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To improve the stability of high-temperature water electrolysis, I prepared membrane electrode assemblies (MEAs) using a decal method and investigated their water electrolysis properties. Nafion 115 and crosslinked sulfonated polyphenylsulfone (CSPPSU) membranes were used. IrO2 was used as the oxygen evolution reaction (OER) catalyst, and Pt/C was used as the hydrogen evolution reaction (HER) catalyst. The conductivity of the CSPPSU membrane at 80 °C and 90% RH (relative humidity) is about four times lower than that of the Nafion 115 membrane. Single-cell water electrolysis was performed while measuring the current density and performing electrochemical impedance spectroscopy (EIS) at cell temperatures from 80 to 150 °C and the stability of the current density over time at 120 °C and 1.7 V. The current density of water electrolysis using Nafion 115 and CSPPSU membranes at 150 °C and 2 V was 1.2 A/cm2 for both. The current density of the water electrolysis using the CSPPSU membrane at 120 °C and 1.7 V was stable for 40 h. The decal method improved the contact between the CSPPSU membrane and the catalyst electrode, and a stable current density was obtained.

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Nafion membrane possesses good ionic conductivity and excellent mechanical stability, which can be used as electrolyte and separator of flexible supercapacitor. However, due to its solid-state structure, it is difficult for the Nafion membrane to permeate in solid-state electrode, which reduces electrochemical surface area, and increases interface resistance. The electrode materials need to be carefully designed to solve the above issues. In this study, Nafion doped polyaniline/graphene oxide composites were designed and synthesized as electrode materials to fabricate flexible supercapacitors based on Nafion membrane. The polyaniline utilization rate and the electrochemical surface area are improved by Nafion doping. In addition, the electrostatic interaction between polyaniline and Nafion can reduce the interface resistance. Graphene oxide can enhance the polyaniline electrochemical stability. The specific capacitances of flexible supercapacitor are 309 and 300F g−1 under flat and bent conditions (at 1 A/g), respectively, which are the maximum values among reported Nafion membrane-based supercapacitors. After 1000 cycles, the capacitance retention rate of supercapacitor with Nafion membrane is 87.2%, which is higher than that with H2SO4 electrolyte (83.0%). Therefore, the Nafion membrane-based flexible supercapacitor has widespread applications in electronic products because of its high performance and good cycling stability.

Understanding the corrosion of spent nuclear fuel is important for the development of long-term storage solutions. However, the risk of radiation contamination presents challenges for experimental analysis. Adapted from the system for analysis at the liquid–vacuum interface (SALVI), we developed a miniaturized uranium oxide (UO2)-attached working electrode (WE) to reduce contamination risk. To protect UO2 particles in a miniatured electrochemical cell, a thin layer of Nafion was formed on the surface. Atomic force microscopy (AFM) shows a dense layer of UO2 particles and indicates their participation in electrochemical reactions. Particles remain intact on the electrode surface with slight redistribution. X-ray photoelectron spectroscopy (XPS) reveals a difference in the distribution of U(IV), U(V), and U(VI) between pristine and corroded UO2 electrodes. The presence of U(V)/U(VI) on the corroded electrode surface demonstrates that electrochemically driven UO2 oxidation can be studied using these cells. Our observations of U(V) in the micro-electrode due to the selective semi-permeability of Nafion suggest that interfacial water plays a key role, potentially simulating a water-lean scenario in fuel storage conditions. This novel approach offers analytical reproducibility, design flexibility, a small footprint, and a low irradiation dose, while separating the α-effect. This approach provides a valuable microscale electrochemical platform for spent fuel corrosion studies with minimal radiological materials and the potential for diverse configurations. [ABSTRACT FROM AUTHOR]

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

Perfluorosulfonic acid Nafion membranes are widely used as an electrolyte in electrolysis processes and in fuel cells. Changing the preparation and pretreatment conditions of Nafion membranes allows for the optimization of their properties. In this work, a Nafion-NMP membrane with a higher conductivity than the commercial Nafion® 212 membrane (11.5 and 8.7 mS∙cm−1 in contact with water at t = 30 °C) and a comparable hydrogen permeability was obtained by casting from a Nafion dispersion in N-methyl-2-pyrrolidone. Since the ion-exchange capacity and the water uptake of these membranes are similar, it can be assumed that the increase in conductivity is the result of optimizing the Nafion-NMP microstructure by improving the connectivity of the pores and channels system. This leads to a 27% increase in the capacity of the membrane electrode assembly with the Nafion-NMP membrane compared to the Nafion® 212 membrane. Thus, the method of obtaining a Nafion membrane has a great influence on its properties and performance of fuel cells based on them. [ABSTRACT FROM AUTHOR]

Understanding the corrosion of spent nuclear fuel is important for the development of long-term storage solutions. However, the risk of radiation contamination presents challenges for experimental analysis. Adapted from the system for analysis at the liquid–vacuum interface (SALVI), we developed a miniaturized uranium oxide (UO2)-attached working electrode (WE) to reduce contamination risk. To protect UO2 particles in a miniatured electrochemical cell, a thin layer of Nafion was formed on the surface. Atomic force microscopy (AFM) shows a dense layer of UO2 particles and indicates their participation in electrochemical reactions. Particles remain intact on the electrode surface with slight redistribution. X-ray photoelectron spectroscopy (XPS) reveals a difference in the distribution of U(IV), U(V), and U(VI) between pristine and corroded UO2 electrodes. The presence of U(V)/U(VI) on the corroded electrode surface demonstrates that electrochemically driven UO2 oxidation can be studied using these cells. Our observations of U(V) in the micro-electrode due to the selective semi-permeability of Nafion suggest that interfacial water plays a key role, potentially simulating a water-lean scenario in fuel storage conditions. This novel approach offers analytical reproducibility, design flexibility, a small footprint, and a low irradiation dose, while separating the α-effect. This approach provides a valuable microscale electrochemical platform for spent fuel corrosion studies with minimal radiological materials and the potential for diverse configurations.

In this study, we performed small-angle X-ray scattering (SAXS) to investigate the structure of Nafion® membranes. The effect of freeze/thaw (F/T) cycles (from ambient temperature down to −40 °C) on the membrane nanostructure was considered for the first time. The SAXS measurements were taken for different samples: a commercial Nafion® 212 membrane swollen in water and methanol solution, and a water-swollen silica-modified membrane. The membrane structure parameters were obtained from the measured SAXS profiles using a model-dependent approach. It is shown that the average radius of water channels (Rwc) decreases during F/T cycles due to changes in the membrane structure as a result of ice formation in the pore volume after freezing. The use of water-methanol solution (methanol content of 20 vol.%) for the membrane soaking prevents changes in the membrane structure during F/T cycles compared to the water-swollen membrane. Modification of the membrane surface with silica (SiO2 content of 20 wt.%) led to a redistribution of water in the membrane volume and resulted in a decrease in Rwc. However, Rwc for the modified membrane did not decrease with the increasing number of F/T cycles due to the involvement of SiO2 in the sorption of membrane water and, therefore, the prevention of ice formation. [ABSTRACT FROM AUTHOR]

Layers on the surface of Nafion polymer membrane, which is used as an electrolyte in low-temperature fuel cells, are prepared by the ion-beam-assisted deposition (IBAD) of platinum as the main active metal and one of the rare-earth metals (Gd, Dy, Ho) as an activating additive. Metal deposition and mixing of the deposited layer with the substrate surface by accelerated (U = 5 kV) ions of the same metal are carried out in an experimental setup, respectively, from the neutral fraction of metal vapors and ionized plasma of a pulsed vacuum (p ~ 10–2 Pa) arc discharge. The composition of the formed layers is studied using scanning electron microscopy, energy-dispersive microanalysis, X-ray fluorescence spectroscopy, and Rutherford backscattering spectrometry. It is found that the resulting layers contained atoms of deposited metals, components of the polymer substrate material, and an oxygen impurity. Their thickness was ~30 nm, the content of each of the deposited metal atoms in the layers was ~n × 1015 cm–2. [ABSTRACT FROM AUTHOR]

To improve the stability of high-temperature water electrolysis, I prepared membrane electrode assemblies (MEAs) using a decal method and investigated their water electrolysis properties. Nafion 115 and crosslinked sulfonated polyphenylsulfone (CSPPSU) membranes were used. IrO 2 was used as the oxygen evolution reaction (OER) catalyst, and Pt/C was used as the hydrogen evolution reaction (HER) catalyst. The conductivity of the CSPPSU membrane at 80 °C and 90% RH (relative humidity) is about four times lower than that of the Nafion 115 membrane. Single-cell water electrolysis was performed while measuring the current density and performing electrochemical impedance spectroscopy (EIS) at cell temperatures from 80 to 150 °C and the stability of the current density over time at 120 °C and 1.7 V. The current density of water electrolysis using Nafion 115 and CSPPSU membranes at 150 °C and 2 V was 1.2 A/cm 2 for both. The current density of the water electrolysis using the CSPPSU membrane at 120 °C and 1.7 V was stable for 40 h. The decal method improved the contact between the CSPPSU membrane and the catalyst electrode, and a stable current density was obtained.

In this work, the effect on the physico-chemical properties of Nafion 117 membrane due to the treatment with HCl, H 2 SO 4 and HNO 3 was studied. Water uptake, crystallinity, proton conductivity and water dynamics were evaluated on treated and non-treated membranes. An increase in the water uptake and conductivity and a decrease in the crystallinity were observed in treated membranes in comparison with the untreated one. The water dynamics, studied by spin-spin NMR relaxometry, suggests that treated membranes have a more uniform channel size distribution. The treatment with HCl and HNO 3 showed higher conductivity and water uptake than H 2 SO 4. [Display omitted] • Modifications in the polymeric channel structure produced by acid treatment. • Changes in the water uptake, crystallinity and proton conductivity due to the acid treatment. • Dynamics of water molecules studied by NMR. [ABSTRACT FROM AUTHOR]

[Display omitted] The local mobility and diffusion of Li+, Na+, and Cs+ cations in Nafion 117 membrane were explored by 7Li, 23Na, and 133Cs spin relaxation and pulsed field gradient NMR techniques. It was shown that the macroscopic mass transfer of cations is controlled by ion motion near sulfonate groups. Lithium and sodium cations, whose hydrated energy is higher than the water hydrogen bond energy, are moving together with water molecules, but cesium cations possessing a low hydrated energy are jumping directly between the neighboring sulfonate groups. [ABSTRACT FROM AUTHOR]

In this work, we printed a Nafion precursor membrane by fused deposition modeling (FDM) rapid prototyping technology and further fabricated IPMCs by electroless plating. The ion-exchange capacity of the Nafion membrane was tested, and the morphology of IPMCs was observed. The electro-mechanical properties of IPMCs under AC voltage inputs were studied, and grasping experiments were performed. The results show that the Nafion membrane after hydrolysis has a good ion-exchange ability and water-holding capacity. SEM observed that the thickness of the IPMC’s electrode layer was about 400 nm, and the platinum layer was tightly combined with the substrate membrane. When using a square wave input of 3.5 V and 0.1 Hz, the maximum current of IPMCs reached 0.30 A, and the displacement and blocking force were 7.57 mm and 10.5 mN, respectively. The new fabrication process ensures the good driving performance of the printed IPMC. And two pieces of IPMCs can capture the irregular objects successfully, indicating the feasibility of printing IPMCs by FDM technology. This paper provides a new and simple method for the fabrication of three-dimensional IPMCs, which can be further applied in flexible grippers and soft robotics.

The development of depolarized electrodes may be considered as an improvement on economic and environmental aspects for the chemistry industry. In this regard, using a hydrogen depolarized anode (HDA) to produce protons from hydrogen oxidation could be coupled with a membrane process to concentrate valuable products. In particular, the actual standard anode used in a recent industrial lithium hydroxide electromembrane process could be replaced by an HDA. This change could lower the electric consumption and production costs. However, this evolution requires the development of an electro cell properly adaptable to the current process. In this study, we propose a proof of concept for this technology with a dedicated installation using a sulfuric acid electrolyte. Based on materials commonly used in the field of fuel cells, which share some fundamental aspects, a general understanding of hydrogen depolarized anodes will be presented. The goal is to develop an electro cell that allows anode monitoring to understand ADH operation and to compare different conditions. In this purpose, different measurements are combined to measure aspects of the ADH such as resistance, mass transfer, and kinetic overpotentials. The proposed architecture can successfully sustain the reaction at 4 kA m−1 with several mV overpotentials. But after several 10-h periods, anode operation deteriorates until reaction failure. The impact of water through the anode is identified as an important parameter to ensure long-term stability. The results obtained in this study are a first step in hydrogen depolarized anode development; they confirm the interest in this technology and identify various improvement pathways to continue its progress. Development of a dedicated electrochemical cell allows testing the ability of a hydrogen depolarized anode to convert hydrogen to protons. The use of materials inspired by fuel cell technology was successfully adapted to a hydrogen depolarized anode. Water migration appears as a key factor, and catalytic layer flooding has to be controlled to prevent cell failure. [ABSTRACT FROM AUTHOR]

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

Nowadays, CO2 electroreduction is gaining special interest as achieving net zero CO2 emissions is not going to be enough to avoid or mitigate the negative effects of climate change. However, the cost of CO2 electroreduction is still very high because of the low efficiency of conversion (around 20%). Therefore, it is necessary to optimize the reaction conditions. Thus, a miniaturized novel membrane reactor was designed and manufactured in this study, with a shorter distance between the electrodes and a reduced volume, compared with CNC-manufactured reactors, using novel stereolithography-based 3D printing. The reduced distance between the two electrodes reduced the electrical resistance and therefore lowered the overpotential necessary to trigger the reaction from −1.6 V to −1.2 V, increasing the efficiency. In addition, the reduction in the volume of the reactor increased the catalyst area/volume ratio, which also boosted the concentration of the products (from FE 18% to FE 21%), allowing their better identification. Furthermore, the smaller volume and reduced complexity of the reactor also improved the testing capacity and decreased the cost of experimentation. The novel miniaturized reactor can help researchers to perform more experiments in a cost/time-effective way, facilitating the optimization of the reaction conditions.

Nafion is a perfluorosulfonic acid polymer that is most commonly used in proton-exchange membrane fuel cells. The processes of pretreatment and formation of such membranes strongly affect their properties. In this work, dispersions of Nafion in various ionic forms and dispersing liquids (ethylene glycol, N,N-dimethylformamide, N-methyl-2-pyrrolidone and isopropyl alcohol–water mixtures in different ratios) were obtained and studied. Membranes fabricated by casting of the various dispersions were also studied. The effect of the nature of the dispersing liquid and the counterion on the properties of Nafion dispersions, the morphology of the polymer in the dispersions and the characteristics of the membranes obtained from them has been shown. Based on the overall results, it can be concluded that the use of perfluorosulfonic acid dispersions in aprotic polar solvents is advisable for obtaining membranes by the casting procedure. This is because it provides optimal polymer morphology in the dispersion, which leads to the formation of films with good selectivity, mechanical and transport properties. The performed investigations show the relationship between the composition of dispersions, the morphology of the polymer and the properties of the membranes formed from them by the casting procedure.

Perfluorosulfonic acid Nafion membranes are widely used as an electrolyte in electrolysis processes and in fuel cells. Changing the preparation and pretreatment conditions of Nafion membranes allows for the optimization of their properties. In this work, a Nafion-NMP membrane with a higher conductivity than the commercial Nafion® 212 membrane (11.5 and 8.7 mS∙cm−1 in contact with water at t = 30 °C) and a comparable hydrogen permeability was obtained by casting from a Nafion dispersion in N-methyl-2-pyrrolidone. Since the ion-exchange capacity and the water uptake of these membranes are similar, it can be assumed that the increase in conductivity is the result of optimizing the Nafion-NMP microstructure by improving the connectivity of the pores and channels system. This leads to a 27% increase in the capacity of the membrane electrode assembly with the Nafion-NMP membrane compared to the Nafion® 212 membrane. Thus, the method of obtaining a Nafion membrane has a great influence on its properties and performance of fuel cells based on them.

Nafion is one of the polymer materials used as polymer electrode membrane (PEM) for fuel cells. However, the electrochemical reaction and water management processes that occur at the catalyst layer affect the performance and degradation of the membrane in the fuel cell resulting in various degradation mechanisms. Understanding the degradation mechanisms of the Nafion membrane in operation, the anhydrous and electrochemical conditions in the fuel cell is highly a necessity as outlined in this review. This review further recommends that further improvement in the Nafion membrane can be made by fabrication and coating the Nafion membrane with materials that can withstand the electrochemical environment in the fuel cell. • Nafion ionion provides a substantial integral part of the PEMFC performance. • Fuel cell environment affects performance and degradation of Nafion. • Degradation mechanisms in Nafion can be identified through electrochemical tests. • The use of Nano-composite materials enhances the durability of Nafion ionion. [ABSTRACT FROM AUTHOR]

In this study, we performed small-angle X-ray scattering (SAXS) to investigate the structure of Nafion® membranes. The effect of freeze/thaw (F/T) cycles (from ambient temperature down to −40 °C) on the membrane nanostructure was considered for the first time. The SAXS measurements were taken for different samples: a commercial Nafion® 212 membrane swollen in water and methanol solution, and a water-swollen silica-modified membrane. The membrane structure parameters were obtained from the measured SAXS profiles using a model-dependent approach. It is shown that the average radius of water channels (Rwc) decreases during F/T cycles due to changes in the membrane structure as a result of ice formation in the pore volume after freezing. The use of water-methanol solution (methanol content of 20 vol.%) for the membrane soaking prevents changes in the membrane structure during F/T cycles compared to the water-swollen membrane. Modification of the membrane surface with silica (SiO2 content of 20 wt.%) led to a redistribution of water in the membrane volume and resulted in a decrease in Rwc. However, Rwc for the modified membrane did not decrease with the increasing number of F/T cycles due to the involvement of SiO2 in the sorption of membrane water and, therefore, the prevention of ice formation.

The influence of optimum UV ray exposure of pristine Nafion polymer membranes on the improvement of proton conductivity and hydrogen fuel cell performance has been examined. Nafion membranes with thickness 183 μm (117), 90 μm (1035), 50 μm (212) and 25 μm (211) were irradiated with ultraviolet rays with doses in the range 0–250 mJ cm−2 and their proton conductivities have been measured with standard method. The Nafion membranes have also been studied by measuring their water uptake, swelling-ratios and porosity using standard procedures. Hydrogen fuel cells with dual serpentine microchannels with active area 1.9 x 1.6 cm-2 were assembled with anode gas diffusion layer, Nafion membrane, cathode gas diffusion layer and other components. An external humidifier was used to humidify hydrogen for the fuel cell. The experimental Results have shown an increase in the value of Nafion proton conductivity with an optimum UV irradiation which depends on the thickness of Nafion membrane: the optimum doses for peak proton conductivity were 196mJ/cm−2 for Nafion 117, 190mJ/cm−2for Nafion 1035, 180mJ/cm−2 for Nafion 212 and 160mJ/cm−2 for Nafion 211. This enhancement of proton conductivity is because of the optimal photo-crosslinking of –SO 3 H groups in Nafion. This causes optimum pore-size in Nafion thereby facilitating increased proton-hopping between –SO 3 H sites in Nafion. Hydrogen fuel cells were developed with pristine as well as with optimal UV irradiated Nafion with thicknesses of 90 and 50 μm. The polarization plots obtained for these devices showed an increase in power densities approximately by a factor of 1.8–2.0 for devices with optimally UV irradiated Nafion. These results indicate that optimal UV irradiation of Nafion is an excellent technique for enhancing power output of hydrogen fuel cells. [Display omitted] • The optimum dose of UV rays on Nafion enhances proton conductivity. • Tuning of pores in Nafion membranes by UV ray irradiation. • Optimization of hydrogen humidification for better power output. • Optimum UV irradiation dose depends on the membrane thickness. [ABSTRACT FROM AUTHOR]

In this work, we printed a Nafion precursor membrane by fused deposition modeling (FDM) rapid prototyping technology and further fabricated IPMCs by electroless plating. The ion-exchange capacity of the Nafion membrane was tested, and the morphology of IPMCs was observed. The electro-mechanical properties of IPMCs under AC voltage inputs were studied, and grasping experiments were performed. The results show that the Nafion membrane after hydrolysis has a good ion-exchange ability and water-holding capacity. SEM observed that the thickness of the IPMC's electrode layer was about 400 nm, and the platinum layer was tightly combined with the substrate membrane. When using a square wave input of 3.5 V and 0.1 Hz, the maximum current of IPMCs reached 0.30 A, and the displacement and blocking force were 7.57 mm and 10.5 mN, respectively. The new fabrication process ensures the good driving performance of the printed IPMC. And two pieces of IPMCs can capture the irregular objects successfully, indicating the feasibility of printing IPMCs by FDM technology. This paper provides a new and simple method for the fabrication of three-dimensional IPMCs, which can be further applied in flexible grippers and soft robotics. [ABSTRACT FROM AUTHOR]

Removing iron, aluminum, and magnesium ions from the primary wet-process phosphoric acid solution (WPA) is a promising strategy for mitigating scaling in downstream processing. Here, Donnan dialysis using Nafion membranes, with HNO 3 as the stripping solution, was proposed and evaluated. The species in WPA as a function of temperature were modeled. The influence of HNO 3 molarity (1–5 M), temperature (25–65 °C), and Nafion membrane type on the metal ion mass transport was systematically studied. The effect of H 3 PO 4 molarity on the metal ion mass transport was analyzed with synthetic WPA solutions, considering the form (free cation or complexed with anions) in which these metal ions transport through the membrane by analyzing the ionic composition of membranes in equilibrium with WPA. The coupled cation diffusion coefficients in membranes are modeled via the Nernst - Planck flux equation. It is found that the cation flux always follows this order: J Mg > J Al > J Fe for WPA. These factors can be attributed to: 1) in WPA Mg appears mostly as Mg2+, while almost all Fe ions and around half the Al ions are in a paired state, giving the bulky Fe(H 2 PO 4)2+, Al(SO 4)+ and Al(SO 4) 2 -, respectively; 2) only solution viscosity influences the Mg2+ transport, while both the solution viscosity and the complexation with anions influence Fe and Al transport; 3) Mg2+ ions have the largest diffusion coefficient in the membrane phase. These metal ions transport in the form of free cations through the membranes. It is concluded that Donnan dialysis is suitable for removing the fast-diffusing Mg2+ ions from diluted WPA, and increasing the solution temperature could enhance the Mg2+ transport rate. [Display omitted] • Removing metal ions from wet-process phosphoric acid (WPA) solution. • Species of Fe, Al and Mg in WPA solution were modeled. • Ionic fluxes through membranes follow the order: Mg2+>Al3+>Fe3+. • Ion pairing and solution viscosity influence Fe, Al transport. • Donnan dialysis was effective for removing Mg2+ from WPA solution. [ABSTRACT FROM AUTHOR]

[Display omitted] Correlation times and diffusion coefficients of water molecules were measured for the first time by 1H spin relaxation and pulsed field gradient NMR in Li+, Na+ and Cs+ ionic forms of Nafion 117 membrane. Hydration numbers of Li+, Na+ and Cs+ cations were calculated. It was shown that at high humidity macroscopic transfer is controlled by the local translational motion of water molecules. [ABSTRACT FROM AUTHOR]

This work provides a comprehensive review on the incorporation of ionic liquid (ILs) into polymer blends and their utilization as proton exchanges membranes (PEM). Various conventional polymers that incorporate ILs are discussed, such as Nafion, poly (vinylidene fluoride), polybenzimidazole, sulfonated poly (ether ether ketone), and sulfonated polyimide. The methods of synthesis of IL/polymer composite membranes are summarized and the role of ionic liquids as electrolytes and structure directing agents in PEM fuel cells (PEMFCs) is presented. In addition, the obstacles that are reported to impede the development of commercial polymerized IL membranes are highlighted in this work. The paper concludes that the presence of certain ILs can increase the conductivity of the PEM, and consequently, enhance the performance of PEMFCs. Nevertheless, the leakage of ILs from composite membranes as well as the limited long-term thermal and mechanical stability are considered as the main challenges that limit the employment of IL/polymer composite membranes in PEMFCs, especially for high-temperature applications.

Summary: A double chamber microbial fuel cell (MFC) reactor with anode and cathode chamber separated by a Nafion proton exchange membrane was developed and performance was evaluated for treatment of electro Fenton pretreated latex processing and production wastewater containing chemical oxygen demand of 2660 and 780 mg L−1, respectively. After 12 days, MFC treatment, the COD reduced to 133 mg/L (96%) and 86 mg/L (88.5%) for latex processing and production wastewater respectively. The MFC treatment system generated electrical energy of 1.57 and 1.04 Wh L−1 for latex processing and production wastewaters respectively that was utilized to drive the electro‐Fenton reactor. These results indicated that effective wastewater treatment, energy production, and discharge standards could be obtained in the system. [ABSTRACT FROM AUTHOR]

We developed a new approach to attach particles onto a conductive layer as a working electrode (WE) in a microfluidic electrochemical cell with three electrodes. Nafion, an efficient proton transfer molecule, is used to form a thin protection layer to secure particle electrodes. Spin coating is used to develop a thin and even layer of Nafion membrane. The effects of Nafion (5 wt% 20 wt%) and spinning rates were evaluated using multiple sets of replicates. The electrochemical performance of various devices was demonstrated. Additionally, the electrochemical performance of the devices is used to select and optimize fabrication conditions. The results show that a higher spinning rate and a lower Nafion concentration (5 wt%) induce a better performance, using cerium oxide (CeO2) particles as a testing model. The WE surfaces were characterized using atomic force microscopy (AFM), scanning electron microscopy-focused ion beam (SEM-FIB), time-of-flight secondary ion mass spectrometry (ToF-SIMS), and X-ray photoelectron spectroscopy (XPS). The comparison between the pristine and corroded WE surfaces shows that Nafion is redistributed after potential is applied. Our results verify that Nafion membrane offers a reliable means to secure particles onto electrodes. Furthermore, the electrochemical performance is reliable and reproducible. Thus, this approach provides a new way to study more complex and challenging particles, such as uranium oxide, in the future.

[Display omitted] The modification of Nafion® membranes with poly(diallyldimethylammonium chloride) (PDDA) in aqueous solutions of isopropanol has been investigated. A remarkable decrease in vanadyl ion permeability (by 3.5 orders of magnitude), accompanied by a decrease in proton conductivity sixfold at most, was found for Nafion membranes modified in 30–35 wt% isopropanol solutions providing a high swelling of the membranes. The Bradford reagent has been used for the detection of PDDA on the membrane surface. [ABSTRACT FROM AUTHOR]

Microbial fuel cells (MFCs) are the most useful technologies for energy production and wastewater treatment due to their low cost and support of the environment. In this study, the membrane fouling and their effects on power generation were investigated using scanning electron microscope (SEM). Results demonstrate that proton exchange membrane (PEM) was affected by biofouling in a two-chamber H-type MFC, which would significantly affect coulombic efficiencies (CEs), and maximum power densities leading to reduced power generation. The power densities of both rice straw and potato peels were 119.35 mW/m2 and 152.55 mW/m2, respectively. Scanning Electron Microscope (SEM) showed substantial accumulation of bacteria and their end-products forming a thick biofilm on the surface of PEM leading to a decrease, if not, preventing the passage of protons from the anode side toward the cathode side. The decline in power generation may result mainly from the biofouling, not of electrodes but, of PEM membrane from both sides (Anode and Cathode) because of improper regular PEM cleaning. • Electricity generation from rice straw using microbial fuel cell technologies. • Characterization of membrane biofouling by SEM and other parameters. • Effect of biofouling on performance of long-term operation of MFC. • The biofouled membrane could be used after cleaning. [ABSTRACT FROM AUTHOR]

Zn2+, Cu2+, and Ni2+ ionic permeabilities through a Nafion 115 membrane, containing sulfonate functional groups capable of cation exchange with metal ions, were measured in this work. Single and binary salt mixtures were prepared at 10, 100, and 1000 ppm concentrations, and the ionic permeabilities and selectivities (α) were measured. The ionic permeabilities were in the 10−6–10−5 cm2/s range, and the order of ion permeability depends on the ionic concentration. At low (10 ppm) concentration, the smaller Ni2+ transported faster than the other two ions and the permeability was dominated by the ionic diffusivity. As the concentration was increased to 100 and 1000 ppm, the ion permeability was increased because more ions were exchanged onto the sulfonate groups. Moreover, Zn2+ became the fastest ion among the three as the ion transport became solubility-controlled at the medium and high concentrations. In spite of the ion permeability order being dependent upon the feed concentration, the separation selectivity was not affected by the presence of co-ions in the tested conditions. The separation selectivity from a binary mixture could be estimated from the permeability ratio obtained from single solutions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nafion doped polyaniline/graphene oxide composites are synthesized for the first time and used as the electrode materials of supercapacitors. • Polyaniline utilization rate and electrochemical surface area are improved by Nafion doping in the Nafion membrane-based supercapacitors. • Graphene oxide can enhance the electrochemical stability of polyaniline in the Nafion doped polyaniline/graphene oxide composites. • Flexible supercapacitor shows 300F g−1 at bent condition, which is the maximum value among reported Nafion membrane-based supercapacitors. • After 1000 cycles, the capacitance retention rate of the composites is 83.0%, which is higher than that of Nafion doped polyaniline (72.1%). Nafion membrane possesses good ionic conductivity and excellent mechanical stability, which can be used as electrolyte and separator of flexible supercapacitor. However, due to its solid-state structure, it is difficult for the Nafion membrane to permeate in solid-state electrode, which reduces electrochemical surface area, and increases interface resistance. The electrode materials need to be carefully designed to solve the above issues. In this study, Nafion doped polyaniline/graphene oxide composites were designed and synthesized as electrode materials to fabricate flexible supercapacitors based on Nafion membrane. The polyaniline utilization rate and the electrochemical surface area are improved by Nafion doping. In addition, the electrostatic interaction between polyaniline and Nafion can reduce the interface resistance. Graphene oxide can enhance the polyaniline electrochemical stability. The specific capacitances of flexible supercapacitor are 309 and 300F g−1 under flat and bent conditions (at 1 A/g), respectively, which are the maximum values among reported Nafion membrane-based supercapacitors. After 1000 cycles, the capacitance retention rate of supercapacitor with Nafion membrane is 87.2%, which is higher than that with H 2 SO 4 electrolyte (83.0%). Therefore, the Nafion membrane-based flexible supercapacitor has widespread applications in electronic products because of its high performance and good cycling stability. [ABSTRACT FROM AUTHOR]

The development and the photophysical behavior of a transparent ion-exchange membrane based on a pH-sensitive polypyridyl ruthenium(II) complex, [(bpy)2RuII(H2bpib)RuII(bpy)2](ClO4)4 (bpy = 2,2′-bipyridine, H2bpib = 1,4-bis([1,10]phenanthroline[5,6-d]-imidazol-2-yl)benzene), are experimentally and theoretically reported. The emission spectra of [(bpy)2RuII(H2bpib)RuII(bpy)2]@Nafion film were observed between pH 2 and pH 11 and showed the highest relative emission intensity at pH 5 (λmaxem = 594.4 nm). The relative emission intensity of the film significantly decreased down to 75% at pH 2 and 11 compared to that of pH 5. The quantum yields (Φ) and lifetimes (τ) showed similar correlations with respect to pH, Φ = 0.13 and τ = 1237 ns at pH 5, and Φ = 0.087 and τ = 1014 ns and Φ = 0.069 and τ = 954 ns at pH 2 and pH 11, respectively. These photophysical data are overall considerably superior to those of the solution, with the radiative- (kr) and non-radiative rate constants (knr) at pH 5 estimated to be kr = 1.06 × 105 s−1 and knr = 7.03 × 105 s−1. Density functional theory calculations suggested the contribution of ligand-to-ligand- and intraligand charge transfer to the imidazolium moiety in Ru-H3bpib species, implying that the positive charge on the H3bpib ligand works as a quencher. The Ru-Hbpib species seems to enhance non-radiative deactivation by reducing the energy of the upper-lying metal-centered excited state. These would be responsible for the pH-dependent “off-on-off” emission behavior.

Abstract “Carbon-based material” has demonstrated a great potential on water purification due to its strong physical adsorption to organic pollutants in the water. Three-dimensional cubic ordered mesoporous carbon (CMK-8), one of the well-known ordered mesoporous carbons, was prepared by using nanocasting method with mesoporous silica (KIT-6) as the template. In this study, CMK-8 blended with Nafion polymer to form a free-standing mesoporous CMK-8-Nafion composite membrane. The synthesis of high crystallinity CMK-8 was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). More than 80% methyl orange (MO) removal efficiency was observed under 254-nm UV irradiation after 120 min. Ninety-two percent recycling performance was remained after four recycling tests, which indicated a reliable servicing lifetime for the water purification. Furthermore, an additional layer of plasmonic silver nanoparticles (Ag NPs) was integrated into this CMK-8-Nafion membrane for higher pollutant removal efficiency, attributing from the generation of plasmon-resonance hot electrons from Ag NPs. A 4-in. CMK-8-Nafion composite membrane was also fabricated for the demonstration of potential large-scale utilization.

Porous IrO2/Ti/IrO2 catalyst electrodes were obtained by coating IrO2 on both sides of three types of porous Ti powder sheets (sample 1, sample 2, and sample 3) using different surface treatment methods, and a hydrogen evolution catalyst electrode was obtained by coating Pt/C on carbon gas diffusion layers. A Nafion115 membrane was used as an electrolyte for the membrane electrode assemblies (MEA). Water electrolysis was investigated at cell temperatures up to 150 °C, and the electrical characteristics of the three types of porous IrO2/Ti/IrO2 catalyst electrodes were investigated. The sheet resistance of sample 1 was higher than those of samples 2 and 3, although during water electrolysis, a high current density was observed due to the nanostructure of the IrO2 catalyst. In addition, the structural stabilities of Nafion and Aquivion membranes up to 150 °C were investigated by using small angle X-ray scattering (SAXS). The polymer structures of Nafion and Aquivion membranes were stable up to 80 °C, whereas the crystalline domains grew significantly above 120 °C. In other words, the initial polymer structure did not recover after the sample was heated above the glass transition temperature.

Here we introduce the new approach to high-efficiency power generation from a salinity difference using conventional nanoporous Nafion membrane. When access areas on each side of nanoporous Nafion membrane are set to be asymmetric, the ratio of ionic current upon a voltage bias of the different polarity also becomes asymmetric, resulting in ionic diode phenomena. When this geometrical ionic diode effect is combined with a salinity gradient, it can help significantly improve the energy conversion efficiency from a salinity difference even under a hyper-saline environment with a large salinity difference, e.g. ∼41% conversion efficiency and ∼120 nW power generation with 1 M KCl and 1000-fold salinity difference, both of which are comparable with the best performances reported in the previous studies. We propose that the decrease in ion concentration polarization at a low salt concentration side is responsible for the enhanced power generation with the membrane having asymmetric access areas. Our approach is simple to implement and can be applicable to any nanoporous membrane to enhance the power generation from a salinity difference. [ABSTRACT FROM AUTHOR]

Sulfonated covalent organic nanosheets (SCONs) with a functional group (−SO 3 H) are effective at reducing ion channels length and facilitating proton diffusion, indicating the potential advantage of SCONs in application for proton exchange membranes (PEMs). In this study, Nafion-SCONs composite membranes were prepared by introducing SCONs into a Nafion membrane. The incorporation of SCONs not only improved proton conductivity, but also suppressed methanol permeability. This was due to the even distribution of ion channels, formed by strong electrostatic interaction between the well dispersed SCONs and Nafion polymer molecules. Notably, Nafion-SCONs-0.6 was the best choice of composite membranes. It exhibited enhanced performance, such as high conductivity and low methanol permeability. The direct methanol fuel cell (DMFC) with Nafion-SCONs-0.6 membrane also showed higher power density (118.2 mW cm−2), which was 44% higher than the cell comprised of Nafion membrane (81.9 mW cm−2) in 2 M methanol at 60 °C. These results enabled us to work on building composite membranes with enhanced properties, made from nanomaterials and polymer molecules. Image 1 • Nanosheets with high proton conductivity were incorporated into Nafion membrane. • Composite membranes showed enhanced proton conductivity and reduced methanol crossover. • Composite membrane showed high power density in fuel cell testing. [ABSTRACT FROM AUTHOR]

Bioelectrochemical systems are devices where organic matter (e.g. wastewater) is oxidized through exoelectrogenic bacteria; this process is a new alternative to energy crisis and to mitigate climate change. If the products of such oxidation are electrons they are called microbial fuel cell (MFC), otherwise if the product is hydrogen these devices are called microbial electrolysis cells (MEC) Mostly, MEC's studies have reported double chamber designs, where the anode and cathode are separated by an ion exchange membrane. Nafion is a proton exchange membrane widely used to study bioelectrochemical devices; however, to our knowledge there are no reports of bipolar membranes (BPM) in these systems. In this study, a double-chambered MEC was constructed to evaluate the performance of the system using Nafion® 117, and FUMASEP® FBM bipolar membrane, separately. Biofilm formation was monitored by cyclic voltammetry and open circuit potential (OCP); maximum power for MFC-Nafion and MFC-BPM were 105.1 and 3.6 mW/m2, respectively. Hydrogen yield and COD removal were significantly different for both MEC systems. Whereas COD removal for MEC-BPM was 44.8%; MEC-Nafion exhibited a COD removal of 87.4%. Solely the latter system produced hydrogen, with a yield of 7.6%. • Wastewater used as substrate with minimum pretreatment and conditioning. • Nafion 117 exhibited a lower internal resistance compared to BPM. • COD removal of the MEC-Nafion system was almost double the MEC-BPM. • Up to 4 mL*L−1*d−1 were solely produced in the MEC-Nafion system. [ABSTRACT FROM AUTHOR]

Nanoheterostructured material composed of sepiolite clay mineral in which is assembled a MgAl layered double hydroxide (LDH) was used in the preparation of Nafion composite electrolyte membranes and their behavior compared to those of membranes filled with the LDH alone. Both, the neat MgAl LDH and the MgAl LDH-sepiolite hybrid materials were obtained via the co-precipitation method. Sepiolite fibers provide a large external surface area for bonding MgAl LDH particles while maintaining high microporosity and water molecules. The nanocomposite membranes were prepared incorporating different amount of LDH or LDH-sepiolite hybrid. Composite membranes present better water retention, good thermal properties and high proton conductivities at high temperatures than the pure Nafion membrane. The proton conductivity at 100 °C and 100% RH reaches a value of 0.13 S/cm for the LDH-sepiolite Nafion membrane whereas is only 0.010 S/cm in the case of the Nafion membrane. Fuel cell tests using Nafion membranes containing LDH or LDH-sepiolite hybrid as composite electrolytes show a good result for the operation of the PEMFC at 80 °C, 100 °C and 110 °C, with a clear favoring effect of the LDH-sepiolite filler for operation at the highest temperatures. • Incorporation of LDH (MgAl) and hybrid MgAl-sepiolite in Nafion membrane. • Improved properties of Nafion membrane; water retention and proton conductivity. • Fuel cells performance of the composite membranes at high temperature. [ABSTRACT FROM AUTHOR]

Abstract The isotopic composition of water (2H/1H and 18O/16O) has been widely used in hydrology, ecology, paleoclimatology and forensic science. However, sampling frequency limits many such studies and there is now a clear need for field-portable mass spectrometer and laser-based spectrometer devices to measure water isotopic composition in-situ and at high temporal resolution. Here we explore the use of Nafion membranes as a potential Membrane Introduction (MI) inlet system for high frequency isotope analysis. As yet, the fractionation behaviour of 2H/1H and 18O/16O isotopic ratios in water transported through Nafion membranes has not been investigated. We quantify this behaviour for water samples with different matrices (organic matter and pollutants) and salinity concentrations across a wide range of isotopic ratios and different membrane thicknesses. Nafion membranes showed no fractionation effects on reported isotope ratios for natural waters. Also no fractionation effects were detected with salinity. Membrane thickness affected slightly the precision and accuracy of the isotopic ratio analysis and our tests showed that thinner Nafion membranes provide better results. However, for samples contaminated with organic matter, the thicker membranes performed better for the 2H/1H isotopic ratio, while for samples contaminated with pollutants, the thicker membranes performed better for the 18O/16O isotopic ratio. Overall, Nafion membranes appear well suited to MI inlet use and our work suggests that the optimal Nafion membrane thickness is 50–150 µm. Highlights • Fractionation of O and H stable isotopes in water through the use of Nafion membranes was examined. • Influence of matrices (organic matter, pollution) on isotopic fractionation was studied. • There was no influence of water salinity on isotopic fractionation. • The use of Nafion membranes as inlet for in-line monitoring of O and H stable isotopes in water is convenient. [ABSTRACT FROM AUTHOR]

Abstract Nafion series cation exchange membranes are extensively investigated and applied in proton exchange membrane fuel cells and flow battery technologies because of their excellent stability and easy availability. However, a deep understanding of their ions transport mechanism and behavior under the alkaline based flow battery media is very limited. Here, the ion transport mechanism through Nafion membrane under alkaline medium is investigated by small-angle X-ray scattering and atomic force microscope techniques. The results indicate that a membrane showed a higher degree of phase separation and larger cluster radius in a NaOH solution than those in a KOH solution, which endows the membrane with a much higher ion conductivity in the NaOH solution. Density functional theory-based simulation also indicates that the adsorption and desorption between the Na+ and the –SO 3 - in Nafion is faster than those of K+. Inspired by these results, an alkaline zinc iron flow battery with a Nafion 212 membrane using NaOH as the supporting electrolyte exhibits a coulombic efficiency of ~ 99% and an energy efficiency of ~ 86% at 80 mA cm−2. This work offers insights into ways to obtain an improved battery performance for the existing as well as the emerging alkaline based flow battery technologies. Graphical abstract fx1 Highlights • Ions transfer behavior and mechanism in Nafion under alkaline media are clarified. • The ions transfer in Nafion is studied via experimental and computational method. • Nafion membrane shows higher ion conductivity in NaOH than those in KOH solution. • A battery using NaOH as supporting electrolyte shows an EE of ~ 86% at 80 mA cm−2. [ABSTRACT FROM AUTHOR]

Ionic electroactive polymer (IEAP) actuators have received interest because of their advantageous properties, including their large displacement, high energy density, light weight, and low power consumption under a low electric field. However, they have a low blocking force under driving, and it is difficult to control the thickness of the ionic polymer membrane. In this study, an IEAP actuator is fabricated using a Nafion membrane with added multiwalled carbon nanotubes to increase the blocking force. A heat press two-step process is also developed to produce a constant and uniform membrane. The fabricated Nafion membrane with 0.2 wt% multiwalled carbon nanotubes has the largest displacement and highest blocking force. As a result, the developed heat press two-step method can be used in various polymer-casting fields, and the fabricated carbon nanotube-based IEAP actuators can serve as useful references in fields such as flexible robotics and artificial muscles.