Modification and durability of carbon paper gas diffusion layer in proton exchange membrane fuel cell

To solve the durability problem caused by carbon corrosion in the porous carbon paper gas diffusion layer (GDL) of proton exchange membrane fuel cell (PEMFC), a Cr₇C₃ ceramic coating on porous carbon paper by molten salt method was prepared. The obtained Cr₇C₃ coating is dense and shows good adherent with the carbon paper. Based on the corrosion resistance testes, it is concluded that the Cr₇C₃ coated carbon paper can keep high chemical stability in the long-time acid immersion accelerated corrosion tests and simulated cathodic proton exchange membrane fuel cells environment. The carbon paper with Cr₇C₃ coating shows a small current density with a value of about 1.1 × 10^?5 A cm^?2 in the potentiostatic polarization test under 1 M H₂SO₄ + 2 ppm HF at 70 °C and1.4 V_SCE for 72 h. Meanwhile, the resistivity of carbon paper with Cr₇C₃ coating prepared is 30% lower than that of pure carbon paper, and the conductivity is 1.5 times that of pure carbon paper.     

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.     

Ionic liquid modified Pt/C electrocatalysts for cathode application in proton exchange membrane fuel cells

The modification of Pt/C catalyst by using ionic liquids to improve their catalyst activities has been reported by many researchers, but their practical behavior in operating fuel cells is still unknown. In this work, we study the ionic liquid modified Pt/C nanoparticle catalysts within cathodes for proton exchange membrane fuel cells. The influence of the ionic liquid amount, adsorption times and dispersing solvents are investigated. The experiment results show the best performance enhancement is achieved through two-time surface modification with 2 wt-% ionic liquid solution. The mechanisms are explored with the attribution to the high oxygen solubility in the ionic liquid enabling an improved oxygen diffusion in micropores and to good hydrophobicity facilitating water expelling from the active sites in fuel cell operation.     

空气自呼吸质子交换膜燃料电池最新研究进展

空气自呼吸质子交换膜燃料电池具有系统体积小、能量密度高、能量转化效率高和清洁无污染、无需复杂的空气供给及增湿系统等优点,是极具商业前景的新一代中小功率便携式电源,其相关研究为燃料电池领域的热点研究课题。本文综述了近年来此类电池在结构、机理、组成元件、性能等方面的研究进展,认为改善阴极催化层孔隙率和疏水性等能显著加快氧气传输和水移除,提高氧气活化能力;气体扩散层的组成、结构和厚度亦影响其气体透过性和水移除效果;合适的结构设计和材料选取能调节池体温度,强化空气对流;膜电极免增湿技术的应用可以维持电池在低湿度下较高质子传导率和系统稳定性,这是空气自呼吸质子交换膜燃料电池实现商业化的重要研究方向。     

以新型渐缩式流道增进质子交换膜燃料电池性能

Based on use of multi-dimensional models, this investigation simulates the performance of a proton exchange membrane fuel cell by varying the channel pattern. In the one-dimensional model, the porosity of the gas diffusion layer is 0.3. The model reveals the water vapor distribution of the fuel cell and demonstrates that the amount of water vapor increases linearly with the reduction reaction adjacent to the gas channel and the gas diffusion layer. Secondly, four novel tapered gas channels are simulated by a two-dimensional model. The model considers the distributions of oxygen, the pressure drop, the amount of water vapor distribution and the polarization curves. The results indicate that as the channel depth decreases, the oxygen in the tapered gas channel can be accelerated and forced into the gas diffusion layer to improve the cell performance. The three-dimensional model is employed to simulate the phenomenon associated with four novel tapered gas channels. The results also show that the best performance is realized in the least tapered gas channel. Finally, an experimentally determined mechanism is found to be consistent with the results of the simulation.     

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。     

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。     

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。     

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。     

Measurements of proton conductivity in the active layer of PEM fuel cell gas diffusion electrodes

This paper reports further studies to understand and optimize the Membrane and Electrode Assembly (MEA) structure in Polymer Electrolyte Membrane Fuel Cells (PEMFCs). The effective proton conductivity in the active catalyst layer was measured as a function of its composition, which consisted of platinum catalyst on carbon support (E-Tek) and Nafion® polymer electrolyte (DuPont de Nemours). The conductivity was calculated from the resistance added to a standard MEA by the addition of an inactive composite layer in the electrolyte path between the anode and cathode. The specific conductivity of the active layer was found to be proportional to the volume fraction of Nafion® in the composite mixture, following the relationship κ^eff_H⁺≈0.078_Nafion+0.004 S cm⁻¹. Modeling studies showed that this ionic conductivity limits the utilized active layer thickness to 20–25 μm.     

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。     

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.     

基于电极修饰质子交换膜燃料电池自增湿研究进展

自增湿对于质子交换膜燃料电池的实际应用具有重要意义。本文从电极组分和结构修饰这一角度出发,介绍了近年来质子交换膜燃料电池自增湿研究的一些重要进展和发展趋势。首先介绍了基于催化层修饰实现质子交换膜燃料电池自增湿的发展状况,指出吸湿性催化剂开发是实现高效自增湿催化层的关键;其次介绍了基于气体扩散层修饰和电极结构改进实现质子交换膜燃料电池自增湿的研究进展,分析了两种方式各自的优缺点,讨论了其后续的发展方向;最后针对现有自增湿工艺存在的问题,提出了未来的研究方向和重点,对这类自增湿研究的发展趋势及应用前景进行了展望,指出吸湿性催化剂研发以及多种工艺协同互补将是今后自增湿质子交换膜燃料电池发展的重要方向。     

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。     

质子交换膜燃料电池内含水气体扩散层的冻结特性研究

为了研究含水气体扩散层（GDL）的冻结特性及水分迁移规律,设计并搭建了含水GDL冻结过程的可视化观测系统。制备了不同润湿性的含水GDL,并对含水GDL的冻结过程进行了可视化实验研究,分析了含水GDL冻结过程中的温度变化,以及润湿性和过冷度对于结冰概率的影响。实验结果表明：含水GDL中的某点突然结冰引发整个GDL内水的过冷状态释放,随后在液固相变的体积膨胀作用下,尚未冻结的过冷水被挤压到GDL孔隙外;疏水性GDL会在更高过冷度下产生冻结现象;随着含水GDL温度的降低,内部过冷水的冻结概率不断增加。本研究探索了含水GDL的冻结特性,可为今后解决质子交换膜燃料电池（PEMFC）冷启动过程中GDL低温冻结问题奠定基础。     

质子交换膜燃料电池双层扩散层特性三维分析

针对直流道质子交换膜燃料电池提出一种混合的两相三维非等温数学模型,考虑了液态水在多孔介质内的毛细流动和分布,分析了双层扩散层结构及碳纤维特性对电池性能的影响。结果表明,扩散层第一层（靠近催化层）厚度对质子膜电导率和气体传递特性有着相互制约的影响,需进行优化;在一定范围内,扩散层第一层碳纤维直径的减小可提高质子膜电导率,有利于电池性能的改善;在保持其他参数不变的前提下,应尽可能提高多孔介质的憎水性和孔隙率以提高电池输出性能。     

Development of gas diffusion layer using water based carbon slurry for proton exchange membrane fuel cells

The micro-porous layer of gas diffusion layers (GDLs) was fabricated with the carbon slurry dispersed in water containing sodium dodecyl sulfate (SDS), by wire rod coating process. The aqueous carbon slurry with micelle-encapsulation was highly consistent and stable without losing any homogeneity even after adding polytetrafluoroethylene (PTFE) binder for hundreds of hours. The surface morphology, contact angle and pore size distribution of the GDLs were examined using SEM, Goniometer and Hg Porosimeter, respectively. GDLs fabricated with various SDS concentrations were assembled into MEAs and evaluated in a single cell PEMFC under diverse operating relative humidity (RH) conditions using H₂/O₂ and H₂/air as reactants. The peak power density of the single cell using the GDLs with optimum SDS concentration was 1400 and 500 mW cm⁻² with H₂/O₂ and H₂/air at 90% RH, respectively. GDLs were also fabricated with isopropyl alcohol (IPA) based carbon slurry for fuel cell performance comparison. It was found that the composition of the carbon slurry, specifically SDS concentration played a critical role in controlling the pore diameter as well as the corresponding pore volumes of the GDLs.     

Numerical optimization of proton exchange membrane fuel cell cathodes

A fuel cell gradient-based optimization framework based on adaptive mesh refinement and analytical sensitivities is presented. The proposed approach allows for efficient and reliable multivariable optimization of fuel cell designs. A two-dimensional single-phase cathode electrode model that accounts for voltage losses across the electrolyte and solid phases and water and oxygen concentrations is implemented using an adaptive finite element formulation. Using this model, a multivariable optimization problem is formulated in order to maximize the current density at a given electrode voltage with respect to electrode composition parameters, and the optimization problem is solved using a gradient-based optimization algorithm. In order to solve the optimization problem effectively using gradient-based optimization algorithms, the analytical sensitivity equations of the model with respect to the design variables are obtained. This approach reduces the necessary computational time to obtain the gradients and improves significantly their accuracy when compared to gradients obtained using numerical sensitivities. Optimization results show a substantial increase in the fuel cell performance achieved by increasing platinum loading and reaching a Nafion mass fraction around 20-30 wt.% in the catalyst layer.     

Performance improvement of ultra-low Pt proton exchange membrane fuel cell by catalyst layer structure optimization

Reducing the loading of noble Pt-based catalyst is vital for the commercialization of proton exchange membrane fuel cell (PEMFC).However,severe mass transfer polarization loss resulting in fuel cell perfor-mance decline will be encountered in ultra-low Pt PEMFC.In this work,mild oxidized multiwalled carbon nanotubes (mMWCNT) were adopted to construct the catalyst layer,and by varying the loading of carbon nanotubes,the catalyst layer structure was optimized.A high peak power density of 1.23 W·cm 2 for the MEA with mMWCNT was obtained at an ultra-low loading of 120 μg·cm-2 Pt/PtRu (both cathode and anode),which was 44.7％ higher than that of MEA without mMWCNT.Better catalyst dispersion,low charge transfer resistance,more porous structure and high hydrophobicity of catalyst layer were ascribed for the reasons of the performance improvement.