质子交换膜燃料电池中抗CO中毒的PtM阳极催化剂

介绍了PtM阳极催化剂加入第二金属组分后对Pt晶体结构、颗粒大小、分散度等方面的影响以及PtM相互之间、PtM与载体之间的相互作用。由于存在这些相互作用，使其改变了Pt的CO中毒特性，导致了不同的反应活化能、反应级数以及CO的表面覆盖率。评述了目前几种主要的催化剂抗CO中毒机理及三组分和多组分催化剂的研究进展。     

Candle Soot as Efficient Support for Proton Exchange Membrane Fuel Cell Catalyst

Candle soot deposited from the candle flame was used as a catalyst support for an anode catalyst in a proton exchange membrane fuel cell. The results showed that Pt/soot hybrids prepared by magnetron sputtering of 5 nm platinum films on candle soot exhibit very high mass activity in the fuel cell, which is more than one order of magnitude higher than that for commercial catalyst. The elementary preparation, high surface‐to‐volume ratio, good conductivity and hydrophobicity make candle soot a promising type of the support for PEMFCs catalyst.     

Development of a Micro Temperature Sensor and 3D Temperature Analysis for a Proton Exchange Membrane Fuel Cell

This study examines the development of micro in situ sensors and analyzed the through‐plane temperature of a fuel cell. Temperature sensing inside a fuel cell is important in fuel cell diagnosis and analysis. Temperature sensors must be adequately small, so that fuel cell performance is maintained and the temperature anywhere inside the cell can be flexibly measured. In this study, a temperature sensor based on a micro‐electromechanical system (MEMS) is designed and fabricated to achieve these objectives. The micro temperature sensor was installed inside a cell to measure through‐plane temperature. The current and voltage of the fuel cell with the micro temperature sensor were measured and compared with those of a fuel cell without the sensor to analyze the effect of the sensor on fuel cell performance. The developed temperature sensor is of resistance temperature detector (RTD) type, with a flexible substrate of polyimide, high sensitivity, and easy installation characteristics. After calibration of the sensors, three sensors were inserted into the cell to measure the through‐plane temperature, and the polarization curve of the cell with and without the micro sensor was compared. Finally, a 3D computational fluid dynamics (CFD) model of a fuel cell was developed and analyzed by comparison of the measured temperature results to determine the accuracy of the model.     

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.     

Alumina–Carbon Nanofibers Nanocomposites Obtained by Spark Plasma Sintering for Proton Exchange Membrane Fuel Cell Bipolar Plates

There is an increasing demand of multifunctional materials for a wide variety of technological developments. Bipolar plates for proton exchange membrane fuel cells are an example of complex functionality components that must show among other properties high mechanical strength, electrical, and thermal conductivity. The present research explored the possibility of using alumina–carbon nanofibers (CNFs) nanocomposites for this purpose. In this study, it was studied for the first time the whole range of powder compositions in this system. Homogeneous powders mixtures were prepared and subsequently sintered by spark plasma sintering. The materials obtained were thoroughly characterized and compared in terms of properties required to be used as bipolar plates. The control on material microstructure and composition allows designing materials where mechanical or electrical performances are enhanced. A 50/50 vol.% alumina–CNFs composite appears to be a very promising material for this kind of application.     

Carbon Nanotubes and Nanohorn Hybrid Composite Buckypaper as Microporous Layer for Proton Exchange Membrane Fuel Cell

In the present work, carbon nanotubes (CNT) and CNT‐carbon nanohorns (CNH) (0, 30, 50, 70 and 100 wt.% CNH) composite Buckypapers (BPs) were fabricated using vacuum filtration technique. Structure and property relation of composite BPs were studied using scanning electron microscope, four probe technique, BET surface area and contact angle measurements. Properties such as electrical conductivity, hydrophobic nature and microstructure of CNT‐30 wt.% CNH composite BP are superior to other composite BP. Hence, CNT‐30 wt.% CNH composite BP is chosen as a microporous layer (MPL) for PEMFCs and tested in fuel cell testing fixture. Polarization studies reveal that the cells performance with composite BPs is comparable with SGL‐MPL based cell. Hydrogen pumping and polarization studies of the cells confirms that composite BPs act as a good MPL at anode as well as cathode at 0.4 to 0.8 V. Hence, CNT‐CNH composite BPs are potential candidates for PEMFC applications.     

A H2SO4 Loaded Polybenzimidazole (PBI) Membrane for High Temperature PEMFC

Sulfuric acid loaded polybenzimidazole (PBI) membranes were prepared with loading levels up to 10.58 (acid molecule per repeat unit of PBI) and characterized with Fourier transform infrared spectroscopy. Ionic conductivity of the PBI–H₂SO₄ membrane was found greater than that of the PBI–H₃PO₄ membrane. Through plane conductivity of a PBI–H₂SO₄ membrane with loading level 9.65 was >0.2 S cm^–1 at 150 °C. However, the conductivity of PBI–H₂SO₄ membrane increased greatly with increasing relative humidity. Membrane electrode assemblies using PBI–H₂SO₄ membrane exhibited better power density performances with pre‐humidified H₂ and air than that with none‐humidified gases. Polymer electrolyte membrane fuel cells with PBI–H₂SO₄ membrane in a single cell fixture demonstrated a peak power density >0.35 W cm^–2 with H₂ and air.     

Impact of Ionomer Content on Proton Exchange Membrane Fuel Cell Performance

The effect of Nafion ionomer content on performance of a proton exchange membrane (PEM) fuel cell operated with home‐made anodic and cathodic electrodes fabricated from a novel metal organic framework (MOF) derived Pt‐based electrocatalyst was investigated via numerical simulation and experimental measurement. First, the parameter sensitivity analysis was performed to identify the most influential parameters of the model. Then, these parameters were calibrated for different fuel cell designs investigated in the current study by employing the corresponding experimental data. Afterwards, the calibrated model was used to examine the impact of Nafion content in the catalyst layer of home‐made electrodes. Finally, the qualitative trend predicted by this model was experimentally surveyed by varying the Nafion content between 10–50 wt.% in the catalyst layer of home‐made electrodes. At the anode side, the performance of home‐made electrode in a PEM fuel cell demonstrated small dependency on Nafion content. For the cathodic home‐made electrode, Nafion content was found to affect the PEM fuel cell performance more strongly. Although the model could correctly capture the impact of Nafion content on calculated polarization curves, the model predicted optimum values significantly deviate from the experimental results. This was related to the several simplifications made during model development.     

Influence of Pyridine‐Polybenzimidazole Film Thickness of Carbon Nanotube Supported Platinum on Fuel Cell Applications

Pyridine‐polybenzimidazole (PyPBI) films of different thickness (∼1.0–2.4 nm) are wrapped on the surfaces of multi‐walled carbon nanotubes (CNTs). To prepare Pt on PyPBI/CNT (Pt‐PyPBI/CNT) catalysts, Pt⁴⁺ ions are immobilized on these PyPBI wrapped CNTs (PyPBI/CNTs) via Lewis acid‐base coordination between Pt⁴⁺ and :N‐ of imidazole groups, followed by reducing Pt⁴⁺ to Pt nanoparticles. The influence of PyPBI film thickness on the Pt particle size, loading and electrochemical surface area, respectively, of Pt‐PyPBI/CNTs is investigated. Fuel cell performances of the PBI/H₃PO₄ based membrane electrode assemblies (MEAs) prepared from these Pt‐PyPBI/CNT catalysts are also evaluated at 160 °C with unhumidified H₂/O₂ gases. Among the catalysts, the Pt‐PyPBI/CNT catalyst with a PyPBI film thickness of ∼1.6 nm (which is around half of the Pt particle size), a Pt loading of ∼44 wt.%, and a Pt particle size of ∼3.3 nm exhibits the best fuel cell performance.     

Development and Evaluation of Gas Diffusion Layer Using Paraffin Wax Carbon for Proton Exchange Membrane Fuel Cells

A gas diffusion layer (GDL) with carbon prepared from paraffin wax was developed for the first time to impart hydrophobicity and porosity for fuel cell application. It is also intended to reduce the non‐functional binder content in the microporous layer and to achieve optimum performance. The topography of the GDL was examined using 3D digital microscope. Membrane electrodes assemblies (MEAs) fabricated with GDLs of paraffin wax carbon (PWC) based microporous layer were evaluated in proton exchange membrane fuel cell between 50 and 100% RH conditions using H₂ and O₂ at ambient pressure. The fuel cell performance of the GDLs fabricated with Pureblack carbon was also evaluated under identical operating conditions for comparison. It was observed that the MEA with GDLs containing PWC showed excellent fuel cell performance at all RH conditions at 80 °C both with H₂/O₂.     

Durability of ABPBI‐based MEAs for High Temperature PEMFCs at Different Operating Conditions

High temperature PEMFCs based on phosphoric acid‐doped ABPBI membranes have been prepared and characterised. At 160 °C and ambient pressure fuel cell power densities of 300 mW cm^–2 (with hydrogen and air as reactants) and 180 mW cm^–2 (with simulated diesel reformate/air) have been achieved. The durability of these membrane electrode assemblies (MEAs) in the hydrogen/air mode of operation at different working conditions has been measured electrochemically and has been correlated to the cell resistivity, the phosphoric acid loss rate and the catalyst particle size. Under stationary conditions, a voltage loss of only –25 μV h^–1 at a current density of 200 mA cm^–2 has been deduced from a 1,000 h test. Under dynamic load changes or during start–stop cycling the degradation rate was significantly higher. Leaching of phosphoric acid from the cell was found to be very small and is not the main reason for the performance loss. Instead an important increase in the catalyst particle size was observed to occur during two long‐term experiments. At high gas flows of hydrogen and air ABPBI‐based MEAs can be operated at temperatures below 100 °C for several hours without a significant irreversible loss of cell performance and with only very little acid leaching.     

Matrix Material Study for in situ Grown Pt Nanowire Electrocatalyst Layer in Proton Exchange Membrane Fuel Cells (PEMFCs)

The cathode electrocatalyst layers were prepared by in situ growing Pt nanowires (Pt‐NWs) in two kinds of matrixes with various Pt loadings for proton exchange membrane fuel cells (PEMFCs). Commercial carbon powder and 20 wt.% Pt/C electrocatalyst were used as the matrix material for the comparison. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), polarization curves tests, and electrochemical impedance spectroscopy (EIS) were carried out to examine the effects of the matrix materials on the Pt‐NW growing and the electrode performance. The optimum Pt‐NW loadings of 0.30 mg cm⁻² in the carbon matrix (CM) and 0.20 mg cm⁻² for the Pt/C matrix (PM) were obtained. The results indicated that the Pt‐NWs grown in the CM had a better crystalline, longer size length and better catalyst activity than those in the PM. The mechanism of the matrix affection is further discussed in this paper.     

Properties of Sulfonated Poly(Arylene Ether Sulfone)/Functionalized Carbon Nanotube Composite Membrane for High Temperature PEMFCs

Composite membranes are prepared using sulfonated poly (arylene ether sulfone) (SPAES) copolymers and the incorporation of functionalized multiwall carbon nanotubes (CNTs) for high temperature (120 °C) proton exchange membrane fuel cells (PEMFCs). The CNT is functionalized with sulfonated groups that are expected to support the improvement of water absorption and mechanical properties. The SPAES copolymers are synthesized with sulfonation degree (DS) = 0.5 and the sulfonated CNT (s‐CNT) is dispersed into the SPAES copolymers in varying ratios to fabricate the composite membranes. In this study, the proton conductivity, water uptake, and single cell test of the composite membrane are investigated for verifying the effects of the enhancement at high temperature and low humidity. The composite membrane containing 0.2 wt.% s‐CNT increases proton conductivity approximately 45% at 120 °C and 50% relative humidity and enhances the tensile strength by about 1.3 times compared to the pristine membrane. However, the proton conductivity and water absorption shows a decline when more than 0.2 wt.% s‐CNT is added in the composite membrane, due to the aggregation of the s‐CNT, which serves as a proton barrier. For the single cell test, the developed composite membrane with 0.2 wt.% s‐CNT exhibits a notable performance for high temperature PEMFC.     

Catalyst Degradation in High Temperature Proton Exchange Membrane Fuel Cells Based on Acid Doped Polybenzimidazole Membranes

Degradation of carbon supported platinum catalysts is a major failure mode for the long term durability of high temperature proton exchange membrane fuel cells based on phosphoric acid doped polybenzimidazole membranes. With Vulcan carbon black as a reference, thermally treated carbon black and multi‐walled carbon nanotubes were used as supports for electrode catalysts and evaluated in accelerated durability tests under potential cycling at 150 °C. Measurements of open circuit voltage, area specific resistance and hydrogen permeation through the membrane were carried out, indicating little contribution of the membrane degradation to the performance losses during the potential cycling tests. As the major mechanism of the fuel cell performance degradation, the electrochemical active area of the cathodic catalysts showed a steady decrease in the cyclic voltammetric measurements, which was also confirmed by the post TEM and XRD analysis. A strong dependence of the fuel cell performance degradation on the catalyst supports was observed. Graphitization of the carbon blacks improved the stability and catalyst durability though at the expense of a significant decrease in the specific surface area. Multi‐walled carbon nanotubes as catalyst supports showed further significant improvement in the catalyst and fuel cell durability.     

Effect of Carbon Dioxide and Ammonia on Polymer Electrolyte Membrane Fuel Cell Stack Performance

Proton exchange membrane fuel cell (PEMFC) performance degrades when impurities are present in the anode fuel gas, referred to as catalyst poisoning. This paper investigates the effect of carbon dioxide and ammonia as impurities in the anode gas of the PEMFC, and found that the presence of CO₂ decreases the performance of the fuel cell by up to 10%. The performance loss depends on the CO₂ concentration and the exposure time. The voltage loss is recoverable on passing pure hydrogen gas, indicating that a permanent poisoning of the catalyst layer has not taken place. Exposure of the fuel cell to ammonia beyond 20 ppm, even for a short duration, causes permanent PEMFC failure, probably due to the deterioration of the membrane.     

Effect of Various Hydrophobic Concentrations and Base Weights of Gas Diffusion Layer for Proton Exchange Membrane Fuel Cells

This study investigates the gas permeability, conductivity and performance of two types of gas diffusion layer (90 g m^–2 and 190 g m^–2) with various hydrophobic treatments. The performance is measured using a single proton exchange membrane fuel cell (PEMFC) with an active area of 25 cm². The results prove that 90 g m^–2 carbon paper has the best current density in 5% hydrophobic concentration. The polarisation curves of fuel cell were plotted by similar operating conditions with different micro‐porous layers (MPLs) on carbon papers surface. These results provide a wide choice of hydrophobic agents. These results concerning the balance between base weights and performance provide important information for the fabrication of stacks and support for industrial applications.     

Conductive Materials for Proton Exchange Membrane Fuel Cell Bipolar Plates Made from PVDF,PET and Co‐continuous PVDF/PET Filled with Carbon Additives

The aim of this work was to develop and characterise electrically conductive materials for proton exchange membrane fuel cells and bipolar plates (BPPs). These BPPs were made from highly conductive blends of polyethylene terephthalate (PET) and polyvinylidene fluoride (PVDF), as matrix phase. The conductive materials were developed from carefully formulated blends composed of conductive carbon black (CB) powder and, in some cases, graphite synthetic flakes mixed with pure PET, PVDF or with PVDF/PET systems. They were first developed by twin‐screw extrusion process then compression‐molded to give BPP final shape. As the developed blends have to meet properties suitable for BPP applications, they were characterised for their rheological properties, electrical through‐plane resistivity (the inverse of conductivity), oxygen permeability, flexural and impact properties. Results showed that lower resistivity was obtained with PVDF/CB blends due to the higher interfacial energy between the PVDF matrix and CB and also the higher density and crystallinity of PVDF, compared to those of PET. It was also observed that the lowest resistivity values were obtained with mixing PVDF and PET at controlled compositions to ensure PVDF/PET co‐continuous morphology. Also, slow cooling rates helped to attain the lowest values of through‐plane resistivity for all studied blends. This behaviour was related to the higher crystallinity obtained with low cooling rates leading to smaller amorphous regions in which carbon particles are much more concentrated.     

Development of Low‐Cost Advanced Composite Bipolar Plate for Proton Exchange Membrane Fuel Cell�

The bipolar plate is one of the most imperative components of proton exchange membrane fuel cells (PEMFC) which consumes up to 80% of weight and near about 50% of the total cost of the cell. Development of cost‐effective composite bipolar plate with high electrical conductivity and high mechanical strength is both technically and economically demanding. In this paper, a low‐cost advanced composite bipolar plate is developed by bulk moulding compression (BMC) technique. It is clear from the experiments that by increasing the matrix volume fraction, bulk density and electrical conductivity of a composite bipolar plate decrease but shore hardness increases. Test results clearly show that best overall properties are achieved when a constant volume fraction of polymer matrix and natural graphite is reinforced with synthetic graphite, carbon black and carbon fibre. This bipolar plate was found to have high conductivity, less porosity and high mechanical strength. The I–V characteristics in single cell test exhibited more uniform power density at both higher and lower current densities     

MEMS微型质子交换膜燃料电池阳极新结构

利用微电子机械技术(MEMS)制备了含有4条脊的点蛇混合阳极新结构,组成自呼吸式微型燃料电池,并与老式阳极结构(含2条脊)比较。研究发现,当阳极的集流条由2增加到4时,流道总长度增大约一倍,电池的极限电流密度和峰值功率密度分别提高18.56%和15.26%,在100~500 mA恒电流放电下,可节省燃料平均达6.18%。流场的深度过深和过浅都不利于电池性能的发挥,在175μm深度时电池的效果最佳,氢气的有效利用率最高;氢气的流速对电池的性能影响不大,10~20 mL/min的流量足以保证燃料供给。