Typical Proton Exchange Membrane Research Articles

Sulfonamide-Sulfonimide Copolymers as Novel, Fluorine-Lean Type of Proton Exchange Membranes for Fuel Cell Application.

In this work, a novel type of fluorine-lean proton exchange membranes is presented, using sulfonamide-sulfonimide functional groups for ion conduction. These groups are constructed on a polystyrene backbone for simple and cost-efficient usage as well as rapid scalability. The polymer is further tailored by adjusting the sulfonamide functionality with various end-groups, namely pentafluorophenyl, 4-fluorophenyl, butyl and octyl groups. These groups affect the pKa, leading to pKa values of 5.7 for the pentafluorophenyl substitution and pKa 10.5 for the alkyl chain. The glass transition temperature of the sulfonamide homopolymers can be reduced from Tg=151 °C (Pentafluorophenyl) to 49 °C (Octyl), making the ionomer more flexible at room temperature. The combination of the non-swelling sulfonamide further mitigates the high water uptake of the sulfonimide while maintaining the nominal ion exchange capacity. This combination leads to extremely high proton conductivities with up to σ=283 mS cm-1 at room temperature, which is clearly outperforming Nafion and approaches values for acid doped systems. This approach can pave the way to a novel type of ion conducting class in proton exchange membrane fuel cells.

Facile construction of polyacrylate membranes with pendent zwitterionic side-chains for high proton conduction

Designing high-performance proton exchange membranes for fuel cells has received tremendous interests and acquired plentiful fruits. However, the complicated preparation process and consequently high cost limit their practical application. This study endeavored to facilely construct a novel type of proton exchange membrane based on polyacrylates which decorated with pendant zwitterionic groups. Chemical structure and micro-morphology of these newly prepared membranes, namely SBPA-x (x = 0, 20, 30,40), were characterized by 1HNMR, FT-IR, XPS, SEM and AFM. Swelling ratio, water uptake and ion exchange capacity were found to be positively correlated with the contents of zwitterionic groups. The hydrophilic zwitterionic groups in the membrane formed a continuous water pathway, which contributed to the proton conductivity. Particularly, SBPA-40 membrane showed the highest proton conductivity of 78.6 mS/cm and the smallest activation energy Ea as 16 kJ/mol at 80 °C and 90 % relative humidity. On the other hand, the other application properties, such as thermal stability, mechanical property and oxidation stability, were also evaluated. Results demonstrated that all the membranes possessed good thermal stability within 300 °C and presented satisfactory mechanical performance by bending and twisting. Besides, the observed power density and open circuit voltage of SBPA-40 membrane were 58.3 mW/cm2 and 0.77 V at 30 °C. In conclusion, the zwitterionic polyacrylate membranes could have prospective application in proton exchange membrane fuel cells.

Design and development of model for proton exchange membrane fuel cell

Fuel prices are rising, and fossil fuel resources are depleting. This fuel is consumed by conventional fuel vehicles, which contributes to increased greenhouse gas emissions and air pollution. Various vehicle technologies have been introduced in modern times. Among these innovations, fuel cell vehicle technology stands out due to its ease of use, robustness, and simplicity. The primary energy source for this system is hydrogen. Fuel cells use hydrogen to generate electricity through a chemical process that does not involve combustion. The purpose of this paper is to describe the design and development of a simulation model for a fuel cell (proton exchange membrane type) vehicle using mathematical equations and the MATLAB/Simulink R2020a software, taking into account all voltage losses and temperature variations of the proton exchange membrane (PEM) type fuel cell. The designed model is validated in two ways: first by generating V-I characteristics for the designed PEM-type fuel cell, and then by performing a performance test in Simulink using the driving cycle on one of the fuel cell vehicles. The obtained simulated results are nearly identical to the expected results, and the designed PEM-type fuel cell performed well in all real-time driving cycle test conditions.

Progress of Heterogeneous Iridium-Based Water Oxidation Catalysts.

The water oxidation reaction (or oxygen evolution reaction, OER) plays a critical role in green hydrogen production via water splitting, electrochemical CO2 reduction, and nitrogen fixation. The four-electron and four-proton transfer OER process involves multiple reaction intermediates and elementary steps that lead to sluggish kinetics; therefore, a high overpotential is necessary to drive the reaction. Among the different water-splitting electrolyzers, the proton exchange membrane type electrolyzer has greater advantages, but its anode catalysts are limited to iridium-based materials. The iridium catalyst has been extensively studied in recent years due to its balanced activity and stability for acidic OER, and many exciting signs of progress have been made. In this review, the surface and bulk Pourbaix diagrams of iridium species in an aqueous solution are introduced. The iridium-based catalysts, including metallic or oxides, amorphous or crystalline, single crystals, atomically dispersed or nanostructured, and iridium compounds for OER, are then elaborated. The latest progress of active sites, reaction intermediates, reaction kinetics, and elementary steps is summarized. Finally, future research directions regarding iridium catalysts for acidic OER are discussed.

Evaluation of radiation stability of electron beam irradiated Nafion® and sulfonated poly(ether ether ketone) membranes

Proton exchange membranes (PEM), which have been commonly used in fuel cells have raised interest for the application in harsh environments involving ionizing radiation. Therefore, radiation stability and ability to sustain their functionality under the radiation environment are of great interest. Within this study, electron beam irradiation in dose range from 50 to 500kGy was used to evaluate the effects of radiation on the physico-chemical and mechanical properties of two types of PEM: commercial Nafion®117 and sulfonated poly(ether-ether-ketone) (SPEEK) with high degree of sulfonation (DS = 0.75±0.5).SPEEK membrane presented higher mechanical and thermal stability compared to that of Nafion® at doses up to 250 kGy, which was evidenced by infrared and electron paramagnetic resonance spectroscopy, thermal analysis, ion chromatography methods. Tensile tests at room temperature and dynamical mechanical analysis of irradiated membranes revealed improved strength, storage modulus at room and elevated temperatures (80°C) for irradiated SPEEK as compared to pristine PEM. For comparison Nafion® exhibited notable deterioration of mechanical properties including elongation at break due to the predominant oxidation and chain scission already at doses exceeding 50 kGy. The study indicated that SPEEK could be perspective replacement of traditional PEM for application in fuel cells exposed to ionising radiation.

Proton exchange membrane from the blend of poly(vinylidene fluoride) and functional copolymer: Preparation, proton conductivity, methanol permeability, and stability

A polymer electrolyte membrane is considered as the heart of fuel cells. Here we report the preparation of proton exchange membranes (PEMs) of poly (vinylidene fluoride) (PVDF) blend poly (methyl methacrylate)-co-poly (sodium-4-styrene sulfonate) (PMMA-co-PSSNa) by solvent evaporation method. Three different types of PEMs have been prepared by using different ratios of PVDF and PMMA-co-PSSNa copolymer. We have investigated the effect of concentration of PVDF on water uptake, ion exchange capacity, mechanical, thermal, and oxidative stability, proton conductivity (Km), and methanol permeability (PM) of the blend membranes. These blend PEMs showed good physicochemical and electrochemical properties along with thermal and oxidative stability. The membrane prepared from PVDF (45% w/w) to PMMA-co-PSSNa (55% w/w) exhibited optimum PM at room temperature (8.38 × 10−7 cm2s−1). This low fuel crossover and high relative selectivity can make our prepared blend membranes a potential candidate in polymer electrolyte membrane fuel cells (PEMFCs) or direct methanol fuel cells (DMFCs).

Mesoscale hydrated morphology of perfluorosulfonic acid membranes

AbstractFuel cells are expected to play an important role in global carbon neutralization and future social development with high conversion efficiency and zero emissions. The core of the fuel cell is the proton exchange membrane (PEM). However, the unclear of the proton transport mechanism in PEMs limits the development of membranes with improved performance. Perfluorosulfonic acid (PFSA) membranes are currently the most widely used type of PEM, and exhibit varying proton transport capabilities with various chemical structures. In this study, the hydration morphology of several PFSA membranes was studied using dissipative particle dynamics. The result shows that under low water content the hydrophilic and hydrophobic phases separated and the water clusters are relatively isolated. The increased water content formed hydrophilic channels, while the increase in equivalent weight decreases the water cluster size and improves water dispersion. Aciplex 1128 shows great variation owing to the presence of a long sulfonic acid terminated side chain in water cluster size and dispersion compared with Nafion. The average diffusivity and mean square displacement results showed similar results. These results will promote the development of high performance PEM for fuel cells.

Design and analysis of global optimization methods for proton exchange membrane fuel cell powered electric vehicle system with single switch DC-DC converter

The Proton Exchange Membrane type Fuel Cells (PEMFC) are playing a major role in the present automotive industry application. The advantages of PEMFC are more reliable, high starting speed, and high efficiency. The PEMFC gives nonlinear V-I and P-I characteristics at diverse operating temperature conditions. As a result, the entire system performance is get reduced. Here, global optimization methodologies are used for the PEMFC system for improving the tracing speed of the Maximum Power Point (MPP). The global optimization methods are classified as Improved Particle Swarm Optimization (IPSO), and Adaptive Cuckoo Search Optimization (ACSO). These techniques are compared at different operating temperature conditions. The merits of global optimization techniques are easy understanding, nonlinear complex problem solving, high efficient, and more reliable when compared to the other classical controllers. The major disadvantage of PEMFC is less output voltage which is step-up by using a single switch boost converter. The proposed fuel cell fed boost converter system is investigated by using a MATLAB/Simulink window.

Variational-principle-optimized porosity distribution in gas diffusion layer of high-temperature PEM fuel cells

Porosity distribution in gas diffusion layer has a significant impact on cell performance by affecting the oxygen transport and the electrical conductivity. This contribution presents a theoretical optimization model for porosity distribution in the cathode gas diffusion layer based on the variational principle. First, the optimization equations for maximizing the total oxygen mass flux diffused through the cathode gas diffusion layer are derived with the constraints of the momentum conservation, the species conservation and the specified average porosity. Then, the application of a typical high-temperature proton exchange membrane fuel cell with twelve parallel flow channels gives the optimized three-dimensional non-uniform porosity distribution that could increase the current density at 0.2 V by 13.7% and the maximum power density by 10.0%. Besides, the optimized porosity distribution also improves the uniformity of oxygen mass fraction field and the current density distribution. Finally, seven design schemes with in-plane non-uniform porosity distribution or thickness-direction linear gradient porosity are proposed and evaluated. The results indicate that the optimized porosity distribution has the best performance, followed by the in-plane non-uniform porosity, and the linear gradient porosity along the thickness direction shows the weakest improvement. This finding further demonstrates the rationality and necessity of the proposed optimization model.

Biomimetic N-Doped Graphene Membrane for Proton Exchange Membranes.

Proton exchange membranes (PEMs) with both high selectivity and high permeance are of great demand in hydrogen-based applications, especially in fuel cells. Although graphene membranes have shown high selectivity of protons over other ions and molecules, the relatively low permeance of protons through perfect pristine graphene restricts its practical applications. Inspired by the nitrogen-assisted proton transport in biological systems, we introduced N-doping to increase the proton permeance and proposed a type of N-doped graphene membranes (NGMs) for proton exchange, which have both high proton permeance and high selectivity. Compared to the state-of-the-art commercial PEMs, the NGMs show significant increases in both areal proton conductivity (2-3 orders of magnitude) and selectivity of proton to methanol (1-2 orders of magnitude). The work realized the controllable tuning of proton permeance of the graphene membrane with N-doping and developed a new type of graphene-based PEMs with high performance for practical applications.

High methanol resistant polyelectrolyte membrane based on semi-crystalline Poly(ether ketone) with densely sulfonated side chain for direct methanol fuel cell

Different from the widely developed amorphous polyelectrolyte membrane materials, semi-crystalline sulfonated poly(ether ketone) (PEK-SPx) membranes composed of crystalline poly(ether ketone) main chain and densely sulfonated side chain are prepared. Wide-angle X-ray diffraction analysis indicates that these membranes manifest crystalline nature. The dimensional stability and methanol resistance of PEK-SPx membranes are greatly enhanced by introduction of semi-crystalline structure. The dimensional change in pure methanol at 60 °C and methanol permeability of PEK-SP20 membrane is only 25.9% and 36 × 10−8 cm2 s−1, respectively. In addition, coupled with excellent thermal stability, oxidative stability, good mechanical property, satisfactory proton conductivity and distinct micro-phase separation, PEK-SP20 membrane exhibits considerable single cell performance. Overall, semi-crystalline PEK-SPx membranes are a promising new type of proton exchange membranes for application in direct methanol fuel cells.

Recent Progress in the Development of Aromatic Polymer-Based Proton Exchange Membranes for Fuel Cell Applications.

Proton exchange membranes (PEMs) play a pivotal role in fuel cells; conducting protons from the anode to the cathode within the cell’s membrane electrode assembles (MEA) separates the reactant fuels and prevents electrons from passing through. High proton conductivity is the most important characteristic of the PEM, as this contributes to the performance and efficiency of the fuel cell. However, it is also important to take into account the membrane’s durability to ensure that it canmaintain itsperformance under the actual fuel cell’s operating conditions and serve a long lifetime. The current state-of-the-art Nafion membranes are limited due to their high cost, loss of conductivity at elevated temperatures due to dehydration, and fuel crossover. Alternatives to Nafion have become a well-researched topic in recent years. Aromatic-based membranes where the polymer chains are linked together by aromatic rings, alongside varying numbers of ether, ketone, or sulfone functionalities, imide, or benzimidazoles in their structures, are one of the alternatives that show great potential as PEMs due totheir electrochemical, mechanical, and thermal strengths. Membranes based on these polymers, such as poly(aryl ether ketones) (PAEKs) and polyimides (PIs), however, lack a sufficient level of proton conductivity and durability to be practical for use in fuel cells. Therefore, membrane modifications are necessary to overcome their drawbacks. This paper reviews the challenges associated with different types of aromatic-based PEMs, plus the recent approaches that have been adopted to enhance their properties and performance.

Electrochemical fabrication of IrOx nanoarrays with tunable length and morphology for solid polymer electrolyte water electrolysis

For a typical Proton exchange membrane (PEM) water electrolysis system, reducing the amount of Ir loading at the anode in membrane electrode assembly (MEA), while maintaining the performance, is still a big challenge. Here, to improve the performance of catalyst layer for oxygen evolution reaction (OER) in an acidic medium, vertical aligned IrOx nanoarrays (IrOx NAs) were synthesized by electrodeposition with TiO2 nanotube arrays (TNTA) as template. By tuning the scan rate in the electrodeposition process, IrOx open-end nanotube arrays with tunable length ranged from 500 nm to 1400 nm and hollow nanorod arrays were obtained due to a diffusion-controlled deposition process. By constructing 3-D electrode of 1-D catalyst with enhanced ion transfer, IrOx NAs performed almost the same current density of OER with 1/20 Ir loading amount compared with commercial IrO2 nanoparticles, which could significantly reduce the cost of catalyst in PEM water electrolyser. Moreover, no apparent current decrease was observed even after 10 h’ anodic polarization under 1.55 V, which exhibit excellent OER durability.

AEM Electrolysis Testing Update and Industrial Device Requirements

Membrane (PEM)-based electrolysis provides an ideal near-term technology to address the growing energy storage demands as intermittent renewable energy becomes more prevalent. While proton exchange membrane (PEM) systems are often viewed as preferred solutions to legacy KOH systems due to the lack of corrosive electrolyte, small footprint, dynamic operating range and ability to generate hydrogen at differential pressure, they still present capital cost challenges. In particular, the platinum group metal catalysts and valve metals for separator and flow field construction required for stability in the acidic environment become a significant cost driver at scale. Alkaline exchange membrane (AEM)-based electrolysis is therefore viewed as a potential replacement to the current PEM systems as a means of driving down the high capital cost. This cost reduction is accomplished by replacing the typical high cost catalyst and materials of cell construction with lower cost metals that would corrode in the acidic PEM environments, but are stable in the alkaline chemistries. In theory, this approach is highly promising, but testing of the current state-of the art has shown the technology gaps between the two platforms in terms of stability, durability, and operating electrical efficiency. Modeling has shown that savings realized in capital cost are typically off-set by an increase in operating expense resulting from the lower activity of the non-PGM catalysts and poor conductivity of the AEM. Additionally, thermal instability of the AEMs require stacks to be operated at lower temperatures than a typical PEM system, impacting conductivity further and slowing kinetics. Recent activities have looked at improving the mechanical properties, through the addition of mechanical reinforcements, to support pressurized operation, while operating temperature and varied concentrations of liquid electrolyte to the water feed have been explored to operationally evaluate the impact on performance and durability. The latter of these operating parameters have been shown by some groups to be effective in reducing cell operating potentials and providing overall voltage stability. However, this solution adds management and additional maintenance of handling the caustics typically used. Efforts at Proton continue to show improvements in short duration operational tests under milder conditions and potential pathways to achieve targets required to compete with incumbent technology. In this talk, some of the advancements achieved and how these have impacted the cost of the hydrogen will be discussed, as well as the longer-term targets that need to be reached in order to be a viable commercial application. Additionally, cost models will be compared along with sensitivity analysis to show how the impact of operating parameters, with regard to the capital and operational expense for the AEM electrolysis technology cost, show the critical areas to focus on to establish equivalence with current PEM systems and what is required to go beyond. Figure 1

3D Metallic Foams as Catalysts for Hydrolysis and Electrooxidation of Sodium Borohydride

Environmental and social challenges that result from the burning of fossil fuels demand clean energy for the world future sustainability. Fuel cells are devices that convert a fuel source into electricity, providing a clean energy solution for both portable and stationary (e.g., electricity production and heating) applications more than any other currently available power source [1]. Amongst low temperature fuel cells, polymer electrolyte fuel cells (with a typical operation temperature of 80 ºC) are receiving great attention due to their characteristically high power density. However, its large-scale development has been hindered by cost competitiveness, engineering design and safety concerns for hydrogen-fueled devices. These drawbacks can be minimized by the use of high specific energy liquid fuels, such as methanol or sodium borohydride (NaBH4) solutions. NaBH4 is of high interest as it can be a direct or indirect fuel to power a direct borohydride fuel cell (DBFC) or a typical proton exchange membrane fuel cell (PEMFC), respectively [1]. In fact, International Energy Agency supports NaBH4 as a sustainable route for fuel cell systems. NaBH4 is a non-fossil derivative and nonflammable compound with high gravimetric hydrogen storage capacity (10.8 wt.%) [2]. As an indirect fuel, NaBH4 produces clean hydrogen through hydrolysis in alkaline medium and ambient conditions, after which the hydrogen (H2) fuel is channeled to a PEMFC where it is oxidized to generate electricity [3]. As a direct fuel, NaBH4 is oxidized in the DBFC anode at ambient conditions, releasing eight electrons at quite negative electrode potentials [3]. In addition, no CO2 is produced, unlike hydrocarbon fuels, which turns the overall NaBH4 route a green approach suitable for portable applications [3]. A catalyst is always required, either to accelerate the hydrogen release or for the borohydride direct electrooxidation, so that the fuel cell can generate sufficient power [3,4]. Precious metals, such as Pt, Ru and their related alloys, can generate high hydrogen rates toward NaBH4 hydrolysis. In the case of borohydride electrooxidation, most catalysts are built from precious metals, such as Au or Ag. Since these materials are expensive, there has been much focus on the use of transition metals [3]. Moreover, transition metals in the alloy form can be beneficial as they can enhance catalytic activity due to synergetic effects [4]. Recently, three-dimensional catalysts with very high porosity and surface areas based on Co have demonstrated high catalytic activity for borohydride hydrolysis [5], while those based on Ni have shown electroactivity for borohydride electrooxidation [6]. The main goal of this work is to develop low-cost catalysts, based on Ni, Co, Cu, and Fe, to be applied both on borohydride hydrolysis for H2 generation and on borohydride electrooxidation, in order to find in which system, PEMFC or DBFC, they are more suitable. The catalysts were produced by electrodeposition technique, a simple one-step and fast process, using the dynamic hydrogen bubble template to create foam-like nanostructures. The ternary Ni-Cu-Fe foams presented the best performance towards borohydride oxidation in terms of the current density per unit gram of catalyst. On the other hand, Co-based foams are superior in fast H2 demand applications by borohydride hydrolysis. Figure 1. SEM image of Ni4Cu48Fe30 foam catalyst.

AEM Electrolysis Progress and Impact on the Cost of Hydrogen

Membrane (PEM)-based electrolysis provides an ideal near-term technology to address the growing energy storage demands as intermittent renewable energy becomes more prevalent. While proton exchange membrane (PEM) systems are often viewed as preferred solutions to legacy KOH systems due to the lack of corrosive electrolyte, small footprint, and dynamic operating range due to the ability of the PEM systems to generate hydrogen at differential pressure, they still present capital cost challenges. In particular, the platinum group metal catalysts and valve metals for separator and flow field construction required for stability in the acidic environment become a significant cost driver at scale. Alkaline exchange membrane (AEM)-based electrolysis is therefore viewed as a potential replacement to the current PEM systems as a means of driving down the high capital cost. This cost reduction is accomplished by replacing the typical high cost catalyst and materials of cell construction with lower cost metals that would corrode in the acidic PEM environments, but are stable in the alkaline chemistries. In theory, this approach is highly promising, but testing of the current state-of the art has shown the technology gaps between the two platforms in terms of stability, durability, and operating electrical efficiency. Modeling has shown that savings realized in capital cost are typically off-set by an increase in operating expense resulting from the lower activity of the non-PGM catalysts and poor conductivity of the AEM. Additionally, thermal instability of the AEMs require stacks to be operated at lower temperatures than a typical PEM system, impacting conductivity further and slowing kinetics. The addition of liquid electrolyte to the water feed has been shown by some groups to be effective in reducing cell operating potentials and providing overall voltage stability. However, this solution adds management and additional maintenance of handling the caustics typically used. Efforts at Proton have shown significant improvements in operation under milder conditions, showing some potential to achieve targets required to compete with incumbent technology. In this talk, some of the advancements achieved and how these have impacted the cost of the hydrogen will be discussed. An example of this improvement is shown in the figure below, where collaborative ionomer research and partnering with a commercial entity for scale-up of catalyst synthesis have translated into an immediate improvement over targets previously established. Additionally, cost models will be compared to show the path needed to establish equivalence with current PEM systems and what is required to go beyond. Figure 1

Enhancing the corrosion resistance of the 2205 duplex stainless steel bipolar plates in PEMFCs environment by surface enriched molybdenum

Surface molybdenum enrichment on 2205 duplex stainless steel was obtained by the ball milling technique. The electrochemical results showed molybdenum enrichment on the surface of 2205 duplex stainless steel improved its corrosion resistance in a typical proton exchange membrane fuel cell environment. This was mainly attributed to higher molybdenum content in the passive film formed on 2205 duplex stainless steel after ball milling. The decreased donor and acceptor concentrations improved significantly the corrosion resistance of surface molybdenum-enriched 2205 duplex stainless steel bipolar plates in the simulated cathodic proton exchange membrane fuel cells environment. In addition, the interfacial contact resistance of the 2205 duplex stainless steel bipolar plates slightly decreased due to surface molybdenum enrichment.

532 Basic experiment on the response characteristics of a proton-exchange membrane type water electrolysis cell accompanied by input of fluctuations electric power by renewable energy

532 Basic experiment on the response characteristics of a proton-exchange membrane type water electrolysis cell accompanied by input of fluctuations electric power by renewable energy

Proton Exchange Membrane Involving Compatible Acid-Base Interaction Towards High Performance and Mechanical Property

Proton exchange membranes (PEMs) are central to determine the fuel cell (FC) performance and durability. The PEMs employed in existing applications are perfluorinated sulfonic acid polymers (PFSAs), such as Nafion by DuPont, Flemion by Asahi Glass, Aquivion by Solvay. For example, it is known that Gore select series membranes (with reinforcement) are adopted to Toyota Mirai on sale since December 2014. However, the PFSAs are not the perfect PEMs when it comes to mass production phase of FC vehicles (FCVs), in light of material cost and its environmental friendliness. FCVs need to be designed as cheaply as possible with a maintained high performance, including durability and safety, of the FC stacks and systems. Many types of PEMs including PFSAs and non-PFSAs have been investigated in academy and industry, however often leading to a complexity of manufacturing themselves (synthesis, processing, raw material price, etc.) and their applicability to existing FC systems. PEMs should be, no matter what type of materials are chosen, as simple as possible towards industrial applicability. For example, multiblock copolymers were heavily discussed for the last decades as an alternative to PFSAs in terms of proton conductivity as a funciton of relative humidity (RH). It is true that the property of such block copolymers would get close to that of PFSAs, however casting doubt on reproducibility/reliability for production phase. Therefore, in this study, a simple method was selected, i.e., blending of simple structural polymers for both acidic and basic functions, with an aim at comparable PEM properties to the state-of-the-art PFSAs represented by Nafion.Acid-base blend membranes based on non-fluorinated hydrocarbon typed chemistry were prepared, by involving syntheses of novel base monomers and polymers. Two kinds of monomers were successfully synthesized via lithiation chemistry using electrophiles including pyridyl groups. The versatility for the monomers towards polycondensations for preparation of the high molecular weights poly(arylene ether sulfone)s was confirmed, after optimizing the reaction conditions against transetherification. Molecular weights (Mn) of the new basic polymers found to be from 20 to 50 kDa, in relation to ca. 35 kDa of one UDEL polymer commercialized by Solvay, as confirmed by gell permeation chromatography. Each of the basic polymers prepared was blended with a disulfonated alternating poly(arylene sulfone) (acid/base = 80/20 wt./wt.). Neutralization treatment prior to the processing was no need in order to form their uniform blend membranes, unlike the case of blending acidic polymers with basic polybenzimidazole. All the acid-base blend membranes showed high proton conductivities and good dimensional stabilities in addition to reasonable mechanical properties. For instance, the proton conductivity at 20%RH of the blend membranes showed superior to that of Nafion, whose IECs ranged till ca. 2.0 meq./g. The water uptake of the membranes under immersed conditions remained below 30 of the lambda (water molecule per sulfonic acid) at water temperatures ranging from room temperature to 90 degrees C. In conclusion, the acid-base blend membranes containing the new basic polymers would be a promising candidate to future PEMs with impact on cost reduction of the FC stack.

Comparison of corrosion behavior between coarse grained and nanocrystalline Ni[sbnd]Fe alloys in chloride solutions and proton exchange membrane fuel cell environment by EIS, XPS and Raman spectra techniques

The corrosion resistance of coarse grained and nanocrystalline NiFe alloys in chloride solutions and proton exchange membrane fuel cell environment was investigated. The nanocrystalline NiFe alloys were obtained by electrodeposition, while coarse grained NiFe alloys were obtained by annealing. The results from electrochemical tests showed that coarse grained NiFe alloys had higher corrosion resistance than nanocrystalline samples in NaCl solution due to more compact passive films formed on the surface of coarse grained NiFe alloys. In addition, Raman spectra test showed that many nanocrystalline boundaries in electrodeposited NiFe alloys promoted the diffusion of nickel, which resulted in the formation of more nickel oxides and nickel hydroxides. However, the electrochemical study showed that coarse grained sample had lower corrosion resistance than nanocrystalline one in a typical proton exchange membrane fuel cell environment. The present study showed that nanocrystalline NiFe alloys were more suitable for the bipolar plates in proton exchange membrane fuel cell environment.