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Nafion, a perfluorosulfonic acid ionomer, has been well-studied for decades due to its key role as an ion-conductive membrane in electrochemical energy conversion and storage applications. When hydrated, this membrane phase separates into a complex hierarchical nanostructure with hydrophilic domains that facilitate ion transport. Hard X-ray scattering has been a powerful technique in understanding Nafion due to its capabilities in capturing the ionomer’s nanophase separated structure, which gives rise to contrast between polymer and water domains. More recently, resonant X-ray scattering, which tunes to elemental absorption edges to provide specificity on constituent elements, has been explored to highlight key interactions related to the sulfonic acid groups within its structure. Here, we study the Nafion nanostructure by combining hard X-ray scattering and tender resonant X-ray scattering (TReXS) at the sulfur K-edge to reveal a mesoscopic feature corresponding to a correlation length of approximately 40 nm that has been challenging to resolve with hard X-ray studies. Additionally, we study the effect of the dispersion solvent composition that plays a key role in the formation of this mesoscale feature. Notably, TReXS can attain high contrast to decipher this mesoscale morphology even for dry polymer membranes under a vacuum, which typically have reduced contrast for hard X-rays. We find that the correlation length of this mesoscale feature decreases with increasing water fraction in the dispersion, which is the opposite trend exhibited by the smaller intercrystalline feature in the same membranes. This study showcases the utility of TReXS to uncover multiscale morphological details in functional polymers that are not always revealed by other methods like hard X-ray scattering. We illustrate this with Nafion, which is a relevant ion-conducting polymer for electrochemical technologies.

Ionomers based on poly(arylene piperidinium)s with varying ion exchange capacities are evaluated in different combinations of anode and cathode electrodes in anion exchange membrane fuel cells. The operational conditions are chosen with an asymmetrical regime including a dry anode with 50% relative humidity at the inlet, and full humidification at the cathode. Polarization and impedance measurements are carried out in potentiostatic steps within 0.3–0.9 V and distribution of relaxation times analysis is utilized to deconvolute resistance contributions. The results show that the best cell performance is achieved with both electrodes utilizing an ionomer with the highest ion exchange capacity (IEC) of 2.79 meq g−1. Cells built exclusively from this ionomer achieved a peak power density of 1.01 W cm−2. Deconvolution of the resistance contributions revealed the impact of water content on the effective charge transfer resistance in both electrodes and a diffusion resistance associated with the movement of water from anode to cathode side. The higher conductivity and water uptake of the high IEC ionomer resulted in a reduction of both resistance contributions, leading to the highest performance under the conditions evaluated. These findings provide important insights into how to tailor the electrode layers for optimum fuel cell output. [ABSTRACT FROM AUTHOR]

Polymer electrolyte membrane fuel cells, which have already been put into practical use in some areas, are expected to become widespread to realize a next-generation sustainable energy society. However, it faces several challenges to its performance and durability. The challenges include Pt particle agglomeration, catalyst degradation, low Pt mass catalyst loading, support material corrosion and mass transport resistance, which lead to reduced catalytic activity, limited fuel cell efficiency and decreased durability. Researchers have investigated multiple strategies to overcome these challenges, such as catalyst alloying, support optimization, advanced synthesis techniques, surface modification, and improved water and gas management. This work focuses on the aforementioned challenges associated with Pt nanocatalysts, catalyst supports, and ionomers in polymer electrolyte fuel cells, offering a comprehensive review and discussion of these issues and the corresponding mitigation approaches. In summation, it is suggested that by addressing these challenges, we can pave the way for developing more efficient, durable, and commercially viable fuel cell systems. • Pt catalyst, low loading, and mass resistance impact the PEM fuel cell. • Pt agglomeration reduces surface area and impairs fuel cell performance. • Catalyst support corrosion is a challenge when optimizing for cell efficiency. • Scalable Pt catalyst manufacturing is crucial; explore cost-effective methods. • Excess ionomer hinders mass transfer, impacting fuel cell efficiency. [ABSTRACT FROM AUTHOR]

Ion-conducting polymers (Ionomers) are critical in catalyst layers (CLs) of proton exchange membrane (PEM) fuel cells and water/vapor-fed electrolyzers, serving essential roles in proton conduction, electronic insulation, and water absorption. This review summarized the physical, chemical and economic parameters of CL ionomers across various PEM modules, focusing on long- and short-side-chain perfluorosulfonic acid (PFSA) ionomers. It also outlines recent efforts in PEM air dehumidification. Characterization methods for ionomer morphology (e.g. rods, swollen clusters, networks) and mass transfer resistance (e.g. ionomer/gas interfacial, catalyst/ionomer interfacial and intra-ionomer) were summarized. Optimal ionomer distribution at electron-proton-gas interfaces is crucial, as proton transfer requiring a thick and connected distribution and gas transport requiring a thin and dispersed distribution. Adjusting ionomer equivalent weight and ratio to catalyst can enhance distribution. Besides, CL ionomer design should emphasize product escape for water electrolyzers and reactant diffusion for vapor ones. Integration of multidimensional and multifunctional techniques, such as visual characterizations of Transmission Electron Microscopy and Nanoscale X-ray computed tomography and numerical simulations of Molecular Dynamics and lattice Boltzmann methods, is recommended for accurate assessment of ionomer behavior. This comprehensive review provides insights into ionomers in CLs, highlighting characterization methods and manipulation strategies, offering guidance for next-generation PEM modules. [ABSTRACT FROM AUTHOR]

Acid‐functionalized polymers enhance the performance of phosphoric‐acid‐doped polybenzimidazoles (PA/PBIs); however, studies on examining the mechanisms driving these enhancements are scarce. Furthermore, the nanophase morphology of PA‐dependent proton‐exchange membranes has been rarely explored, despite its direct role in the distribution of PA and protonic conduction. In this study, theoretical and experimental analyses to evaluate the microphase separation, particularly the formation and in situ transformation of a two‐phase interface, in a defect‐free polyphenylene ionomer (SPP‐QP) with excellent integrity are performed. SPP‐QP serves as a fortifying agent with an enhanced microphase‐separation ability within PA/PBI‐based membranes. Specifically, the distinct swelling behavior of PA results in the formation of PA‐rich and PA‐poor regions. Thus, the formation of a durable interface that is impervious to PA degradation between SPP‐QP and PBI is critical for facilitating microphase separation. A single cell composed of the composite membrane offers a peak power density of 719 mW cm−2 at 160 °C. Moreover, the durability of a single cell is much longer than 150 h. The results obtained in this study provide insights into the micromorphology and membrane properties observed in the presence of PA. [ABSTRACT FROM AUTHOR]

In this work, a numerical approach is presented to reconstruct the ionomer three-dimensional distribution in the microstructure of the cathode catalyst layer (CCL) of a polymer electrolyte membrane fuel cell (PEMFC) from a 3D segmented image of the CCL obtained by focused ion beam-scanning electron microscopy (FIB-SEM). Three forms of ionomer are distinguished: the ionomer filaments, the coating ionomer and the inter-carbon grains ionomer. The ionomer filaments are identified by applying a filtering procedure to the size distribution in the segmented solid phase obtained via a maximum sphere inscription algorithm. The coating ionomer is reconstructed via a filtering procedure of the curvature distribution computed over the interface between the two segmented phases from the consideration that concave regions are preferential ionomer accumulation zones during the drying step of the CCL fabrication procedure. This procedure of coating controlled by the local curvature is applied until a desired value of coverage is reached. In a last step, catalyst nanoparticles, also not visible in the FIB-SEM image, are reconstructed in the image. • Ionomer coating is numerically reconstructed in a FIB-SEM image. • The ionomer coating is of variable thickness. • A small fraction of the ionomer forms protrusions in the pore space. • A significant fraction of the ionomer is in between the carbon grains. [ABSTRACT FROM AUTHOR]

The oxygen effective diffusion and proton effective conductivity tensors of a cathode catalyst layer (CCL) are computed using a two-scale approach on CCL microstructure three-dimensional images obtained by focused ion beam-scanning electron microscopy (FIB-SEM) after reconstruction of the ionomer distribution. The results show that the obtained tensors are not isotropic. It is also found that some off-diagonal components are not negligible in the case of the proton effective conductivity tensor. The simulations confirm that Knudsen diffusion has a significant impact on oxygen diffusion. The results are comparable to those obtained in previous works on synthetic images as regards the oxygen effective diffusion through-plane component but differ as regards the proton conductivity through-plane component. Contrary to previous works using synthetic images which tend to underestimate the proton conductivity, they are globally in better agreement with experimental data. The results also show that the effective proton conductivity is heterogeneous at the scale of the computational domains typically considered in several previous works due to the variability in the ionomer distribution at this scale. The impact of liquid water in the primary pores on the proton transport is explored and found to have a significant impact. • The oxygen effective diffusion tensor is computed from 3D digital images of a PEMFC catalyst layer (CL). • The proton effective conductivity tensor is computed from 3D digital images of the CL microstructure. • Liquid water in the primary pores has a noticeable impact on the proton transport. • Results on the proton transport validate the considered ionomer spatial distribution. [ABSTRACT FROM AUTHOR]

Owing to its high production volume and wide range of applications, polyethylene has gained a great deal of attention, but its low surface energy and non-polar nature have limited its application in some important fields. In this study, ethylene/11-iodo-1-undecene copolymers were prepared and used as the intermediates to afford a series of imidazolium-based ionomers bearing methanesulfonate (CH3SO3−), trifluoromethanesulfonate (CF3SO3−), or bis(trifluoromethane)sulfonimide (Tf2N−) counteranions. The tensile test results showed that the stress-at-break (7.8–25.6 MPa) and the elongation-at-break (445%–847%) of the ionomers could be adjusted by changing the counterion species and the ionic group contents. Most importantly, the ionomers exhibited marvelous antibacterial activities against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The ionomers bearing Tf2N− exhibited antibacterial activities >99% against both S. aureus and E. coli when ionic content reached 9.1%. The imidazolium-based ionomers prepared in this work demonstrated excellent comprehensive properties, especially high-efficient and broad-spectrum antibacterial ability, exhibiting the potential for the application as the antibacterial materials in packaging, medical, and other fields. [ABSTRACT FROM AUTHOR]

Polypropylene (PP) is chemically modified with maleic anhydride (MAH) and cross-linked with zinc oxide at different concentrations by melt mixing. The grafting process is conducted at two different temperatures, 150 °C and 180 °C. Using relatively high concentrations of initiator a grafting degree sufficient for cross-linking is achieved. FTIR spectroscopy confirms that a lower processing temperature leads to a significantly higher grafting efficiency. The concentration of stearic acid influences the neutralization degree of the cyclic anhydride grafts significantly, and, therefore, a mechanism has been proposed to explain this behaviour. The DSC thermograms of the grafted samples reveal secondary melting points at lower temperatures attributable to the interactions between the polar grafts. Samples grafted at the lower processing temperature undergo long-chain branching and exhibit complex thermal behaviour. Rheological analysis shows that ionic cross-linking has improved the melt properties; the analysis also reveals the formation of a dual-phase morphology developed with cross-linking and supports the proposed mechanism. Dynamic-mechanical thermal analysis proves the mechanical stability at elevated temperatures and reveals the cross-linked samples' ion-hopping temperatures. Tensile testing is also performed to evaluate the mechanical properties of cross-linked samples. [ABSTRACT FROM AUTHOR]

Proton exchange membrane fuel cells (PEMFCs) have garnered considerable interest owing to their high conversion efficiency and eco-friendliness. However, the components of PEMFCs are prone to degradation caused by generated radicals, hindering their widespread application. To counteract the chemical attack of radicals on PEMFC components, the key solution is to incorporate radical scavengers, as they can effectively eliminate harmful radicals. Ce-based scavengers exhibit the highest radical scavenging capacity, whereas they are susceptible to dissolution and may exert poisoning effects on ionomers, thereby impacting proton conductivity and gas mass transfer. Additionally, Ce-based radical scavengers may degraded and migrated due to varying chemical and electrochemical conditions. This study delves into the scavenging mechanisms and influences of Ce-based radical scavengers. Furthermore, it addresses the issues of poisoning and migration and outlines appropriate measures to mitigate these challenges. This review aims to offer an innovative solution to enhance the durability of PEMFCs. [Display omitted] • Reviewed the scavenging mechanisms of Ce-based radical scavengers and their effects. • Discussed the poisoning effects of Ce-based radical scavengers and provided some mitigation strategies. • Highlighted the migration of Ce species and the corresponding stabilization strategies. • Presented the technical challenges and future development prospects of Ce-based radical scavengers. [ABSTRACT FROM AUTHOR]

Research into enhancing the performance and durability of anion exchange membrane (AEM)‐based water electrolysis (AEMWE) cells has primarily aimed to facilitate commercialization efforts and improve the chemical stability of AEMs, with anion exchange ionomers (AEIs) playing an increasingly important role. This study aimed to reduce ionomer swelling and enhance AEM–catalyst adhesion via AEM–ionomer crosslinking within a membrane electrode assembly (MEA), using allyl‐ and quaternary ammonium‐functionalized poly(phenylene oxide) (PPO), allyl‐m‐PPO, as both the AEM and AEI. Bis(aryl azide) was added as a crosslinker to an ionomer solution to generate the MEA, which was heated to induce allyl–azide crosslinks at the membrane–ionomer interface. Peel test indicated an increased adhesion at both electrodes for the crosslinked x‐allyl‐0.05‐PPO (5 mol% allyl content relative to the total ion‐conducting head group content). Further, x‐allyl‐0.05‐PPO exhibited a smaller voltage increase due to crosslinking compared to TA‐PPO, signifying a notable improvement in durability. [ABSTRACT FROM AUTHOR]

The microstructures of the ionomer–catalyst interfaces in the catalyst layers are important for the fuel cell performance because they determine the distribution of the active triple-phase boundaries. Here, we investigate the ionomer–catalyst interactions in hydroxide exchange membrane fuel cells (HEMFCs) using poly(aryl piperidinium) and compare them with proton exchange membrane fuel cells (PEMFCs). It is found that different catalyst layer microstructures are between the two types of fuel cell. The ionomer/carbon (I/C) ratio does not have a remarkable impact on the HEMFC performance, while it has a strong impact on the PEMFC performance, indicating the weaker interaction between the HEMFC ionomer and catalyst. Molecular dynamics simulations demonstrate that the HEMFC ionomer tends to distribute on the carbon support, unlike the PEMFC ionomer, which heavily covers the Pt nanoparticles. These results suggest that the poisoning effect of the ionomer on the catalyst is much weaker in HEMFCs, and the improved ionomer/catalyst interaction is beneficial for the HEMFC performances. [ABSTRACT FROM AUTHOR]

An ionomer strategy is introduced to deal with two major performance‐limiting issues for the proton exchange membrane fuel cells (PEMFCs) operating under low platinum (Pt) and low humidity. Specifically, the highly hydrophilic multiple‐valence Anderson‐type polyoxometalate (POM) cluster, [MnMo6O18(OH)6]3−, is chosen to covalently graft the perfluorinated polymer, substituting for sulfonate groups as proton carriers in perfluorosulfonic acid (PFSA). The structural and electrochemical characterizations indicate that this POM cluster, with large size, charges delocalization among multiple terminal oxygen atoms, and high hygroscopicity, can prevent the ionomer adsorption, which is believed to induce dense backbone crystallization to hinder O2 permeation at Pt/PFSA interface, and lead to ionomer assemblies with large and well‐connected hydrophilic domains, which are recognized as the channels for efficient oxygen transport as well as proton conduction. Besides, the involvement of redox Mn ions in POM clusters makes the ionomer have capability to scavenge peroxides, which are known as the major chemical agents to degrade the MEA components. Consequently, fuel‐cell cathodes using the POM‐grafted ionomers exhibit significantly lower local O2 transport resistance and higher proton conductivity as compared with the PFSA‐based electrodes; and accordingly, the fuel cells exhibit much‐increased output performance at 50% relative humidity and impressive performance stability. [ABSTRACT FROM AUTHOR]

Commercial-scale generation of carbon-containing chemicals and fuels by means of electrochemical CO2 reduction (CO2R) requires electrolyzers operating at high current densities and product selectivities. Membrane-electrode assemblies (MEAs) have been shown to be suitable for this purpose. In such devices, the cathode catalyst layer controls both the rate of CO2R and the distribution of products. In this study, we investigate how the ionomer-to-catalyst ratio (I:Cat), catalyst loading, and catalyst-layer thickness influence the performance of a cathode catalyst layer containing Ag nanoparticles supported on carbon. In this paper, we explore how these parameters affect the cell performance and establish the role of the exchange solution (water vs. CsHCO3) behind the anode catalyst layer in cell performance. We show that a high total current density is best achieved using an I:Cat ratio of 3 at a Ag loading of 0.01–0.1 mgAg/cm2 and with a 1.0 M solution of CsHCO3 circulated behind the anode catalyst layer. For these conditions, the optimal CO partial current density depends on the voltage applied to the MEA. The work also reveals that the performance of the cathode catalyst layer is limited by a combination of the electrochemically active surface area and the degree to which mass transfer of CO2 to the surface of the Ag nanoparticles and the transport of OH− anions away from it limit the overall catalyst activity. Hydration of the ionomer in the cathode catalyst layer is found not to be an issue when using an exchange solution. The insights gained allowed for a Ag CO2R MEA that operates between 200 mA/cm2 and 1 A/cm2 with CO faradaic efficiencies of 78–91%, and the findings and understanding gained herein should be applicable to a broad range of CO2R MEA-based devices.

Proton exchange membrane fuel cells (PEMFCs) offer significant potential in the field of next-generation mobility applications. Incomplete ionomer impregnation in reinforced composite membranes (RCMs) deteriorates the performance and durability of PEMFCs because the proton conductivity of RCMs decreases and the gas permeability increases in a single cell. In this study, the impregnation into RCMs was improved by introducing fluorocarbon and hydrocarbon (CF–CH)-based hybrid surfactants into the ionomer solution. The improved impregnation was confirmed using contact angle and proton conductivity measurements, Fourier transform infrared spectroscopy (FTIR), focused ion beam-scanning electron microscopy (FIB-SEM), and energy dispersive X-ray spectroscopy (EDS). In a single cell, the performance and durability of the RCM with the CF-CH hybrid surfactant were better than those of the RCM impregnated with only the ionomer due to the lower membrane resistance and hydrogen crossover in the former. The RCM with the CF-CH hybrid surfactant exhibited a current density of 1.2 A cm−2 at 0.6 V and peak power density of 740 mW cm−2 in a single cell. Thus, high-performance and durable RCMs of PEMFCs can be efficiently fabricated by introducing the surfactant in an ionomer solution. This can significantly advance the mobility applications of fuel cells. • CF-CH-based hybrid surfactants were used for fabricating reinforced composite membranes. • Surfactants improved proton conductivity and wettability of ionomer on membrane. • Overall durability and performance of a single cell improved using this membrane. • The hydrogen crossover and membrane resistance decreased using this membrane. [ABSTRACT FROM AUTHOR]

Carbon support has an important influence on the catalyst ink properties. The interaction between carbon support, solvent, and ionomer determines the dispersion of ink clusters. In this study, the effects of dispersion time, solvent, and ionomer on the cluster properties are studied. It is found that the shear time of 8 h is conducive to the fragmentation of catalyst particles, and isopropanol and ionomer D2020 has good dispersion for mesoporous carbon support with high specific surface area. The median diameter of catalyst clusters is effectively reduced from 1537 to 1014 nm, and 10 wt% solid content of ink is more conducive to slit coating. The increase of the ionomer content is helpful to reduce the catalyst layer cracks. When the mass ratio of dry ionomer to carbon(I/C) is larger than 0.85, the cracks of the catalyst layer are significantly reduced. The results of I–V curve tests show that when I/C = 0.85, the cell has the best polarization performance. The single cell voltage is 0.709 V at 1 A cm−2, and the power density is 1128.51 mW cm−2 at 2 A cm−2. The results of electrochemical impedance spectroscopy (EIS) are also consistent with the polarization curve test results. • The influence of ionomer on catalyst ink and fuel cell performance are analyzed. • The clusters size, Zeta potential and rheology of the ink are investigated. • The shear time, type of solvent and ionomer of the ink are optimized. • The I/C ratio and the solid content of the ink are optimized. • MEA with optimized parameters has good electrochemical performance. [ABSTRACT FROM AUTHOR]

It is well-established that the composition of catalyst slurry significantly impacts the formation of the catalyst layer in proton exchange membrane fuel cells (PEMFCs), particularly concerning the morphology and size of agglomerates. These aspects play a crucial role in determining the structure of the three-phase interface and the number of effective catalyst sites. This study explores the influence of various parameters and solvents used during slurry preparation on the size and morphology of agglomerate particles. Our research results indicate that the particle size in the slurry can be reduced to 212.8 nm, through high pressure, prolonged duration, and lower temperature, while higher temperatures will lower the surface potential of particles, causing to re-aggregate. Changes in pH and Zeta potential reflect variations in ionomer solvation during the aggregation of the slurry. Augmenting water content contracts ionomer agglomerate morphology, enhancing surface particle morphology on the catalyst layer, promoting pore formation, ameliorating drainage capacity (particularly under high current density), increase the polarization voltage and power density to 0.632V@2A cm−2 and 1.26W @ 2A cm−2. [Display omitted] • Temperature-induced particle recombination during dispersion was investigated. • The evolution of ionomer morphology during slurry placement was investigated. • Explored the influence of Zeta-potential on coating structure. • Clarified the relationship between agglomerates and polarization performance. [ABSTRACT FROM AUTHOR]

The alkaline fuel cell is subject to extensive research owing to its fast kinetic response relative to acidic media. However, the efficiency of the catalytic layer at the electrodes depends on the amount and distribution of ionomers present there. It is crucial to have the right ionomer concentration to have the best cell performance. Additionally, the membrane thickness is a significant parameter that affects the system performance in alkaline fuel cells. This research studies the best alkaline fuel cell performance using the membrane electrode assembly preparation parameters. The prepared membrane electrode assembly consists of catalyst layers containing Fumion, a commercial anion exchange ionomer, as a binding agent, sandwiched a Fumasep, a well‐known commercial anion exchange membrane. This work elucidates the single‐cell alkaline fuel cell performance by quantifying the influence of Fumion concentrations (~20–60 wt.%) within the catalytic layer and Fumasep thicknesses (30, 75 and 130 μm). The best concentration of Fumion was found to be 50 wt.%, culminating in the maximum peak power density of 67 mW cm−2 achieved by the FAA‐3‐PK‐75. Meanwhile, FAA‐3‐PK‐130 exhibited the highest open‐circuit potential with lowest power density at 53 mW cm−2. These findings may serve as a valuable guide for membrane electrode assembly preparation in alkaline fuel cells. [ABSTRACT FROM AUTHOR]

We report the development of novel self‐healing binary thermoplastic elastomeric blends of Zn2+‐neutralized poly[ethylene‐co‐(methacrylic acid)] (Zn‐ionomer) and styrene–butadiene–styrene block copolymer (SBS). Zn‐ionomer/SBS blends were prepared by the melt‐blending technique using a twin‐screw extruder with three mass ratios of 75/25, 50/50 and 25/75. Structure, phase morphology and thermal as well as tensile properties of the samples were characterized. Fourier transform infrared spectroscopy results indicated the presence of two types of polymeric materials and their interactions. Scanning electron microscopy images confirmed the miscibility of blend components which remarkably influenced the properties of the blends. The optimum peak degradation temperature of Zn‐ionomer/SBS (75/25 wt%) blend was observed to be 484 °C. The ratio of the tensile strength of the healed specimens to that of the original specimens was implemented to quantitatively evaluate the self‐healing efficiency of the materials. The self‐healing efficiencies were calculated to be 55.42%, 58.36% and 60.75% for Zn‐ionomer samples healed for 4, 8 and 16 h, respectively. All of the blend samples exhibited self‐healing behavior and the self‐healing efficiency was more than that of virgin Zn‐ionomer which may be credited to the high mobility of SBS segments in the blends. The healing efficiency was increased with an increase of SBS content in the blends and also heat energy facilitated the healing process. The self‐healing efficiencies of Zn‐ionomer/SBS (25/75 wt%) blend sample were calculated to be 75.09%, 80.27% and 80.87%, respectively, for 4, 8 and 16 h of healing time at 100 °C. A comparison of optical micrographs of the cut area of samples (before healing and after the healing process) was also made and self‐healing of the blend materials was observed. © 2023 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

The small specific entropy of mixing of high molecular weight polymers implies that most blends of dissimilar polymers are immiscible with poor physical properties. Historically, a wide range of compatibilization strategies have been pursued, including the addition of copolymers or emulsifiers or installing complementary reactive groups that can promote the in situ formation of block or graft copolymers during blending operations. Typically, such reactive blending exploits reversible or irreversible covalent or hydrogen bonds to produce the desired copolymer, but there are other options. Here, we argue that ionic bonds and electrostatic correlations represent an underutilized tool for polymer compatibilization and in tailoring materials for applications ranging from sustainable polymer alloys to organic electronics and solid polymer electrolytes. The theoretical basis for ionic compatibilization is surveyed and placed in the context of existing experimental literature and emerging classes of functional polymer materials. We conclude with a perspective on how electrostatic interactions might be exploited in plastic waste upcycling.

The endeavor to develop high‐performance electrochemical energy applications has underscored the growing importance of comprehending the intricate dynamics within an electrode's structure and their influence on overall performance. This review investigates the complexities of electrode‐ionomer interactions, which play a critical role in optimizing electrochemical reactions. Our examination encompasses both microscopic and meso/macro scale functions of ionomers at the electrode‐ionomer interface, providing a thorough analysis of how these interactions can either enhance or impede surface reactions. Furthermore, this review explores the broader‐scale implications of ionomer distribution within porous electrodes, taking into account factors like ionomer types, electrode ink formulation, and carbon support interactions. We also present and evaluate state‐of‐the‐art techniques for investigating ionomer distribution, including electrochemical methods, imaging, modeling, and analytical techniques. Finally, the performance implications of these phenomena are discussed in the context of energy conversion devices. Through this comprehensive exploration of intricate interactions, this review contributes to the ongoing advancements in the field of energy research, ultimately facilitating the design and development of more efficient and sustainable energy devices. [ABSTRACT FROM AUTHOR]

Gas diffusion electrodes (GDEs) mediate the transport of reactants, products and electrons for the electrocatalytic CO2 reduction reaction (CO2RR) in membrane electrode assemblies. The random distribution of ionomer, added by the traditional physical mixing method, in the catalyst layer of GDEs affects the transport of ions and CO2. Such a phenomenon results in elevated cell voltage and decaying selectivity at high current densities. This paper describes a pre-confinement method to construct GDEs with homogeneously distributed ionomer, which enhances mass transfer locally at the active centers. The optimized GDE exhibited comparatively low cell voltages and high CO Faradaic efficiencies (FE > 90%) at a wide range of current densities. It can also operate stably for over 220 h with the cell voltage staying almost unchanged. This good performance can be preserved even with diluted CO2 feeds, which is essential for pursuing a high single-pass conversion rate. This study provides a new approach to building efficient mass transfer pathways for ions and reactants in GDEs to promote the electrocatalytic CO2RR for practical applications. [ABSTRACT FROM AUTHOR]

Studying the ORR activity of platinum-based electrocatalysts is an urgent task in the development of materials for proton-exchange membrane fuel cells. The catalytic ink composition and the formation technique of a thin layer at the RDE play a significant role in studying ORR activity. The use of a polymer ionomer in the catalytic ink provides viscosity as well as proton conductivity. Nafion is widely used as an ionomer for research both at the RDE and in the MEA. The search for ionomers is a priority task in the development of the MEA components to replace Nafion. The study also considers the possibility of using the LF4-SK polymer as an alternative ionomer. The comparative results on the composition and techniques of applying the catalytic layer using LF4-SK and Nafion ionomers are presented, and the influence of the catalytic ink composition on the electrochemical characteristics of commercial platinum–carbon catalysts and a highly efficient platinum catalyst based on an N-doped carbon support is assessed. [ABSTRACT FROM AUTHOR]

Most commercially available polymers are synthesized from compounds derived from petroleum, a finite resource. Because of this, there is a growing interest in the synthesis of new polymeric materials using renewable monomers. Following this concept, this work reports on the use of muconic acid as a renewable source for the development of new polyamides that can be used as proton-exchange membranes. Muconic acid was used as a comonomer in polycondensation reactions with 4,4′-(hexafluoroisopropylidene)bis(p-phenyleneoxy)dianiline, 2,5-diaminobencensulfonic acid, and 4,4′-diamino-2,2′-stilbenedisulfonic acid as comonomers in the synthesis of two new series of partially renewable aromatic–aliphatic polyamides, in which the degree of sulfonation was varied. Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (1H, 13C, and 19F-NMR) techniques were used to confirm the chemical structures of the new polyamides. It was also observed that the degree of sulfonation was proportional to the molar ratio of the diamines in the feed. Subsequently, membranes were prepared by casting, and a complete characterization was conducted to determine their decomposition temperature (Td), glass transition temperature (Tg), density (ρ), and other physical properties. In addition, water uptake (Wu), ion-exchange capacity (IEC), and proton conductivity (σp) were determined for these membranes. Electrochemical impedance spectroscopy (EIS) was used to determine the conductivity of the membranes. MUFASA34 exhibited a σp value equal to 9.89 mS·cm−1, being the highest conductivity of all the membranes synthesized in this study. [ABSTRACT FROM AUTHOR]

Among existing water electrolysis (WE) technologies, anion-exchange-membrane water electrolyzers (AEMWEs) show promise for low-cost operation enabled by the basic solid-polymer electrolyte used to conduct hydroxide ions. The basic environment within the electrolyzer, in principle, allows the use of non-platinum-group metal catalysts and less-expensive cell components compared to acidic-membrane systems. Nevertheless, AEMWEs are still underdeveloped, and the degradation and failure modes are not well understood. To improve performance and durability, supporting electrolytes such as KOH and K2CO3 are often added to the water feed. The effect of the anion interactions with the ionomer membrane (particularly other than OH-), however, remains poorly understood. We studied three commercial anion-exchange ionomers (Aemion, Sustainion, and PiperION) during oxygen evolution (OER) at oxidizing potentials in several supporting electrolytes and characterized their chemical stability with surface-sensitive techniques. We analyzed factors including the ionomer conductivity, redox potential, and pH tolerance to determine what governs ionomer stability during OER. Specifically, we discovered that the oxidation of Aemion at the electrode surface is favored in the presence of CO32-/HCO3- anions perhaps due to the poor conductivity of that ionomer in the carbonate/bicarbonate form. Sustainion tends to lose its charge-carrying groups as a result of electrochemical degradation favored in basic electrolytes. PiperION seems to be similarly negatively affected by a pH drop and low carbonate/bicarbonate conductivity under the applied oxidizing potential. The insight into the interactions of the supporting electrolyte anions with the ionomer/membrane helps shed light on some of the degradation pathways possible inside of the AEMWE and enables the informed design of materials for water electrolysis.

Fuel-cell catalyst layers (CLs) are porous electrodes that are fabricated from CL inks: colloidal dispersions of catalyst particles and ion-conducting polymer (ionomer), dispersed in solvent(s). The complex interactions between the ink components ultimately dictate CL microstructure and electrochemical performance. To control the CL formation process and optimize fuel-cell performance, knowledge of these ink interactions is vital. In this review, we analyze data from ink-focused papers to elucidate how ink parameters (solvent type, ionomer-to-carbon ratio, etc.) impact ink interactions and CL performance. We then discuss these results in the context of the current understanding of two critical ink interactions: ionomer/solvent and ionomer/catalyst particle interactions.

The plasticization effect by the addition of nonpolar bis(2-ethylhexyl) phthalate (dioctyl phthalate) (DOP) on the glass transition temperatures (Tgs) of poly(styrene-Na methacrylate) (PSMANa) ionomers was investigated. The matrix Tg (Tg,m) and cluster Tg (Tg,c) of the ionomers dropped linearly as the DOP content in the PSMANa ionomers enhanced, only when the phase separation of DOP did not occur. Since the Tg,m and Tg,c of the ionomer increased somewhat linearly with increasing ion content of the ionomer, simple equations were obtained to express the Tgs of the ionomers using the ion contents (x mol%) and the DOP contents (y wt%) of the ionomers; Tg,m (°C) = 121 + 3.0x + 2.8y and Tg,c (°C) = 171 + 6.3x + 2.6y. According to the x-ray scattering results, for the ionomer containing 6.4 mol% of ions, the distance between scattering centers increased from 21 to 22 Å when ca. 40 wt% of DOP was added. This suggested that the DOP promoted the mobility of the styrene chains, enhancing the formation of multiplets. On the other hand, for the ionomer containing 22.4 mol% of ions, when ca. 40 wt% was added, the distance between multiplets widened from 18 to 21 Å. [ABSTRACT FROM AUTHOR]

This work evaluates the effects of maleic anhydride grafted ethylene-propylene-diene rubber (EPDM-g-MAH) on the processing characteristics, compatibility and mechanical properties of EPDM/Ionomer blends. Dynamic vulcanization process was used to fabricate thermoplastic vulcanizates (TPVs) of different compositions using EPDM polymers and high acid (HA60D) or mid acid (MA60D) containing thermoplastic ionomers. The addition of EPDM-g-MAH in EPDM/Ionomer blends had a predominant role as a compatibilizing agent, which affected the processability and properties of the final material. The tensile properties showed significant improvement with increasing the content of compatibilizer in the vulcanizates. The microscopical analysis of fracture surfaces further supported the heterogeneous nature of the blends and compatibility of the polymer phases. The concept was based on a simple ionic crosslinking reaction between carboxyl groups present in the ionomer and zinc oxide (ZnO), where the formation of reversible Zn2+ covalent crosslinks exhibits the self-healing behavior. The combination of blending and ionic cross-linking improved not only mechanical properties but also improved self-healing performance. The self-healing nature of the TPVs has been identified by scratch resistance test, where the ternary blends (EPDM/Ionomer/EPDM-g-MAH) showed 100% healing efficiency of the scratch surface at 89°C for 24 h. [ABSTRACT FROM AUTHOR]

The optimized design of the catalyst layer (CL) plays a vital role in improving the performance of polymer electrolyte membrane fuel cells (PEMFCs). The need to improve transport and catalyst activity is especially important at low Pt loading, where local oxygen and ionic transport resistances decrease the performance due to an inevitable reduction in active catalyst sites. In this work, local oxygen and ionic transport are analyzed using direct numerical simulation on virtually reconstructed microstructures. Four morphologies are examined: (i) heterogeneous, (ii) uniform, (iii) uniform vertically-aligned, and (iv) meso-porous ionomer distributions. The results show that the local oxygen transport resistance can be significantly reduced, while maintaining good ionic conductivity, through the design of high porosity CLs ( ε ≃ 0.6–0.7) with low agglomerated ionomer morphologies. Ionomer coalescence into thick films can be effectively mitigated by increasing the uniformity of thin films and reducing the tortuosity of ionomer distribution (e.g., good ionomer interconnection in supports with a vertical arrangement). The local oxygen resistance can be further decreased by the use of blended ionomers with enhanced oxygen permeability and meso-porous ionomers with oxygen transport routes in both water and ionomer. In summary, achieving high performance at low Pt loading in next-generation CLs must be accomplished through a combination of high porosity, uniform and low tortuosity ionomer distribution, and oxygen transport through activated water. [ABSTRACT FROM AUTHOR]

Hydrogen fuel cell technology is gaining significant attention as a promising alternative for decarbonizing automotive vehicles. At the heart of hydrogen fuel cell technology is the electrode, composed of catalysts, supports, binders, and pores, which facilitates the half‐cell reactions and often governs the efficiency of fuel cells. Over the last decade, scientists have made great strides in discovering catalyst, support, and binder materials featuring unique nanostructures and compositions that significantly enhance the efficiency of those devices. While innovations must continue, we must not overlook how these materials are put together to form an electrode and how it impacts the overall efficiency. This perspective article discusses the urgent need for developing alternative electrodes for designing next generation hydrogen fuel cells. [ABSTRACT FROM AUTHOR]

[Display omitted] Ag nanoparticles (Ag NPs) are among the most promising candidates to replace Pt as the catalyst for the oxygen reduction reaction (ORR) in anion exchange membrane fuel cells (AEMFCs). However, synthesizing size-controlled Ag NPs with efficient catalytic performance is still challenging. Herein, uniform Ag NPs are produced through a γ-radiation induced synthesis route in aqueous solutions, using the ionomer PTPipQ100 as both an efficient size regulator in the synthesis and a conductor of hydroxide ions during the ORR process. The origin of the size control is mainly attributed to the affinity of the ionomer to metallic silver. The resulting Ag NPs covered with ionomer layers can be applied as model catalysts for ORR. The nanoparticles that were prepared using 320 ppm ionomer in the reaction solution turned out to be coated with a ∼ 1 nm thick ionomer layer and exhibited superior ORR activity as compared to other Ag NPs of similar size studied here. The improved electrocatalytic performance can be attributed to the optimal ionomer coverage that enables fast oxygen diffusion, as well as interactions at the Ag-ionomer interface which promote the desorption of OH intermediates from the Ag surface. This work demonstrates the advantage of using an ionomer as the capping agent to produce efficient ORR catalysts. [ABSTRACT FROM AUTHOR]

For proton-exchange membrane (PEM) water electrolyzers to be commercially feasible, PEMs must perform over long lifetimes in liquid environments under compression while maintaining mechanical stability. A hydrated environment, while inherent for operation and conductivity, undermines PEM stability. Mechanical stability of PEMs is commonly characterized in tension, which is not applicable to electrolyzers, wherein PEMs could undergo high pressures. In this study, a compression creep procedure is developed using a custom-designed setup to monitor creep response of hydrated PEMs. Our results show that PEMs exhibit continuous creep response under compression over 24 h, with a dependence on the applied pressure and hydration state.

Perfluorosulfonic acid (PFSA) ionomers are an important class of materials that many electrochemical devices rely on as their ion-conducting electrolyte. Often, PFSA films are prepared through solution-processing techniques. Previous research has demonstrated that the solvent environment affects PFSA dispersion conformation, but it is not clear to what extent (if at all) these conformational effects persist for thin films and membranes upon casting, nor how dispersion solvent impacts film formation during the drying process. Here, we explore these questions by systematically examining the effect of water and n-propanol mixtures on PFSA thin-film formation and structure, membrane structure, and resulting properties. Using a combination of in situ, time-resolved grazing incidence X-ray scattering and tender wide-angle X-ray scattering, it is shown that films prepared from high-water-concentration dispersions exhibit stronger interactions and arrangement upon drying, and possess larger network domain sizes than those prepared from low-water-concentration dispersions. These stronger interactions likely manifest in greater network connectivity, as evidenced by enhanced conductivity for membranes and decreased water uptake for thin films. Significantly, these solvent-induced differences persist even after thermal annealing. It is clear that the dispersion solvent choice is a critical parameter controlling PFSA nano- and mesoscale structure and presents an important dial with which to direct PFSA macroscale properties.

Aim: Discoloration in ionomeric materials occurs by absorption of substances, so color stability is important because these materials are of choice to restore class V. The purpose of the current study was to evaluate the color stability of a giomer, a conventional glass ionomer and a resin-modified glass ionomer exposed to different beverages with different immersion times. Materials and Methods: This in vitro experimental and longitudinal study had 135 discs were sampled in total (2mm thick × 8mm in diameter) distributed in three equal groups (n = 45): Beautifil II, Vitremer, and Ketac Universal. Each group was divided into three equal subgroups (n = 15 each group) and immersed in three different staining solutions: coffee, Coca-Cola®, and red wine. Color change was recorded with the Vita Easyshade® spectrophotometer after 1h, 24h, and 1 week of immersion. Measures of central tendency and dispersion were calculated. Kruskal-Wallis and Friedman nonparametric H tests were used to compare independent measures. The Bonferroni post hoc was used considering a significance level of P < 0.05. Results: Beautifil II (P <0.05) and Ketac Universal (P < 0.05) showed significant differences with respect to color variation (ΔE) when comparing exposure to Coca-Cola® versus exposure to coffee and red wine for 1h, 24h, and 1 week. Vitremer showed no significant differences when exposed to Coca-Cola®, coffee, and red wine for 1h, 24h, and 1 week (P = 0.607, P = 0.276, and P = 0.134, sequentially). All three restorative materials, after 1 hour immersed in CocaCola®, showed ΔE < 3.3 and Beautifil II obtained ΔE = 3.12 after 24h immersed in the same beverage. Conclusion: Coffee and red wine significantly varied the color of Beautifil II and Ketac Universal over time. Beautifil II and Ketac Universal showed significantly more pigmentation with red wine and less with Coca-Cola® at 1 week immersion. Vitremer showed no significant differences when exposed to Coca-Cola®, coffee, and red wine at all times tested. There were clinically acceptable variations for all three restorative materials immersed in Coca-Cola for 1h. This clinical threshold was only maintained for the Beautifil II giomer up to 24h of immersion in the same beverage. [ABSTRACT FROM AUTHOR]

This study focuses on the thermal properties and structural features of blends consisting of thermoplastic starch (TPS) and poly(ethylene-co-methacrylic acid) copolymer (EMAA) or its ionomer form (EMAA-54Na). The aim is to investigate how carboxylate functional groups of the ionomer form intervene in blends compatibility at the interface of the two materials and how this impacts their properties. Two series of blends (TPS/EMAA and TPS/EMAA-54Na) were produced with an internal mixer, with TPS compositions between 5 and 90 wt%. Thermogravimetry shows two main weight losses, indicating that TPS and the two copolymers are primarily immiscible. However, a small weight loss existing at intermediate degradation temperature between those of the two pristine components reveals specific interactions at the interface. At a mesoscale level, scanning electron microscopy confirmed thermogravimetry results and showed a two-phase domain morphology, with a phase inversion at around 80 wt% TPS, but also revealed a different surface appearance evolution between the two series. Fourier-transformed infrared spectroscopy analysis also revealed discrepancies in fingerprint between the two series of blends, analysed in terms of additional interactions in TPS/EMAA-54Na coming from the supplementary sodium neutralized carboxylate functions of the ionomer. [ABSTRACT FROM AUTHOR]

In this study, after blending with ionomer to expand the use of PA11, the stress-stain properties of these blends were investigated. In particular, the ionomers blended with PA11 differed in polarities, Tgs, and types of ionic groups, and the effects of these variables on the mechanical properties of the blends were studied. First, it was found that the relatively non-polar ionomer seemed to have stronger interactions between ionic groups and polar functional groups with non-polar PA11 than the polar ionomer. Second, the ion pairs of the ionomer tended to form ionic aggregates when the strength of interaction between ion pairs increased, so the ionomer did not interact with PA11 effectively rather phase-separated. Third, when the Tg of the ionomer was relatively low, the ionomer seemed to act as a softening agent and help the PA11 chains move easily while molding the samples at high temperatures. In addition, the high Tg ionomers were found to behave as hard fillers in the PA11 blends. It was also suggested that the interfacial adhesion between PA11 and the ionomer was good when the strength of ionic interaction was relatively weak and the Tg of the ionomer was not too low. [ABSTRACT FROM AUTHOR]

In this work we prepared poly(styrene-co-methacrylate) ionomers neutralized with three different monovalent cations and added these ionomers to heavy oil to determine how the ionomer affected asphaltenes dispersion in the heavy oil. First, it was found that ionomers neutralized with smaller-sized cations led to better dispersion of asphaltenes in heavy oil. Second, ionomers neutralized with smaller-sized cations were observed to slow the asphaltene aggregation process. Third, it was found that the concentration of the ionomer exhibiting the best asphaltene dispersibility depended on which cation neutralized the ionomer. The above results suggested that the strength of the interactions between the ions of the ionomer and the strength of the interactions between the cations of the ionomer and the functional groups of the asphaltenes were very important factors for the ionomers to act as effective asphaltene dispersants. The SAXS results also showed that the ionomer neutralized with smaller-sized cations induced asphaltene dispersion in heavy oil relatively well. The addition of poly(styrene-co-methacrylate) ionomers further improved the dispersion of asphaltenes in heavy oil as the size of the monovalent cation neutralizing the ionomer decreased. In addition, ionomers neutralized with smaller sized cations resulted in slower asphaltene aggregation. Also, the concentration of the ionomer in the heavy oil for the best asphaltene dispersion depended on the cation type of the ionomers. The above results indicated that the strength of the interactions between the ions of the ionomer and the strength of the interactions between the cations of the ionomer and the functional groups of the asphaltenes were very important factors for the ionomers to act as effective asphaltene dispersants. [ABSTRACT FROM AUTHOR]

In the past, platinum–copper catalysts have proven to be highly active for the oxygen reduction reaction (ORR), but transferring the high activities measured in thin-film rotating disk electrodes (TF-RDEs) to high-performing membrane electrode assemblies (MEAs) has proven difficult due to stability issues during operation. High initial performance can be achieved. However, fast performance decay on a timescale of 24 h is induced by repeated voltage load steps with H2/air supplied. This performance decay is accelerated if high relative humidity (>60% RH) is set for a prolonged time and low voltages are applied during polarization. The reasons and possible solutions for this issue have been investigated by means of electrochemical impedance spectroscopy and distribution of relaxation time analysis (EIS–DRT). The affected electrochemical sub-processes have been identified by comparing the PtCu electrocatalyst with commercial Pt/C benchmark materials in homemade catalyst-coated membranes (CCMs). The proton transport resistance (Rpt) increased by a factor of ~2 compared to the benchmark materials. These results provide important insight into the challenges encountered with the de-alloyed PtCu/KB electrocatalyst during cell break-in and operation. This provides a basis for improvements in the catalysts' design and break-in procedures for the highly attractive PtCu/KB catalyst system. [ABSTRACT FROM AUTHOR]

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Novel electrolyte is being pursued toward exploring Zn chemistry in zinc ion batteries. Here, a fluorine-free liquid crystal (LC) ionomer-type zinc electrolyte is presented, achieving simultaneous regulated water activity and long-range ordering of conduction channels and SEI. Distinct from water network or local ordering in current advances, long-range ordering of layered water channels is realized. Via manipulating water activity, conductivities range from "0.34 to 15 mS cm-1, and electrochemical window can be tuned from "2.3-4.3 V. The Zn|Zn symmetric cell with LC gel exhibits highly reversible Zn stripping/plating at 5 mA cm-2 and 5 mAh cm-2 for 800 h, with retained ordering of water channels. The capability of gel for inducing in situ formation of long-range ordered layer SEI associated with alkylbenzene sulfonate anion is uncovered. V2O5/Zn cell with the gel shows much improved cycling stability comparing to conventional zinc electrolytes, where the preserved structure of V2O5 is associated with the efficiently stabilized Zn anode by the gel. Via long-range ordering-induced regulation on ion transport, electrochemical stability, and interfacial reaction, the development of LC electrolyte provides a pathway toward advancing aqueous rechargeable batteries. [ABSTRACT FROM AUTHOR]

Intelligent Eucommia ulmoides rubber (EUR) and ionomer Surlyn resin (SR) blends were prepared and studied in this manuscript. This is the first paper to combine EUR with SR to prepare blends with both the shape memory effect and self-healing capability. The mechanical, curing, thermal, shape memory and self-healing properties were studied by a universal testing machine, differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA), respectively. Experimental results showed that the increase in ionomer content not only improved mechanical and shape memory properties but also endowed the compounds with excellent self-healing ability under the appropriate environmental conditions. Notably, the self-healing efficiency of the composites reached 87.41%, which is much higher than the efficiency of other covalent cross-linking composites. Therefore, these novel shape memory and self-healing blends can expand the use of natural Eucommia ulmoides rubber, such as in special medical devices, sensors and actuators. [ABSTRACT FROM AUTHOR]

In this study, the water absorption of poly(styrene-co-itaconate) PSITNa ionomers, having two ion pairs in an ionic repeat unit, was investigated. Plotting the water absorption data as a function of the ionic repeat unit content revealed that the PSITNa ionomer exhibited more water uptake than the poly(styrene-co-methacrylate) PSMANa ionomer, having one Na–carboxylate ion pair per ionic repeat unit. On the other hand, when the water absorption data were simply expressed as a function of the ion content, it was found that the PSMANa ionomer showed more water absorption than the PSITNa ionomer. These results and the SAXS results suggested that to increase the degree of water absorption of the ionomer, it would be better for the ion pairs of the ionomer to form aggregates with other ion pairs rather than to exist alone in the matrix. In addition, it was observed that the degree of water absorption of the ionomer gradually improved as the size of the cation used for neutralization of the ionomer increased. These results and morphological results indicated that when the strength of interaction between ion pairs was weakened, the number of ionic aggregates decreased, and, at the same time, the ionic aggregates readily absorbed water due to weak interaction between ion pairs in the aggregates. The water absorption of poly(styrene-co-itaconate) PSITNa ionomers was investigated. It was found that to increase the degree of water absorption of the ionomer, it would be better for the ion pairs of the ionomer to form ionic aggregates with other ion pairs rather than to exist alone in the matrix. In addition, when the strength of interaction between ion pairs was weakened, the ionic aggregates readily absorbed water due to weak interaction between ion pairs in the ionic aggregates. [ABSTRACT FROM AUTHOR]

Open-cathode polymer electrolyte membrane fuel cells (PEMFCs) utilize a unique air-cooled system design to eliminate the humidifiers, air compressor, and liquid cooling loop of conventional, liquid-cooled PEMFC systems, thereby greatly reducing system cost. However, the open-cathode PEMFC performance is restricted by poor humidification, high membrane and charge transfer resistances, and overheating due to inefficient thermal and water management. This work aims to strategically modify the membrane electrode assembly (MEA) design to overcome these issues and achieve high open-cathode PEMFC performance that approaches that of liquid-cooled systems. The use of thinner membrane along with short side chain ionomer is found to elevate the cell performance due to increased water retention at the cathode catalyst layer (CCL) and decreased ohmic losses. Thinner gas diffusion layers with high porosity enable additional cell performance increment by improving oxygen availability at the CCL. An overall current density rise of 88% at 0.6 V and 53% at 0.4 V is achieved by the strategically designed MEA for open-cathode cells. The enhanced power density enabled by the custom MEA can both reduce the stack cost and expand the power range of open-cathode PEMFCs, thus expanding their potential use for low-cost fuel cell system applications.

Studying the ORR activity of platinum-based electrocatalysts is an urgent task in the development of materials for proton-exchange membrane fuel cells. The catalytic ink composition and the formation technique of a thin layer at the RDE play a significant role in studying ORR activity. The use of a polymer ionomer in the catalytic ink provides viscosity as well as proton conductivity. Nafion is widely used as an ionomer for research both at the RDE and in the MEA. The search for ionomers is a priority task in the development of the MEA components to replace Nafion. The study also considers the possibility of using the LF4-SK polymer as an alternative ionomer. The comparative results on the composition and techniques of applying the catalytic layer using LF4-SK and Nafion ionomers are presented, and the influence of the catalytic ink composition on the electrochemical characteristics of commercial platinum–carbon catalysts and a highly efficient platinum catalyst based on an N-doped carbon support is assessed.

This study aimed to evaluate the possibility of reusing industrial scraps of Surlyn® ionomer by obtaining blends with Low-Density Polyethylene (LDPE). Blends of LDPE and Surlyn® scraps were obtained by extrusion with compositions ranging from 25 to 75 wt% of the ionomer. Their melt flow index (MFI), morphology (SEM), mechanical (tensile, flexural, impact tests) and thermal properties (DSC, TGA, HDT tests) were analyzed. The morphology of the blends presented two phases, indicating the immiscibility of phases. Surlyn® incorporation promoted a decrease in the degree of crystallinity of LDPE and a slight increase in the thermal decomposition temperature. In addition, Surlyn® decreased the decomposition rate of LDPE. However, the decrease in the degree of crystallinity did not affect the mechanical properties of the blends. Incorporating ionomer in LDPE promoted an increase in tensile and flexural strength, tensile and flexural modulus and strain at break. Impact strength decreased with increasing ionomer concentration.

Abstract Novel electrolyte is being pursued toward exploring Zn chemistry in zinc ion batteries. Here, a fluorine‐free liquid crystal (LC) ionomer‐type zinc electrolyte is presented, achieving simultaneous regulated water activity and long‐range ordering of conduction channels and SEI. Distinct from water network or local ordering in current advances, long‐range ordering of layered water channels is realized. Via manipulating water activity, conductivities range from ≈0.34 to 15 mS cm−1, and electrochemical window can be tuned from ≈2.3–4.3 V. The Zn|Zn symmetric cell with LC gel exhibits highly reversible Zn stripping/plating at 5 mA cm−2 and 5 mAh cm−2 for 800 h, with retained ordering of water channels. The capability of gel for inducing in situ formation of long‐range ordered layer SEI associated with alkylbenzene sulfonate anion is uncovered. V2O5/Zn cell with the gel shows much improved cycling stability comparing to conventional zinc electrolytes, where the preserved structure of V2O5 is associated with the efficiently stabilized Zn anode by the gel. Via long‐range ordering‐induced regulation on ion transport, electrochemical stability, and interfacial reaction, the development of LC electrolyte provides a pathway toward advancing aqueous rechargeable batteries.

Catalyst layers (CL) composed of catalyst composites and an ionomer are key components in polymer electrolyte membrane fuel cells (PEMFCs). In particular, the preparation conditions of the CL, starting from the dispersion of the catalyst composite dispersion with an ionomer, largely affect the PEMFC performance. In this study, the effects of alcohol content in the dispersion solvent were investigated using two binary mixtures composed of water and ethanol. In addition, Pt-loaded carbon black (CB) and Pt-loaded polymer-wrapped CB were used as the catalyst composites to study the effects of the alcohol contents on the interaction between ionomer and surface of the carbon supports. The CL prepared using the water-rich (80 wt% water) solvent achieved a higher PEMFC performance compared to that using the alcohol-rich (13 wt% water) solvent, which is ascribed to the stronger interaction between the ionomer and CB surface under water-rich conditions. Using the polymer-wrapped CB, the difference of the PEMFC performance between the CLs from the water-rich and alcohol-rich dispersions was minimal because of the comparable interaction between the ionomer and wrapping polymer surface in both solvents. Therefore, the control of the interaction between the ionomer and catalyst composites is crucial to controlling the PEMFC performance. • Ionomer adsorption on Pt/C is Langmuir-type and varies depending on ink solvents. • Water-rich solvent affords higher ionomer adsorption and higher PEMFC performance. • Ionomer adsorption is increased when carbon is coated by polybenzimidazole (PBI). • PBI coating enables higher ionomer adsorption even in alcohol-rich solvent. • Ionomer adsorption in inks reflects to ionomer distribution in PEMFC catalyst layer. [ABSTRACT FROM AUTHOR]

Commercial‐scale generation of carbon‐containing chemicals and fuels by means of electrochemical CO2 reduction (CO2R) requires electrolyzers operating at high current densities and product selectivities. Membrane‐electrode assemblies (MEAs) have been shown to be suitable for this purpose. In such devices, the cathode catalyst layer controls both the rate of CO2R and the distribution of products. In this study, we investigate how the ionomer‐to‐catalyst ratio (I:Cat), catalyst loading, and catalyst‐layer thickness influence the performance of a cathode catalyst layer containing Ag nanoparticles supported on carbon. In this paper, we explore how these parameters affect the cell performance and establish the role of the exchange solution (water vs. CsHCO3) behind the anode catalyst layer in cell performance. We show that a high total current density is best achieved using an I:Cat ratio of 3 at a Ag loading of 0.01–0.1 mgAg/cm2 and with a 1.0 M solution of CsHCO3 circulated behind the anode catalyst layer. For these conditions, the optimal CO partial current density depends on the voltage applied to the MEA. The work also reveals that the performance of the cathode catalyst layer is limited by a combination of the electrochemically active surface area and the degree to which mass transfer of CO2 to the surface of the Ag nanoparticles and the transport of OH− anions away from it limit the overall catalyst activity. Hydration of the ionomer in the cathode catalyst layer is found not to be an issue when using an exchange solution. The insights gained allowed for a Ag CO2R MEA that operates between 200 mA/cm2 and 1 A/cm2 with CO faradaic efficiencies of 78–91%, and the findings and understanding gained herein should be applicable to a broad range of CO2R MEA‐based devices. [ABSTRACT FROM AUTHOR]

Aiming to tackle the serious brittleness problem of polylactic acid（PLA），PLA-based multiphase blends are prepared by melting reactive blending with hydroxyl functionalized ionomer as the toughening agent and compatibilizer containing epoxy groups. The structures and properties of the blends are characterized by scanning electron microscopy（SEM），Fourier transform infrared spectrometer（FT-IR），differential scanning calorimetry（DSC）and mechanical properties tests. The synergistic compatibilization and toughening effects of epoxy soybean oil（ESO），polyethylene glycol diglycidyl ether（PEGDE）and ethylene-methyl acrylateglycidyl methacrylate （AX8900） terpolymer are compared and analyzed. The results show that the compatibilization effect is closely related to the content and position of the epoxy group in the additives，which presenting different toughening effects. The addition of AX8900 can effectively improve the toughness of the blend system to obtain balanced mechanical properties. However，ESO tends to lead to crosslinking，which limits the toughening efficiency. PEGDE mainly shows a plasticizing effect，leading to the reduction of tensile strength. The results demonstrate modification of the PLA blends by reactive blending with different epoxy additives and hydroxy-containing polymers is an effective strategy for the development of high-performance biobased PLA materials. [ABSTRACT FROM AUTHOR]