PEMFC用亲水型薄层MEA的制备及其性能

本文提出一种新颖简易的方法制备PEMFC的亲水型薄层MEA,其阴、阳极催化层Pt担量分别为0. 4和 0. 2mg/cm2.实验发现,在亲水型MEA的表面上,有大量钟乳石状细微颗粒存在,从而使电极催化层的比表面积增大.在小电流密度区( <1A/cm2 ),亲水型MEA的极化性能差于Pt担量为 0. 7mg/cm2的疏水型常规MEA,但在大电流密度区( >2A/cm2 ),则前者的极化性能优化后者;亲水型MEA的最大输出比功率为1. 23W/cm2,高于疏水型电极的 1. 19W/cm2;在大电流密度区,亲水型MEA中的Pt电化学比活性也明显高于疏水型电极.     

MEA with double-layered catalyst cathode to mitigate methanol crossover in DMFC

Methanol permeation is one of the key problems for direct methanol fuel cell (DMFC) applications. It is necessary to change the structure of the cathode of membrane electrode assembly (MEA). Therefore, a novel MEA with double-layered catalyst cathode was prepared in this paper. The double-layered catalyst consists of PtRu black as inner catalyst layer and Pt black as outer catalyst layer. The inner catalyst layer is prepared for oxidation of the methanol permeated from anode. The results indicate that this double-layered catalyst reduced the effects of methanol crossover and assimilated mixed potential losses. The performance of MEA with double-layered catalyst cathode was 52.2 mW cm⁻², which was a remarkable improvement compared with the performance of MEA with traditional cathode. The key factor responsible for the improved performance is the optimization of the electrode structure.     

A novel membrane electrode assembly for improving the efficiency of the unitized regenerative fuel cell

A novel membrane electrode assembly (MEA) for unitized regenerative fuel cell (URFC) has been developed. The MEA was fabricated to improve the efficiency of the URFC by a Nafion-pyrolyzed method. The polarization curves for fuel cell and water electrolysis modes of URFC operation both were investigated. The MEA improved water management and minimized mass transport limitations. The URFC using the novel MEA exhibited a high water electrolysis performance and a much higher fuel cell performance than that of the URFC using the conventional MEA. The efficiency of fuel cell and round-trip enhanced 13.5% and 10.8% at 700 mA/cm² with the novel MEA respectively.     

Investigation of a novel MEA for direct dimethyl ether fuel cell

In this study, we presented the novel membrane electrode assembly (MEA) for direct dimethyl ether fuel cell (DDFC). The anode diffusion layer of the MEA consisted of hydrophilic region and hydrophobic region (with a ratio of region areas of 1:1). The electrochemical impedance spectra analyses revealed that the mass transfer resistance of novel MEA was lower than that of completed hydrophilic or hydrophobic MEA. The performance of novel MEA for DDFC was enhanced due to the promotion the mass transport of DME fuel at 50 °C. The constant current operation curves showed that the performance decay ratio of the novel MEA was lower than that of conventional MEAs. It indicated that the novel MEA benefited the long-term operation of DDFC.     

Study of a highly durable low-humidification membrane electrode assembly using crosslinked polyvinyl alcohol for polymer electrolyte membrane fuel cells

A low-humidification membrane electrode assembly (MEA) for polymer electrolyte membrane fuel cells (PEMFCs) is prepared by adding the hydrophilic polymer: polyvinyl alcohol (PVA) to the anode catalyst layer. Glutaraldehyde (GA) is employed as a crosslinking agent for PVA to prevent washing from the anode during cell operation. This is confirmed by an immersion test in deionized water for 2 h. A single cell test is conducted at 80 °C, ambient pressure, and 50 % relative humidity. Although MEA containing 1 wt% non-crosslinked PVA shows the best initial performance (788 mA cm^?2 at 0.6 V), a considerable performance decrease of 41 % is observed following a 100-h durability test. However, MEA containing 5 wt% crosslinked PVA demonstrates enhanced durability, with little performance decline after 100 h of constant current operation. This strongly suggests that crosslinked PVA plays a crucial role in a low-humidification MEA at low humidity levels.     

A novel electrode architecture for passive direct methanol fuel cells

The supply of cathode reactants in a passive direct methanol fuel cell (DMFC) relies on naturally breathing oxygen from ambient air. The successful operation of this type of passive fuel cell requires the overall mass transfer resistance of oxygen through the layered fuel cell structure to be minimized such that the voltage loss due to the oxygen concentration polarization can be reduced. In this work, we propose a new membrane electrode assembly (MEA), in which the conventional cathode gas diffusion layer (GDL) is eliminated while utilizing a porous metal structure for transporting oxygen and collecting current. We show theoretically that the new MEA enables a higher mass transfer rate of oxygen and thus better performance. The measured polarization and constant-current discharging behavior showed that the passive DMFC with the new MEA yielded better and much more stable performance than did the cell having the conventional MEA. The EIS spectrum analysis further demonstrated that the improved performance with the new MEA was attributed to the enhanced transport of oxygen as a result of the reduced mass transfer resistance in the fuel cell system.     

Designing AI-Aided Analysis and Prediction Models for Nonprecious Metal Electrocatalyst-Based Proton-Exchange Membrane Fuel Cells

Traditionally, a larger number of experiments are needed to optimize the performance of the membrane electrode assembly (MEA) in proton-exchange membrane fuel cells (PEMFCs) since it involves complex electrochemical, thermodynamic, and hydrodynamic processes. Herein, we introduce artificial intelligence (AI)-aided models for the first time to determine key parameters for nonprecious metal electrocatalyst-based PEMFCs, thus avoiding unnecessary experiments during MEA development. Among 16 competing algorithms widely applied in the AI field, decision tree and XGBoost showed good accuracy (86.7 % and 91.4 %) in determining key factors for high-performance MEA. Artificial neural network (ANN) shows the best accuracy (R2=0.9621) in terms of predictions of the maximum power density and a decent reproducibility (R2>0.99) on uncharted I–V polarization curves with 26 input features. Hence, machine learning is shown to be an excellent method for improving the efficiency of MEA design and experiments.     

Improvement of the proton exchange membrane fuel cell performances by optimization of the hot pressing process for membrane electrode assembly

The present study deals with PEM fuel cells, namely with the optimization of the hot pressing process for membrane electrode assembly (MEA) fabrication. Designs of experiments (DoE) have been used for evaluating the effect of hot pressing parameters (pressure, temperature, and time) on the MEA electrical performances. Full factorial 2³ DoE showed that the most important parameter is the pressing temperature. Surface response methodology indicated a non-monotonous behavior of the MEA electrical performances with respect to the pressing temperature. The MEA electrical performances increased with the pressing temperature in the temperature range from 100 to 115 °C, and decreased significantly in the temperature range from 115 to 130 °C. This behavior was attributed to drastic changes of the Nafion® 112 membrane properties and membrane/electrode interface over this temperature range. Observations of the MEA cross-section structure by scanning electron microscopy confirmed such hypotheses. Thermo-mechanical properties of Nafion® as determined by dynamic scanning calorimetry allowed estimating the glass transition temperature at ca. T _g?≈?117 °C in the conditions of the present study. The higher H₂/air fuel cell performance of ca. 0.8 W cm^?2 was obtained with the optimized pressing temperature for MEA fabrication of ca. 115 °C close to the T _g temperature of Nafion® 112, whereas for higher temperature the structure of the Nafion® membrane and of the membrane–electrode interface is damaged.     

A novel MEA architecture for improving the performance of a DMFC

Direct methanol fuel cell (DMFC) consisting of a double-catalytic layered membrane electrode assembly (MEA) provide higher performance than that with the traditional MEA. This novel structured MEA includes a hydrophilic inner catalyst layer and a traditional electrode with an outer catalyst layer, which was made using both catalyst coated membrane (CCM) and gas diffusion electrode (GDE) methods. The inner catalyst was PtRu black on anode and Pt black on cathode. The outer catalyst was carbon supported Pt–Ru/Pt on anode and cathode, respectively. Thus in the double-catalytic layered electrodes three gradients were formed: catalyst concentration gradient, hydrophilicity gradient and porosity gradient, resulting in good mass transfer, proton and electron conducting and low methanol crossover. The peak density of DMFC with such MEA was 19 mW cm⁻², operated at 2 M CH₃OH, 2 atm oxygen at room temperature, which was much higher than DMFC with traditional MEA.     

硫化氢燃料电池的无机质子传导膜与MEA制备和性能

制备了硫化氢固体氧化物燃料电池的无机质子传导膜和膜-电极-组装(MEA)。用扫描电镜(SEM)和电化学阻抗(EIS)技术表征了无机质子传导膜和MEA的形貌与性能。研究了不同膜厚和掺杂或没有掺杂Li₂WO₄组分的传导膜和MEA的性能。结果表明，与没有掺杂Li₂WO₄组分制备的MEA相比，掺杂了Li₂WO₄组分制备的MEA的电导提高了一个数量级，掺杂了Li₂WO₄制备的MEA硫化氢燃料电池在操作条件下具有更好的化学稳定性和电化学性能。以Mo-Ni-S为主要成分的复合阳极、0.8 mm厚和组成为67wt% Li₂SO₄ + 8wt% Li₂WO₄ + 25wt% Al₂O₃复合材料制备的质子传导膜、NiO为主要组分的复合阴极构成的MEA硫化氢燃料电池，在650、700和750 ℃时，最大输出功率密度分别达到50、85和130 mW·cm^-2，最大电流密度分别为200、350和480 mA·cm^-2。     

碳纤维基PtSn催化剂直接乙醇燃料电池制备及性能研究

采用自制的碳纤维基PtSn催化剂薄膜作为阳极催化剂,商用Pt/C作为阴极催化剂,Nafion 115膜作为质子交换膜,通过热压制成膜电极,组装平板型直接乙醇燃料单电池,搭建测试系统并进行性能的测试,研究了温度、乙醇浓度、溶液流量、进气流量等参数对DEFC的影响。结果表明,当乙醇溶液浓度为1.0 mol/L、溶液进样流量为1.0 mL/min、溶液温度为80 ℃、氧气进样流量为100 mL/min时结果较优,单电池的最高功率密度达18.2 mW/cm²。     

直接甲醇燃料电池电催化机理及多孔电极传质过程研究

直接甲醇燃料电池以其独特的优势被业界人士视为本世纪最有可能实现商业化的燃料电池. 因此,众多研究院所和公司展开了深入研究,取得了瞩目的成就. 本文分析了膜电极结构的电催化和多孔电极传质过程的机制,并结合制备工艺、有序多层结构以及电池内部传输过程,讨论了近年来膜电极在直接甲醇燃料电池相关的研究进展.     

Impact of Membrane Types and Catalyst Layers Composition on Performance of Polymer Electrolyte Membrane Fuel Cells

Performance of a low temperature polymer electrolyte membrane fuel cell (PEMFC) is highly dependent on the kind of catalysts, catalyst supports, ionomer amount on the catalyst layers (CL), membrane types and operating conditions. In this work, we investigated the influence of membrane types and CL compositions on MEA performance. MEA performance increases under all practically relevant load conditions with reduction of the membrane thickness from 50 to 15 μm, however further decrease in membrane thickness from 15 to 10 μm leads to reduction in cell voltage at high current loads. A thick anode CL is found to be beneficial under wet operating conditions assuming more pore space is provided to accommodate liquid water, whereas under dry operating conditions, an intermediate thickness of the anode CL is beneficial. When studying the impact of catalyst layer thickness, too thin a catalyst layer again shows reduced performance due to increased ohmic resistance ruled out the performance of the MEAs which have identical Pt crystallite sizes on the cathode CLs i. e. the thinnest the cathode CL, the highest the voltage were achieved at a defined current load. Adaptation of the operating conditions is highly anticipated to achieve the highest MEA performance.     

降低直接甲醇燃料电池浓差极化的含磺化碳管阻水夹层的构建

采用直接接枝法, 将来自对氨基苯磺酸的苯磺酸官能团引入氧化多壁碳纳米管, 制得磺化多壁碳纳米管(SO₃-MCNT). 再以SO₃-MCNT为填料, 以Nafion离聚物为黏结剂, 利用超声喷涂在商业N212质子交换膜一侧构建了新的膜层, 获得了一种复合膜(SO₃-MCNT?N212). 使用SO₃-MCNT?N212制备燃料电池膜电极(MEA), 并用于直接甲醇燃料电池(DMFC)测试. 与使用普通N212膜的膜电极相比, 该膜电极的性能得到明显提升. 进一步分析表明, SO₃-MCNT膜层的引入降低了阳极向阴极的跨膜水迁移作用, 缓解了阴极的水淹, 从而降低了浓差极化, 提升了膜电极的性能.     

Nafion乳液法制备燃料电池膜电极组件

本文提出一种制作燃料电池膜电极组件的新方法.该法特点在于用非极性溶剂代替传统的极性溶剂配制催化剂-Nafion混合物,从而催化层可直接涂覆到Nafion膜表面制成MEA,而不引起Nafion膜的溶胀,适合规模制作.本法所得MEA中的催化剂利用率与目前流行的转移法相近,以氢氧燃料电池的方式于常温下工作取得令人满意的初步放电结果.     

低铂膜电极结构优化途径

膜电极是质子交换膜燃料电池的核心组件,长期以来,在衣院士的指导下,我国高度重视膜电极技术的开发. 目前,燃料电池的研发和产业化进入了一个新的时代,对膜电极提出来更高的要求,特别是在降低铂载量方面,提出了0.125 mg·W^-1的挑战性指标. 本文从活化极化、欧姆极化和传质极化三个方面分析了低铂载量情况下电池性能下降的原因,提出应重点关注催化剂在燃料电池工作区间（0.6 V ~ 0.8 V)的催化活性,并讨论了用电荷传输阻抗作为催化剂活性指示符的合理性. 从优化潜力来说,传质极化优化>活化极化优化>欧姆极化优化. 催化层结构优化是实现低铂目标的关键,重点是解决离子聚合物（ionomer）传递质子和阻碍气体的矛盾.     

DMFC寿命测试过程中膜电极的表面和结构研究(英文)

设计并组装单电池寿命测试系统,测试直接甲醇燃料电池(DMFC)的运行寿命,获得不同运行时间下单电池的极化和功率曲线.测试结束后,分别对运行过的膜电极(MEA)催化剂(铂黑和铂钌黑)和Nafion117(膜作XRD,HRTEM,FTIR及Raman等表征.考察在长期运行条件下电池寿命性能与膜电极中催化剂的颗粒大小、分布、形态、表面物种以及膜的结构之间的关系.寿命测试结果表明,单电池在不同运行阶段其性能变化也不同.运行前200 h,电池性能衰减较显著;运行200~704 h性能较稳定,运行1 002 h后电池性能恶化.波谱实验发现,单电池长期运行后,其膜电极的阴、阳极催化剂颗粒变大.电池寿命性能的衰退伴随膜电极微结构、表面组成、催化剂/膜界面结构的变化以及Nafion 117(膜的老化.     

In situ observation of the water distribution across a PEFC using high resolution neutron radiography

The water distribution across the membrane electrolyte assembly (MEA) of a working polymer electrolyte fuel cell (PEFC) was observed in situ using neutron radiography. In order to resolve the distribution between the different layers of the MEA, in plane imaging (cell membrane parallel to the beam) was used. Unprecedented spatial resolution for neutron radiography was obtained using a new detector system available at PSI combined with specific anisotropic resolution enhancement methods. A detrimental effect on performance of excessive water content in the cathode GDL was observed. Depending on the operating condition, a strong separation of the water content between ribs and channel was observed, particularly in the cathode GDL.     

Recent advances in integrating platinum group metal-free catalysts in proton exchange membrane fuel cells

Platinum group metal (PGM)-free catalysts are promising low-cost materials for the oxygen reduction reaction in proton exchange membrane fuel cells (PEMFCs). A variety of chemical precursors and synthesis methods have been proposed to increase their catalytic activity. In comparison, significantly less attention has been dedicated to the integration of these PGM-free catalysts into operating electrodes by investigating the role of the membrane electrode assembly (MEA) fabrication on the PEMFC performance. We discuss here some remarkable performance improvements recently achieved by tuning catalyst loading, ionomer content, and ink solvent composition, and call for further explorations of the ink processing and MEA fabrication to improve performance.     

碳纸对燃料电池自增湿性能的影响

使用TGP-H-028(0.28mm),TGP-H-060(0.19mm),TGP-H-030(0.11mm)等3种Toray碳纸制备膜电极,将组装燃料电池进行极化曲线与交流阻抗分析发现,厚碳纸TGP-H-028对自增湿发电性能略为有利,其最大功率密度比TGP-H-030薄碳纸高0.05W/cm²左右;用聚四氟乙烯乳液疏水处理TorayTGP-H-060碳纸,制备的MEA的自增湿电性能随着聚四氟乙烯质量分数(20%～40%)的升高而增大,最大功率密度升高至0.25W/cm²左右.当聚四氟乙烯质量分数继续升高到60%时,电性能开始下降,并比质量分数为40%的聚四氟乙烯的电性能低.