Ce-radical Scavenger-Based Perfluorosulfonic Acid Aquivion® Membrane for Pressurised PEM Electrolysers.

A Ce-radical scavenger-based perfluorosulfonic acid (PFSA) Aquivion® membrane (C98 05S-RSP) was developed and assessed for polymer electrolyte membrane (PEM) electrolyser applications. The membrane, produced by Solvay Specialty Polymers, had an equivalent weight (EW) of 980 g/eq and a thickness of 50 µm to reduce ohmic losses at a high current density. The electrochemical properties and gas crossover through the membrane were evaluated upon the formation of a membrane-electrode assembly (MEA) in a range of temperatures between 30 and 90 °C and at various differential pressures (ambient, 10 and 20 bars). Bare extruded (E98 05S) and reinforced (R98 05S) PFSA Aquivion® membranes with similar EWs and thicknesses were assessed for comparison in terms of their performance, stability and hydrogen crossover under the same operating conditions. The method used for the membrane manufacturing significantly influenced the interfacial properties, with the electrodes affecting the polarisation resistance and H2 permeation in the oxygen stream, as well as the degradation rate, as observed in the durability studies.

Superacid Resin-Based Heterogeneous Catalysts for the Selective Acylation of 1,2-Methylenedioxybenzene.

In this work, we firstly report on the use of highly active and selective Aquivion superacid resins as heterogeneous catalysts for the acylation of 1,2-methylenedioxybenzene (MDB) with propionic anhydride (AP). The reaction was investigated and optimized using solvent-free conditions to selectively produce 3,4-methylenedioxypropiophenone (MDP1P), a key intermediate for the manufacture of active ingredients used in insecticide formulations with a volume of production of roughly 3000 t/y. Interestingly, Aquivion-based catalysts allows to work in mild reaction conditions (i. e. 80 °C), obtaining MDP1P yields as high as 44 % after only 1 h of reaction (selectivity 83 %). A detailed study of the AP reactivity demonstrated its tendency to promote oligomerization reactions that, as confirmed by ex-situ and in-situ FT-ATR analyses, caused the deactivation of the catalyst forming surficial carbonaceous residues. In this context, a fast oxidation of the resin surface organic residues using a diluted HNO3 (or H2 O2 ) solution was proven to be an efficient method to regenerate the catalyst, which can be reused for several reaction cycles. The results obtained in preliminary scale-up tests were basically unaffected by the reaction volume (up to 800 mL), paving the way for possible future applications of the process.

Improving PFSA Membranes Using Sulfonated Nanodiamonds.

Aquivion®-type perfluorosulfonic acid membranes with a polytetrafluoroethylene backbone and short side chains with sulfonic acid groups at the ends have great prospects for operating in hydrogen fuel cells. To improve the conducting properties of membranes, various types of nanofillers can be used. We prepared compositional Aquivion®-type membranes with embedded detonation nanodiamond particles. Nanodiamonds were chemically modified with sulfonic acid groups to increase the entire amount of ionogenic groups involved in the proton conductivity mechanism in compositional membranes. We demonstrated the rise of proton conductivity at 0.5-2 wt.% of sulfonated nanodiamonds in membranes, which was accompanied by good mechanical properties. The basic structural elements, conducting channels in membranes, were not destroyed in the presence of nanodiamonds, as follows from small-angle neutron scattering data. The prepared compositional membranes can be used in hydrogen fuel cells to achieve improved performance.

Effect of Dispersing Solvents for an Ionomer on the Performance of Copper Catalyst Layers for CO2 Electrolysis to Multicarbon Products.

To explore the effects of solvent-ionomer interactions in catalyst inks on the structure and performance of Cu catalyst layers (CLs) for CO2 electrolysis, we used a "like for like" rationale to select acetone and methanol as dispersion solvents with a distinct affinity for the ionomer backbone or sulfonated ionic heads, respectively, of the perfluorinated sulfonic acid (PFSA) ionomer Aquivion. First, we characterized the morphology and wettability of Aquivion films drop-cast from acetone- and methanol-based inks on flat Cu foils and glassy carbons. On a flat surface, the ionomer films cast from the Aquivion and acetone mixture were more continuous and hydrophobic than films cast from methanol-based inks. Our study's second stage compared the performance of Cu nanoparticle CLs prepared with acetone and methanol on gas diffusion electrodes (GDEs) in a flow cell electrolyzer. The effects of the ionomer-solvent interaction led to a more uniform and flooding-tolerant GDE when acetone was the dispersion solvent (acetone-CL) than when we used methanol (methanol-CL). As a result, acetone-CL yielded a higher selectivity for CO2 electrolysis to C2+ products at high current density, up to 25% greater than methanol-CL at 500 mA cm-2. Ethylene was the primary product for both CLs, with a Faradaic efficiency for ethylene of 47.4 ± 4.0% on the acetone-CL and that of 37.6 ± 5.5% on the methanol-CL at a current density of 300 mA cm-2. We attribute the enhanced C2+ selectivity of the acetone-CL to this electrode's better resistance to electrolyte flooding, with zero seepage observed at tested current densities. Our findings reveal the critical role of solvent-ionomer interaction in determining the film structure and hydrophobicity, providing new insights into the CL design for enhanced multicarbon production in high current densities in CO2 electrolysis processes.

Electrochemical Performance of Symmetric Solid-State Supercapacitors Based on Carbon Xerogel Electrodes and Solid Polymer Electrolytes.

For the development and optimization of solid-state symmetrical supercapacitors, herein, we propose using carbon-based electrodes and sodium- and lithium-form Aquivion electrolyte membranes, which serve as the separator and electrolyte. Carbon xerogels, synthesized using microwave-assisted sol-gel methodology, with designed and controlled properties were obtained as electrode materials. Commercial activated carbon (YP-50F, "Kuraray Europe" GmbH) was used as the active material for comparison. Notably, the developed solid-state symmetrical supercapacitors provide sufficiently high specific capacitances of 105-110 F g-1 at 0.2 A g-1, along with an energy density of 4.5 Wh kg-1 at 300 W kg-1, and a voltage window of 0-1.2 V in aqueous environments, also demonstrating an excellent cycling stability for up to 10,000 charge/discharge cycles. These results can demonstrate the potential applications of carbon xerogel as the active electrode material and cation exchange membrane as the electrolyte in the development of solid-state supercapacitor devices.

Perfluorosulfonic Acid Membranes with Short and Long Side Chains and Their Use in Sensors for the Determination of Markers of Viral Diseases in Saliva.

The development of accessible express methods to determine markers of viral diseases in saliva is currently an actual problem. Novel cross-sensitive sensors based on Donnan potential with bio-comparable perfluorosulfonic acid membranes for the determination of salivary viral markers (N-acetyl-L-methionine, L-carnitine, and L-lysine) were proposed. Membranes were formed by casting from dispersions of Nafion or Aquivion in N-methyl-2-pyrollidone or in a mixture of isopropyl alcohol and water. The influence of the polymer equivalent weight and the nature of dispersing liquid on water uptake, ion conductivity, and slope of Donnan potential for the membranes in H+ and Na+ form was investigated. The varying of the sorption and transport properties of perfluorosulfonic acid membranes provided a change in the distribution of the sensor sensitivity to N-acetyl-L-methionine, L-carnitine, and L-lysine ions, which was necessary for multisensory system development. The simultaneous determination of three analytes, and the group analysis of them in artificial saliva solutions, was performed. The errors of N-acetyl-L-methionine and L-carnitine determination were 4-12 and 3-11%, respectively. The determination of L-lysine was complicated by its interaction with Ca2+ ions. The error of the group analysis was no greater than 9%. The reverse character of the viral markers' sorption by the membranes provided long-term sensor operation.

Aquivion perfluorosulfonic superacid as an effective catalyst for selective epoxidation of vegetable oils.

The acid-promoted epoxidation of vegetable oils was studied using a variety of acidic ion exchange resins as heterogeneous acid catalysts. Quantitative and selective epoxidation of a series of vegetable oils with different composition of saturated, mono-, di- and tri-unsaturated fatty acids was obtained upon identification of the more efficient catalyst and experimental conditions. Furthermore, optimized reaction conditions were successfully applied to the epoxidation of a waste cooking oil, thus extending our procedure to the valorization of a biowaste, an area of increasing importance within a more sustainable society. The use of quantitative 1HNMR besides making accurate evaluation of the amounts of reagents to be employed and of the selectivity, allowed facile and rapid quantification of mono-, di- and tri-epoxides, thus providing an indirect indication on the fatty acid composition of the vegetable oils, even in the presence of very low quantities of linolenic acid.

Permeation of Ternary Mixture Containing H2S, CO2 and CH4 in Aquivion® Perfluorosulfonic Acid (PFSA) Ionomer Membranes.

Aquivion® E87-12S Perfluorosulfonated acid ionomer material (PFSA) has been studied as a membrane technology for natural gas sweetening from CO2, H2S due to its interesting chemical and mechanical stability and good separation performance for polar compounds in humid environments. In the present work, permeation of the H2S/CO2/CH4 ternary mixture in this short-side PFSA chain was investigated at pressures up to 10 bar, temperatures up to 50 °C, and in a range of relative humidity (RH) from 20% to 90%. The results obtained confirm the strong dependence of Aquivion® on water activity and temperature, and its ability to separate gases based on their water solubility without substantial differences between pure and mixed gas experiments. Indeed, even when tested in ternary mixture, the permeation behavior remains similar to that observed for pure components and binary mixtures. In particular, the permeability of H2S is higher than that of CO2 and methane CH4, reaching values of 500 Barrer at 50 °C and 80% RH, against 450 and 23 Barrer for the other two gases respectively. Additionally, when tested at higher pressures of up to 10 bar under humid conditions, the membrane properties remained largely unchanged, thus confirming the overall stability and durability of Aquivion® E87-12S in acid environments.

New Generation of Compositional Aquivion®-Type Membranes with Nanodiamonds for Hydrogen Fuel Cells: Design and Performance.

Compositional proton-conducting membranes based on perfluorinated Aquivion®-type copolymers modified by detonation nanodiamonds (DND) with positively charged surfaces were prepared to improve the performance of hydrogen fuel cells. Small-angle neutron scattering (SANS) experiments demonstrated the fine structure in such membranes filled with DND (0-5 wt.%), where the conducting channels typical for Aquivion® membranes are mostly preserved while DND particles (4-5 nm in size) decorated the polymer domains on a submicron scale, according to scanning electron microscopy (SEM) data. With the increase in DND content (0, 0.5, and 2.6 wt.%) the thermogravimetric analysis, potentiometry, potentiodynamic, and potentiotatic curves showed a stabilizing effect of the DNDs on the operational characteristics of the membranes. Membrane-electrode assemblies (MEA), working in the O2/H2 system with the membranes of different compositions, demonstrated improved functional properties of the modified membranes, such as larger operational stability, lower proton resistance, and higher current densities at elevated temperatures in the extended temperature range (22-120 °C) compared to pure membranes without additives.

Impact of DAA/water composition on PFSA ionomer conformation.

Performance of a proton exchange membrane fuel cell (PEMFC) is significantly determined by the structure and composition of the electrode layer. Electrode layers are formed from inks consisting of platinum-doped carbon black particles, perfluorosulfonic acid (PFSA) ionomer and a dispersing solvent. Interaction between these materials mainly influences suspension stability, ionomer conformation and therewith layer morphology. We characterize the interplay between a short sidechain (SSC) PFSA ionomer (Aquivion® D79-25BS) and a solvent mixture (diacetone alcohol (DAA) and water with different weight ratios) by using Hansen solubility/dispersibility parameters (HSP) and by experimental tests. It was found that HSPs are well suitable to describe the ionomer/solvent interactions. In particular, the HSP difference in terms of the hydrogen bonds is responsible for the poor affinity between ionomer and solvent at low DAA concentrations. With increasing DAA content the affinity between ionomer and solvent increases as indicated by better matching HSPs. For an ionomer concentration of 4 wt%, Aquivion always forms molecular solutions for all DAA-in-water mixing ratios. Self-organization of the ionomer molecules changes from densely packed/collapsed molecules with highly deprotonated sulfonic acid side groups at low DAA concentrations to unfolded Aquivion molecules with a low dissociation degree of the sulfonic acid groups at high DAA concentrations.

Influence of Ionomer Content in the Catalytic Layer of MEAs Based on Aquivion® Ionomer.

Perfluorinated sulfonic acid (PFSA) polymers such as Nafion® are widely used for both electrolyte membranes and ionomers in the catalytic layer of membrane-electrode assemblies (MEAs) because of their high protonic conductivity, σH, as well as chemical and thermal stability. The use of PFSA polymers with shorter side chains and lower equivalent weight (EW) than Nafion®, such as Aquivion® PFSA ionomers, is a valid approach to improve fuel cell performance and stability under drastic operative conditions such as those related to automotive applications. In this context, it is necessary to optimize the composition of the catalytic ink, according to the different ionomer characteristics. In this work, the influence of the ionomer amount in the catalytic layer was studied, considering the dispersing agent used to prepare the electrode (water or ethanol). Electrochemical studies were carried out in a single cell in the presence of H2-air, at intermediate temperatures (80-95 °C), low pressure, and reduced humidity ((50% RH). %). The best fuel cell performance was found for 26 wt.% Aquivion® at the electrodes using ethanol for the ink preparation, associated to a maximum catalyst utilization.

Efficient conversion of d-mannitol into 1,2:5,6-diacetonide with Aquivion-H as a recyclable catalyst.

Heterogeneous solid catalysis by the commercially available perfluorosulfonic ionomer Aquivion-H allowed 1,2:5,6-diacetonide of d-mannitol (1), immediate precursor of important unichiral C3-synthons, to be efficiently obtained from d-mannitol and 2,2-dimethoxypropane in DMF at room temperature. The 1,2-monoacetonide, whose intermediate formation is the rate-limiting step, could be almost completely converted into 1 with limited concurrent transformation of 1 into triacetonides. In line with recent literature reports, these results indicate that heterogeneous catalysis by Aquivion-H surpasses the performances of homogeneous acidic catalysis assuring, presumably for its peculiar morphology, a higher product selectivity. Easy recovery at the end of the reaction and recyclability are additional advantages of this solid acid catalyst.

Solar Hydrogen Generation from Ambient Humidity Using Functionalized Porous Photoanodes.

Solar hydrogen is a promising sustainable energy vector, and steady progress has been made in the development of photoelectrochemical (PEC) cells. Most research in this field has focused on using acidic or alkaline liquid electrolytes for ionic transfer. However, the performance is limited by (i) scattering of light and blocking of catalytic sites by gas bubbles and (ii) mass transport limitations. An attractive alternative to a liquid water feedstock is to use the water vapor present as humidity in ambient air, which has been demonstrated to mitigate the above problems and can expand the geographical range where these devices can be utilized. Here, we show how the functionalization of porous TiO2 and WO3 photoanodes with solid electrolytes-proton conducting Aquivion and Nafion ionomers-enables the capture of water from ambient air and allows subsequent PEC hydrogen production. The optimization strategy of photoanode functionalization was examined through testing the effect of ionomer loading and the ionomer composition. Optimized functionalized photoanodes operating at 60% relative humidity (RH) and Tcell = 30-70 °C were able to recover up to 90% of the performance obtained at 1.23 V versus reverse hydrogen electrode (RHE) when water is introduced in the liquid phase (i.e., conventional PEC operation). Full performance recovery is achieved at a higher applied potential. In addition, long-term experiments have shown remarkable stability at 60% RH for 64 h of cycling (8 h continuous illumination-8 h dark), demonstrating that the concept can be applicable outdoors.

Mechanocatalytic Depolymerization of Cellulose With Perfluorinated Sulfonic Acid Ionomers.

Here, we investigated that the mechanocatalytic depolymerization of cellulose in the presence of Aquivion, a sulfonated perfluorinated ionomer. Under optimized conditions, yields of water soluble sugars of 90-97% were obtained using Aquivion PW98 and PW66, respectively, as a solid acid catalyst. The detailed characterization of the water soluble fraction revealed (i) the selective formation of oligosaccharides with a DP up to 11 and (ii) that depolymerization and reversion reactions concomitantly occurred during the mechanocatalytic process, although the first largely predominated. More importantly, we discussed on the critical role of water contained in Aquivion and cellulose on the efficiency of the mechanocatalytic process.

Aquivion-Carbon Composites with Tunable Amphiphilicity for Pickering Interfacial Catalysis.

A key demand in biomass conversion is how to achieve high reactivity with immiscible reagents with the use of neither cosolvents nor additives. Pickering interfacial catalysis encompassing the design of amphiphilic catalysts behaving concomitantly as emulsifiers offers an elegant solution. In this study, we prepared a systematic series of amphiphilic Aquivion-carbon composites by the hydrothermal carbonization of guar gum with Aquivion perfluorosulfonic superacid. By tuning the Aquivion-carbon composition, materials with tunable hydrophilic-lipophilic properties could be prepared, showing high versatility for conducting biphasic reactions without stirring. In particular, an optimal formulation based on 5:1 Aquivion-carbon could be developed, showing high activity in the transesterification reaction of glyceryl trioleate with methanol at 100 °C with good reusability due to the genesis of stable Pickering emulsions.

Understanding the Thermal Properties of Precursor-Ionomers to Optimize Fabrication Processes for Ionic Polymer-Metal Composites (IPMCs).

Ionic polymer-metal composites (IPMCs) are one of many smart materials and have ionomer bases with a noble metal plated on the surface. The ionomer is usually Nafion, but recently Aquivion has been shown to be a promising alternative. Ionomers are available in the form of precursor pellets. This is an un-activated form that is able to melt, unlike the activated form. However, there is little study on the thermal characteristics of these precursor ionomers. This lack of knowledge causes issues when trying to fabricate ionomer shapes using methods such as extrusion, hot-pressing, and more recently, injection molding and 3D printing. To understand the two precursor-ionomers, a set of tests were conducted to measure the thermal degradation temperature, viscosity, melting temperature, and glass transition. The results have shown that the precursor Aquivion has a higher melting temperature (240 °C) than precursor Nafion (200 °C) and a larger glass transition range (32⁻65°C compared with 21⁻45 °C). The two have the same thermal degradation temperature (~400 °C). Precursor Aquivion is more viscous than precursor Nafion as temperature increases. Based on the results gathered, it seems that the precursor Aquivion is more stable as temperature increases, facilitating the manufacturing processes. This paper presents the data collected to assist researchers in thermal-based fabrication processes.