Nafion/Analcime and Nafion/Faujasite composite membranes for polymer electrolyte membrane fuel cells

The Nafion/zeolite composite membranes were synthesized for polymer electrolyte fuel cells (PEMFCs) by adding zeolite in the matrix of Nafion polymer. Two kinds of zeolites, Analcime and Faujasite, having different Si/Al ratio were used. The physico-chemical properties of the composite membranes such as water uptake, ion-exchange capacity, hydrogen permeability, and proton conductivity were determined. The fabricated composite membranes showed the significant improvement of all tested properties compared to that of pure Nafion membrane. The maximum proton conductivity of 0.4373 S cm⁻¹ was obtained from Nafion/Analcime (15%) at 80 °C which was 6.8 times of pure Nafion (0.0642 S cm⁻¹ at 80 °C). Conclusively, Analcime exhibited higher improvement than Faujasite.     

Nafion functionalized carbon nanohorns as catalyst support for proton exchange membrane fuel cells

Carbon nanohorns (CNHs) are synthesized by DC arc-discharge method in helium atmosphere. The synthesized CNHs are heat treated and then functionalized with Nafion. Platinum is reduced onto Nafion functionalized CNHs through ethylene glycol reduction method. Pt/Nafion-CNHs catalysts are prepared by varying deposition times from 1 to 7 h. Detailed characterization of CNHs and the catalyst is performed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy, X-ray diffraction (XRD) and thermo gravimetric analysis (TGA). Membrane electrode assemblies are prepared by decal method and electrode performance is analyzed using hydrogen pumping technique. SEM and TGA analysis of soot indicates relatively high level purity of CNHs. TEM and XRD analysis of catalyst with 6 h deposition time reveals that Pt nanoparticles are uniformly deposited on multiwall CNHs surface with particle size of 3–4 nm. Hydrogen pumping studies reveals that Nafion functionalized CNHs act as good catalyst support without hindering electron transfer at electrodes. Hence, these graphitic carbon supports have potential application for high power density applications.     

Solution blown sulfonated poly(ether sulfone)/poly(ether sulfone) nanofiber‐Nafion composite membranes for proton exchange membrane fuel cells

A composite membrane of sulfonated poly(ether sulfone) (SPES)/poly(ether sulfone) (PES) nanofiber (NF) mat impregnated with Nafion was prepared and evaluated for its potential use as a proton conductor for proton exchange membrane (PEM) fuel cells. The supporting composite nanofibrous mat was prepared by solution blowing of a mixture of SPES/PES solution. The characteristics of the SPES/PES NF and the composite membrane, such as morphology, thermal stability, and performance of membrane as PEMs, were investigated. The performance of composite membranes was compared with that of Nafion117. The introduction of solution blown NFs to composite membranes modestly improved proton conductivity, water swelling, and methanol permeability. Therefore, composite membrane containing SPES/PES NFs can be considered as a novel PEM for fuel cell applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42572.     

Polybenzimidazole/poly(tetrafluoro ethylene) composite membranes for high temperature proton exchange membrane fuel cells

A porous poly(tetrafluoro ethylene) (PTFE) thin film (thickness 16 ± 2 μm) is used as a supporting material for polybenzimidazole (PBI) to prepare the PBI/PTFE composite membrane (thickness 38 ± 2 μm). The perfluorosulfonic acid resin (Nafion) is used as a coupling agent at the interface between PTFE and PBI to improve the bonding between PBI and PTFE. The composite membrane, after doping with phosphoric acid, is used to prepare membrane electrode assemblies (MEAs). A 450 h continuous fuel cell life test at 160 °C with a fixed current density i = 200 mA cm⁻² and a 20 cycles cell on/off test, in which the fuel cell is operated at 160 °C with i = 200 mA cm⁻² for 12 h and then switched off at room temperature in an ambient environment for 12 h per cycle, are performed. Both tests show good fuel cell performances.     

An inorganic/organic self-humidifying composite membranes for proton exchange membrane fuel cell application

With an aim to operate the proton exchange membrane fuel cells (PEMFCs) with dry reactants, an inorganic/organic self-humidifying membrane based on sulfonated polyether ether ketone (SPEEK) hybrid with Cs_2.5H_0.5PW₁₂O₄₀ supported Pt catalyst (Pt-Cs2.5 catalyst) has been investigated. The Pt-Cs2.5 catalysts incorporated in the SPEEK matrix provide the site for catalytic recombination of permeable H₂ and O₂ to form water, and meanwhile avoid short circuit through the whole membrane due to the insulated property of Cs_2.5H_0.5PW₁₂O₄₀ support. Furthermore, the Pt-Cs2.5 catalyst can adsorb the water and transfer proton inside the membrane for its hygroscopic and proton-conductive properties. The structure of the SPEEK/Pt-Cs2.5 composite membrane was characterized by XRD, FT-IR, SEM and EDS. Comparison of the physicochemical and electrochemical properties, such as ion exchange capacity (IEC), water uptake and proton conductivity between the plain SPEEK and SPEEK/Pt-Cs2.5 composite membrane were investigated. Additive stability measurements indicated that the Pt-Cs2.5 catalyst showed improved stability in the SPEEK matrix compared to the PTA particle in the SPEEK matrix. Single cell tests employing the SPEEK/Pt-Cs2.5 self-humidifying membrane and the plain SPEEK membrane under wet or dry operation conditions and primary 100 h fuel cell stability measurement were also conducted in the present study.     

Incorporating sepiolite and kaolinite to improve the performance of SPEEK composite membranes for proton exchange membrane fuel cells

SPEEK polymer based thermally crosslinked polymer membranes are prepared by sol-gel synthesis using kaolinite and sepiolite clays as additives. Characterization tests, ie, mechanical stability, thermal gravimetric analysis, ion exchange capability, swelling properties, water uptake capacities, electrochemical impedance spectroscopy analysis, and Fourier transform infrared spectroscopy (FTIR) analysis of the membranes were conducted. The sepiolite and kaolinite addition enhanced the thermal stability and the thermal crosslinking reduced the swelling capacity of the synthesized membranes. Proton conductivity results were increased from 0.172 to 0.268 S cm⁻¹ by adding 9% of kaolinite, and to 0.329 S cm⁻¹ at 80°C by adding 9% of sepiolite to the SPEEK membrane's polymer structure. The fuel cell current density and potential measurements of 141 mA cm⁻² and 84.6 mW cm⁻² were found respectively at 0.6 V for the SPEEK/S9 membrane, whereas values of 600 mA cm⁻² and 348 mW cm⁻² were found for the Nafion commercial membrane.     

A composite electrolyte membrane containing high-content sulfonated carbon spheres for proton exchange membrane fuel cells

Sulfonated carbon spheres (SCS) were employed with perfluorinated ionomers as a binder to make proton-conducting electrolyte membranes for polymer electrolyte membrane fuel cells (PEMFC). Hot-pressing produced a symmetric, thin membrane with SCS particles concentrated in the center of the membrane. Relative to Nafion, the SCS materials showed higher density of sulfonic acid groups and increased water retention capacity of the membrane. This is the favorable condition for effective back diffusion of water from cathode preventing dehydration of membrane. As a result, the SCS membrane showed much better performance in single cell PEMFC operation than Nafion membrane. The membrane also showed much improved tolerance to chemical degradation by oxygen radical species.     

质子交换膜燃料电池用全氟磺酸复合膜性能研究

以醇和水为混合溶剂,在高温高压下制得了全氟磺酸树脂回收液,并用FYPFSA溶液改善了回收液的成膜性能,然后以PTFE多孔膜为增强材料,制成全氟磺酸/PTFE复合膜用于质子交换膜燃料电池,对复合膜的物理化学性能和电化学性能进行了测定.在41.5℃、p(H2)=0.03 MPa、P(O2)=0.2 MPa条件下用复合膜CM1组装的电池最大功率密度达到0.4 W/cm2.     

Novel crosslinked AB‐type polyphenylquinoxaline membranes for high‐temperature proton exchange membrane fuel cells

AB‐type polyphenylquinoxaline (ABPPQ) membranes exhibit great mechanical properties and thermal properties for high‐temperature proton exchange membranes (PEMs). However, they dissolve in high‐concentration phosphoric acid (PA) during acid doping. In order to improve the PA resistant of ABPPQ, crosslinked ABPPQ membranes were prepared using sulfuric acid. The crosslinked ABPPQ membranes showed high PA resistance. The acid content of PA‐doped membranes decreased slightly with crosslinking, but the crosslinked polyphenylquinoxaline (CPPQ)‐20 membrane could reach 2.5 × 10^?2 S/cm proton conductivity at 160°C. Membrane electrode assemblies were fabricated with an active area of 4 cm² and Pt loading of 1 mg/cm². A startup and shutdown test (operated at 150°C with 0.2 A/cm² for 12 h and then 12 h off at room temperature) and a 30‐day long‐term durability test (150°C with 0.2 A/cm²) were conducted. In the startup and shutdown test, the crosslinked membranes showed a low open‐circuit voltage decay rate of 0.15 mV/h. In the 30‐day long‐term durability test, the voltage decay rate was 0.039 mV/h. In both tests, the crosslinked membranes showed a stable performance. Therefore, the crosslinked ABPPQ membranes can be regarded as a novel material for high‐temperature PEM fuel cells. POLYM. ENG. SCI., 59:2169–2173, 2019. © 2019 Society of Plastics Engineers     

Sulfonated hydrocarbon membranes for medium-temperature and low-humidity proton exchange membrane fuel cells (PEMFCs)

This review summarizes efforts in developing sulfonated hydrocarbon proton exchange membranes (PEMs) with excellent long-term electrochemical fuel cell performance in medium-temperature and/or low-humidity proton exchange membrane fuel cell (PEMFC) applications. Sulfonated hydrocarbon PEMs are alternatives to commercially available perfluorosulfonic acid ionomers (PFSA, e.g., Nafion^®) that inevitably lose proton conductivity when exposed to harsh operating conditions. Over the past few decades, a variety of approaches have been suggested to optimize polymer architectures and define post-synthesis treatments in order to further improve the properties of a specific material. Strategies for copolymer syntheses are summarized and future challenges are identified. Research pertaining to the sulfonation process, which is carried out in the initial hydrocarbon PEM fabrication stages, is first introduced. Recent synthetic approaches are then presented, focusing on the polymer design to enhance PEM performance, such as high proton conductivity even with a low ion exchange capacity (IEC) and high dimensional stability. Polymer chemistry methods for the physico-chemical tuning of sulfonated PEMs are also discussed within the framework of maximizing the electrochemical performance of copolymers in membrane-electrode assemblies (MEAs). The discussion will cover crosslinking, surface fluorination, thermal annealing, and organic–inorganic nanocomposite approaches.     

Optimisation of polypyrrole/Nafion composite membranes for direct methanol fuel cells

Acidic and neutral Nafion^® 115 perfluorosulphonate membranes have been modified by in situ polymerization of pyrrole using Fe(III) and H₂O₂ as oxidizing agents, in order to decrease methanol crossover in direct methanol fuel cells. Improved selectivities for proton over methanol transport and improved fuel cell performances were only obtained with membranes that were modified while in the acid form. Use of Fe(III) as the oxidizing agent can produce a large decrease in methanol crossover, but causes polypyrrole deposition on the surface of the membrane. This increases the resistance of the membrane, and leads to poor fuel cell performances due to poor bonding with the electrodes. Surface polypyrrole deposition can be minimized, and surface polypyrrole can be removed, by using H₂O₂. The use of Nafion in its tetrabutylammonium form leads to very low methanol permeabilities, and appears to offer potential for manipulating the location of polypyrrole within the Nafion structure.     

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。     

Cathode catalyst layer design for proton exchange membrane fuel cells

To improve water management and enhance the catalyst utilization of the cathode catalyst layer of proton exchange membrane (PEM) fuel cells, the effects of polytetrafluoroethylene (PTFE) addition in the catalyst ink and the loading pattern of the catalyst layer were investigated. Two types of catalyst ink were used: a typical one without PTFE (Pt on carbon support + Nafion) and another type added with PTFE (Pt on carbon support + Nafion + PTFE). In exploring the effect of PTFE addition into the conventional full loading pattern of catalyst layer, the presence of 10% PTFE in the catalyst layer improved the cell performance (34% increase of maximum power density) and the optimum Pt loading for the PTFE-added catalyst layer was 0.25 mg/cm². Two catalyst layer loading patterns created in this work were the strip and chess patterns. Each pattern consists of equal areas of several hydrophilic and hydrophobic segments. The hydrophilic segments were formed by using the ink with PTFE while the hydrophilic had no PTFE. For the catalyst loading pattern effect, the cell achieved the highest performance with the chess pattern, followed by the strip and full loading pattern for the case of 0.5 mg/cm² Pt loading having a thick catalyst layer of 50-μm thickness. On the other hand, for the case of 0.25 mg/cm² Pt loading forming a thin catalyst layer of ～30-μm thickness, the catalyst loading pattern had no effect on the cell’s performance.     

Sulfonated aromatic hydrocarbon polymers as proton exchange membranes for fuel cells

This article reviews recent studies on proton exchange membrane (PEM) materials for polymer electrolyte fuel cells. In particular, it focuses on the development of novel sulfonated aromatic hydrocarbon polymers for PEMs as alternatives to conventional perfluorinated polymers. It is necessary to improve proton conductivity especially under low-humidity conditions at high operating temperatures to breakthrough the current aromatic PEM system. Capable strategies involve the formation of well-connected proton channels by microphase separation between hydrophilic and hydrophobic domains and the increase of the ion exchange capacity of PEMs while keeping water resistance. Herein, we introduce novel molecular designs of sulfonated aromatic hydrocarbon polymers and their performance as PEMs.     

Modification of Nafion membranes with ternary composite materials for direct methanol fuel cells

Composite membranes for direct methanol fuel cells (DMFCs) were prepared by using Nafion115 membrane modification with polyvinyl alcohol (PVA), polyimide (PI) and 8-trimethoxysilylpropyl glycerin ether-1,3,6-pyrenetrisulfonic acid (TSPS). The performance of the composite membranes was evaluated in terms of water sorption, dimensional stability, thermal stability, proton conductivity, methanol permeability and cell performance. The proton conductivity was slightly decreased by 1-3% compared with Nafion115, which still kept the high proton conduction of Nafion115. The methanol permeability of Nafion/PI-PVA-TSPS composite membranes was remarkably reduced by 35-55% compared with Nafion115. The power density of DMFCs with Nafion/PI-PVA-TSPS composite membranes reached to 100 mW/cm², exceeding that with Nafion115 (68m W/cm²).     

Nafion质子交换膜的表观形态分析

介绍了Nafion质子交换膜的膜传导原理与微观结构,测定了离子交换容量和吸水溶胀率,并对干燥状态、湿润状态及表面涂覆催化剂的质子交换膜表观形态进行检测分析。试验结果表明:Nafion117质子交换膜离子交换容量为1.29 mol/kg;Nafion117质子交换膜的吸水率与溶胀率随水温升高而增大,质子交换膜的尺寸稳定性受温度影响明显。水浴处理可有效减少膜表面的尖簇状凸起,增大孔隙与凹陷,降低膜的不平整度,提高催化剂分子粘结的牢固性,有利于在膜表面直接涂刷催化剂,可得到较为均匀稳定的催化层,从而减少电解过程中催化剂的损失,防止膜的局部退化对整体设备性能产生影响。     

圆柱形质子交换膜燃料电池的研究

目前质子交换膜燃料电池(PEMFC)多为平板型板框式结构,介绍了一种圆柱形新型结构的质子交换膜燃料电池。制备了外径6 mm,壁厚为1 mm的微型阳极圆管,采用涂覆法制备阳极微孔层和阴阳极的催化层,热滚压法制作膜电极(MEA),并解决了气体进出、密封与电极的引出等方面问题。应用三维软件进行结构设计,并用模拟分析软件ANSYS进行热和静力分析,最后组装成圆柱形质子交换膜燃料电池。当氢气压力为0.2 MPa、常温常压下工作时,开路电压为0.8 V,功率密度可达到8.3 mW/cm2。     

聚吡咯在质子交换膜燃料电池中的应用

聚吡咯（polypyrrole,PPy）具有长链状共轭结构及多孔的载体形貌,且显示出高电导率、良好稳定性和无毒等优点,但PPy结构疏松且热稳定性和导电性不如碳材料。本文简述了PPy修饰载体后能为催化反应提供高效的电子和质子传导网络,并能通过改善载体表面形态更好地分散Pt,提高Pt的利用率。此外,本文还概述了聚吡咯类过渡金属复合催化剂在质子交换膜燃料电池（PEMFC）中表现出良好的氧还原反应（ORR）性能,且可通过优化合成条件、改变各成分的质量比、热处理或掺杂等方法提高此类非铂催化剂的性能。最后提出可利用M-PPy-C和Pt的协同效应,制备高活性和耐久性良好的Pt/M-PPy-C催化剂。     

Electrodeposition-fabricated PtCu-alloy cathode catalysts for high-temperature proton exchange membrane fuel cells

Pt electrocatalysts in high-temperature proton exchange membrane fuel cells (HT-PEMFCs) containing phosphoric acid (PA)-doped polymer membranes are prone to poisoning by leaked PA. We performed a preliminary density functional theory (DFT) study to investigate the relationship between the electronic structure of Pt surfaces and their adsorption of PA. Excess charge on Pt was found to weaken its bonding with the oxygen in PA, thus presenting a strategy for the fabrication of PA-resistant catalyst materials. Consequently, PtCu-alloy catalysts with various compositions were prepared by electrodeposition. The morphologies and crystalline structures of the alloys were strongly dependent on alloy composition. Moreover, the Pt atoms in the PtCu-alloy catalysts were found to be in an electron-rich state, similar to that of the excessively charged Pt simulated in the DFT study. As a result, the oxygen reduction reaction activities of the PtCu-alloy catalysts were superior to that of a Pt-only catalyst, regardless of the presence of PA. In the absence of PA, the higher activity of the PtCu-alloy catalysts was ascribable to conventional alloying effects, while the increased activity in the presence of PA was largely due to the enhanced resistance to PA poisoning. Therefore, PtCu-alloy catalysts easily prepared by electrodeposition were found to be strong candidate materials for HT-PEMFC electrodes.     

基于无机固体酸的燃料电池用质子交换膜的研究进展

概述了基于无机固体酸的燃料电池用质子交换膜的发展背景以及研究现状,较详细地介绍了这类电解质膜的导电机理及其在机理方面的研究,展望了其发展前景,也提出了固体酸电解质膜应用中必须解决的问题.