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[Display omitted] Exploring the intrinsic relationship between the network structure and the performance of catalyst layer (CL) by rational design its structure is of paramount importance for proton exchange membrane (PEM) electrolyzers. This study reveals the relative effect of polymeric dispersion evolution on oxygen evolution reaction (OER) performance and cell voltage loss and linked to CL network structure. The results show that although the dispersed particle size of the ionomer and ink increases with increasing the solubility parameter (δ) difference between the mixed solvent and the ionomer, MeOH-cat (ink from MeOH aqueous solution) has the largest ionomer and ink particle size resulting in the poorest stability, but has comparable OER overpotential to that of IPA-cat (249 mV@10 mA cm−2), which has the smallest dispersed size. While at 100 mA cm−2, the overpotential of the ink rises as the particle size increases, suggesting that the electrode structure becomes more influential as the current density increases. Quantitatively analyzed the electrolyzers' voltage losses and determined that the CL from MeOH-cat has the lowest kinetic overpotential. However, its performance is the worst because of the insufficient network structure of CL, resulting in an output of 1.96 V at 1.5 A cm−2. Comparatively, the CL from IPA-cat has the highest kinetic overpotential yet can achieve the greatest performance of 1.76 V at 2 A cm−2 due to its homogeneous network structure and optimal mass transport. Furthermore, the performance variation becomes more pronounced as current density rises. Hence, this study highlights the significant impact of CL structure on electrolyzer's performance. To improve performance in PEM water electrolysis technology, especially for large work current density, it is crucial to enhance the CL's network structure. [ABSTRACT FROM AUTHOR]

The significant role of the cathodic binder in modulating mass transport within the catalyst layer (CL) of fuel cells is essential for optimizing cell performance. This investigation focuses on enhancing the membrane electrode assembly (MEA) through the utilization of a short‐side‐chain perfluoro‐sulfonic acid (SSC‐PFSA) ionomer as the cathode binder, referred to as SSC‐MEA. This study meticulously visualizes the distinctive interpenetrating networks of ionomers and catalysts, and explicitly clarifies the triple‐phase interface, unveiling the transport‐friendly microstructure and transport mechanisms inherent in SSC‐MEA. The SSC‐MEA exhibits advantageous microstructural features, including a better‐connected ionomer network and well‐organized hierarchical porous structure, culminating in superior mass transfer properties. Relative to the MEA bonded by long‐side‐chain perfluoro‐sulfonic acid (LSC‐PFSA) ionomer, noted as LSC‐MEA, SSC‐MEA exhibits a notable peak power density (1.23 W cm−2), efficient O2 transport, and remarkable proton conductivity (65% improvement) at 65 °C and 70% relativity humidity (RH). These findings establish crucial insights into the intricate morphology‐transport‐performance relationship in the CL, thereby providing strategic guidance for developing highly efficient MEA. [ABSTRACT FROM AUTHOR]

Electrochemical CO2 reduction (eCO2R) stands as a pivotal technology for carbon recycling by converting CO2 into value‐added products. While significant strides have been made in generating multi‐carbon (C2+) products like ethylene (C2H4) and ethanol (C2H5OH) at industrial‐scale current densities with high Faradaic efficiency (FE), cathode flooding and (bi)carbonate salt accumulation remain a fundamental concern in an alkaline electrolyte. In this work, ion‐conducting polymers are used to tailor the micro‐environment mitigating cathode flooding and salt precipitation and thus, enhancing the local CO2 availability. The impact of cation and anion exchange ionomer layers, specifically Nafion and Sustainion XA‐9 are examined on overall eCO2R performance. The use of an ultra‐thin bilayer configuration significantly reduces cathode flooding and salt accumulation by ≈58% compared to commercial anion exchange membrane (AEM). Alongside, cation infusion improves the C─C bond formation inducing a favorable micro‐environment for selective C2+ formation. This cation‐infused bilayer ionomer (CIBLI) achieves a high partial current density of ≈284 mA cm−2 toward C2+ products maintaining a stable eCO2R performance for 24 hours (h). This scalable approach of directly deposited ultra‐thin CIBLI offers a minimal conversion energy of 117 GJ/ ton C2+ products with an energy efficiency (EE) of 29% at 350 mA cm−2 current density in one‐step CO2 conversion. [ABSTRACT FROM AUTHOR]

The relationship between the mechanical, electrical, and morphological properties of annealed films based on short-side-chain perfluorinated sulfonic acid ionomer (SSCI) with an Aquivion structure was systematically investigated using dynamic mechanical analysis (DMA), small-angle X-ray scattering (SAXS), and impedance spectroscopy. Annealing the membranes at temperatures of 140, 150, and 160 °C—above the glass transition temperature of SSCI—and the nature of the liquid phase in the polymer dispersion significantly influence the structural parameters of the membranes, specifically the size of the conductive channels formed by hydrophilic sulfonic acid groups. SAXS and AFM analyses revealed that membranes cast from N,N-dimethylacetamide (DMAA) exhibit a denser, less structured morphology, resulting in lower hydrogen permeability (φ = 4.6 ± 0.7 nmol/m/s/MPa), comparable to the commercial Nafion 211 membrane (φ = 6.5 nmol/m/s/MPa), but with significantly lower proton conductivity (35 ± 5 mS/cm) than Nafion 211 (95 mS/cm). In contrast, membranes obtained from a water-alcohol mixture showed a well-defined structure (SAXS, AFM), with proton conductivity values ranging from 70 to 103 mS/cm, comparable to Nafion 211. However, the hydrogen permeability of these membranes varied significantly depending on the annealing conditions (φ = 5.5–65.3 nmol/m/s/MPa). SAXS data indicated that the membranes had a similar degree of crystallinity (11–13%) but differed in the positions of the ionomer peak and matrix knee, which are associated with variations in the size of the conductive channels and account for the observed differences in ionic conductivity. Membranes annealed at 150 °C, which exhibited hydrogen permeability and ionic conductivity values close to those of the commercial Nafion 211 membrane, were used to fabricate membrane electrode assemblies (MEA). The electrochemical characteristics of these MEAs were investigated at 30 and 60 °C, 100% relative humidity, at both atmospheric pressure and 200 kPa overpressure. At a current density of 1.75 A/cm2, the fabricated membranes demonstrated power outputs of up to 550 and 950 mW/cm2, which are comparable to, and even exceed, those of the commercial Nafion 211 membrane (700 mW/cm2). However, despite the high-power performance, significant membrane degradation was observed after 10,000 cycles in durability tests. These findings contribute to a better understanding of the relationship between the electrochemical properties and the structure of short-side-chain perfluorinated sulfonic acid ionomers with an Aquivion-type structure and are expected to enhance their application in fuel cells. [Display omitted] • The effect of annealing temperature on PFSA films properties has been studied. • Films based on dispersion ROH/H 2 O and DMAA differ in ionic conductivity. • MEA based on films annealed at 150 °C shown power density up to 950 mW/cm2. [ABSTRACT FROM AUTHOR]

[Display omitted] Short-side-chain perfluorosulfonic acid (SSC-PFSA) ionomers with high ion-exchange-capacity are promising candidates for high-temperature proton exchange membranes (PEMs) and catalyst layer (CL) binders. The solution-casting method determines the importance of SSC-PFSA dispersion characteristics in shaping the morphology of PEMs and CLs. Therefore, a thorough understanding of the chain behavior of SSC-PFSA in dispersions is essential for fabricating high-quality PEMs and CLs. In this study, we have employed multiple characterization techniques, including dynamic light scatting (DLS), small-angle X-ray scattering (SAXS), and cryo-transmission electron microscope (Cryo-TEM), to fully study the chain aggregation behaviors of SSC-PFSA in water–ethanol solvents and elucidate the concentration-dependent self-assembly process. In dilute dispersions (2 mg/mL), SSC-PFSA assembles into mono-disperse rod-like aggregates, featuring a twisted fluorocarbon backbone that forms a hydrophobic stem, and the sulfonic acid side chains extending outward to suit the hydrophilic environment. As the concentration increases, the radius of rod particles increases from 1.47 to 1.81 nm, and the mono-disperse rod particles first form a "end-to-end" configuration that doubles length (10 mg/mL), and then transform into a swollen network structure in semi-dilute dispersion (20 mg/mL). This work provides a well-established structure model for SSC-PFSA dispersions, which is the key nanostructure to be inherited by PEMs. [ABSTRACT FROM AUTHOR]

Tomographic imaging of time-evolving samples is a challenging yet important task for various research fields. At the nanoscale, current approaches face limitations of measurement speed or resolution due to lengthy acquisitions. We developed a dynamic nanotomography technique based on sparse dynamic imaging and 4D tomography modeling. We demonstrated the technique, using ptychographic x-ray computed tomography as its imaging modality, on resolving the in situ hydration process of polymer electrolyte fuel cell (PEFC) catalyst. The technique provides a 40-time increase in temporal resolution compared to conventional approaches, yielding 28 nm half-period spatial and 12 min temporal resolution. The results allow a quantitative characterization of the water intake process inside PEFC catalysts with nanoscale resolution, which is crucial for understanding their electrochemical mechanisms and optimizing their performance. Our technique enables high-speed operando nanotomography studies and paves the way for wider application of dynamic tomography at the nanoscale. [ABSTRACT FROM AUTHOR]

In this study, we synthesized a series of ABA-type vitrimers by crosslinking the short A moieties of precursors with a bifunctional crosslinker and evaporating the small molecular byproduct. The vitrimer samples thus prepared exhibit linear viscoelasticity dependent on the length of A moiety as well as the content of the crosslinks. When the average number of A monomers per end moiety m=1.1, the crosslinker can only extend the chain but not crosslink the chain. When m becomes 2.8 or higher, introducing a crosslinker first leads to the gelation, whereas excess in crosslinker molecules leads opening of the crosslinking sites and accordingly reentry into the sol regime. Surprisingly, a further increase in the length of the A moieties increases the relaxation time much weaker than the exponential increase seen for the physically crosslinked ABA-type ionomers. We attribute this difference to the distinct relaxation mechanisms: the relaxation of the vitrimer samples is based on relatively independent exchange reactions, which contrasts with the ABA-type ionomers that relax through the collective hopping of connected ionic groups from one ion aggregate to another. [ABSTRACT FROM AUTHOR]

The actual ionomer distribution in the catalyst layer is revealed by integrating multiple electrochemical methods. Different catalyst layer interfaces are formed with varying ionomer contents. Uneven distribution of ionomers will lead to a low ECSA, causing high local oxygen transport resistance. Though the uniformity of ionomer distribution can be improved by increasing ionomer contents, it will enlarge the oxygen transport distance from the bulk of the catalyst layer to active sites, thereby increasing the local oxygen transport resistance. The former has a more obvious impact on PEMFC performance. [Display omitted] In view of a catalyst layer (CL) with low-Pt causing higher local transport resistance of O 2 (R local), we propose a multi-study methodology that combines CO poisoning, the limiting current density method, and electrochemical impedance spectroscopy to reveal how real CL interfaces dominate R local. Experimental results indicate that the ionomer is not evenly distributed on the catalyst surface, and the uniformity of ionomer distribution does not show a positive correlation with the ionomer content. When the ionomer coverage on the supported catalyst surface is below 20 %, the ECSA is only 10 m2·g−1, and the ionomer coverage on the supported catalyst surface reaches 60 %, the ECSA is close to 40 m2·g−1. The ECSA has a positive correlation with ionomer coverage. Because the ECSA is measured by CO poisoning, it can be inferred that the platinum contacted with ionomer can generate effective active sites. Furthermore, a more uniform distribution of ionomer can create additional proton transport channels and reduce the distance for oxygen transport from the catalyst layer bulk to the active sites. A higher ECSA and a shorter distance for oxygen transport will reduce the R local , leading to better performance. [ABSTRACT FROM AUTHOR]

Sulfonated poly(oxy‐1,4‐phenylene‐oxy‐1,4‐phenylenecarbonyl‐1,4‐phenylene) also known as SPEEK is a chemically robust cation conductor with good solution processability. A thin film (approx. 0.7 μm) coated asymmetrically over a 10 μm diameter microhole in a Teflon substrate film (5 μm thickness) produces ionic diode effects in aqueous electrolyte media even at high ionic strengths up to 2 M NaCl. The enhancement in the ionic diode performance under high salt conditions is tentatively attributed to a (partial) switch from a concentration polarisation effect (dominant for high diode currents) to interfacial polarisation (dominant at low current; proposed for molecularly rigid ionomers). Ionic strength effects on the diode performance seem relatively low further indicative of a mechanism for the diode effect caused by interfacial polarisation without significant concentration polarisation. Preliminary comparison of diode phenomena in aqueous HCl, LiCl, NaCl, and MgCl2 reveals cation specific effects due to interaction with the polymer. [ABSTRACT FROM AUTHOR]

Electrochemical CO2 reduction (ECR) holds great potential to alleviate the greenhouse effect and our dependence on fossil fuels by integrating renewable energy for the electrosynthesis of high-value fuels from CO2. However, the high thermodynamic energy barrier, sluggish reaction kinetics, inadequate CO2 conversion rate, poor selectivity for the target product, and rapid electrocatalyst degradation severely limit its further industrial-scale application. Although numerous strategies have been proposed to enhance ECR performances from various perspectives, scattered studies fail to comprehensively elucidate the underlying effect-performance relationships toward ECR. Thus, this review presents a comparative summary and a deep discussion with respect to the effects strongly-correlated with ECR, including intrinsic effects of materials caused by various sizes, shapes, compositions, defects, interfaces, and ligands; structure-induced effects derived from diverse confinements, strains, and fields; electrolyte effects introduced by different solutes, solvents, cations, and anions; and environment effects induced by distinct ionomers, pressures, temperatures, gas impurities, and flow rates, with an emphasis on elaborating how these effects shape ECR electrocatalytic activities and selectivity and the underlying mechanisms. In addition, the challenges and prospects behind different effects resulting from various factors are suggested to inspire more attention towards high-throughput theoretical calculations and in situ/operando techniques to unlock the essence of enhanced ECR performance and realize its ultimate application. [ABSTRACT FROM AUTHOR]

For cost reduction and environmental‐friendly manufacturing, it is highly demanded to replace the current perfluorinated sulfonic acid‐based membrane in polymer electrolyte membrane fuel cells (PEMFCs) with inexpensive and readily available hydrocarbon‐based (HC) membranes. However, HC membranes suffer from profound dimensional changes caused by swelling and shrinking during operation, especially in automotive applications. These changes lead to severe mechanical degradation and shorten the service life of PEMFC. Herein, a multibar coating system is developed to manufacture HC/polytetrafluoroethylene (PTFE) composite membrane. This system facilitates capillary‐rise infiltration with the aid of an optimal amount of residual alcohol solvent on the PTFE. To address compatibility issues between PTFE and HC‐ionomer solutions, the effects of residual alcohol solvent on tuning the PTFE surface are investigated by controlling systemic parameters and performing diverse mechanical, optical, and electrochemical measurements. Based on its enhanced mechanical toughness (≈30.04%) and superior impregnation properties, the constructed HC/PTFE composite membrane exhibited more than seven‐fold improvement in mechanical durability under repeated accelerated wet–dry conditions compared with an unsupported pristine HC membrane while also mitigating performance loss (≈5.84%). [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]

Single ion conducting gel polymer electrolytes (GPEs) are characterized as having a certain amount of ionic liquid or solvent incorporated into a single ion-conducting polymer matrix and may afford the advantages of high conductivity and low electrolyte polarization under battery operation. Single ion conducting polymers often suffer from low conductivity due to their reliance on polymer segmental motion to achieve sufficient ion mobility. However, by incorporating specific solvents into a single ion conducting matrix, mobility of the polymer can be enhanced while still maintaining the advantages of single ion conduction. Although many of the solvents used to swell GPEs are mixtures of flammable organic solvents (such as dimethyl carbonate), there are many potential non-reactive, low vapor pressure solvents that could effectively solvate alkali-ion based GPEs and plasticize the polymer matrix to enhance ion conductivity. Adipate-based solvents are a group of non-volatile plasticizers with low viscosities and low vapor pressures at room temperature derived from adipic acid. The ester groups in these solvents may effectively solvate alkali ions such as Na+, leading to higher conductivity, while circumventing issues of flammability found in current alkali-ion conducting electrolytes. This study investigates the properties of sodium-ion conducting GPEs that have been swollen with varying adipate-based solvents and the subsequent dielectric response from the solvent addition. Dielectric relaxation spectroscopy was used to characterize the Na+ conductivity, static dielectric constant, ion-conducting content, and mobility of the membranes before and after the non-volatile solvent uptake. Understanding this relationship will pave the path toward safer, more efff cient solid-state polymer electrolytes for battery applications. [ABSTRACT FROM AUTHOR]

Anion exchange membrane water electrolysis (AEMWE) has gained attention as an attractive alternative to alkaline and proton exchange membrane water electrolysis (PEMWE) due to its high efficiency and low hydrogen unit cost. However, the long‐term durability of AEMWE is ≈10 times lower than that of PEMWE, which typically operates for 40 000 h. Here, a new design strategy is presented for aryl ether‐free PFPBPF‐QA anion exchange membranes with interstitial alkyl chains in the conducting groups and polymer backbone. The rationally designed PFPBPF‐4‐QA, with a suitable ion exchange capacity, shows high ionic conductivity, mechanical properties, alkaline stability, and stronger membrane‐ionomer contact properties at the catalyst layers. A single AEMWE cell using PFPBPF‐4‐QA demonstrated a voltage decay rate of 2 mV kh−1 at 1.0 A cm−2, which is significantly lower than that reported for AEMWEs and Nafion‐based PEMWEs. Additionally, a large‐sized 1‐cell AEMWE stack utilizing PFPBPF‐4‐QA with an active area of 63.6 cm2 achieved an energy conversion efficiency of 80.2% and a voltage decay rate of 1.5 mV kh−1 for 2 000 h, with over 90% of the initial efficiency maintained for over 49 095 h based on an exponential fitting calculation. [ABSTRACT FROM AUTHOR]

Medium-temperature proton exchange membrane fuel cells (MT PEMFCs) operating at 100° to 120°C have improved kinetics, simplified thermal and water management, and broadened fuel tolerance compared with low-temperature PEMFCs. However, high temperatures lead to Nafion ionomer dehydration and exacerbate gas transportation limitations. Inspired by osmolytes found in hyperthermophiles, we developed a-aminoketone– linked covalent organic framework (COF) ionomers, interwoven with Nafion, to act as “breathable” proton conductors. This approach leverages synergistic hydrogen bonding to retain water, enhancing hydration and proton transport while reducing oxygen transport resistance. For commercial Pt/C, the MT PEMFCs achieved peak and rated power densities of 18.1 and 9.5 Watts per milligram of Pt at the cathode at 105°C fueled with H2 and air, marking increases of 101 and 187%, respectively, compared with cells lacking the COF. [ABSTRACT FROM AUTHOR]

Flexible zinc‐air batteries are leading power sources for next‐generation smart wearable electronics. However, flexible zinc‐air batteries suffer from the highly‐corrosive safety risk and limited lifespan due to the absence of reliable solid‐state electrolytes (SSEs). Herein, a single‐anion conductive SSE with high‐safety is constructed by incorporating a highly amorphous dual‐cation ionomer into a robust hybrid matrix of functional carbon nanotubes and polyacrylamide polymer. The as‐fabricated SSE obtains dual‐penetrating ionomer‐polymer networks and hierarchical ionic highways, which contribute to mechanical robustness with 1200 % stretchability, decent water uptake and retention, and superhigh ion conductivity of 245 mS ⋅ cm−1 and good Zn anode reversibility. Remarkably, the flexible solid‐state zinc‐air batteries delivers a high specific capacity of 764 mAh ⋅ g−1 and peak power density of 152 mW ⋅ cm−2 as well as sustains excellent cycling stability for 1050 cycles (350 hours). This work offers a new paradigm of OH− conductors and broadens the definition and scope of OH− conductors. [ABSTRACT FROM AUTHOR]

Membrane capacitive deionization (MCDI) is an emerging water desalination platform that is compact, electrified, and does not require high‐pressure piping. Herein, highly conductive poly(phenylene alkylene) ion‐exchange membranes (IEMs) are micropatterned with different surface geometries for MCDI. The micropatterned membranes increase the interfacial area with the liquid stream leading to a 700 mV reduction in cell voltage when operating at constant current (2 mA cm−2; 2000 ppm NaCl feed) while improving the energy normalized adsorbed salt (ENAS) value by 1.4 times. Combining the micropatterned poly(phenylene alkylene) IEMs with poly(phenylene alkylene) ionomer‐filled electrodes reduces the cell voltage by 1000 mV and improves the ENAS values by 2.3 times relative to the base case. This reduction in cell voltage allows for higher current density operation (i.e., 3–4 mA cm−2). The reduction in cell voltage is ascribed to the ameliorating ohmic resistances related to ion transport at the membrane‐process stream interface and in the carbon cloth electrode. Finally, porous ionic conductors are implemented into the spacer channel with flat and micropatterned IEM configurations and ionomer infiltrated electrodes. For the configuration with flat IEMs, the porous ionic conductor improves ENAS values across the current density regime (2–4 mA cm−2), while for micropatterned IEMs it gets improved only at 4 mA cm−2. [ABSTRACT FROM AUTHOR]

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The catalyst layers (CLs) electrode is the key component of the membrane electrode assembly (MEA) in proton exchange membrane fuel cells (PEMFCs). Conventional electrodes for PEMFCs are composed of carbon-supported, ionomer, and Pt nanoparticles, all immersed together and sprayed with a micron-level thickness of CLs. They have a performance trade-off where increasing the Pt loading leads to higher performance of abundant triple-phase boundary areas but increases the electrode cost. Major challenges must be overcome before realizing its wide commercialization. Literature research revealed that it is impossible to achieve performance and durability targets with only high-performance catalysts, so the controllable design of CLs architecture in MEAs for PEMFCs must now be the top priority to meet industry goals. From this perspective, a 3D ordered electrode circumvents this issue with a support-free architecture and ultrathin thickness while reducing noble metal Pt loadings. Herein, we discuss the motivation in-depth and summarize the necessary CLs structural features for designing ultralow Pt loading electrodes. Critical issues that remain in progress for 3D ordered CLs must be studied and characterized. Furthermore, approaches for 3D ordered CLs architecture electrode development, involving material design, structure optimization, preparation technology, and characterization techniques, are summarized and are expected to be next-generation CLs for PEMFCs. Finally, the review concludes with perspectives on possible research directions of CL architecture to address the significant challenges in the future. [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]

Relative humidity (RH), platinum-to-carbon (Pt/C) ratio, and ionomer content considerably affect the mass and proton transport of proton exchange membrane fuel cells (PEMFCs), thereby affecting their performance and gas distribution quality. This study is the first to investigate the combined effects of the Pt/C ratio and RH on the performance and oxygen distribution uniformity of a graded ionomer cathode catalyst layer (CCL) with different average ionomer contents. The results show that all graded ionomer CCLs outperform the uniform CCL at a high Pt/C ratio of 0.55, regardless of the RHs and average ionomer contents. However, whether the graded ionomer CCL enhances or weakens the performance is mainly determined by the RH and the average ionomer content when the Pt/C ratio is reduced to 0.35. Specifically, when the Pt/C ratio is 0.35, the graded ionomer distributions exhibit inferior performance to the uniform CCL at a lower average ionomer content and lower RH owing to the larger ohmic loss. However, the impact of the concentration loss outweighs that of the ohmic loss, which is the main factor responsible for the superior performance of the graded ionomer distributions when the average ionomer content and RH are high. Besides, both a reduction in the Pt/C ratio and an increase in RH deteriorate the oxygen distribution uniformity of the graded ionomer CCLs with different average ionomer contents at medium and high current densities of operations. Moreover, the graded ionomer CCLs with low upstream ionomer contents achieve more uniform oxygen distributions than the opposite CCL structures at high current densities of operations under different RH values and average ionomer contents. [Display omitted] • Joint effect of Pt/C ratio and relative humidity on graded ionomer CCL is studied. • Graded ionomer CCL outperform uniform CCL at high Pt/C ratio. • Impact of graded ionomer on performance rely on relative humidity at low Pt/C ratio. • Reduce in Pt/C ratio and rise in relative humidity reduce gas distribution quality. • Graded ionomer CCL with low upstream ionomer gets more uniform oxygen distribution. [ABSTRACT FROM AUTHOR]

Designing suitable anion exchange ionomers is critical to improving the performance and in situ durability of anion exchange membrane water electrolyzers (AEMWEs) as one of the promising devices for producing green hydrogen. Herein, highly gas‐permeable and dimensionally stable anion exchange ionomers (QC6xBA and QC6xPA) are developed, in which bulky cyclohexyl (C6) groups are introduced into the polymer backbones. QC650BA‐2.1 containing 50 mol% C6 composition shows 16.6 times higher H2 permeability and 22.3 times higher O2 permeability than that of QC60BA‐2.1 without C6 groups. Through‐plane swelling of QC650BA‐2.1 decreases to 12.5% from 31.1% (QC60BA‐2.1) while OH− conductivity slightly decreases (64.9 and 56.2 mS cm−1 for QC60BA‐2.1 and QC650BA‐2.1, respectively, at 30 °C). The water electrolysis cell using the highly gas permeable QC650BA‐2.1 ionomer and Ni0.8Co0.2O in the anode catalyst layer achieves two times higher performance (2.0 A cm−2 at 1.69 V, IR‐included) than those of the previous cell using in‐house ionomer (QPAF‐4‐2.0) (1.0 A cm−2 at 1.69 V, IR‐included). During 1000 h operation at 1.0 A cm−2, the QC650BA‐2.1 cell exhibits nearly constant cell voltage with a decay rate of 1.1 µV h−1 after the initial increase of the cell voltage, proving the effectiveness of the highly gas permeable and dimensionally stable ionomer in AEMWEs. [ABSTRACT FROM AUTHOR]

The porous structures of the catalyst layer (CL) for proton exchange membrane (PEM) fuel cells were reconstructed using the sphere-based simulated annealing (SA) method, in which different carbon sphere diameters, carbon phase fractions, ionomer loadings, and porosities were achieved to simulate different samples. The pore-scale simulation model based on the random walk algorithm was developed to evaluate the tortuosity in the CL. The results show that the carbon phase fraction, particularly the carbon sphere diameter, significantly influences the tortuosities in both pores and ionomer. Larger carbon spheres contribute to tightening the solid phase and enlarging the pore size within the CL, thereby affecting the pore structure and the ionomer distribution. The tortuosity obtained from the random walk algorithm aligns well with those from pore-scale diffusion and flow simulations using the Lattice–Boltzmann method (LBM). The random walk algorithm has the highest efficiency of the three methods in calculating the tortuosity of the CL when the porosity is less than 0.2, demonstrating its wider applicability. This study further proposes formulas for predicting the tortuosities in both pores and ionomer, which are closer to actual CLs than empirical equations. In addition, the present work confirms that the structural randomness resulting from the reconstruction method used in this work has little effect on the tortuosity, indicating that a small number of reconstructed samples suffice for investigating transport processes in the CL. Overall, our research contributes to the prediction of the properties of real porous media in energy engineering. Practical Applications: This manuscript reports on the reconstruction of the catalyst layer in proton exchange membrane fuel cells using the simulated annealing method under some appropriate assumptions. A pore-scale simulation using a random walk algorithm was performed to compute the tortuosity both in the pores and in the ionomer, which is compared with pore-scale diffusion and flow simulations using the Lattice–Boltzmann method. A parametric study for several geometric parameters was carried out. Some conclusions are drawn from the results of the pore-scale simulations, and several formulas are proposed accordingly. This study helps to predict the tortuosity in the porous structure closer to the actual porous medium than the empirical equations. Meanwhile, the proposed tortuosity formulas improve the accuracy of the macroscopic models compared to using the assumed transmission parameter values. In addition, structural randomness analysis is explored, which will further reduce the workload in actual engineering calculations and improve computational efficiency. [ABSTRACT FROM AUTHOR]

A model for performance of an axially symmetric pore with the curved generatrix is developed. Oxygen transport along the pore axis and in the radial direction through a thin ionomer film separating the pore volume from the Pt/C surface is taken into account. A performance functional is formulated, and the Euler–Lagrange equation is solved numerically for an optimal pore shape. This shape is close to a cubic paraboloid converging toward the membrane. Polarization curves show superior performance of the optimal pore over the cylindrical pore of the same active (side) surface area. The results suggest the shape of optimal ionomer loading for low‐Pt electrodes. [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]

Like batteries, fuel cells provide an inherently clean source of energy with no adverse environmental impact during operation. The utilization of methanol as a fuel is advantageous: it has an energy density of about 6 kWh/kg, which is, much higher than that of other commercialized batteries. This review is focused on the core of a DMFC, i.e., the symmetric membrane, in particular on the block copolymers used for its preparation as an alternative to well-known Nafion. The synthesis of block copolymer ionomers based on different building block types, with special emphasis on the critical issue of methanol permeability and proton/methanol selectivity, as well as the effect of block length and crosslinking are described and discussed. [ABSTRACT FROM AUTHOR]

Electrostatic clutches offer electrically programmable control of system stiffness, providing significant advantages in various robotic and haptic applications. However, conventional dielectric‐based electrostatic clutches require high operating voltages, often surpassing several kilovolts, while most low‐voltage electro‐adhesives are unsuitable for electrostatic clutches due to their intrinsic tackiness, resulting in a low switching ratio and reversibility. Here, an electrostatic clutch based on ionomer heterojunctions on rigid electrodes, encased within soft elastomers, capable of switching the system stiffness more than 530‐fold at an operating voltage of just 1 V is presented. Under the reverse bias, the formation of an ionic double layer at the ionomer heterojunction interface enables strong electrostatic adhesion of stiff electrodes at low voltage, yet low tackiness of ionomers allows almost free sliding at the forward bias. The performance of these electrostatic clutches across various geometries and voltages based on the fracture mechanics model is explored. Within this framework, by adjusting the clutch compliance, a force capacity of 50 N cm−2, powered by a 1.5 V battery with an on/off ratio over 250 is achieved, outperforming the latest electrostatic clutches in operating voltage and switching ratio. [ABSTRACT FROM AUTHOR]

The composition and morphology of the cathode catalyst layer (CCL) have a significant impact on the performance and stability of polymer electrolyte membrane fuel cells (PEMFC). Understanding the primary degradation mechanism of the CCL and its influencing factors is crucial for optimizing PEMFC performance and durability. Within this work, we present comprehensive in-situ characterization data focused on cathode catalyst degradation. The dataset consists of 36 unique durability tests with over 4000 testing hours, including variations in the cathode ionomer to carbon ratio, platinum on carbon ratio, ionomer equivalent weight, and carbon support type. The applied accelerated stress tests were conducted with different upper potential limits and relative humidities. Characterization techniques including IV-curves, limiting current measurements, electrochemical impedance spectroscopy, and cyclic voltammetry were employed to analyse changes in performance, charge and mass transfer, and electrochemically active surface area of the catalyst. The aim of the dataset is to improve the understanding of catalyst degradation by allowing comparisons across material variations and provide practical information for other researchers in the field. [ABSTRACT FROM AUTHOR]

Ionomers are important to electrode function in energy conversion devices, such as fuel cells and electrolyzers, as the catalyst‐binding nanometer‐thick films under confinement, which compromises mass transport of species. Mitigating confinement effects is necessary for improved performance of polymer electrolyte fuel cells. Studies on perfluorosulfonic acid (PFSA) ionomers provided insights into origins of transport resistances, but limited improvements by current strategies necessitate a need for alternative chemistries to enhance film function. This work investigates new ionomers based on sidechain modifications of PFSA to tune local acidity and structure. Their application‐relevant properties (hydration, thermal‐transition) and nanomorphology are systematically characterized using environmental ellipsometry and grazing‐incidence X‐ray scattering, respectively, to develop chemistry‐structure‐property relationships in thin‐film motif (≤100 nm). Introducing acid sites to sidechains improves hydration and nano‐phase‐separation but reduce chain mobility. Replacing the hydrophilic end‐groups with hydrophobic perfluoro‐groups enhances mobility but disrupts phase‐separation. Although modifying sidechain functional groups alters ionomer‐substrate interactions (Pt/C), chemistry has greater influence on structure‐properties. Proton conductivity correlates with hydration, regardless of chemistry. This work improves the fundamental understanding of chemistry‐function relationships of ionomers by providing a novel means to independently control their side‐chain vs. end‐group and observe resulting effects on interfacial properties to modulate electrode function in electrochemical technologies. [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]

Cention N is an alkasite restorative material, containing alkaline fillers. Cention N is thought to be able to release hydroxyl ions, calcium, and fluoride ions, which can counteract an acidic pH. The goal of this research is to compare the antibacterial activity of Cention N with Glass Ionomer Fuji IX GP, and assure the results with pH findings. Ten cylindrical molds from each of the two groups--Cention N (alkasite) and Fuji IX (GIC): were examined. The specimens were infected with S. mutans, lactobacilli, and E. faecalis and put on agar plates at 37°C. Then at various periods, including 5, 10, 20, 30 minutes, 12, and 24 hours, the groups' growth inhibition zones' diameters were observed and studied after 48 hours. We used a 0.05 level of confidence to do one-way ANOVA and Tukey's HSD tests on the data. The results were validated using PH analyses. Antimicrobial activity against S. mutans, lactobacilli, and E. faecalis was considerably greater in Cention N compared to Fuji IX at 5, 10, 20, 30 minutes, and 12, 24 hours (P<0.05). Because of its ability to prevent caries, cention N might be a good substitute for glass ionomers. [ABSTRACT FROM AUTHOR]

In this manuscript, we explore the effect of pH on the selectivity of a hydrothermally synthesized nanostructured γ‐MnO2 electrocatalyst in the alkaline environment. Selectivity of electrodeposited γ‐MnO2 toward oxygen evolution reaction (OER) in 0.5 M NaCl at pH 12 has been demonstrated by Fujimura et al (Mat. Sci. Eng. A267 (1999) 254–259). Herein, we extend the pH region from pH 8.2 to pH 13 and demonstrate by thin‐film rotating disk electrode (RDE) method that the catalyst is selective toward the OER at current densities up to ca 15 mA/cm2 in the entire range of pH, if buffer is utilized to mitigate the effect of local pH. In synthetic seawater, at pH 8.2, the catalyst is not selective toward the OER. The analysis of the OER Tafel slopes at low current densities (<3 mA/cm2) shows that the slopes were not affected by pH in 0.5 M NaCl solutions, which suggests the same OER mechanism. At the same time, reaction rate decreased with decrease in pH. Nafion ionomer in the catalyst layer may adversely affect the catalyst's performance at pH ≤12 by limiting diffusion of OH− ions through the Nafion film. Catalyst layers need to be carefully designed to avoid negative effects of Nafion. [ABSTRACT FROM AUTHOR]

Glass ionomer cement (GIC) is composed of anionic polyacrylic acid and a silica-based inorganic powder. GIC is used as a filling material in the decayed cavity of the tooth; therefore, compatibility with the tooth tissue is essential. In the present study, we aimed to improve the histocompatibility of GIC by introducing nano-hydroxyapatite (nHA), a component of teeth, into a silica-based inorganic powder. CFAS-nHA was prepared by chemically bonding nanorod hydroxyapatite (nHA) to the surface of calciumfluoroaluminosilicate (CFAS). The synthesis of CFAS-nHA was confirmed using Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The prepared CFAS-nHA was mixed with polyacrylic acid and cured to prepare GIC containing nHA (GIC-nHA). Cytocompatibility tests of GIC-nHA and GIC were performed using osteoblasts. Osteoblast activity and bone formation ability were superior after GIC-nHA treatment than after control GIC treatment. This enhanced histocompatibility is believed to be due to the improvement of the biological activity of osteoblasts induced by the HA introduced into the GIC. Therefore, to enhance its compatibility with dental tissues, GIC could be manufactured by chemically bonding nHA to the surface of GI inorganic powder. [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]

Synthesiszing highly catalytically active and stable non noble metal oxygen evolution reaction (OER) catalysts with controlled coordination environments at room temperature and probing the relationship between coordination environments and active centers remain challenging. Herein, a series of monomeric particles composed of different coordination environments, Fe–(NH2)4–C, Fe–(NH2)3/OH–C, Fe–(NH2)/(OH)3–C and Fe–(NH2)2/(OH)2–C, were synthesized by means of the response of chitosan salt (HACC) ionomers to pH values in solution at room temperature. The experimental results show that the active center of amine catalysts enables them to exhibit enhanced performance with a low overpotential of 255 mV at 10 mA cm−2 maintaining favorable stability (only 1.3% loss of current density after 12 h) for the OER in a low amino coordination environment (Fe–NH2/(OH)3–C). Therefore, the selection of a suitable coordination environment is the key to the synthesis of efficient and highly stable ionomer-based catalysts. This work provides a practical reference for the design of efficient catalysts in the future. [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]

Perfluorosulfonated anionic ionomers are known for their robust ion conductivity and chemical and mechanical stability. However, the structure and transport property degradation of perfluorinated cationic polymers (PfCPs) are not well understood. Herein, we propose an ion-exchange strategy to identify the structural degradation, ion transport mechanisms, and architectural reformation of PfCPs. Particularly, we demonstrate that the utility of a –SO2–N+ strategy employing the Menshutkin reaction cannot yield reliable PfCPs and anion-exchange membranes, but can yield an unreliable zwitterionic intermediate (cations–anions molar ratio is approximately 7.6%). Moreover, the degradation products were efficiently reformed as proton exchange membranes (PEMs), and the as-reformed PEMs achieved an ion-exchange capacity (IEC) value (0.89 mmol g−1), meanwhile retaining more than 94.7% of their initial capacity. Furthermore, the fuel cell assembled with reformed PEMs displayed a power density of 0.91 Wcm−2 at 2.32 A cm−2, which was 90.1% of that of the robust perfluorosulfonic acid PEMs. Our combined findings shed some fresh light on the state of understanding of the structure–property relationship in PfCPs. [ABSTRACT FROM AUTHOR]

Continuously improving performance and reducing cost targets for oxygen evolution reaction (OER) drive a growing interest in optimizing functionalities of ionomer binders in catalyst layer. The actual properties of catalysts significantly depend on the applied ionomers. Herein, we systematically examine five perfluorinated acid ionomers binders for OER on IrO x catalysts, including four Aquivion® short side chain ionomers and a long side chain Nafion™. Electrochemical measurements indicate that a combination of short side chain and increased equivalent weight can facilitate OER due to the optimized ionomer-catalyst interactions. Meanwhile, ionomers impact on OER by adjusting mass transport behaviors rather than reaction pathways. The accelerated durability tests further reveal that the long side chain and higher equivalent weight can decrease activity losses from 50% to 28%, implying enhancement of long-term electrochemical stability. Therefore, combining the advanced ionomer chemistry with the interfacial science provides a new opportunity to facilitate OER for energy conversion and storage. [Display omitted] • Illustrating ionomer-dependent oxygen evolution well from interface science. • Short side chain and high equivalent weight facilitate acidic oxygen evolution. • Long side chain and high equivalent weight improve electrochemical stability. • Ionomer greatly impacts on interfacial mass transport but not reaction pathways. [ABSTRACT FROM AUTHOR]

Background: Zeolite can release antimicrobial silver ions in a targeted and controlled manner for an extended time, selectively inhibiting the growth of pathogenic oral bacteria when added to dental materials. The objective of this study was to investigate the effect of the addition of zeolite to silver-reinforced glass ionomer cement on the release of silver ions over time. Methods: Five concentrations of silver–zeolite (0%, 0.5%, 1%, 2%, 4% wt) were incorporated into silver-reinforced GIC in the form of 10 mm × 2 mm circular disks (n = 5). The disks were incubated in deionized water at 37 °C and ion release from the samples was measured at 1, 2, 7, and 30 days after immersion by inductively coupled atomic emission spectroscopy. Results: Incorporating silver–zeolite increased silver ion release from silver-reinforced GIC disks compared to the control disks (p < 0.05), while incorporating zeolite alone had no effect. Higher concentrations of added silver–zeolite resulted in increased silver ion release. Sustained silver ion release was observed for up to 30 days. Conclusion: Adding silver–zeolite to silver-reinforced GIC may enhance its extended antibacterial effect in the oral cavity. [ABSTRACT FROM AUTHOR]

The spin-lattice relaxation rates (R1) of fluorine nuclei in perfluorosulfonic acid (PFSA) ionomer membranes and their precursor solid perfluorosulfonyl fluoride (PFSF) were measured by fast field-cycling (FFC) NMR relaxometry. The XRD profiles of PFSA and PFSF are similar and show a characteristic peak, indicating the alignment of main chains. While the SAXS profiles of the PFSA membranes show two peaks, those of the solid PFSF lack the ionomer peak which is characteristic of hydrophilic side chains in the PFSA ionomer membranes. The Larmor frequency dependence of R1 obeys power law and the indices are dependent on the sample and temperature. The indices of the PFSA membranes change from −1/2 to −1 along with the Larmor frequency and temperature dependence decrease, which is consistent with the generalized defect diffusion model. Estimated activation energies are in good agreement with those obtained from dynamical mechanical analysis and dielectric spectroscopy, indicating the segmental motion of the backbones as the common origin of these observations. On the other hand, the index changes to −3/4 in the case of the PFSFs, which has been predicted by the reptation model. [ABSTRACT FROM AUTHOR]

Ensuring the stable operation of proton exchange membrane fuel cells is conducive to their real-world application. A promising direction for stabilizing electrodes is the stabilization of the ionomer via the formation of surface compounds with graphene. A comprehensive study of the (electrochemical, chemical, and thermal) stability of composites for fuel cell electrodes containing a modifying additive of few-layer graphene was carried out. Electrochemical stability was studied by cycling the potential on a disk electrode for 5000 cycles. Chemical stability was assessed via the resistance of the composites to H2O2 treatment using ion-selective potentiometry. Thermal stability was studied using differential thermal analysis. Composites were characterized by UV-Vis spectroscopy, Raman spectroscopy, EDX, and SEM. It was shown that graphene inhibits Nafion degradation when exposed to heat. Contrariwise, Nafion is corrosive to graphene. During electrochemical and chemical exposure, the determining change for carbon-rich composites is the carbon loss (oxidation) of the carbon material. In the case of carbon-poor composites, the removal of fluorine and sulfur from the Nafion polymer with their partial replacement by oxygen prevails. In all cases, the F/S ratio is stable. The dispersity of Nafion in a sample affects its chemical stability more than the G/Nafion ratio does. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study is to assess the micro-tensile bond strength and the mode of failure of a bioactive hybrid self-adhesive composite (Surefil one) under various dentin conditions. Methods: Thirty-two extracted human molar teeth were used to test the micro-tensile bond strength of Surefil one under different dentine conditions (no treatment, 37% phosphoric acid etching, and universal adhesive) in comparison with a resin-modified glass ionomer (RIVA). All restorations were light cure-bonded onto flat dentine and then sectioned into beams. Then, fractured specimens were observed under a light microscope to evaluate the mode of failure. Results: The Surefil one no-treatment group (NTG) exhibited the highest micro-tensile bond strength. Furthermore, there was no statistically significant difference observed between the Surefil one adhesive group (EAG) and the Surefil one acid etch group (EG). However, compared to other groups, the resin-modified glass ionomer (RIVA) produced the lowest results, which are statistically significant. Conclusion: Surefil one offers superior bond strength values when compared to resin-modified glass ionomers. Furthermore, Surefil one requires no dentin condition and has more straightforward clinical steps. [ABSTRACT FROM AUTHOR]

[Display omitted] Fe N C single atom catalysts (SACs) have attracted great interest due to their highly active FeN 4 sites. However, the pyrolysis treatment often leads to inevitable metal migration and aggregation, which reduces the catalytic activity. Moreover, due to the Fenton reaction caused by Fe N C in alkaline and acidic solutions, the presence of Fe and peroxide in electrodes may generate free radicals, resulting in serious degradation of the organic ionomer and the membrane. Herein, we report an original strategy of introducing Co single atoms into Fe N C catalysts, forming atomically dispersed bimetallic active sites (Fe Co NC) and improving the activity and stability of the catalyst. Benefiting from this strategy, Fe Co NC catalyst exhibits excellent oxygen reduction reaction (ORR) activity in alkaline media (E 1/2 = 0.88 V) and in acidic media (E 1/2 = 0.77 V). As the cathode of Zn-air battery (ZAB), Fe Co NC shows an excellent peak power density of 142.8 mW cm−2 and a specific capacity of 806.6 mAh/g Zn. This work provides a novel avenue to optimize and enhance the ORR performance of atomic dispersed Fe N C catalysts. [ABSTRACT FROM AUTHOR]

The hydration of perfluorinated sulfonic-acid ionomers is the most important phenomenon that determines their transport and electrical properties. To bridge the gap between the macroscopic electrical properties and the microscopic water-uptake mechanism, we investigated the hydration process of a Nafion membrane using ambient-pressure x-ray photoelectron spectroscopy (APXPS) from vacuum up to ∼90% relative humidity at room temperature. The O 1s and S 1s spectra provided a quantitative analysis of the water content (λ) and the transformation of the sulfonic acid group (–SO3H) to its deprotonated type (–SO3−) during the water-uptake process. Taking advantage of a specially designed two-electrode cell, the conductivity of the membrane was determined by electrochemical impedance spectroscopy before APXPS measurements with the same conditions, thereby establishing the connection between the electrical properties and the microscopic mechanism. By means of ab initio molecular dynamics simulations based on density functional theory, the core-level binding energies of O- and S-containing species in the Nafion + H2O system were obtained. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to compare the cell toxicity and biological characteristics of Ketac GIC (glass-ionomer cement), Nexus RMGIC (resin-modified glass-ionomer cement), and RelyX RC (resin cement) in human periodontal stem cells (PDSCs). Materials and Methods: To compare the effects of Ketac GIC, Nexus RMGIC, and RelyX RC on PDSCs, the cements were diluted from 1:2 to 1:8. PDSCs were then treated with the serially diluted cements with or without N-acetyl-cysteine (NAC), and cell survival was measured using water-soluble tetrazolium salt (WST-1) assay. Intracellular reactive oxygen species (ROS) was measured using 2',7'-dichlorofluorescin diacetate (DCFDA), and western blot analysis was performed to observe phosphorylation and activation of extracellular signal-regulated kinase (ERK) by Nexus RMGIC or RelyX RC. Results: Cell death and proliferation were dose-dependently reduced following Nexus RMGIC or RelyX RC treatment. In addition, Nexus RMGIC or RelyX RC showed an increase intracellular ROS generation compared to Ketac GIC. Pretreatment with NAC confirmed the suppression of cell toxicity and ROS generation induced by Nexus RMGIC or RelyX RC. Nexus RMGIC or RelyX RC activates ERK phosphorylation, not p38 phosphorylation, in PDSCs. Conclusion: This study showed that the treatment with Nexus RMGIC or RelyX generates intracellular ROS and cell death through the ERK signaling pathway in PDSCs. In contrast, these effects were not observed with Ketac GIC, indicating that resin-based materials may have cytotoxic and genotoxic effects on PDSCs. [ABSTRACT FROM AUTHOR]

Transport of ions through solid polymeric electrolytes (SPEs) involves a complicated interplay of ion solvation, ion-ion interactions, ion-polymer interactions, and free volume. Nonetheless, prevailing viewpoints on the subject promote a significantly simplified picture, likening ion transport in a polymer to that in an unstructured fluid at low solute concentrations. Although this idealized liquid transport model has been successful in guiding the design of homogeneous electrolytes, structured electrolytes provide a promising alternate route to achieve high ionic conductivity and selectivity. In this perspective, we begin by describing the physical origins of the idealized liquid transport mechanism and then proceed to examine known cases of decoupling between the matrix dynamics and ionic transport in SPEs. Specifically we discuss conditions for "decoupled" mobility that include a highly polar electrolyte environment, a percolated path of free volume elements (either through structured or unstructured channels), high ion concentrations, and labile ion-electrolyte interactions. Finally, we proceed to reflect on the potential of these mechanisms to promote multivalent ion conductivity and the need for research into the interfacial properties of solid polymer electrolytes as well as their performance at elevated potentials.