高温质子交换膜研究进展

高温质子交换膜燃料电池（HT-PEMFCs）因其具有催化剂CO耐受性良好,能量转化率高,水热管理简单等优点,成为了能源领域重要的研究方向之一。高温质子交换膜（HTPEM）是它的主要部件之一,分别以水、磷酸分子和咪唑分子为质子传导载体分析了目前HTPEM的研究现状,比较后得出了以磷酸为质子载体的HTPEM性能最佳的结论,指出了研究中尚存的问题,并展望了未来HTPEM可能的研究方向。     

A Three‐Dimensional Non‐isothermal Model of High Temperature Proton Exchange Membrane Fuel Cells with Phosphoric Acid Doped Polybenzimidazole Membranes

High temperature proton exchange membrane fuel cells (HT‐PEMFCs) with phosphoric acid doped polybenzimidazole (PBI) membranes have gained tremendous attentions due to its attractive advantages over conventional PEMFCs such as faster electrochemical kinetics, simpler water management, higher carbon monoxide (CO) tolerance and easier cell cooling and waste heat recovery. In this study, a three‐dimensional non‐isothermal model is developed for HT‐PEMFCs with phosphoric acid doped PBI membranes. A good agreement is obtained by comparing the numerical results with the published experimental data. Numerical simulations have been carried out to investigate the effects of operating temperature, phosphoric acid doping level of the PBI membrane, inlet relative humidity (RH), stoichiometry ratios of the feed gases, operating pressure and air/oxygen on the cell performance. Numerical results indicate that increasing both the operating temperature and phosphoric acid doping level are favourable for improving the cell performance. Humidifying the feed gases at room temperature has negligible improvement on the cell performance, and further humidification is needed for a meaningful performance enhancement. Pressurising the cell and using oxygen instead of air all have significant improvements on the cell performance, and increasing the stoichiometry ratios only helps prevent the concentration loss at high current densities.     

An isothermal model of a laboratory intermediate temperature fuel cell using PBI doped phosphoric acid membranes

A two-dimensional isothermal model is described for an intermediate temperature fuel cell using a phosphoric acid doped polybenzimidazole (PBI) membrane. The model considered the membrane-electrode-assembly and gas flow channels. All the major transport phenomena were taken into account except the cross-over of species through the membrane. The catalyst layers were treated as spherical catalyst agglomerates with porous inter-agglomerate spaces. The inter-agglomerate spaces are filled with a mixture of electrolyte (hot phosphoric acid) and polytetrafluoroethylene (PTFE). The model was validated against experimental data and used to study the influence of the catalyst layer properties on performance. Through the analyses of the effectiveness factor the model showed that utilisation of catalyst particles was very low at high current densities. At these conditions, the reaction occurs mainly on the surface of the agglomerate. An optimum phosphoric acid loading was found from the model simulations. The model was also used to demonstrate the resistance of the intermediate temperature fuel cell to anode poisoning by CO.     

用于质子交换膜燃料电池的高温无机质子传导材料研究进展

质子交换膜是质子交换膜燃料电池（PEMFC）的核心部件，其主要作用是传导质子。无机质子传导材料作为一种新型的质子传导介质，近年来逐渐引起了人们的关注。本文主要介绍了小分子磷酸、无机沸石材料、固体酸和无机氧化物陶瓷材料等几种高温无机质子传导材料，并对它们的性能和特点进行了评述。主要结论如下：小分子磷酸质子传导率高，但是容易泄露；无机沸石材料化学稳定性好，但质子传导率尚有提高的空间；无机氧化物陶瓷材料力学性能和化学温度性能均很好，但质子传导率相对较低；固体酸质子传导率优异，高温稳定性也好，是最有希望在PEMFC中获得推广应用的材料。     

用于高温质子交换膜燃料电池的聚合物电解质膜研究进展

高温质子交换膜燃料电池在降低燃料电池水热管理复杂性、催化剂中毒方面有明显优势;可改善电池阴阳两极尤其是阴极氧气还原反应的动力学特性,提高电池的效率。聚合物电解质膜作为关键材料之一,在高温时易失水导致质子传导率降低、机械强度和热稳定性不高等问题。本文基于磺酸、磷酸和离子液体等不同质子传递介质,对高温聚合物电解质膜进行综述,比较了各类聚合物电解质膜的优缺点及应用时存在的问题,着重探讨嵌段共聚物在高温聚合物电解质膜方面的潜在应用,指出离子液体的添加不但可作为质子载体,而且在构建嵌段聚合物结构方面可发挥"诱导剂"作用。提出通过分子设计可更好了解嵌段聚合物的空间构效关系,进而通过结构设计提高膜的质子传导性能和稳定性。     

Effect of operating conditions on energy efficiency for a small passive direct methanol fuel cell

Energy conversion efficiency was studied in a direct methanol fuel cell (DMFC) with an air-breathing cathode using Nafion 117 as electrolyte membrane. The effect of operating conditions, such as methanol concentration, discharge voltage and temperature, on Faradic and energy conversion efficiencies was analyzed under constant voltage discharge with quantitative amount of fuel. Both of Faradic and energy conversion efficiencies decrease significantly with increasing methanol concentration and environmental temperature. The Faradic conversion efficiency can be as high as 94.8%, and the energy conversion efficiency can be as high as 23.9% if the environmental temperature is low enough (10 °C) under constant voltage discharge at 0.6 V with 3 M methanol for a DMFC bi-cell. Although higher temperature and higher methanol concentration can achieve higher discharge power, it will result in considerable losses of Faradic and energy conversion efficiencies for using Nafion electrolyte membrane. Development of alternative highly conductive membranes with significantly lower methanol crossover is necessary to avoid loss of Faradic conversion efficiency with temperature and with fuel concentration.     

High Molecular Weight Polybenzimidazole Membranes for High Temperature PEMFC

High temperature operation of proton exchange membrane fuel cells under ambient pressure has been achieved by using phosphoric acid doped polybenzimidazole (PBI) membranes. To optimize the membrane and fuel cells, high performance polymers were synthesized of molecular weights from 30 to 94 kDa with good solubility in organic solvents. Membranes fabricated from the polymers were systematically characterized in terms of oxidative stability, acid doping and swelling, conductivity, mechanical strength and fuel cell performance and durability. With increased molecular weights the polymer membranes showed enhanced chemical stability towards radical attacks under the Fenton test, reduced volume swelling upon the acid doping and improved mechanical strength at acid doping levels of as high as about 11 mol H₃PO₄ per molar repeat polymer unit. The PBI‐78kDa/10.8PA membrane, for example, exhibited tensile strength of 30.3 MPa at room temperature or 7.3 MPa at 130 °C and a proton conductivity of 0.14 S cm^–1 at 160 °C. Fuel cell tests with H₂ and air at 160 °C showed high open circuit voltage, power density and a low degradation rate of 1.5 μV h^–1 at a constant load of 300 mA cm^–2.     

Recent advances in polybenzimidazole/phosphoric acid membranes for high‐temperature fuel cells

Proton exchange membrane fuel cells are one of the most promising technologies for sustainable power generation in the future. In particular, high‐temperature proton exchange membrane fuel cells (HT‐PEMFCs) offer several advantages such as increased kinetics, reduced catalyst poisoning and better heat management. One of the essential components of a HT‐PEMFC is the proton exchange membrane, which has to possess good proton conductivity as well as stability and durability at the required operating temperatures. Amongst the various membrane candidates, phosphoric acid‐impregnated polybenzimidazole‐type polymer membranes (PBI/PA) are considered the most mature and some of the most promising, providing the necessary characteristics for good performance in HT‐PEMFCs. This review aims to examine the recent advances made in the understanding and fabrication of PBI/PA membranes, and offers a perspective on the future and prospects of deployment of this technology in the fuel cell market. © 2014 Society of Chemical Industry     

On a new degradation mode for high-temperature polymer electrolyte fuel cells: How bipolar plate degradation affects cell performance

The contribution of the bipolar plate material to the overall degradation of a high temperature membrane electrode assembly (HT MEA) for polymer electrolyte fuel cells (PEFCs) is studied in terms of performance decrease, phosphoric acid uptake in the bipolar plates and change of surface morphology of the bipolar plates. Two different high temperature graphite composites, a surface treated graphite and a gold coated stainless steel flowfield and the respective MEAs are compared after operation at 180 °C. Both graphite surface treatment and gold coating lead to negligible uptake of the electrolyte and ensure low degradation rates, whereas the composite plates exhibit high uptake of acid from the MEA into the surface near bulk. Apparent MEA degradation caused by acid redistribution from the MEA to the increasingly porous plates is observed in terms of increased ohmic cell resistances and reduction of catalyst utilization as consequence of acid loss from the catalyst layers.     

Polymerelektrolytmembranen für Hoch‐ und Niedertemperatur‐Brennstoffzellen aus strahlungsinduzierter Pfropfcopolymerisation

Radiation‐induced graft copolymerization of hydroxyethyl methacrylate with hydroxyethyl acrylate, acrylic acid or glycidyl methacrylate on ethylene tetrafluoroethylene (ETFE) films allow for tailor‐made synthesis of membranes for high and low temperature fuel cell applications. According to the operating temperatures proton conductivity may be achieved via doping with phosphoric acid or a two‐step sulfonation of the functional monomers. Fuel cell tests provide power densities and internal resistances, which indicate that the membranes are suitable for high and low temperature fuel cells.     

Alternatives toward proton conductive anhydrous membranes for fuel cells: Heterocyclic protogenic solvents comprising polymer electrolytes

Fuel cells are gaining increasing attention as a clean and promising technology for energy conversion. One of the key benefits of fuel cells compared to other methods is the direct energy conversion that enables the achievement of high efficiency. The electrolyte membrane is the most essential parts of a fuel cell unit, and consequently has been the subject of considerable research and development. Among the various types of proton conducting electrolytes examined for fuel cell applications, polymer electrolyte membranes (PEMs) are regarded as viable candidates since they enable operation of the cells at desirably low temperatures. This review describes recent progress in the design and development of high performance proton conducting PEMs, including the analysis of the design requirements and strategies for development of advanced PEMs for operation in anhydrous conditions. Some of the most widely used types of azole heterocycles are introduced and compared, particularly in terms of their performance characteristics in polyacids containing different functional groups. In addition, the latest research studies and progress in the field of azole-containing and azole-functionalized electrolyte systems are discussed and reviewed.     

三种燃料电池发电技术

燃料电池是一种新型的能量转换装置，本文详细介绍了磷酸型、熔融碳酸盐型以及固体氧化物电解质型三种主要类型的燃料电池的单电池结构、材料、设计及研究方向等几个方面的问题。     

PBI‐Based Polymer Membranes for High Temperature Fuel Cells – Preparation,Characterization and Fuel Cell Demonstration

Proton exchange membrane fuel cell (PEMFC) technology based on perfluorosulfonic acid (PFSA) polymer membranes is briefly reviewed. The newest development in alternative polymer electrolytes for operation above 100 °C is summarized and discussed. As one of the successful approaches to high operational temperatures, the development and evaluation of acid doped polybenzimidazole (PBI) membranes are reviewed, covering polymer synthesis, membrane casting, acid doping, physicochemical characterization and fuel cell testing. A high temperature PEMFC system, operational at up to 200 °C based on phosphoric acid‐doped PBI membranes, is demonstrated. It requires little or no gas humidification and has a CO tolerance of up to several percent. The direct use of reformed hydrogen from a simple methanol reformer, without the need for any further CO removal, has been demonstrated. A lifetime of continuous operation, for over 5000 h at 150 °C, and shutdown‐restart thermal cycle testing for 47 cycles has been achieved. Other issues such as cooling, heat recovery, possible integration with fuel processing units, associated problems and further development are discussed.     

Polymer membranes for high temperature proton exchange membrane fuel cell: Recent advances and challenges

Proton-exchange membrane fuel cells (PEMFCs) are considered to be a promising technology for efficient power generation in the 21st century. Currently, high temperature proton exchange membrane fuel cells (HT-PEMFC) offer several advantages, such as high proton conductivity, low permeability to fuel, low electro-osmotic drag coefficient, good chemical/thermal stability, good mechanical properties and low cost. Owing to the aforementioned features, high temperature proton exchange membrane fuel cells have been utilized more widely compared to low temperature proton exchange membrane fuel cells, which contain certain limitations, such as carbon monoxide poisoning, heat management, water leaching, etc. This review examines the inspiration for HT-PEMFC development, the technological constraints, and recent advances. Various classes of polymers, such as sulfonated hydrocarbon polymers, acid-base polymers and blend polymers, have been analyzed to fulfill the key requirements of high temperature operation of proton exchange membrane fuel cells (PEMFC). The effect of inorganic additives on the performance of HT-PEMFC has been scrutinized. A detailed discussion of the synthesis of polymer, membrane fabrication and physicochemical characterizations is provided. The proton conductivity and cell performance of the polymeric membranes can be improved by high temperature treatment. The mechanical and water retention properties have shown significant improvement., However, there is scope for further research from the perspective of achieving improvements in certain areas, such as optimizing the thermal and chemical stability of the polymer, acid management, and the integral interface between the electrode and membrane.     

聚醚砜-聚乙烯吡咯烷酮高温聚合物电解质膜及燃料电池堆性能研究

基于磷酸掺杂聚苯并咪唑膜（PA/PBI）的高温聚合物电解质膜燃料电池具有高的输出功率和优异的稳定性,然而PBI膜昂贵的价格和复杂的制备工艺限制了高温聚合物电解质膜燃料电池的商业化应用。本研究以成本低和制备工艺简单的聚醚砜-聚乙烯吡咯烷酮（PES-PVP）膜的商业化应用为目标,小规模制备了幅宽为40 cm的PES-PVP复合膜,证实了流延法放大制备PES-PVP复合膜的可行性。PES-PVP膜中每个PVP重复单元的吸附量达4.9个磷酸（PA）分子,且在180℃的质子电导率达85 mS·cm^-1。此外,尺寸为165 cm²的PA/PES-PVP高温膜电极在150℃的输出功率达0.19 W·cm^-2@0.6 V,与同尺寸的商业化PA/PBI高温膜电极的输出功率相当,并在近3000 h的寿命测试中展示出良好的稳定性。最后,将PA/PES-PVP高温膜电极（单片有效面积200 cm²）组装高温膜燃料电池短堆,其中基于3片膜电极的短堆展现出良好的电堆启停稳定性;基于20片膜电极电堆的峰值功率达1.15 kW。以上结果表明所制备的PA/PES-PVP是一种性能优良、价格便宜的高温聚合物电解质膜材料,并且基于该膜材料组装的高温聚合物电解质膜电池和电堆性能优异。本研究工作为高温聚合物电解质膜燃料电池关键材料和电堆的国产化提供了研究基础。     

Electrical efficiencies of methane fired, high- and low- temperature fuel cell power plants

The important system difference between power plants based on low temperature and high temperature fuel cells is that gas reforming and shift conversion is thermally decoupled from the cell in low temperature cell power plants whereas the gas process steps are performed at close to the elevated fuel cell temperatures in high temperature fuel cell power plants. This article elucidates the consequences: assuming equal electrical efficiencies for the respective cells (50%) it is shown that thermal decoupling leads to energy and exergy losses and sizably lower electrical system efficiencies because heat for the generation of the process steam necessitates the combustion of methane. Also hydrogen losses in the step for preferential oxidation of carbon monoxide (Selox process) and several heat transfer steps add to the lower efficiency of low temperature systems. Low temperature fuel cell power plants need 15–17% more fuel than high temperature fuel cell power plants for the same amount of electric energy. The theoretical comparison of an adiabatic LT and HT fuel cell process reveals that, with postulated electrical cell efficiencies of 50%, the theoretical electrical efficiency of the LT process is 6–7% points lower than that for the HT-process (35 vs. 41%). For exergy efficiencies also taking into account rejected heats, the numbers read 43 and 58%.     

高温车用燃料电池的发展及现状综述

燃料电池车以其能量转化效率高、绿色环保、噪音低等优点，被认为是替代传统化石能源汽车最有前景的新能源汽车。目前车用燃料电池的工作温度一般都低于80℃，低温的工作环境使其面临着诸多问题，如复杂的水管理和CO中毒等。通过提高质子交换膜燃料电池（PEMFC）的工作温度可以缓解这些问题，提高燃料电池的性能。然而，高温的工作环境也会对燃料电池带来诸多挑战，如膜脱水、催化剂团聚、冷启动速度缓慢等。要促进高温（90～120℃）车用燃料电池的快速发展，需要对其问题及解决方法进行分析。本文从电堆比功率、膜电极、双极板、进气方式、加湿方式等方面，介绍燃料电池的发展现状及存在的问题，包括Nafion膜和催化剂的热稳定问题、双极板的耐腐蚀问题、流道的气体分配问题、进气方式和加湿方式的优化以及冷启动问题。指出通过掺杂亲水性氧化物改善Nafion膜的高温性能；将Pt合金化及采用介孔炭提高催化剂的稳定性和电化学活性；镀层不锈钢金属双极板可以增强耐腐蚀性；3D流场等新型流场结构及提高进气温度、速度可以提高气体的均匀性；采用自增湿方式可以简化电堆结构等解决方法，以期对燃料电池车的进一步发展起到引导作用。     

Investigation of phosphoric acid and water transport in the high temperature proton exchange membrane fuel cells using a multiphase model

A three-dimensional, nonisothermal, and multiphase model of high temperature proton exchange membrane fuel cells is built to investigate water and phosphoric acid transportation, in which a spherical agglomerate model considering catalyst layer structure and liquid saturation is applied to determine the electrochemical kinetics in the cathode catalyst layer. Experimental polarization curve, water proportion in the anode outlet gas, and phosphoric acid distribution are selected for validation. It is found that the simulated results can represent the experimental data with reasonable accuracy. Based on the model, the effects of current density and stoichiometry on the variable distributions are analyzed. The results show that water in anode is mainly from cathode by concentration diffusion of liquid water, and the proportion of anode outlet water to the total produced water decreases slightly with the increase of current density. A higher current density leads to a greater electromigration of phosphoric acid from cathode to anode and a higher liquid phase fraction in anode, while a lower phosphoric acid concentration in the fuel cells.