEMFC的应用前景,并指出了PEMFC研究当前需要解决的技术问题及其发展趋势.     

Membrane performance comparison in a proton exchange membrane fuel cell (PEMFC) stack

A 5-cell proton exchange membrane fuel cell (PEMFC) stack with different types of membrane electrode assemblies (MEAs) was tested to compare their performances and electrochemical characteristics. The experimental data were obtained with a stack of 5 cells and active area of 125 cm². The stack consisted of different Nafion^® and hydrocarbon membranes with the same types of electrocatalyst. The membranes were installed in different cells and in the same stack. Polarization and voltage measurement data were obtained to compare their performances at different temperatures and anode humidity conditions. Also, impedance spectroscopy data were obtained in similar manner to compare the differences in their resistance.     

High temperature proton exchange membrane fuel cell using a sulfonated membrane obtained via H2SO4 treatment of PEEK-WC

A method for the sulfonation of PEEK-WC, a glassy poly(ether ether ketone) with sulphuric acid is presented. Depending on the reaction time, polymers with ion exchange capacity (IEC) from 0.30 to 0.76 meq_H⁺/g are obtained, as determined by titration with NaOH solutions. The thermal properties of the polymers were studied by differential scanning calorimetry, showing that the glass transition temperature increases with increasing degree of sulfonation, from 224 °C for pure PEEK-WC to 246 °C for the polymer having an IEC of 0.76 meq_H⁺/g. The sulfonated polymers were used to prepare proton exchange membranes for possible application in fuel cells. Dense membranes were prepared by solvent evaporation, using DMA as the solvent. The transport properties of the membranes were determined in terms of water uptake and permeability for hydrogen and oxygen. Electrochemical characterization was performed by measuring cell voltage and power density curves as a function of current density at different working temperatures and the results were compared with those of a commercial Nafion membrane. A power density of 284 mW/cm² was obtained for S-PEEK-WC membrane at 120 °C in H₂/air fuel cell, slightly above the corresponding value found for Nafion.     

Effect of gas diffusion layer compression on the performance in a proton exchange membrane fuel cell

This study investigates the gas permeability, bulk density, thickness and conductivity of two types of gas diffusion layer (OC14, NC14) as a function of the compressed thickness. The compression of a gas diffusion layer reduces gas permeability and contact resistance. The performance is measured using a single proton exchange membrane fuel cell (PEMFC) with an active area of 25 cm². The results provide an optimum value of compression ratio that maximizes the cell performance. For OC14 the optimum compression ratio is about 64%, whereas for NC14 it is 59%. The best performances are 375 mA/cm² and 296 mA/cm² at 0.7 V, respectively. These results concerning the balance between compression and performance provide vital information for the fabrication of stacks and support for industrial applications.     

质子交换膜燃料电池研究及应用现状

介绍了国内外质子交换膜燃料电池(PEMFC)研究的整体现状及水平,分别讨论了PEMFC的3个关键部件:质子交换膜的材料要求,电化学反应催化剂的特点,膜电极的组成、制备工艺和最新进展,重点讨论了全氟磺酸型质子交换膜的类型、优缺点和当前的研究方向。在此基础上,追述了近年来国内外以PEMFC作为电动汽车动力源的实际应用情况,并指出应用PEMFC存在的问题。可以看到,PEMFC具有广阔的应用前景,将会在电动汽车方面得到最早的商业化应用。     

Basic examination of membrane electrode assembly of proton exchange membrane fuel cell considering heat deterioration

The purpose of this research is to develop a standard preparation method for membrane electrode assemblies (MEAs). Therefore, the preparation method for multilayered MEAs with gas diffusion layers (GDLs) and the degree to which polymer membranes deteriorate by heating were studied. As a result, improvement of power density by making multi catalyst layers provides a solution to some problems found in thin polymer membranes. In addition, it was found that improving the diffusion of gas through two-layer GDLs in cathode (duct side: carbon paper, catalyst layer side: carbon cross) results in a cross leak reduction. Moreover, a making condition of MEAs was optimized by varying the temperatures used for the multi catalyst layers and two-layer GDLs. The analysis of heat deterioration of the Nafion membrane using X-ray photoelectron spectroscopy (XPS) indicates that the optimal hot press temperature is 130 °C.     

Multiblock sulfonated-fluorinated poly(arylene ether)s for a proton exchange membrane fuel cell

New proton exchange membranes were prepared and evaluated as polymer electrolytes for a proton exchange membrane fuel cell (PEMFC). Sulfonated-fluorinated poly(arylene ether) multiblocks (MBs) were synthesized by nucleophilic aromatic substitution of highly activated fluorine terminated telechelics made from decafluorobiphenyl with 4,4′-(hexafluoroisopropylidene)diphenol and hydroxyl-terminated telechelics made from 4,4′-biphenol and 3,3′-disulfonated-4,4′-dichlorodiphenylsulfone. Membranes with various sulfonation levels were successfully cast from N-methyl-2-pyrrolidinone. An increase sulfonated block size in the copolymer resulted in enhanced membrane ion exchange capacity and proton conductivity. The morphological structure of MB copolymers was investigated by tapping mode atomic force microscopy (TM-AFM) and compared with those of Nafion^® and sulfonated poly(arylene ether) random copolymers. AFM images of MBs revealed a very well defined phase separation, which may explain their higher proton conductivities compared to the random copolymers. The results are of particular interest for hydrogen/air fuel cells where conductivity at high temperature and low relative humidity is a critical issue.     

Diffusion in porous functional materials: Zeolite gas separation membranes, proton exchange membrane fuel cells, dye sensitized solar cells

The function of numerous technical apparatus and processes is diffusion controlled. In three cases studies, the diffusion of molecules, ions and electrons in gas separation membranes, fuel cell membranes and dye sensitized solar cells is discussed. In novel functional materials often an overlap of transport due to a concentration and/or a potential gradient takes place. The transport parameters measured in materials evaluation such as impedance spectroscopy can reflect a physical situation which is different from that of the working device. A detailed fundamental knowledge of various factors is necessary to fully understand the nature of transport as a basis to optimise the corresponding functional materials.     

Prediction of methanol and water fluxes through a direct methanol fuel cell polymer electrolyte membrane

Development of a direct methanol fuel cell (DMFC) mass flux model, using conventional transport theory, is presented and used to predict the fluid phase superficial velocity, methanol and water molar fluxes, and the chemical species (methanol and water) dimensionless concentration profiles in the polymer electrolyte membrane, Nafion^® 117, of a DMFC. Implementation of these equations is illustrated to generate the numerical data as functions of the variables such as the pressure difference across the membrane, methanol concentration at the cell anode, temperature, and position in the membrane.     

Development of a residence time distribution method for proton exchange membrane fuel cell evaluation

New in situ and minimally invasive methods are needed to quantify the presence of liquid water and ice within operating proton exchange membrane fuel cells. A volume sensitive residence time distribution technique was developed based on CO₂ tracer and infrared detection. The method, components and operation are detailed (tracer injection and detection, data scaling, calibration, and pressure correction). The measurement system was characterized by an electronic signal processing response time of 43 ms, accuracy and repeatability better than 0.5-5% error in transit time measurement and sufficient sensitivity to detect less than 10% changes in flow field channel and gas diffusion electrode void volumes. Results obtained with a simplified model fuel cell (single flow field channel, absence and presence of a gas diffusion layer) revealed the presence of two time resolved mechanistic steps for negative tracer step cases (convective tracer removal from flow field channel, diffusive tracer removal from gas diffusion layer). A one-dimensional model was derived using convective diffusion in flow field channels and cross-flow tracer exchange proportional to the concentration difference between flow field channel and gas diffusion electrode. Numerical computations showed good agreement with the model fuel cell experimental results.     

中压氢-氧质子交换膜燃料电池的运行特性

通过设计阴极流道宽度为1 mm与2 mm的单电池,研究了不同温度下闭口中压氢-氧质子交换膜燃料电池的运行特性。结果表明：(1)2 mm的电池有较好的闭口稳定运行特性,在800 mA·cm-2下,1 mm的电池闭口运行时,大约经过3 min,电压从0.7 V下降到0.5V,而2 mm的流场结构能实现电池53 min的运行;(2)电池性能随温度的升高而下降,相对于65℃运行,温度为80℃时,1mm的电池闭口运行时,大约经过1.7 min,电压从0.69 V下降到0.5 V,此时为维持电池的高性能运行,氧气侧所需的排放时间越短;(3)电池的内阻随温度的升高而增大,高温时增幅较小。     

Medium-chain-length poly-3-hydroxyalkanoates-carbon nanotubes composite as proton exchange membrane in microbial fuel cell

Medium-chain-length poly-3-hydroxyalkanoates (PHA) and carboxyl group-functionalized multiwalled carbon nanotubes (MC) were used to fabricate a composite membrane for application in a double-chambered microbial fuel cell (MFC). MC was composited into PHA at 5%, 10%, and 20% w/w via ultrasound dispersion blending method. PHA-MC composite was compared with Nafion 117 as proton exchange membrane in MFC operated with palm oil mill effluent (POME) wastewater. The composite exhibited prerequisite separator membrane characteristics. The dispersion of MC in the polymer matrix increased its interfacial surface area and water uptake properties. PHA-MC10% membrane in MFC showed maximum power density of 361?mW/m², which was comparable with Nafion 117 (372?mW/m²). Internal resistance decrease, chemical oxygen demand (COD) removal, coulombic efficiency (CE), and conductivity of the PHA-MC10% were superior to Nafion 117. The environmental-friendly material could provide an alternative towards realizing practical MFC application.     

质子交换膜燃料电池膜中气态水管理模型

分析质子交换膜燃料电池的膜水含量与运行参数的关系,从工程方法的角度建立水传输模型.模型分析得到,要提高膜的水合程度,需要通过增湿反应气体.过高的增湿反应气体又会引起阴极扩散层水的泛滥,需通过调节反应气体流量来缓解水的泛滥.为保证膜的高水合程度和低的阴极扩散层水的泛滥,建立了膜水含量的神经网络控制模型,为电池水管理奠定了基础.     

燃料电池用碱性膜材料的研究进展

碱性膜直接甲醇燃料电池因为结合了质子交换膜燃料电池和液体碱燃料电池的优点而产生自身独特的性质,使其可以在一定程度上弥补质子交换膜燃料电池以及液体碱燃料电池的缺点而尤其引人关注。其中碱性膜电解质为碱性膜燃料电池的核心组件,其性能直接关系到燃料电池的性能及寿命。截至目前,关于碱性膜材料的制备及应用方面的报道较多,涉及的碱性膜电解质的种类也较多。本文以燃料电池用碱性膜电解质为综述内容,对国内外关于碱性膜电解质的研究报道进行系统的梳理和介绍。     

Preparation of low-platinum-loading electrocatalysts using electroless deposition method for proton exchange membrane fuel cell systems

One promising preparative method that offers the potential for improved platinum (Pt) dispersion of electrocatalysts is electroless deposition (ED). In this study, the effects of multiwalled carbon nanotubes (MWCNTs) pretreatment and synthesis procedure on properties of the four catalysts, synthesized by ED method, have been considered. The results of energy-dispersive X-ray spectroscopy (EDS), X-ray dot-mapping, X-ray fluorescence (XRF) and cyclic voltammetry (CV) analyses showed that using palladium (Pd) precursor during two-step sensitization-activation coating procedure gives uniform Pt particles distribution on MWCNTs with low aggregation and high specific surface area (∼80 m² g⁻¹). In addition, to investigate the performance of the synthesized catalysts in experimental fuel cell system, thin-film method was used to fabricate the membrane electrode assemblies (MEAs). Obtaining the polarization curves for the fabricated MEAs (Pt loading ∼0.4 mg cm⁻²) and a commercial MEA (ElectroChem, Pt loading ∼1 mg cm⁻²) demonstrated that the catalyst prepared by two-step sensitization-activation coating procedure possesses a good performance despite of its lower Pt content.     

质子交换膜燃料电池动态过程的数值模拟

为描述质子交换膜燃料电池的动态过程,发展了一个基于计算流体动力学的非稳态、非等温的三维两相流数学模型.应用模型对一蛇形流道结构的质子交换膜燃料电池单体进行了数值计算,得到了电池启动过程中电池阴极侧膜表面温度和电流密度等特征参数的动态过程变化曲线.最后,分析了阴极入口速度、湿度和电池电压阶跃变化后电池特性的动态响应特性.结果表明：电池的启动时间和阶跃响应时间均为秒的数量级,与大多数模型模拟的结果相一致.     

Non-isothermal effects of single or double serpentine proton exchange membrane fuel cells

Mathematical models on transport processes and reactions in proton exchange membrane (PEM) fuel cell generally assume an isothermal cell behavior for sake of simplicity. This work aims at exploring how a non-isothermal cell body affects the performance of PEM fuel cells with single and double serpentine cathode flow fields, considering the effects of flow channel cross-sectional areas. Low thermal conductivities of porous layers in the cell and low heat transfer coefficients at the surface of current collectors, as commonly adopted in cell design, increase the cell temperature. High cell temperature evaporates fast the liquid water, hence reducing the cathode flooding; however, the yielded low membrane water content reduces proton transport rate, thereby increasing ohmic resistance of membrane. An optimal cell temperature is presented to maximize the cell performance.     

Preparation of proton exchange membranes based on crosslinked polytetrafluoroethylene for fuel cell applications

We prepared proton exchange membranes by the γ-ray-induced post grafting of styrene into crosslinked polytetrafluoroethylene (PTFE) films and subsequent sulfonation. The degree of grafting was controlled in the range of 7-75% by the crosslinking density of the PTFE matrix as well as the grafting conditions. Under our preparation conditions, the films at the grafting yield of ≥30% were found to produce ion exchange membranes with a homogeneous distribution of sulfonic acid groups. The resulting membranes showed a large ion exchange capacity up to 2.9 meq g⁻¹, which exceeded the performance of commercially available perfluorosulfonic acid films such as Nafion; nevertheless, they appeared to be dimensionally stable in water. These should undoubtedly result from the use of the crosslinked PTFE films as graft substrates and make our ion exchange membranes promising for applications to polymer electrolyte fuel cells.     

质子交换膜燃料电池强化传质

传质问题制约着燃料电池性能的提高。通过理论分析、Fluent模拟,针对质子交换膜燃料电池流道中加凸台和电极扩散层开孔两种方法,分别研究其对强化电池内部传质的效果。结果表明,上述两种方式均能有效强化电池内部传质,提高电池性能。但是加凸台增加了风机的寄生功率,综合性能提升不显著。     

氧化石墨烯在燃料电池质子交换膜中的应用

保护环境，开发环保型能源，对人类和社会具有重要意义。质子交换膜燃料电池由于其能量转化率高，可实现零排放，近年来引起了电池领域研究者们的兴趣。氧化石墨烯（GO）由于存在活性氧官能团，可以和离子型聚合物进行复合以制备复合质子交换膜。氧化石墨烯类的复合质子交换膜应用于燃料电池时可以提高膜在高温低湿度条件下的质子传导率，降低甲醇渗透率，提高电池的功率密度。本文首先介绍了氧化石墨烯的制备方法，然后从不同的离子型聚合物基质复合质子交换膜的类别出发，详细介绍了氧化石墨烯在Nafion、聚醚醚酮、聚苯并咪唑和壳聚糖等不同种类的离子型聚合物中的应用现状及作用机理，同时对其在质子交换膜的应用方面存在的问题及应用前景做了评论和展望。