An efficient barrier toward vanadium crossover in redox flow batteries: The bilayer [Nafion/(WO3)x] hybrid inorganic-organic membrane

Characterization of Quaternary-Ammonium-Based Ionogel Membranes for Application in Proton Exchange Membrane Fuel Cells

In recent years, the quest to advance fuel cell technologies has intensified, driven by the imperative to reduce reliance on hydrocarbon-derived fuels and mitigate pollutant emissions. Proton exchange membranes are a critical material of fuel cell technologies. The potential of ionic liquid-based polymer inclusion membranes or ionogels for proton exchange membrane fuel cells (PEMFCs) has recently appeared. Thermal stability, SEM-EDX characterization, NMR and IR characterization, thermogravimetric analysis, ion exchange capacity, and water uptake are key properties of these membranes which need to be investigated. In this work, ionogel based on quaternary ammonium salts, such as [N8,8,8,1+][Cl-], [N8,8,8,1+][Br-], and [N8-10,8-10,8-10,1+][Cl-] in various compositions with poly(vinyl chloride) are extensively studied and characterized based on those key properties. The best properties were obtained when a quaternary ammonium cation was combined with a bromide anion. Finally, ionogels are tested in microbial fuel cells. Microbial fuel cells based on the ionogel reach a maximum of 147 mW/m2, which represents 55% of the reference membrane (Nafion 212). These results indicate that we still have the possibility of improvement through the appropriate selection of the cation and anion of the ionic liquid. Overall, the promise of ionogel membranes as a viable alternative in fuel cell applications has been demonstrated.

Ultra-Thin Ion Exchange Membranes by Low Ionomer Blending for Energy Harvesting

Exploring the utilization of ion exchange membranes (IEMs) in salinity gradient energy harvesting, a technique that capitalizes on the salinity difference between seawater and freshwater to generate electricity, this study focuses on optimizing PVDF to Nafion ratios to create ultra-thin membranes. Specifically, our investigation aligns with applications such as reverse electrodialysis (RED), where IEMs facilitate selective ion transport across salinity gradients. We demonstrate that membranes with reduced Nafion content, particularly the 50:50 PVDF:Nafion blend, retain high permselectivity comparable to those with higher Nafion content. This challenges traditional understandings of membrane design, highlighting a balance between thinness and durability for energy efficiency. Voltage-current analyses reveal that, despite lower conductivity, the 50:50 blend shows superior short-circuit current density under salinity gradient conditions. This is attributed to effective ion diffusion facilitated by the blend's unique microstructure. These findings suggest that blended membranes are not only cost-effective but also exhibit enhanced performance for energy harvesting, making them promising candidates for sustainable energy solutions. Furthermore, these findings will pave the way for advances in membrane technology, offering new insights into the design and application of ion exchange membranes in renewable energy.

Green Synthesis of Cation Exchange Membranes: A Review

Cation exchange membranes (CEMs) play a significant role in the transition to a more sustainable/green society. They are important components for applications such as water electrolysis, artificial photosynthesis, electrodialysis and fuel cells. Their synthesis, however, is far from being sustainable, affecting safety, health and the environment. This review discusses and evaluates the possibilities of synthesizing CEMs that are more sustainable and green. First, the concepts of green and sustainable chemistry are discussed. Subsequently, this review discusses the fabrication of conventional perfluorinated CEMs and how they violate the green/sustainability principles, eventually leading to environmental and health incidents. Furthermore, the synthesis of green CEMs is presented by dividing the synthesis into three parts: sulfonation, material selection and solvent selection. Innovations in using gaseous SO3 or gas-liquid interfacial plasma technology can make the sulfonation process more sustainable. Regarding the selection of polymers, chitosan, cellulose, polylactic acid, alginate, carrageenan and cellulose are promising alternatives to fossil fuel-based polymers. Finally, water is the most sustainable solvent and many biopolymers are soluble in it. For other polymers, there are a limited number of studies using green solvents. Promising solvents are found back in other membrane, such as dimethyl sulfoxide, Cyrene™, Rhodiasolv® PolarClean, TamiSolve NxG and γ-valerolactone.

Electrochemical Properties and Structure of Membranes from Perfluorinated Copolymers Modified with Nanodiamonds

In this study, we aimed to design and research proton-conducting membranes based on Aquivion®-type material that had been modified with detonation nanodiamonds (particle size 4-5 nm, 0.25-5.0 wt. %). These nanodiamonds carried different functional groups (H, OH, COOH, F) that provided the hydrophilicity of the diamond surface with positive or negative potential, or that strengthened the hydrophobicity of the diamonds. These variations in diamond properties allowed us to find ways to improve the composite structure so as to achieve better ion conductivity. For this purpose, we prepared three series of membrane films by first casting solutions of perfluorinated Aquivion®-type copolymers with short side chains mixed with diamonds dispersed on solid substrates. Then, we removed the solvent and the membranes were structurally stabilized during thermal treatment and transformed into their final form with -SO3H ionic groups. We found that the diamonds with a hydrogen-saturated surface, with a positive charge in aqueous media, contributed to the increase in proton conductivity of membranes to a greater rate. Meanwhile, a more developed conducting diamond-copolymer interface was formed due to electrostatic attraction to the sulfonic acid groups of the copolymer than in the case of diamonds grafted with negatively charged carboxyls, similar to sulfonic groups of the copolymer. The modification of membranes with fluorinated diamonds led to a 5-fold decrease in the conductivity of the composite, even when only a fraction of diamonds of 1 wt. % were used, which was explained by the disruption in the connectivity of ion channels during the interaction of such diamonds mainly with fluorocarbon chains of the copolymer. We discussed the specifics of the mechanism of conductivity in composites with various diamonds in connection with structural data obtained in neutron scattering experiments on dry membranes, as well as ideas about the formation of cylindrical micelles with central ion channels and shells composed of hydrophobic copolymer chains. Finally, the characteristics of the network of ion channels in the composites were found depending on the type and amount of introduced diamonds, and correlations between the structure and conductivity of the membranes were established.

A Comparative Study of Nafion 212 and Sulfonated Poly(Ether Ether Ketone) Membranes with Different Degrees of Sulfonation on the Performance of Iron-Chromium Redox Flow Battery

For an iron-chromium redox flow battery (ICRFB), sulfonated poly(ether ether ketone) (SPEEK) membranes with five various degrees of sulfonation (DSs) are studied. To select the SPEEK membrane with the ideal DS for ICRFB applications, the physicochemical characteristics and single-cell performance are taken into consideration. Following all the investigations, it has been determined that the SPEEK membrane, which has a DS of 57% and a thin thickness of 25 μm, is the best option for replacing commercial Nafion 212 in ICRFB. Firstly, it exhibits a better cell performance according to energy efficiency (EE) and coulombic efficiency (CE) at the current density range between 40 mA cm-2 and 80 mA cm-2. Additionally, it has a more stable EE (79.25-81.64%) and lower discharge capacity decay rate (50%) than the Nafion 212 (EE: 76.74-81.45%, discharge capacity decay: 76%) after 50 charge-discharge cycles, which proves its better oxidation stability as well. In addition, the longer self-discharge time during the open-circuit voltage test further demonstrates that this SPEEK membrane could be employed for large-scale ICRFB applications.

Polarization Processes in Nafion Composite Membranes Doped with Rare-Earth Metals

Dielectric spectroscopy (frequency range f = 100…107 Hz and temperatures T = 293…403 K (accuracy 0.5 K), measuring voltage applied to the sample was 1.0 V) was used to study composite materials based on perfluorosulfonic membranes with inclusions of rare-earth elements, in particular, europium (III) and terbium (III) chlorides. The dispersion of the permittivity and the presence of maxima, corresponding to losses, were revealed, which indicates that relaxation processes of various natures were present. The membrane layers under investigation are characterized by relaxation parameters that correspond to a symmetrical distribution of relaxers over relaxation times. The spectrum of relaxers changed when terbium and europium metal impurities were introduced into the polymer matrix. The investigation of these polymer systems demonstrated a power-law dependence of the specific conductivity on frequency. A decrease in the exponent with increasing temperature indicates the existence of a traditional hopping mechanism for charge transfer. The observed changes in the dielectric permittivity and specific conductivity are due to a change in the nature of polarization processes because of the strong interaction of metal (terbium and europium) ions with the polymer matrix of Nafion.

Anion Exchange Membranes Based on Chemical Modification of Recycled PET Bottles

This study presents an innovative and effective solution for recycling PET bottles as raw for producing anion exchange membranes (AEMs) for electrochemical applications. This approach reduces the demand for pristine materials, a key principle of the circular economy and sustainability. PET was subjected to chemical modification by introducing cationic functional groups followed by methylation and OH- exchange process. The amination synthesis was optimized based on reaction time. The results indicate that ion exchange capacity, water uptake, and swelling ratio properties mainly depend on the degree of cationic functionalization. The optimized AEM exhibits ionic conductivity of 5.3 × 10-2 S·cm-1 and alkaline stability of 432 h in 1 M KOH at 80 °C. The membrane properties before and after the alkaline treatment were investigated using Fourier-transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy analysis. Computational chemistry analysis was employed to gain further insights into the membrane degradation mechanisms and pathways under alkaline conditions. This research and its findings are a step toward using recycled materials in the field of AEM technology.

Modified Membranes for Redox Flow Batteries-A Review

In this review, the state of the art of modified membranes developed and applied for the improved performance of redox flow batteries (RFBs) is presented and critically discussed. The review begins with an introduction to the energy-storing chemical principles and the potential of using RFBs in the energy transition in industrial and transport-related sectors. Commonly used membrane modification techniques are briefly presented and compared next. The recent progress in applying modified membranes in different RFB chemistries is then critically discussed. The relationship between a given membrane modification strategy, corresponding ex situ properties and their impact on battery performance are outlined. It has been demonstrated that further dedicated studies are necessary in order to develop an optimal modification technique, since a modification generally reduces the crossover of redox-active species but, at the same time, leads to an increase in membrane electrical resistance. The feasibility of using alternative advanced modification methods, similar to those employed in water purification applications, needs yet to be evaluated. Additionally, the long-term stability and durability of the modified membranes during cycling in RFBs still must be investigated. The remaining challenges and potential solutions, as well as promising future perspectives, are finally highlighted.

Quantitative Study of Charge Distribution Variations on Silica-Nafion Composite Membranes under Hydration Using an Approximation Model

Understanding the ionic structure and charge transport on proton exchange membranes (PEMs) is crucial for their characterization and development. Electrostatic force microscopy (EFM) is one of the best tools for studying the ionic structure and charge transport on PEMs. In using EFM to study PEMs, an analytical approximation model is required for the interoperation of the EFM signal. In this study, we quantitatively analyzed recast Nafion and silica-Nafion composite membranes using the derived mathematical approximation model. The study was conducted in several steps. In the first step, the mathematical approximation model was derived using the principles of electromagnetism and EFM and the chemical structure of PEM. In the second step, the phase map and charge distribution map on the PEM were simultaneously derived using atomic force microscopy. In the final step, the charge distribution maps of the membranes were characterized using the model. There are several remarkable results in this study. First, the model was accurately derived as two independent terms. Each term shows the electrostatic force due to the induced charge of the dielectric surface and the free charge on the surface. Second, the local dielectric property and surface charge are numerically calculated on the membranes, and the calculation results are approximately valid compared with those in other studies.

Study of Innovative GO/PBI Composites as Possible Proton Conducting Membranes for Electrochemical Devices

The appeal of combining polybenzimidazole (PBI) and graphene oxide (GO) for the manufacturing of membranes is increasingly growing, due to their versatility. Nevertheless, GO has always been used only as a filler in the PBI matrix. In such context, this work proposes the design of a simple, safe, and reproducible procedure to prepare self-assembling GO/PBI composite membranes characterized by GO-to-PBI (X:Y) mass ratios of 1:3, 1:2, 1:1, 2:1, and 3:1. SEM and XRD suggested a homogenous reciprocal dispersion of GO and PBI, which established an alternated stacked structure by mutual π-π interactions among the benzimidazole rings of PBI and the aromatic domains of GO. TGA indicated a remarkable thermal stability of the composites. From mechanical tests, improved tensile strengths but worsened maximum strains were observed with respect to pure PBI. The preliminary evaluation of the suitability of the GO/PBI X:Y composites as proton exchange membranes was executed via IEC determination and EIS. GO/PBI 2:1 (IEC: 0.42 meq g^-1; proton conductivity at 100 °C: 0.0464 S cm^-1) and GO/PBI 3:1 (IEC: 0.80 meq g^-1; proton conductivity at 100 °C: 0.0451 S cm^-1) provided equivalent or superior performances with respect to similar PBI-based state-of-the-art materials.

Investigation of Fumasep® FAA3-50 Membranes in Alkaline Direct Methanol Fuel Cells

This paper describes the use of a commercial Fumasep^® FAA3-50 membrane as an anion exchange membrane (AEM) in alkaline direct methanol fuel cells (ADMFCs). The membrane, supplied in bromide form, is first exchanged in chloride and successively in the hydroxide form. Anionic conductivity measurements are carried out in both a KOH aqueous solution and in a KOH/methanol mixture. AEM-DMFC tests are performed by feeding 1 M methanol, with or without 1 M KOH as a supporting electrolyte. A maximum power density of 5.2 mW cm^-2 at 60 °C and 33.2 mW cm^-2 at 80 °C is reached in KOH-free feeding and in the alkaline mixture, respectively. These values are in good agreement with some results in the literature obtained with similar experimental conditions but with different anion exchange membranes (AEMs). Finally, methanol crossover is investigated and corresponds to a maximum value of 1.45 × 10^-8 mol s^-1 cm^-2 at 50 °C in a 1 M KOH methanol solution, thus indicating that the Fumasep^® FAA3-50 membrane in OH form is a good candidate for ADMFC application.

An Economical Composite Membrane with High Ion Selectivity for Vanadium Flow Batteries

The ion exchange membrane of the Nafion series widely used in vanadium flow batteries (VFBs) is characterized by its high cost and high vanadium permeability, which limit the further commercialization of VFBs. Herein, a thin composite membrane enabled by a low-cost microporous polyethylene (PE) substrate and perfluorosulfonic acid (PFSA) resin is proposed to reduce the cost of the membrane. Meanwhile, the rigid PE substrate limits the swelling of the composite membrane, which effectively reduces the penetration of vanadium ions and improves the ion selectivity of the composite membrane. Benefiting from such a rational design, a VFB assembled with the PE/PFSA composite membrane exhibited a higher coulombic efficiency (CE ≈ 96.8%) compared with commercial Nafion212 at 200 mA cm^-2. Significantly, the energy efficiency maintained stability within 200 cycles with a slow decay rate. In practical terms, the thin PE/PFSA composite membrane with low cost and high ion selectivity can make an ideal membrane candidate in VFBs.

Modified Cellulose Proton-Exchange Membranes for Direct Methanol Fuel Cells

A direct methanol fuel cell (DMFC) is an excellent energy device in which direct conversion of methanol to energy occurs, resulting in a high energy conversion rate. For DMFCs, fluoropolymer copolymers are considered excellent proton-exchange membranes (PEMs). However, the high cost and high methanol permeability of commercial membranes are major obstacles to overcome in achieving higher performance in DMFCs. Novel developments have focused on various reliable materials to decrease costs and enhance DMFC performance. From this perspective, cellulose-based materials have been effectively considered as polymers and additives with multiple concepts to develop PEMs for DMFCs. In this review, we have extensively discussed the advances and utilization of cost-effective cellulose materials (microcrystalline cellulose, nanocrystalline cellulose, cellulose whiskers, cellulose nanofibers, and cellulose acetate) as PEMs for DMFCs. By adding cellulose or cellulose derivatives alone or into the PEM matrix, the performance of DMFCs is attained progressively. To understand the impact of different structures and compositions of cellulose-containing PEMs, they have been classified as functionalized cellulose, grafted cellulose, acid-doped cellulose, cellulose blended with different polymers, and composites with inorganic additives.

Study on Purging Strategy of Polymer Electrolyte Membrane Fuel Cell under Different Operation Conditions

The commercial proton exchange membrane fuel cell (PEMFC) system needs to be equipped with the capacity to survive a harsh environment, including sub-freezing temperatures. The cold start of PEMFC brings about great technical challenges, mainly due to the ice blockage in the components, which seriously hinders the multi physical transmission process. A multiscale, two-dimensional model was established to explore the gas purging in PEMFC under different electrochemical reaction intensities. The results indicate that the optimal case is obtained by B3-1 with a power density of 0.796 W cm−2, and the power density increases first and then decreases, followed by stoichiometric flow ratio (ξ) changes. It is worth noting that the water mole fraction in the PEM is closely related to the water concentration gradient. However, the differences in the initial water distribution in porous media have little bearing on the condensed water in the gas channel, and the liquid water in the gas diffusion layer (GDL) is preferably carried away ahead of other porous parts. The results also show that the increase in the purge speed and temperature can remove the excess water on GDL and the catalytic layer in a short time. For a nitrogen-based purge, the operating condition in case B3-1 is shown as the best strategy based on the output performance and economic analysis during the shutdown and purge process.

Cross-Linked Sulfonated Poly(arylene ether sulfone) Membrane Using Polymeric Cross-Linkers for Polymer Electrolyte Membrane Fuel Cell Applications

Cross-linked membranes for polymer electrolyte membrane fuel cell application are prepared using highly sulfonated poly(arylene ether sulfone) (SPAES) and polymeric cross-linkers having different hydrophilicities by facile in-situ casting and heating processes. From the advantage of the cross-linked structures made with the use of polymeric cross-linkers, a stable membrane can be obtained even though the polymer matrix with a very high degree of sulfonation was used. In particular, hydrophilic cross-linker is found to be effective in improving physicochemical properties of the cross-linked membranes and at the same time showing reasonable proton conductivity. Accordingly, membrane electrode assembly made from the cross-linked membrane prepared by using hydrophilic polymeric cross-linker exhibits outstanding cell performance under high temperature and low relative humidity conditions (e.g., maximum power density of 176.4 mW cm^-2 at 120 °C and 40% RH).

Design and Utilization of a Direct Methanol Fuel Cell

This study introduces a step-by-step, summarized overview of direct methanol fuel cell (DMFC) fundamentals, thermodynamic-electrochemical principles, and system evaluation factors. In addition, a parametric investigation of a JENNY 600S DMFC is conducted to simulate cell performance behavior under varying operating conditions. The system is mathematically modeled and solved in MATLAB and accounts for multi-irreversibilities such as the activation and ohmic and concentration overpotentials. The performance of the modeled system was validated against theoretical and experimental results from the literature. The results indicated that increasing the fuel cell's operating temperature yields enhanced output cell voltages due to enhanced methanol oxidation reactions. Nevertheless, the maximum efficiency limits of the fuel cell tend to decrease with an increase in temperature. In addition, the model has also depicted that enhanced output cell voltages are associated with increased oxygen consumption, resulting in the lower exit flowrates of the reactants.

Efficiency Analysis of Fuel Cell Components with Ionic Poly-Arylether Composite Membrane

We use polyethylene glycol as an additive to explore how the hydrogen bonding of this additive changes the properties of SA8 blended sulfonated polyetheretherketone (SPEEK) composite films. We mixed a 5%wt polyethylene glycol solution into a 12.5%wt SA8 solution, and then prepared a film with a total weight of 40 g at a ratio of 1:99. The SA8 (PEG) solution was prepared and then mixed with 5%wt SPEEK solution, and a film-forming solution with a total weight of 8g in different mixing ratios was created. Polyethylene glycol (PEG) was mixed into the sulfonated polyarylether polymer SA8 to form physical cross-linking. Therefore, the sulfonated polyether ether ketone SPEEK was mixed in, and it exhibited good thermal stability and dimensional stability. However, there was some decrease in proton conductivity as the proportion of SPEEK increased. Although SPEEK mixed with sulfonated polymer reduces the proton conductivity, the physical cross-linking of PEG can improve the proton conductivity of the composite membrane, and adding SPEEK can not only solve the problem of the high sulfonation film swelling phenomenon, it can also improve the dimensional stability of the film through the hydrogen bonding force of PEG and obtain a composite film with excellent properties.

Effect of Organo-Silanes Structure on the Properties of Silane-Crosslinked Membranes Based on Cardo Polybenzimidazole PBI-O-PhT

Polybenzimidazoles (PBI) doped with phosphoric acid (PA) are promising electrolytes for medium temperature fuel cells. Their significant disadvantage is a partial or complete loss of mechanical properties and an increase in hydrogen permeability at elevated temperatures. Covalent silanol crosslinking is one possible way to stabilize PBI membranes in the presence of PA. Three organo-substituted silanes, namely (3-Bromopropyl)trimethoxysilane (SiBr), trimethoxy [2-(7-oxabicyclo [4.1.0]hept-3-yl)ethyl]silane (Si-biC) and (3-Glycidyloxypropyl)trimethoxysilane (KH 560), were used as covalent crosslinkers of PBI-O-PhT in order to determine the effect of the silane structure and crosslinking degree on membrane properties. The crosslinking degree was 1-50%. All crosslinked membranes were characterized by impedance and IR-spectroscopy. The mechanical properties, morphology, stability and hydrogen permeability of the membranes were determined. In the case of silanes with linear substituents (SiBr, KH 560), a denser structure is formed, which is characterized by greater oxidative stability and lower hydrogen permeability in comparison to the silane with a bulk group. All the crosslinked membranes have a higher mechanical strength compared with the initial PBI-O-PhT membrane both before and after doping with PA. Despite the hardening of the polymer matrix of the membranes, their proton conductivity changes insignificantly. It was shown that cross-linked membranes can be used in fuel cells.

Characterization of Commercial Polymer-Carbon Composite Bipolar Plates Used in PEM Fuel Cells

Bipolar plates represent a crucial component of the PEM fuel cell stack. Polymer-carbon composites are recognized as state-of-the-art materials for bipolar plate manufacturing, but their use involves a compromise between electrical and heat conductivity, mechanical strength and costs. Thus, all key parameters must be considered when selecting a suitable plate satisfying the demands of the desired application. However, data relevant to commercial materials for such selection are scarce in the open literature. To address this issue, 13 commercially available polymer-carbon composites are characterised in terms of the following parameters: through-plane conductivity, hydrogen permeability, mechanical strength, water uptake, density, water contact angle and chemical stability. None of the materials tested reached the DOE target for electrical conductivity, while five of the materials met the target for flexural strength. The overall best-performing material showed a conductivity value of 50.4 S·cm^-1 and flexural strength of 40.1 MPa. The data collected provide important supporting information in selecting the materials most suitable for the desired application. In addition, the key parameters determined for each bipolar plate supply important input parameters for the mathematical modelling of fuel cells.

Microstructure Reconstruction and Multiphysics Dynamic Distribution Simulation of the Catalyst Layer in PEMFC

Due to the complexity of both material composition and the structure of the catalyst layer (CL) used in the proton-exchange membrane fuel cell (PEMFC), conjugated heat and mass transfer as well as electrochemical processes simultaneously occur through the CL. In this study, a microstructure model of CL was first reconstructed using images acquired by Nano-computed tomography (Nano-CT) of a real sample of CL. Then, the multiphysics dynamic distribution (MPDD) simulation, which is inherently a multiscale approach made of a combination of pore-scale and homogeneous models, was conducted on the reconstructed microstructure model to compute the corresponded heat and mass transport, electrochemical reactions, and water phase-change processes. Considering a computational domain with the size of 4 um and cube shape, this model consisting of mass and heat transport as well as electrochemical reactions reached a stable solution within 3 s as the convergence time. In the presence of sufficient oxygen, proton conduction was identified as the dominant factor determining the strength of the electrochemical reaction. Additionally, it was concluded that current density, temperature, and the distribution of water all exhibit similar distribution trends, which decrease from the interface between CL and the proton-exchange membrane to the interface between CL and the gas-diffusion layer. The present study not only provides an in-depth understanding of the mass and heat transport and electrochemical reaction in the CL microstructure, but it also guides the optimal design and fabrication of CL components and structures, such as improving the local structure to reduce the number of dead pores and large agglomerates, etc.

Nanocomposite Membranes Based on Fluoropolymers for Electrochemical Energy Sources

The physicochemical and transport properties (ion-exchange capacity, water content, diffusion permeability, conductivity, and current-voltage characteristic) of a series of perfluorinated membranes with an inert fluoropolymer content from 0 to 40%, obtained by polymer solution casting, were studied. Based on the analysis of the parameters of the extended three-wire model, the effect of an inert component on the path of electric current flow in the membrane and its selectivity were estimated. The mechanical characteristics of the membranes, such as Young's modulus, yield strength, tensile strength, and relative elongation, were determined from the dynamometric curves. The optimal amount of the inert polymer in the perfluorinated membrane was found to be 20%, which does not significantly affect its structure and electrotransport properties but increases the elasticity of the obtained samples. Therefore, the perfluorinated membrane with 20% of inert fluoropolymer is promising for its application in redox flow batteries and direct methanol fuel cells.

Precise Control of the Preparation of Proton Exchange Membranes via Direct Electrostatic Deposition

In this work, we reported a novel preparation method for a proton exchange membrane (PEM) named, the direct electrostatic deposition method. In theory, any required thickness and size of PEM can be precisely controlled via this method. By direct electrostatic spraying of Nafion solution containing amino modified SiO2 nanoparticles onto a metal collector, a hybrid membrane of 30 μm thickness was fabricated. The DMFC assembled with a prepared ultrathin membrane showed a maximum power density of 124.01 mW/cm2 at 40 °C and 100% RH, which was 95.29% higher than that of Nafion. This membrane formation method provides potential benefits for the preparation of ultrathin PEMs.

Analysis of Ionic Domain Evolution on a Nafion-Sulfonated Silica Composite Membrane Using a Numerical Approximation Model Based on Electrostatic Force Microscopy

It is important to characterize the proton transport mechanisms of proton exchange membranes (PEMs). Electrostatic force microscopy (EFM) is used to characterize the ionic structures of membranes. In this study, we attempted to quantitatively analyze the proton conductivity enhancement of Nafion-sulfonated silica (SSA) composite membranes with variations in the ionic channel distribution. This study involved several steps. The morphology and surface charge distribution of both membranes were measured using EFM. The measured data were analyzed using a numerical approximation model (NAM) that was capable of providing the magnitude and classification of the surface charges. There were several findings of ionic channel distribution variations in Nafion-SSA. First, the mean local ionic channel density of Nafion-SSA was twice as large as that of the pristine Nafion. The local ionic channel density was non-uniform and the distribution of the ionic channel density of Nafion-SSA was 23.5 times larger than that of pristine Nafion. Second, local agglomerations due to SSA were presumed by using the NAM, appearing in approximately 10% of the scanned area. These findings are meaningful in characterizing the proton conductivity of PEMs and imply that the NAM is a suitable tool for the quantitative assessment of PEMs.

A Brief Review of Poly(Vinyl Alcohol)-Based Anion Exchange Membranes for Alkaline Fuel Cells

Anion exchange membrane fuel cells have unique advantages and are thus gaining increasing attention. Poly(vinyl alcohol) (PVA) is one of the potential polymers for the development of anion exchange membranes. This review provides recent studies on PVA-based membranes as alternative anion exchange membranes for alkaline fuel cells. The development of anion exchange membranes in general, including the types, materials, and preparation of anion exchange membranes in the last years, are discussed. The performances and characteristics of recently reported PVA-based membranes are highlighted, including hydroxide conductivity, water uptake, swelling degree, tensile strength, and fuel permeabilities. Finally, some challenging issues and perspectives for the future study of anion exchange membranes are discussed.

Enhancement of the Green H2 Production by Using TiO2 Composite Polybenzimidazole Membranes

This study reports the hydrogen production using TiO₂ based composite polybenzimidazole membranes through the SO₂ depolarized electrolysis that requires lower energy input than the direct water electrolysis. Composite membranes prepared and studied in this work showed very promising results in terms of proton conductivity, chemical stability, and crossover. Thus, a reduction in SO₂ crossover was observed with the increase of the concentration of TiO₂, obtaining reductions as high as 42% with the 3.0 wt% TiO₂-PBI membrane at 120 °C. Higher hydrogen production rates and Faradaic efficiencies were achieved by all the composite membranes, with an optimum for the 1.0 wt% TiO₂-PBI membrane (with this membrane, the production of hydrogen increased a 53% at 110 °C and a 49% at 120 °C as compared with the standard PBI membrane), demonstrated the benefit of the use of composite membranes with respect to the standard one for green hydrogen production.

Numerical Parametric Investigation of Nonaqueous Vanadium Redox Flow Batteries

Nonaqueous redox flow batteries are promising candidates for large-scale energy storage technologies. However, the effect of structural design and key factors limiting the performance are still not thoroughly understood. In this work, we constructed a physical model to study the effect of various design parameters on the performance of such a battery. It was found that the kinetics of redox reaction was improved with active material concentration and electrode surface area. The modeling results also showed that the local current density was much higher in the vicinity of membrane than near the current collector due to relatively low ionic conductivity of electrolytes. Furthermore, decreasing the electrode thickness and increasing the membrane conductivity both reduced the voltage loss associated with ohmic resistance, thereby resulting in improved battery performance. The obtained numerical simulation results would be helpful not only for understanding the physicochemical process in nonaqueous vanadium flow batteries but also for future structural optimization of these batteries.

Cellulose Nanocrystals Crosslinked with Sulfosuccinic Acid as Sustainable Proton Exchange Membranes for Electrochemical Energy Applications

Nanocellulose is a sustainable material which holds promise for many energy-related applications. Here, nanocrystalline cellulose is used to prepare proton exchange membranes (PEMs). Normally, this nanomaterial is highly dispersible in water, preventing its use as an ionomer in many electrochemical applications. To solve this, we utilized a sulfonic acid crosslinker to simultaneously improve the mechanical robustness, water-stability, and proton conductivity (by introducing -SO₃⁻H⁺ functional groups). The optimization of the proportion of crosslinker used and the crosslinking reaction time resulted in enhanced proton conductivity up to 15 mS/cm (in the fully hydrated state, at 120 °C). Considering the many advantages, we believe that nanocellulose can act as a sustainable and low-cost alternative to conventional, ecologically problematic, perfluorosulfonic acid ionomers for applications in, e. fuel cells and electrolyzers.

Possibility to Alter Dynamics of Luminescence from Surface of Polymer Membrane with Ultrasonic Waves

The temporal dynamics of luminescence from the surface of Nafion polymer membranes have been studied. In fact, the polymer membrane was soaked in liquids with different contents of deuterium. The test liquids were ordinary (natural) water (deuterium content equal to 157 ppm) and deuterium-depleted water (deuterium content is equal to 3 ppm). Simultaneously with the excitation of luminescence, the Nafion plate was irradiated with ultrasonic pulses, having a duration of 1 μs. The ultrasonic waves were generated with different repetition rates and amplitudes, and irradiated the surface of Nafion in the geometry of grazing or normal incidence. Luminescence regimes were studied when the membrane was irradiated with one ultrasonic wave (one piezoelectric transducer) or two counter-propagating waves (two piezoelectric transducers). It turned out that ultrasonic waves, which fall normal to the membrane interface, do not affect the dynamics of luminescence. At the same time, in the case of ultrasonic irradiation in the grazing incidence geometry, sharp jumps in the luminescence intensity occur, and the behavior of these jumps substantially depends on the mode of irradiation: one or two piezoelectric transducers. This allows for control of the dynamics of luminescence from the polymer surface. In accordance with this model, the possibility of altering the luminescence dynamics is due to the effect of unwinding the polymer fibers from the surface toward the liquid bulk upon soaking. It is important that such unwinding does not occur in deuterium-depleted water, which was confirmed in a direct experiment with dynamic light scattering from polydisperse aqueous suspensions of Nafion nanometer-sized particles; these suspensions were prepared in ordinary water and deuterium-depleted water. Thus, ultrasonic irradiation affects the dynamics of luminescence only when Nafion is swollen in ordinary water; in the case of deuterium-depleted water this effect is missed.

Modeling and Experimental Investigation of the Anode Inlet Relative Humidity Effect on a PEM Fuel Cell

External humidification has been used as a flexible water management strategy for the proton exchange membrane fuel cell (PEMFC). To study the anode inlet relative humidity (ARH) effect on the performance of PEMFC, the anode inlet water content (AIWC) model is established, including condensation rates and water activity. A comparable analysis between the AIWC model, Fluent model and experiment is conducted at 60 °C operating temperature, four different anode relative humidities (25%, 50%, 75% and 100%), and 100% cathode relative humidity (CRH). The species distributions of water content and hydrogen concentration are presented and analyzed. The results show the relative error of the voltage results derived from the AIWC model has been reduced by 3.2% (the original is 4.6% in the Fluent model) especially at 240 mA·cm−2 for 50% ARH. An increase in hydrogen humidity can improve the PEMFC output at low ARH (25% and 50%). Meanwhile, at high ARH (100%), the excess water produced does not play a positive role. At 50% ARH, the water content and hydrogen distribution are more uniform all over the anode channels.

Development of WO3-Nafion Based Membranes for Enabling Higher Water Retention at Low Humidity and Enhancing PEMFC Performance at Intermediate Temperature Operation

The proton exchange membrane (PEM) represents a pivotal material and a key challenge in developing fuel cell science and hydrogen technology. Nafion is the most promising polymer which will lead to its commercialisation. Hybrid membranes of nanosized tungsten oxide (WO₃) and Nafion were fabricated, characterised, and tested in a single cell. The incorporation of 10 wt% WO₃ resulted in 21% higher water uptake, 11.7% lower swelling ratio, almost doubling the hydration degree, and 13% higher mechanical stability of the hybrid membrane compared to the Nafion XL. Compared to commercial Nafion XL, the rNF-WO-10 hybrid membrane showed an 8.8% and 20% increase in current density of the cell at 0.4 V operating at 80 and 95 °C with 1.89 and 2.29 A/cm², respectively. The maximum power density has increased by 9% (0.76 W/cm²) and 19.9% (0.922 W/cm²) when operating at the same temperatures compared to the commercial Nafion XL membrane. Generally, considering the particular structure of Nafion XL, our Nafion-based membrane with 10 wt% WO₃ (rNF-WO-10) is a suitable PEM with a comparable performance at different operating conditions.

Ionomer Membranes Produced from Hexaarylbenzene-Based Partially Fluorinated Poly(arylene ether) Blends for Proton Exchange Membrane Fuel Cells

In this study, a series of high molecular weight ionomers of hexaarylbenzene- and fluorene-based poly(arylene ether)s were synthesized conveniently through condensation and post-sulfonation modification. The use a of blending method might increase the stacking density of chains and affect the formation both of interchain and intrachain proton transfer clusters. Multiscale phase separation caused by the dissolution and compatibility differences of blend ionomer in high-boiling-point solvents was examined through analysis and simulations. The blend membranes produced in this study exhibited a high proton conductivity of 206.4 mS cm−1 at 80 °C (increased from 182.6 mS cm−1 for precursor membranes), excellent thermal resistance (decomposition temperature > 200 °C), and suitable mechanical properties with a tensile strength of 73.8−77.4 MPa. As a proton exchange membrane for fuel cell applications, it exhibits an excellent power efficiency of approximately 1.3 W cm−2. Thus, the ionomer membranes have strong potential for use in proton exchange membrane fuel cells and other electrochemical applications.

Variation Characteristic Analysis of Water Content at the Flow Channel of Proton Exchange Membrane Fuel Cell

The performance of proton exchange membrane fuel cells (PEMFCs) is directly affected by the nonlinear variations in water content. To study the variation in water content and its effect on PEMFC performance, the water condensation rate (WCR) model is established, which determines the proportional relationship between evaporation and condensation rates in terms of the switch function, and the two-phase flow evolution and pressure drop are considered as well. The WCR model is imported into Fluent software through a user-defined function for simulation, and the test system is established under different operating conditions. Then, the contours of H2O molar concentrations and polarization curves are analyzed and compared. The results show that the condensation rate value of the cathode channel is from 1.05 to 1.55 times higher than that of the anode channel. The WCR model can predict the variation in water content and improve the accuracy of the performance calculation by from 9% to 31%. The accuracy of the WCR model is especially improved, by 31%, at high current densities compared with the Fluent model when the inlet pressure is 30 kPa.

TiO2 Containing Hybrid Composite Polymer Membranes for Vanadium Redox Flow Batteries

In recent years, vanadium redox flow batteries (VRFB) have captured immense attraction in electrochemical energy storage systems due to their long cycle life, flexibility, high-energy efficiency, time, and reliability. In VRFB, polymer membranes play a significant role in transporting protons for current transmission and act as barriers between positive and negative electrodes/electrolytes. Commercial polymer membranes (such as Nafion) are the widely used IEM in VRFBs due to their outstanding chemical stability and proton conductivity. However, the membrane cost and increased vanadium ions permeability limit its commercial application. Therefore, various modified perfluorinated and non-perfluorinated membranes have been developed. This comprehensive review primarily focuses on recent developments of hybrid polymer composite membranes with inorganic TiO₂ nanofillers for VRFB applications. Hence, various fabrications are performed in the membrane with TiO₂ to alter their physicochemical properties for attaining perfect IEM. Additionally, embedding the -SO₃H groups by sulfonation on the nanofiller surface enhances membrane proton conductivity and mechanical strength. Incorporating TiO₂ and modified TiO₂ (sTiO₂, and organic silica modified TiO₂) into Nafion and other non-perfluorinated membranes (sPEEK and sPI) has effectively influenced the polymer membrane properties for better VRFB performances. This review provides an overall spotlight on the impact of TiO₂-based nanofillers in polymer matrix for VRFB applications.

Robust Adamantane-Based Membranes with Enhanced Conductivity for Vanadium Flow Battery Application

Membranes with high conductivity, high selectivity, and high stability are urgently needed for high-power-density vanadium flow batteries (VFBs). Enhancing membrane conductivity presents many challenges, often resulting in sacrificing membrane selectivity and mechanical strength. To overcome this, new robust adamantane-based membranes with enhanced conductivity are constructed for VFB. Low-content basic piperazine (IEC = 0.78 mmol g⁻¹) and hydrophilic hydroxyl groups are introduced into highly rigid, hydrophobic adamantane containing poly(aryl ether ketone) backbone (PAPEK) and then selectively swelled to induce microphase separation and form ion transport pathways. The highly rigid and hydrophobic PAPEK exhibits high swelling resistance and provides the membranes with slight swelling, high selectivity, and high mechanical strength. The selective swelling temperature has a significant influence on the areal resistance of the resulting membrane, e.g., the PAPEK-130 membrane, when selectively swelled at 130 °C, has low areal resistance (0.22 Ω∙cm²), which is approximately two-fifths that of the PAEKK-60 membrane (treated at 60 °C, 0.57 Ω∙cm²). Consequently, the resulting PAPEK membranes exhibit low swelling, high selectivity, and low areal resistance, with the VFB constructed with a PAPEK-90 membrane exhibiting excellent energy efficiency (91.7%, at 80 mA∙cm⁻², and 80.0% at 240 mA∙cm⁻²) and stable cycling performance for 2000 cycles.

Nafion Swelling in Salt Solutions in a Finite Sized Cell: Curious Phenomena Dependent on Sample Preparation Protocol

When a membrane of Nafion swells in water, polymer fibers “unwind” into the adjoining liquid. They extend to a maximum of about ~300 μm. We explore features of Nafion nanostructure in several electrolyte solutions that occur when the swelling is constrained to a cell of size less than a distance of 300 μm. The constraint forces the polymer fibers to abut against the cell windows. The strongly amphiphilic character of the polymer leads to a shear stress field and the expulsion of water from the complex swollen fiber mixture. An air cavity is formed. It is known that Nafion membrane swelling is highly sensitive to small changes in ion concentration and exposure to shaking. Here we probe such changes further by studying the dynamics of the collapse of the induced cavity. Deionized water and aqueous salt solutions were investigated with Fourier IR spectrometry. The characteristic times of collapse differ for water and for the salt solutions. The dynamics of the cavity collapse differs for solutions prepared by via different dilution protocols. These results are surprising. They may have implications for the standardization of pharmaceutical preparation processes.

ZnS Quantum Dots Decorated on One-Dimensional Scaffold of MWCNT/PANI Conducting Nanocomposite as an Anode for Enzymatic Biofuel Cell

This study aims to design a new nanocomposite as a supporting material for wiring the enzyme to develop a bioanode in the enzymatic biofuel cell (EBFC). In this work, polyaniline-based nanocomposite was synthesized by in situ polymerization of aniline monomer. The zeta potential study of the nanofillers was carried out, which reveals the interaction between the nanofillers. The synthesized nanocomposite (MWCNT/ZnS/AgNWs/PANI) was characterized by analytical techniques, such as Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction spectroscopy (XRD). Furthermore, the surface morphology and the in-depth information of the synthesized nanocomposite were displayed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. In addition, the as-synthesized nanocomposite and the designed bioanode underwent the electrochemical assessment using different electrochemical techniques such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV) for evaluating the electrochemical behavior of the fabricated anodes. The electrochemically regulated bioanode (MWCNT/ZnS/AgNWs/PANI/Frt/GOx) obtained an open-circuit voltage of 0.55 V and produced a maximal current density of 7.6 mA cm⁻² at a glucose concentration of 50 mM prepared in phosphate buffer solution (PBS) (pH 7.0) as a supporting electrolyte at a scan rate of 100 mV s⁻¹.

Review on Material and Design of Anode for Microbial Fuel Cell

Microbial Fuel Cell (MFC) is a bio-electrochemical system that generates electricity by anaerobic oxidation of substrates. An anode is the most critical component because the primary conversion of wastewater into electrons and protons takes place on the surface of the anode, where a biofilm is formed. This paper describes the essential properties of the anode and classifies its types according to the material used to make it. Anode material is responsible for the flow of electrons generated by the microorganism; hence biocompatibility and conductivity can considered to be the two most important properties. In this paper, the various modification strategies to improve the performance of anodes of MFC are explained through the review of researchers’ published work in this field. The shape and size of the anode turned out to be very significant as the microbial growth depends on the available surface area. The attachment of biofilm on the surface of an anode largely depends on the interfacial surface chemistry. Methods for improving MFC performance by altering the anode material, architecture, biocompatibility, and longevity are discussed with a future perspective giving special importance to the cost.

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.

Thin-Reinforced Anion-Exchange Membranes with High Ionic Contents for Electrochemical Energy Conversion Processes

Ion-exchange membranes (IEMs) are a core component that greatly affects the performance of electrochemical energy conversion processes such as reverse electrodialysis (RED) and all-vanadium redox flow battery (VRFB). The IEMs used in electrochemical energy conversion processes require low mass transfer resistance, high permselectivity, excellent durability, and also need to be inexpensive to manufacture. Therefore, in this study, thin-reinforced anion-exchange membranes with excellent physical and chemical stabilities were developed by filling a polyethylene porous substrate with functional monomers, and through in situ polymerization and post-treatments. In particular, the thin-reinforced membranes were made to have a high ion-exchange capacity and a limited degree of swelling at the same time through a double cross-linking reaction. The prepared membranes were shown to possess both strong tensile strength (>120 MPa) and low electrical resistance (<1 Ohm cm²). As a result of applying them to RED and VRFB, the performances were shown to be superior to those of the commercial membrane (AMX, Astom Corp., Japan) in the optimal composition. In addition, the prepared membranes were found to have high oxidation stability, enough for practical applications.

Preparation and Separation Properties of Electrospinning Modified Membrane with Ionic Liquid Terminating Polyimide/Polyvinylpyrrolidone@Polydopamine

In this paper, superhydrophilic polyimide (PI) membranes were prepared using the electrostatic spinning method, capped with a hydrophilic ionic liquid (IL), and blended with polyvinylpyrrolidone (PVP). Using this preparation, the surface of the fiber membranes was coated in polydopamine (PDA) by means of an in-growth method. Scanning electron micrographs showed prepared blend films can form continuous fibers, for whom the distributions of diameter and pore were uniform. Post-modification (carried out by adding hydrophilic substances), the ability of the membrane surface to adhere to water was also significantly improved. The water contact angle was reduced from 128.97 ± 3.86° in unmodified PI to 30.26 ± 2.16°. In addition, they displayed a good separation effect on emulsified oil/water mixtures. The membrane flux reached a maximum value of 290 L·m⁻²·h⁻¹, with a maximum separation efficiency reached of more than 99%. After being recycled 10 times, the separation efficiency maintained a level exceeding 95%. The purpose of this study is to demonstrate the simplicity and efficiency of this experiment, thereby providing new ideas for the future application of membrane separation technology in wastewater treatment.

Family Tree for Aqueous Organic Redox Couples for Redox Flow Battery Electrolytes: A Conceptual Review

Redox flow batteries (RFBs) are an increasingly attractive option for renewable energy storage, thus providing flexibility for the supply of electrical energy. In recent years, research in this type of battery storage has been shifted from metal-ion based electrolytes to soluble organic redox-active compounds. Aqueous-based organic electrolytes are considered as more promising electrolytes to achieve "green", safe, and low-cost energy storage. Many organic compounds and their derivatives have recently been intensively examined for application to redox flow batteries. This work presents an up-to-date overview of the redox organic compound groups tested for application in aqueous RFB. In the initial part, the most relevant requirements for technical electrolytes are described and discussed. The importance of supporting electrolytes selection, the limits for the aqueous system, and potential synthetic strategies for redox molecules are highlighted. The different organic redox couples described in the literature are grouped in a "family tree" for organic redox couples. This article is designed to be an introduction to the field of organic redox flow batteries and aims to provide an overview of current achievements as well as helping synthetic chemists to understand the basic concepts of the technical requirements for next-generation energy storage materials.

Review of the Development of First-Generation Redox Flow Batteries: Iron-Chromium System

The iron-chromium redox flow battery (ICRFB) is considered the first true RFB and utilizes low-cost, abundant iron and chromium chlorides as redox-active materials, making it one of the most cost-effective energy storage systems. ICRFBs were pioneered and studied extensively by NASA and Mitsui in Japan in the 1970-1980s, and extensive studies on ICRFBs have been carried out over the past few decades. In addition, ICRFB is considered to be one of the most promising directions for cost-effective and large-scale energy storage applications, as its cost can theoretically be lower than that of zinc-bromine and all-vanadium RFBs, giving it the potential for large-scale promotion. With the resolution of problems such as hydrogen evolution and electrolyte intermixing, the ICRFB technology is moving out of the laboratory and striving for greater power and more stable industrialization requirements. This Review summarizes the history, development, and research status of key components (carbon-based electrode, electrolyte, and membranes) in the ICRFB system, aiming to give a brief guide to researchers who are involved in the related subject.

Temperature-Induced Precipitation of V2O5 in Vanadium Flow Batteries—Revisited

The maximum operation temperature of the vanadium solution in vanadium flow batteries is typically limited to 40 °C to prevent the damaging thermal precipitation of V2O5. Therefore, the operation of batteries at high ambient temperatures is an important aspect to tackle for stationary storage. In the present work, a comprehensive study of the high temperature stability of redox solutions for vanadium flow batteries was performed. In particular, focus was placed on a comparison between batch and in operando precipitation experiments. It was found that, despite being a widely used method in the literature, caution should be taken when assessing the precipitation through capacity fade due to the large influence of external oxidation and cycling parameters, plausibly leading to an incorrect interpretation of the results. The in operando experiments consistently show a precipitation temperature almost 10–20 °C higher than in the batch tests at a 100% state of charge for the same time lapse.

Future-Oriented Experimental Characterization of 3D Printed and Conventional Elastomers Based on Their Swelling Behavior

The present study investigates different elastomers with regard to their behavior towards liquids such as moisture, fuels, or fuel components. First, four additively manufactured materials are examined in detail with respect to their swelling in the fuel component toluene as well as in water. The chemical nature of the materials is elucidated by means of infrared spectroscopy. The experimentally derived absorption curves of the materials in the liquids are described mathematically using Fick's diffusion law. The mechanical behavior is determined by uniaxial tensile tests, which are evaluated on the basis of stress and strain at break. The results of the study allow for deriving valuable recommendations regarding the printing process and postprocessing. Second, this article investigates the swelling behavior of new as well as thermo-oxidatively aged elastomers in synthetic fuels. For this purpose, an analysis routine is presented using sorption experiments combined with gas chromatography and mass spectrometry and is thus capable of analyzing the swelling behavior multifacetted. The transition of elastomer constituents into the surrounding fuel at different aging and sorption times is determined precisely. The change in mechanical properties is quantified using density measurements, micro Shore A hardness measurements, and the parameters stress and strain at break from uniaxial tensile tests.

Renewable Energy in the Sustainable Development of Electrical Power Sector: A Review

The electrical power sector plays an important role in the economic growth and development of every country around the world. Total global demand for electric energy is growing both in developed and developing economies. The commitment to the decarbonization of economies, which would mean replacing fossil fuels with renewable energy sources (RES) as well as the electrification of transport and heating as a means to tackle global warming and dangerous climate change, would lead to a surge in electricity consumption worldwide. Hence, it appears reasonable that the electric power sector should embed the principles of sustainable development into its functioning and operation. In addition, events such as the recent European gas crisis that have emerged as a result of the massive deployment of renewables need to be studied and prevented. This review aims at assessing the role of the renewable energy in the sustainable development of the electrical power sector, focusing on the energy providers and consumers represented both by businesses and households that are gradually becoming prosumers on the market of electric energy. Furthermore, it also focuses on the impact of renewables on the utility side and their benefits for the grid. In addition, it identifies the major factors of the sustainable development of the electrical power sector.

Investigation on the Microscopic/Macroscopic Mechanical Properties of a Thermally Annealed Nafion® Membrane

The Nafion® electrolyte membrane, which provides a proton pathway, is an essential element in fuel cell systems. Thermal treatment without additional additives is widely used to modify the mechanical properties of the membrane, to construct reliable and durable electrolyte membranes in the fuel cell. We measured the microscopic mechanical properties of thermally annealed membranes using atomic force microscopy with the two-point method. Furthermore, the macroscopic property was investigated through tensile tests. The microscopic modulus exceeded the macroscopic modulus over all annealing temperature ranges. Additionally, the measured microscopic modulus increased rapidly near 150 °C and was saturated over that temperature, whereas the macroscopic modulus continuously increased until 250 °C. This mismatched micro/macroscopic reinforcement trend indicates that the internal reinforcement of the clusters is induced first until 150 °C. In contrast, the reinforcement among the clusters, which requires more thermal energy, probably progresses even at a temperature of 250 °C. The results showed that the annealing process is effective for the surface smoothing and leveling of the Nafion® membrane until 200 °C.