结构参数对质子交换膜燃料电池阴极有序催化层的影响

建立了质子交换膜燃料电池阴极有序催化层的稳态数学模型,目的是研究催化层厚度、铂载量、电解质体积含量和碳载体直径等设计参数对催化层性能的影响。模型方程涉及质子、电子和氧气的传递以及电化学反应等过程。计算结果与实验数据吻合。模拟表明,一定范围内较薄的催化层有利于性能提高,但厚度太小反而不利;提高电解质体积含量和铂载量可以明显改进催化层工作特性,但存在优化值,高于此值,催化层性能迅速下降;较细的碳载体直径会适当改善催化层性能。     

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.     

Performance analysis of the ordered and the conventional catalyst layers in proton exchange membrane fuel cells

Two steady-state, one-dimensional models of the cathode active layer for the proton exchange membrane fuel cell, a conventional active layer model with the agglomerate structure and an ordered active layer model, have been compared. The model equations account for the Tafel kinetics of oxygen reduction reaction, proton migration and oxygen diffusion in the polymer electrolyte and gas pores. The polarization curves simulated by the ordered active layer predict a superior performance than the conventional active layer model even with lower platinum loadings. Analysis of the overpotential contributions indicates that the better performance of the ordered catalyst layer can be attributed to the reduction of concentration polarization. Simulation results also reveal that the ordered active layer gives more uniform oxygen concentration and overpotential distributions while the conventional catalyst layer shows more evenly distributed local current source. The present results will be helpful for practical fuel cell designs.     

In situ grown carbon nanotubes on carbon paper as integrated gas diffusion and catalyst layer for proton exchange membrane fuel cells

In situ grown carbon nanotubes (CNTs) on carbon paper as an integrated gas diffusion layer (GDL) and catalyst layer (CL) were developed for proton exchange membrane fuel cell (PEMFC) applications. The effect of their structure and morphology on cell performance was investigated under real PEMFC conditions. The in situ grown CNT layers on carbon paper showed a tunable structure under different growth processes. Scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) demonstrated that the CNT layers are able to provide extremely high surface area and porosity to serve as both the GDL and the CL simultaneously. This in situ grown CNT support layer can provide enhanced Pt utilization compared with the carbon black and free-standing CNT support layers. An optimum maximum power density of 670 mW cm⁻² was obtained from the CNT layer grown under 20 cm³ min⁻¹ C₂H₄ flow with 0.04 mg cm⁻² Pt sputter-deposited at the cathode. Furthermore, electrochemical impedance spectroscopy (EIS) results confirmed that the in situ grown CNT layer can provide both enhanced charge transfer and mass transport properties for the Pt/CNT-based electrode as an integrated GDL and CL, in comparison with previously reported Pt/CNT-based electrodes with a VXC72R-based GDL and a Pt/CNT-based CL. Therefore, this in situ grown CNT layer shows a great potential for the improvement of electrode structure and configuration for PEMFC applications.     

Cobalt based non-precious electrocatalysts for oxygen reduction reaction in proton exchange membrane fuel cells

Cobalt based non-precious metal catalysts were synthesized using chelation of cobalt (II) by imidazole followed by heat-treatment process and investigated as a promising alternative of platinum (Pt)-based electrocatalysts in proton exchange membrane fuel cells (PEMFCs). Transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements were used to characterize the synthesized CoN_x/C catalysts. The activities of the catalysts towards oxygen reduction reaction (ORR) were investigated by electrochemical measurements and single cell tests, respectively. Optimization of the heat-treatment temperature was also explored. The results indicate that the as-prepared catalyst presents a promising electrochemical activity for the ORR with an approximate four-electron process. The maximum power density obtained in a H₂/O₂ PEMFC is as high as 200 mW cm⁻² with CoN_x/C loading of 2.0 mg cm⁻².     

Effect of carbon paper substrate of the gas diffusion layer on the performance of proton exchange membrane fuel cell

Gas diffusion layers (GDLs) were fabricated using non-woven carbon paper substrates with various thicknesses developed by Hollingsworth & Vose Co. Highly consistent carbon slurry containing Pureblack carbon and vapor grown carbon fiber (3:1 ratio) with 25 wt.% Teflon was prepared by using a dispersion agent, Novec-7300 in isopropyl alcohol. Micro-porous layer was coated by using a fully automated Coatema coating tool with a uniform carbon loading of 2.6-3 mg cm⁻² using carbon slurry. The surface morphology, contact angle and pore size distribution of the GDLs were examined using SEM, Goniometer and Hg Porosimeter, respectively. Various cathode GDLs assembled into MEAs were evaluated in a single cell PEMFC under various operating relative humidity (RH) conditions using H₂/O₂ and H₂/air as reactants. The peak power density of the single cell using the optimum carbon paper substrate thickness was about 1400 and 700 mW cm⁻² with H₂/O₂ and H₂/air at 60% RH, respectively. It was found that the pore diameter as well as the corresponding pore volumes of the GDLs played a key role in exhibiting the optimum fuel cell performance.     

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.     

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.     

质子交换膜燃料电池催化剂性能增强方法研究进展

发展低成本、高性能的燃料电池催化剂是实现燃料电池商业化的关键。目前,铂基催化剂仍是动力燃料电池不可替代的主催化剂。本文综述了最近几年燃料电池催化剂增强方面的研究进展,探讨了新型催化剂材料的设计与制备以及提高催化剂活性或稳定性的方法,包括表面修饰、包覆、合金化、几何与电子结构以及晶体结构的调变、催化剂/载体相互作用等手段。开发高活性和高稳定性的非铂类催化剂是燃料电池催化剂的发展趋势和努力方向。其中,提高非铂燃料电池催化剂可靠性、稳定性和活性,迫切需要在燃料电催化理论、非铂催化剂理性设计、燃料电池水热管理、有序化膜电极等方面取得创新和突破。     

质子交换膜燃料电池仿真模型研究进展

质子交换膜燃料电池具有高效清洁等优势,是一种潜力巨大的绿色能源技术。数学模型作为一种合理可靠的工具,通过模拟电池内部的电化学传热传质过程,研究运行参数和结构参数对电池性能和寿命的影响,可以指导电池的优化设计。本文综述了近年来燃料电池催化层、气体扩散层和流道的研究模型,整理了各部件建模的影响因素和优化方法,以期对燃料电池建模以及电池各部件的优化设计起到参考作用。文中指出,考虑到现在仿真存在的局限性,未来主要研究方向为燃料电池系统研究与机理模型的结合、催化层微观结构的建模、非贵金属催化剂建模、气体扩散层衰减模型研究、大面积流道模型、三维模型温度分布研究以及全尺寸质子交换膜燃料电池模型的开发。     

Water flooding and pressure drop characteristics in flow channels of proton exchange membrane fuel cells

Water flooding of the flow channels is one of the critical issues to the design and operation of proton exchange membrane fuel cells (PEMFCs). The liquid water and total pressure drop characteristics both in the anode and cathode parallel flow channels of an operating PEMFC were experimentally studied. The gas/liquid two-phase flow both in the anode and cathode flow channels was observed, and the total pressure drop between the inlet and outlet of the flow field was measured. The effects of cell temperature, current density and operating time on the total pressure drop were investigated. The results indicated that the total pressure drop in the flow channels mainly depends on the resistance of the liquid water in the flow channels to the gas flow, and the different flow patterns distinguish the total pressure drops in the flow field. Clogging by water columns result in a higher pressure drop in the flow channels. The total pressure drop measurement can be considered as an in situ diagnoses method to characterize the degree of the flow channels flooding. The liquid water in the cathode flow channels was much more than that in the anode flow channels. The pressure drop in the cathode flow channels was higher than that in the anode flow channels. During the fuel cell operation, the cell performance decreased gradually and the pressure drop both in the anode and the cathode flow channels increased. The rate of flooding at the cathode side reached 49.56% under experimental conditions after 78 min of operation. However, it was zero at the anode side.     

多孔纳米碳纤维作为质子交换膜燃料电池微孔层的性能

质子交换膜燃料电池膜电极中的微孔层结构对改善体系的水管理能力,提升膜电极的整体性能发挥重要作用。本文通过静电纺丝和后续热处理的方法制备了多孔纳米碳纤维（PCNF）,并以此构建膜电极的微孔层。与炭黑颗粒作为微孔层呈现出紧密堆积结构不同,由PCNF搭建的微孔层结构疏松呈现三维贯通状。膜电极的发电测试表明,以多孔纳米碳纤维作为微孔层（MPL-PCNF）的膜电极其最大功率密度达70.0mW/cm²,远高于炭黑颗粒为微孔层（MPL-CB）的膜电极（58.1mW/cm²）,而没有微孔层（Ref）结构的膜电极最大功率密度仅为27.7mW/cm²,显示出PCNF作为微孔层材料的明显优势。     

质子交换膜燃料电池有序化膜电极研究进展

质子交换膜燃料电池的发展和应用是促进现代生活方式低碳环保化的最重要路径之一。膜电极是质子交换膜燃料电池的核心部件,实现膜电极结构的有序化是同时满足低铂载量和高电化学性能要求的关键。本文系统总结和分析了最近有关有序化膜电极的相关研究进展。与发展较为缓慢的质子导体有序化相比,以催化剂有序化和催化剂载体有序化为路径实现的有序化膜电极结构优化已经得到快速发展,对于促进质子交换膜燃料电池规模化应用表现出极大的发展潜力。     

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.     

相变材料用于质子交换膜燃料电池的热管理

质子交换膜燃料电池（PEMFC）因能量转化率高且环境友好,成为新一代能源动力的选择。通过分析温度对PEMFC运行性能的重要影响说明对电池进行有效热管理的重要性,按照主动冷却和被动冷却的分类方式对目前PEMFC热管理的研究现状进行归纳和综述,着重介绍运用相变材料的电池热管理系统中材料的选择和强化传热的方法,并对该领域未来研究方向进行了展望。     

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。     

质子交换膜燃料电池研究进展

质子交换膜燃料电池（proton exchange membrane fuel cell, PEMFC）因具有效率高、功率密度大、排放产物仅为水、低温启动性好等多方面优点,被公认为下一代车用动力的发展方向之一。然而,目前PEMFC在耐久性和成本方面距离商业化的要求还存在一定差距。为攻克上述两大难题,需要燃料电池全产业链的共同努力和进步。本文回顾了近年来质子交换膜燃料电池从催化剂、膜电极组件、电堆到燃料电池发动机全产业链的研究进展和成果,梳理出单原子催化剂、非贵金属催化剂、特殊形貌催化剂、有序化催化层、高温质子交换膜、膜电极层间界面优化、一体化双极板-扩散层、氢气系统循环等研究热点。文章指出,催化层低铂/非铂化、质子交换膜超薄化、膜电极组件梯度化/有序化、燃料电池运行高温化、自增湿化是未来的发展趋势,迫切需要进一步的创新与突破。     

基于膜电极的质子交换膜微生物燃料电池

通过采用传统电化学燃料电池的技术和材料,以寻求提高微生物燃料电池的电流密度,制作基于膜电极的微生物燃料电池。通过构建温控压力机,制作了一系列膜电极(MEA),并对作为正极的多种碳材料进行了筛选。使用定制的玻璃微生物燃料电池来放置膜电极和培养Geobacter sulfurreducens,对产生的电流进行评价。细胞的生长以乙醇为唯一碳源,因而代表了一种新型的乙醇/氧气燃料电池。相比以前的设计,基于膜电极的微生物燃料电池的电极表面每个单位会多产生出100倍的电流,并且可以被长久使用。     

微型质子交换膜燃料电池设计与性能分析

This study describes a novel micro proton exchange membrane fuel cell (PEMFC) (active area, 2.5 cm2). The flow field plate is manufactured by applying micro-electromechanical systems (MEMS) technology to silicon substrates to etch flow channels without a gold-coating. Therefore, this investigation used MEMS technology for fabrication of a flow field plate and presents a novel fabrication procedure. Various operating parameters, such as fuel temperature and fuel stoichiometric flow rate, are tested to optimize micro PEMFC performance. A single micro PEMFC using MEMS technology reveals the ideal performance of the proposed fuel cell. The optimal power density approaches 232.75 mW•cm－1 when the fuel cell is operated at ambient condition with humidified, heated fuel.     

Effect of direct liquid water injection and interdigitated flow field on the performance of proton exchange membrane fuel cells

Proper water management is vital to ensuring successful performance of proton exchange membrane fuel cells. The effectiveness of the direct liquid water injection scheme and the interdigitated flow field design towards providing adequate gas humidification to maintain membrane optimal hydration and alleviating the mass transport limitations of the reactants and electrode flooding is investigated. It is found that the direct liquid water injection used in conjunction with the interdigitated flow fields as a humidification technique is an extremely effective method of water management. The forced flow-through-the-electrode characteristic of the interdigitated flow field (1) provides higher transport rates of reactant and products to and from the inner catalyst layers, (2) increases the hydration state and conductivity of the membrane by bringing its anode/membrane interface in direct contact with liquid water and (3) increases the cell tolerance limits for excess injected liquid water, which could be used to provide simultaneous evaporative cooling. Experimental results show substantial improvements in performance as a result of these improvements.