Membrane Fuel Cell Applications Research Articles

Investigation of the Impact of an Electric Field on Polymer Electrolyte Membranes for Fuel Cell Applications

A systematic study was carried out on Nafion® 112 membranes to evaluate the effects of different electric field strengths on the structural and electrical properties of the membranes. The membranes were subjected to different electric field strengths (0, 40, 80, and 140 MV/m) at a temperature of 90 °C. Proton conductivity was measured using an LCR meter, revealing that conductivity values varied with the electric field strengths, with the optimal conductivity observed at 40 MV/m. Positron annihilation lifetime (PAL) spectroscopy provided insights into the free volume structure of the membranes, showing an exponential increase in the hole volume size as the electric field strength increased. It was also found that the positronium intensity of the Nafion® 112 membranes was influenced by their degree of crystallinity, which decreased with higher electric field strengths. This indicates complex interactions between structural changes and the effects of the electric field. Dielectric studies of the membranes were characterized over a frequency range of 50 Hz to 5 MHz, demonstrating adherence to Jonscher’s law. The Jonscher’s power law’s s-parameter values increased with the electric field strength, suggesting a transition from a hopping conduction mechanism to more organized ionic transport. Overall, the study emphasizes the relationship between the free volume, crystallinity, and macroscopic characteristics, such as ionic conductivity. The study highlights the potential to adjust membrane performance by varying the electric field.

Synthesis and Evaluation of Reduced Graphene Oxide (rGO) Supported on Ni3O4 as Spinel‐Based Cathode Catalyst for the Effective Anion‐Exchange Membrane Fuel Cell Application

AbstractOxygen reduction reaction (ORR) stability and catalytic activity in high‐durability anion exchange membrane fuel cells (AEMFCs) can be improved using graphene‐supported spinel‐based Ni3O4 cathode catalysts. Here, we describe a simple and economical hydrothermal method for synthesizing reduced graphene oxide (rGO) supported on Ni3O4. The atomic‐level contribution of the Ni−Ni and Ni−O bonds to the chemical structure of nickel oxide was confirmed by X‐ray photoelectron and absorption spectroscopy studies. Due to the force of the void for oxygen created by nickel atoms, Ni3O4@rGO for the ORR exhibited enhanced stability and catalytic activity (E1/2=0.761 V and over 30,000 CV cycles). A single AEMFC cell achieved the greatest power density and long‐term durability using a Ni3O4@rGO cathode, suggesting improved endurance despite the minimal voltage decrease (power density 29.6 mW cm−2, endurance for 25 h). These findings offer insights and point to opportunities for developing metal oxide–based AEMFCs.

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.

Biopolymers‐Based Proton Exchange Membranes For Fuel Cell Applications: A Comprehensive Review

AbstractNafion has been dominating the proton exchange membrane (PEM) market because of its adequacy for the proton exchange operation. However, because of its high cost, low performance at low relative humidity, and finally environmental unfriendliness, researchers have been developing and working on Nafion alternatives. In this review, we assess how biopolymers present an opportunity as an eco‐friendly material able to replace the conventional Nafion membrane in proton exchange membrane fuel cells (PEMFC). Chitosan and cellulose were the most studied in literature owing to their abundance in nature, low cost, and high affinity for water, which are sought‐after properties for PEM. In addition to that, their ease of modification through their hydroxyl or amine groups represents an opportunity to further enhance their characteristics and thus meet the criteria of diverse applications. The use of biopolymers as an adequate PEM is facing many challenges. Having a practical proton conductivity and securing the physicochemical stability of the biopolymers in fuel cell operating conditions are two of the most important challenges to overcome. Promising strategies to simultaneously address these challenges such as crosslinking, making interpenetrated networks, and making blends and composites are reported.

Design and Development of Copper Trimesic Acid Anchored sPEEK/Polyimide Composite Membranes for Fuel Cell Applications

AbstractElectrolyte membranes play a critical role as their properties directly influences the performance of fuel cell. A copper‐based metal organic framework (MOF) anchored polymeric blend membrane was developed for fuel cell application. Cu‐MOF serves as an excellent filler material due to its small size, high degree of crystallinity and surface area. Through XRD analysis well defined crystallite sites was evidenced and the average crystallite size measured ∼ 0.3 Å. The acidic functional group in MOF interacts with sulfonic acid (−SO3H) group in sulfonated polyetheretherketone (sPEEK) matrix which further improves proton conduction via. hydrogen bonding interaction. With the as‐prepared sPEEK as the matrix; polyimide (PI) was blended to improve its processibility and thermal stability. Cu‐MOF loaded composite membranes (X wt.% Cu‐MOF‐sPEEK/PI) were prepared and characterized. To assess the suitability of the developed membranes for proton exchange membrane fuel cell (PEMFC) applications, ion exchange capacity (IEC), water uptake and proton conductivity was measured. 3 wt.% Cu‐MOF‐2‐sPEEK/PI membrane displayed an IEC value of 2.35 meq g−1 with a water uptake of 38.18 % and proton conductivity of 0.0711 S cm−1. Overall, the experimental results of the prepared membranes revealed that they act as an efficient proton exchange membrane (PEM) for PEMFCs.

Review on Chitosan and Two-Dimensional MoS2-Based Proton Exchange Membrane for Fuel Cell Application: Advances and Perspectives

Review on Chitosan and Two-Dimensional MoS₂-Based Proton Exchange Membrane for Fuel Cell Application: Advances and Perspectives

Computational Approaches to Alkaline Anion-Exchange Membranes for Fuel Cell Applications.

Anion-exchange membranes (AEMs) are key components in relatively novel technologies such as alkaline exchange-based membrane fuel cells and AEM-based water electrolyzers. The application of AEMs in these processes is made possible in an alkaline environment, where hydroxide ions (OH-) play the role of charge carriers in the presence of an electrocatalyst and an AEM acts as an electrical insulator blocking the transport of electrons, thereby preventing circuit break. Thus, a good AEM would allow the selective transport of OH- while preventing fuel (e.g., hydrogen, alcohol) crossover. These issues are the subjects of in-depth studies of AEMs-both experimental and theoretical studies-with particular emphasis on the ionic conductivity, ion exchange capacity, fuel crossover, durability, stability, and cell performance properties of AEMs. In this review article, the computational approaches used to investigate the properties of AEMs are discussed. The different modeling length scales are microscopic, mesoscopic, and macroscopic. The microscopic scale entails the ab initio and quantum mechanical modeling of alkaline AEMs. The mesoscopic scale entails using molecular dynamics simulations and other techniques to assess the alkaline electrolyte diffusion in AEMs, OH- transport and chemical degradation in AEMs, ion exchange capacity of an AEM, as well as morphological microstructures. This review shows that computational approaches can be used to investigate different properties of AEMs and sheds light on how the different computational domains can be deployed to investigate AEM properties.

Electrospun Poly(Styrene-Co-Vinylbenzyl Chloride-Co-Acrylonitrile) Nanofiber Mat as an Anion Exchange Membrane for Fuel Cell Applications.

A nanofiber mat of styrene−co−vinylbenzyl chloride−co−acrylonitrile copolymer as an anion exchange membrane (AEM) was synthesized via the electrospinning of organic reaction mixtures. The synthesized membranes were characterized using FT-IR spectroscopy for structural analysis. The AEM demonstrated a high ionic conductivity mainly due to the phase segregation in the membrane structure, as analyzed by transmission electron microscopy (TEM). The membrane properties such as water uptake, swelling ratio, and ion exchange capacity, as well as ionic conductivity, varied with the chemical composition. With the molar ratio of styrene, vinylbenzyl chloride, and acrylonitrile at 3:5:2, the highest ionic conductivity of 0.214 S cm−1 at 80 °C was observed. Additionally, the AEM retained 94% of original conductivity after 72 h of soaking in 1 M KOH solution.

Anion Exchange Membranes for Fuel Cell Application: A Review.

The fuel cell industry is the most promising industry in terms of the advancement of clean and safe technologies for sustainable energy generation. The polymer electrolyte membrane fuel cell is divided into two parts: anion exchange membrane fuel cells (AEMFCs) and proton exchange membrane fuel cells (PEMFCs). In the case of PEMFCs, high-power density was secured and research and development for commercialization have made significant progress. However, there are technical limitations and high-cost issues for the use of precious metal catalysts including Pt, the durability of catalysts, bipolar plates, and membranes, and the use of hydrogen to ensure system stability. On the contrary, AEMFCs have been used as low-platinum or non-platinum catalysts and have a low activation energy of oxygen reduction reaction, so many studies have been conducted to find alternatives to overcome the problems of PEMFCs in the last decade. At the core of ensuring the power density of AEMFCs is the anion exchange membrane (AEM) which is less durable and less conductive than the cation exchange membrane. AEMFCs are a promising technology that can solve the high-cost problem of PEMFCs that have reached technological saturation and overcome technical limitations. This review focuses on the various aspects of AEMs for AEMFCs application.

Fabrication, Properties, and Performance of Polymer Nanocomposite Ion Exchange Membranes for Fuel Cell Applications: A Review

The membrane in a fuel cell plays an essential role in permeating the ionic charges of positive and negative ions without passing the fuels and electrons through it. The membrane's common materials are perfluorinated polymer, non-fluorinated or hydrocarbon polymer, and natural polymer. The physicochemical properties of the membrane have the most significant influence on the performance of fuel cells in terms of mechanical stability, ionic conductivity, power output, and cell operation longevity. The incorporation of nanoparticles into polymeric-based materials improved the membrane's properties by suppressing fuel crossover, improving water retention, and increasing ionic mobility across the membrane. The effect of incorporating nanoparticles is determined by their type, size, shape, surface acidity, and relationship to the polymer matrix. The blending, sol-gel, and infiltration methods are used to develop the nanocomposite membrane. Compared to a commercial membrane in a fuel cell application, most of these membranes demonstrated superior cell performance. Based on published literature, this review briefly described the design and influence of specific advanced nanomaterials incorporated in polymer matrix toward membrane performance.

Microwave Assisted Grafting of Polyethylene Membrane Through Imidazolium and Pyridinium Moieties for Anion Exchange Membranes in Fuel Cell Applications

Microwave Assisted Grafting of Polyethylene Membrane Through Imidazolium and Pyridinium Moieties for Anion Exchange Membranes in Fuel Cell Applications

Dual Functionalized Graphene Oxide Incorporated with Sulfonated Polyolefin Proton Exchange Membrane for Fuel Cell Application

Dual Functionalized Graphene Oxide Incorporated with Sulfonated Polyolefin Proton Exchange Membrane for Fuel Cell Application

Study on Control of Polymeric Architecture of Sulfonated Hydrocarbon-Based Polymers for High-Performance Polymer Electrolyte Membranes in Fuel Cell Applications.

Polymer electrolyte membrane fuel cell (PEMFC) is an eco-friendly energy conversion device that can convert chemical energy into electrical energy without emission of harmful oxidants such as nitrogen oxides (NOx) and/or sulfur oxides (SOx) during operation. Nafion®, a representative perfluorinated sulfonic acid (PFSA) ionomer-based membrane, is generally incorporated in fuel cell systems as a polymer electrolyte membrane (PEM). Since the PFSA ionomers are composed of flexible hydrophobic main backbones and hydrophilic side chains with proton-conducting groups, the resulting membranes are found to have high proton conductivity due to the distinct phase-separated structure between hydrophilic and hydrophobic domains. However, PFSA ionomer-based membranes have some drawbacks, including high cost, low glass transition temperatures and emission of environmental pollutants (e.g., HF) during degradation. Hydrocarbon-based PEMs composed of aromatic backbones with proton-conducting hydrophilic groups have been actively studied as substitutes. However, the main problem with the hydrocarbon-based PEMs is the relatively low proton-conducting behavior compared to the PFSA ionomer-based membranes due to the difficulties associated with the formation of well-defined phase-separated structures between the hydrophilic and hydrophobic domains. This study focused on the structural engineering of sulfonated hydrocarbon polymers to develop hydrocarbon-based PEMs that exhibit outstanding proton conductivity for practical fuel cell applications.

Highly Durable Ether-Free Polyfluorene-Based Anion Exchange Membranes for Fuel Cell Applications.

The preparation of anion exchange membranes (AEMs) with excellent chemical and dimensional stability and high conductivity faces several challenges. In the present work, a novel ether-free durable polyfluorene (PF) without fluorine-bearing pendant piperidinium groups was synthesized by the Suzuki cross-coupling reaction. Alkyl groups were introduced into the backbone of PF to enhance the solubility and flexibility of PF-based AEMs, and the transparent and flexible polymer membrane showed a high conductivity of 80.44 mS cm-1 and excellent alkaline stability in 2 M KOH solution at 80 °C. Although the membrane possesses a high ion exchange capacity (IEC) (2.49 mequiv g-1), it exhibits a low swelling ratio (9.4% at 80 °C), excellent mechanical properties, and dimensional stability. The H2/O2 single cell assembled with PFPE-Pi exhibited a maximum power density of 661 mW cm-2 at a current density of 1280 mA cm-2 at 80 °C. The present work provides a simple and effective strategy for the preparation of ether-free polyfluorene-based AEMs with high conductivity, excellent mechanical properties, and dimensional stability for application in alkaline fuel cells.

Nafion/Surface Modified Ceria Hybrid Membranes for Fuel Cell Application.

Low chemical durability of proton exchange membranes is one the main factors limiting their lifetime in fuel cells. Ceria nanoparticles are the most common free radical scavengers. In this work, hybrid membranes based on Nafion-117 membrane and sulfonic or phosphoric acid functionalized ceria synthesized from various precursors were prepared by the in situ method for the first time. Ceria introduction led to a slight decrease in conductivity of hybrid membranes in contact with water. At the same time, conductivity of membranes containing sulfonic acid modified ceria exceeded that of the pristine Nafion-117 membrane at 30% relative humidity (RH). Hydrogen permeability decreased for composite membranes with ceria synthesized from cerium (III) nitrate, which correlates with their water uptake. In hydrogen-air fuel cells, membrane electrode assembly fabricated with the hybrid membrane containing ceria synthesized from cerium (IV) sulfate exhibited a peak power density of 433 mW/cm2 at a current density of 1080 mA/cm2, while operating at 60 °C and 70% RH. It was 1.5 times higher than for the pristine Nafion-117 membrane (287 mW/cm2 at a current density of 714 mA/cm2).

Branched, Side-Chain Grafted Polyarylpiperidine Anion Exchange Membranes for Fuel Cell Application

Branched, Side-Chain Grafted Polyarylpiperidine Anion Exchange Membranes for Fuel Cell Application

Preparation and Characterization of a Novel Sulfonated Titanium Oxide Incorporated Chitosan Nanocomposite Membranes for Fuel Cell Application.

In this study, nano-TiO2 sulfonated with 1,3-propane sultone (STiO2) was incorporated into the chitosan (CS) matrix for the preparation of CS/STiO2 nanocomposite membranes for fuel cell applications. The grafting of sulfonic acid (–SO3H) groups was confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis and energy-dispersive X-ray spectroscopy. The physicochemical properties of these prepared membranes, such as water uptake, swelling ratio, thermal and mechanical stability, ion exchange capacity and proton conductivity, were determined. The proton conducting groups on the surface of nano-TiO2 can form continuous proton conducting pathways along the CS/STiO2 interface and thus improve the proton conductivity of CS/STiO2 nanocomposite membranes. The CS/STiO2 nanocomposite membrane with 5 wt% of sulfonated TiO2 showed a proton conductivity (0.035 S·cm−1) equal to that of commercial Nafion 117 membrane (0.033 S·cm−1). The thermal and mechanical stability of the nanocomposite membranes were improved because the interfacial interaction between the -SO3H group of TiO2 and the –NH2 group of CS can restrict the mobility of CS chains to enhance the thermal and mechanical stability of the nanocomposite membranes. These CS/STiO2 nanocomposite membranes have promising applications in proton exchange membrane fuel cells.

Co-Tri MOF -Impregnated Aquivion® Composite Membrane for Fuel Cell Application

A membrane electrode assembly (MEA) is regarded as a center of the polymer electrolyte membrane fuel cell (PEMFC), and a solid electrolyte membrane is an indispensable component of the MEA. Reducing the ohmic resistance while improving mechanical stability is a challenge to membrane research and development. In polymeric proton exchange membranes (PEMs), Metal−organic frameworks (MOFs) have gained a great deal of attention as filler materials because of their tenability and designability. Aquivion® is a state-of-the-art membrane used in fuel-cell and electrolysis applications because of its mechanical stability and elevated proton conductivity. Considering the theory of coordination networks, the conductivity of short-side-chain (SSC) Aquivion® has been improved by incorporating the highly proton-conductive Metal-Organic Framework (MOF), namely, Co-tri MOF {[(Co(bpy)(H2O)4](Hbtc).(H2O)1.5}n. The proton conductivity of the 1 wt.% Co-tri MOF/Aquivion® composite membrane is significantly increased by 66% than that of the pristine Aquivion® membrane, 3.5 times that of cast Nafion® membrane. The effect of Co-tri MOF on the Aquivion® membrane structural morphology and thermal properties were investigated by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Thermal gravimetric analysis (TGA) and Scanning Electron Microscopy (SEM). The composite membrane showed an improved in ion conductivity and cell performance compared to the pristine Aquivion® membrane.

Self-Humidifying Proton Exchange Membranes for Fuel Cell Applications: Advances and Challenges

Polymer electrolyte fuel cells (PEFCs) provide efficient and carbon-free power by converting the hydrogen chemical energy. The PEFCs can reach their greatest performance in humidified condition, as proton exchange membranes (PEMs) should be humidified for their proton transportation function. Thus, external humidifiers are commonly employed to increase the water content of reactants. However, being burdened with external humidifiers can make the control of PEFCs complicated and costly, in particular for transportation application. To overcome this issue, self-humidifying PEMs have been introduced, with which PEFC can be fed by dry reactants. In fact, internal humidification is accomplished by produced water from the recombination of permeated hydrogen and oxygen gases on the incorporated platinum catalysts within the PEM. While the water production agent remains constant, there is a broad range of additives that are utilized to retain the generated water and facilitate the proton conduction path in the PEM. This review paper has classified the aforementioned additives in three categories: inorganic materials, proton-conductive materials, and carbon-based additives. Moreover, synthesis methods, preparation procedures, and characterization tests are overviewed. Eventually, self-humidifying PEMs endowed with platinum and different additives are compared from performance and stability perspectives, such as water uptake, proton conductivity, fuel cell performance, gas cross-over, and the overall durability. In addition, their challenges and possible solutions are reviewed. Considering the concerns regarding the long-term durability of such PEMs, it seems that further investigations can be beneficial to confirm their reliability for prolonged PEFC operation.

Spectroscopic Study of Reinforced Cross-Linked Polymeric Membranes for Fuel Cell Application.

Acid-doped reinforced polymer electrolyte membranes for high-temperature polymer electrolyte membrane fuel cell applications (HT PEMFCs) are presented and spectroscopically studied. Fully aromatic polyethers are employed bearing main chain pyridine units as the proton accepting sites, which have two different substitution patterns of the pyridine units, namely, 2,5- or 2,6-pyridine. This fact enables control of the solubility and of the acid doping ability of the polymeric membranes. Reinforcement is accomplished via incorporation of a PTFE woven fabric during the casting procedure for fabrication of the membranes. High acid uptake of the reinforced membranes was maintained for the 2,6-pyridine-based copolymers with high pyridine unit content. Studies of the swelling behavior of these reinforced membranes revealed that they expand mainly along the z-axis, which helps to avoid extensive damage in case of humidity or temperature changes during the fuel cell operation. Additionally, spectroscopic techniques are employed, namely, X-ray photoelectron spectroscopy, X-ray photoelectron spectroscopy with depth profile, near-edge X-ray absorption fine structure, and reflection electron energy loss spectroscopy, for the in-depth study of the two copolymer membranes doped with phosphoric acid. Through these spectroscopic evaluations, modifications in the membranes’ chemical structure, orientation, composition, and electronic structure after the reinforcement and doping processes were elaborated and unveiled.