Fenton's Test Research Articles

Optimal method for preparing sulfonated polyaryletherketones with high ion exchange capacity by acid‐catalyzed crosslinking for proton exchange membrane fuel cells

AbstractSulfonated polyaryletherketones (SPAEK) bearing four sulfonic acid groups on the phenyl side groups were synthesized. The benzophenone moiety of polymer backbone was further reduced to benzydrol group with sodium borohydride. The membranes were crosslinked by acid‐catalyzed Friedel‐Crafts reaction without sacrifice of sulfonic acid groups and ion exchange capacity (IEC) values. Crosslinked membranes with the same IEC value but different water uptake could be prepared. The optimal crosslinking condition was investigated to achieve lower water uptake, better chemical stability (Fenton's test), and higher proton conductivity. In addition, the hydrophilic ionic channels from originally course and disordered could be modified to be narrow and continuous by this crosslinking method. The crosslinked membranes, CS4PH‐40‐PEKOH (IEC = 2.4 meq./g), reduced water uptake from 200 to 88% and the weight loss was reduced from 11 to 5% during the Fenton test compared to uncrosslinked one (S4PH‐40‐PEK). The membrane showed comparable proton conductivity (0.01–0.19 S/cm) to Nafion 212 at 80°C from low to high relative humidity (RH). Single H2/O2 fuel cell based on the crosslinked SPAEK with catalyst loading of 0.25 mg/cm2 (Pd/C) exhibited a peak power density of 220.3 mW/cm2, which was close to that of Nafion 212 (214.0 mW/cm2) at 80°C under 53% RH. These membranes provide a good option as proton exchange membrane with high ion exchange capacity for fuel cells.

Highly Proton Conductive Sulfonyl Imide Based Polymer Blended from Poly(arylene ether sulfone) and Parmax-1200 for Fuel Cells.

Thermally and chemically stable, sulfonyl imide-based polymer blends have been prepared from sulfonimide poly(arylene ether sulfone) (SI-PAES) and sulfonimide Parmax-1200 (SI-Parmax-1200) using the solvent casting method. Initially, sulfonimide poly(arylene ether sulfone) (SI-PAES) polymers have typically been synthesized via direct polymerization of bis(4-chlorophenyl) sulfonyl imide (SI-DCDPS) and bis(4-fluorophenyl) sulfone (DFDPS) with bisphenol A (BPA). Subsequently, SI-Parmax-1200 has been synthesized via post-modification of the existing Parmax-1200 polymer followed by sulfonation and imidization. The SI-PAES/SI-Parmax-1200 blend membranes show high ion exchange capacity ranging from 1.65 to 1.97 meq/g, water uptake ranging from 22.8 to 65.4% and proton conductivity from 25.9 to 78.5 mS/cm. Markedly, the SI-PAES-40/SI-Parmax-1200 membrane (blended-40) exhibits the highest proton conductivity (78.5 mS/cm), which is almost similar to Nafion 117® (84.73 mS/cm). The thermogravimetric analysis (TGA) and Fenton's test confirm the excellent thermal and chemical stability of the synthetic polymer blends. Furthermore, the scanning electron microscopy (SEM) study shows a distinct phase separation at the hydrophobic/hydrophilic segments, which facilitate proton conduction throughout the ionic channel of the blend polymers. Therefore, the synthetic polymer blends represent an alternative to Nafion 117® as proton exchangers for fuel cells.

Highly Dispersed CeOx Hybrid Nanoparticles for Perfluorinated Sulfonic Acid Ionomer-Poly(tetrafluoethylene) Reinforced Membranes with Improved Service Life.

CeOx hybrid nanoparticles were synthesized and evaluated for use as radical scavengers, in place of commercially available Ce(NO3)3 and CeO2 nanoparticles, to avoid deterioration of the initial electrochemical performance and/or spontaneous aggregation/precipitation issues encountered in polymer electrolyte membranes. When CeOx hybrid nanoparticles were used for membrane formation, the resulting membranes exhibited improved proton conductivity (improvement level = 2–15% at 30–90 °C), and thereby electrochemical single cell performance, because the –OH groups on the hybrid nanoparticles acted as proton conductors. In spite of a small amount (i.e., 1.7 mg/cm3) of introduction, their antioxidant effect was sufficient enough to alleviate the radical-induced decomposition of perfluorinated sulfonic acid ionomer under a Fenton test condition and to extend the chemical durability of the resulting reinforced membranes under fuel cell operating conditions.

Silicone‐containing polymer blend electrolyte membranes for fuel cell applications

AbstractPolymer electrolyte membranes are developed from blends of chemically durable silicone‐containing epoxy (Si‐Epoxy) and proton conducting sulfonic polyimide (SPI). A charge‐transfer (CT) complex is formed between electron‐donating dihydroxynaphthalene units in Si‐Epoxy, and electron‐accepting naphthalenediimide units in SPI, as confirmed via X‐ray diffraction and visible spectroscopy. The blend membranes show comparable mechanical strength to Nafion 211, but the elongation to break is much lower, indicating better resistance to deformation under strain stress, attributed to CT complex formation. The chemical durability of the blend membranes was much higher than pure SPI according to Fenton's test, also attributed to CT complex formation. Meanwhile, the proton conductivity is dependent on the sulfonic acid content of the SPI, which in turn affects the fuel cell performance. The maximum proton conductivity was measured to be 23.1 mS cm−1 at 80°C and 90 %RH for a 1:1 blend, and the membranes were successfully incorporated into PEFCs.

Grafting free radical scavengers onto polyarylethersulfone backbones for superior chemical stability of high temperature polymer membrane electrolytes

The chemical durability is a critical issue to proton exchange membranes (PEMs) for using as the electrolyte in proton exchange membrane fuel cells (PEMFCs). Herein, chemically stable membranes were prepared by grafting organic free radical scavengers (R) including 2-mercapto-1-methylimidazole (MIm), 3-mercapto-1,2,4-triazole (MTz) and 2-mercaptobenzimidazole (BIm) onto backbones of polyarylethersulfone (PAES), respectively. Having a phosphoric acid (PA) doping level of around 200 wt%, the PAES-MIm and PAES-MTz membranes exhibit, separately, anhydrous proton conductivities of 78.3 and 63.3 mS cm−1 at 180 °C, tensile stress at break of 7.8 and 9.4 MPa at room temperature, and a peak power density of 423 mW cm−2 and 358 mW cm−2 at 160 °C with a fuel cell fueling with non-humidified gases of H2 and O2. The properties of the prepared PAES-MIm and PAES-MTz membranes with and without performing the Fenton tests were all investigated on tensile stress, methanol permeability, anhydrous proton conductivity, and polarization curves of single fuel cells, respectively. The results indicate that the grafted free radical scavengers significantly enhanced the chemical stability and retarded the degradation of the PAES-R membranes. After suffered the Fenton test under harsh conditions (H2O2, 3 wt%, Fe2+, 4 ppm at 68 °C) for 60 and 100 h, a peak power density of 320 and 291 mW cm−2 is still achieved at 140 °C by the acid doped PAES-MIm membranes, respectively. Characterizations on the morphology by scanning electron microscope (SEM), and structure by Raman spectroscopy of the prepared membranes were made as well.

Cross-Linked SPEEK–PEG–APTEOS-Modified CaTiO3 Perovskites for Efficient Acid–Base Cation-Exchange Membrane Fuel Cell

Nanocomposite membranes are synthesized by the combination of sulfonated poly(ether ether ketone) (SPEEK), poly(ethylene glycol) (PEG), and 3-aminopropyl triethoxysilane (APTEOS)-modified CaTiO3. From thermogravimetric analysis (TGA) and mechanical and Arrhenius studies, it is seen that the covalent cross-linking of PEG with SPEEK exhibits a lower weight loss (91.84 wt %) at 120 °C than SPEEK (88.19 wt %). Moreover, higher activation energy (Ea) and tensile stress values are obtained in the order of 26.23 kJ/mol and 23.32 MPa, respectively. The APTEOS-modified CaTiO3 nanoparticles impregnated into the SPEEK/PEG membrane cause the acid–base proton hopping mechanism (HSO3/NH2) and induce a more compact structure. The nanocomposite membranes possess exceptional proton conductivity, thermal, oxidative, and physicochemical properties than SPEEK. Further, 6 wt % functionalized CaTiO3 in the SPEEK/PEG membrane manifests the highest values of proton conductivity, current density, and power density at 80 °C in 100% RH of 65.32 mS cm–1, 403 mA cm–2, and 90 mW cm–2 with an open-circuit voltage (OCV) of 0.90 V, respectively. This membrane retains 95.37 wt % original weight during 3 h of the Fenton test.

Structural investigation on bulky aliphatic-aromatic poly(aryl sulfone)s for fuel cell performance

This paper is focused on the structure-properties relationship of synthesized sulfonated poly(aryl sulfone)s comprised of a bulky aliphatic-aromatic structure. Nucleophilic aromatic substitution together with a coupling step was used to prepare random copolymers with excellent film-forming ability. High thermal, mechanical, and dimensional stability of membranes ascribed to the presence of rigid aromatic sections. The oxidative stability of the optimized membrane with a 50% degree of sulfonation (Z-50) was studied in ex-situ and in-situ accelerated degradation tests. The results were evaluated by Fenton test, scanning electron microscope, nuclear magnetic resonance spectrometry, and open-circuit voltage test. The voltage decay of 0.62 mV/h was attained during 100 h open-circuit voltage test at 80 °C under 100% relative humidity. Temperature and relative humidity-dependent impedance and high-frequency resistance of membranes revealed the structural benefit of membranes. Polarization and performance curves of the optimized sample were collected at three temperatures of 80, 100, and 120 °C under 100% relative humidity. The examination of the membrane polarization under 30–100% relative humidity at the temperature of 80 °C showed a current density of about 732.7 mA/cm2 even at 30% relative humidity. The design of such bulky aliphatic-aromatic poly(aryl sulfone) was responsible for this result.

Enhancement of oxidative stability of PEM fuel cell by introduction of HO• radical scavenger in Nafion ionomer

The coordination complex of 18-crown-6 ether/cerium ions (CRE/Ce) is embedded in Nafion ionomer between catalyst and membrane layers in fabrication of membrane electrode assembly (MEA). The anti-oxidation effects of CRE/Ce on ionomer and MEA are investigated not only by Fenton's test but also by FT-IR and XPS, ex-situ and in-situ fluoride ion (F−) emission rate, and cell performance measurements. While Ce3+ plays an excellent role in scavenging HO• radicals, CRE alleviates migration of cerium ions out of the ionomer during cell operation. Both ex-situ and in-situ degradation rate tests show that the systems containing CRE/Ce emits much lower amount of fluoride and sulfonate (SO3−) ions than those without CRE/Ce. The open-circuit voltage (OCV) test at low humidity (30%) show that the cell containing the CRE/Ce is still alive even after 300 h operation, while other cells without it are terminated before it.

Formulation and characterization of crosslinked polyvinyl alcohol (PVA) membranes: effects of the crosslinking agents

The article addresses the formulation and characterization of the polyvinyl alcohol membrane (PVA) with citric acid, succinic acid and their mixing as crosslinking agents. PVA is highly hydrophilic and has excellent film (membrane) properties. Chemical crosslinking is the most common approach to stabilize and produce PVA membranes with enhanced mechanical resistance. Thus, we prepared membranes with variable PVA and crosslinking agents. The thermal properties of the membranes were analyzed using thermogravimetric method (TGA), while the functional groups formed in the membrane were determined using Fourier-transform infrared spectroscopy. The water absorption of the membranes was determined by the degree of swelling. The oxidative stability was obtained using the Fenton test. The ion exchange capacity was also evaluated. Membrane structure, morphology and surface properties were analyzed by topography and adhesion force using atomic force microscopy. The scanning electron microscopy was used to elucidate the fractures. The results indicated that the membranes exhibited roughness uniformly distributed, indicating homogeneous films and excellent crosslinking features allied to enhanced adhesion and strength properties with good stability.

Stability of ionic-covalently cross-linked PBI-blended membranes for SO2 electrolysis at elevated temperatures

In this study, the effect of component composition on the chemical stability of the developed ionic-covalently cross-linked PBI-blended membrane concept from earlier studies for application in SO2 electrolysis at elevated temperatures (>100 °C) is further investigated. Three different acid-base ratios were studied by blending a partially fluorinated sulfonated arylene main-chain polymer (SFS) with polybenzimidazole (F6PBI) and a partially or non-fluorinated bromo-methylated polymer (BrPAE). In addition two different alkylated imidazoles (EMIm and TMIm) were included as quaternization agents. Accordingly, twelve different PBI-blended membranes were produced in this study. The suitability of these membranes for SO2 electrolysis at elevated temperatures was determined in terms of i) the H2SO4 stability (80 wt% H2SO4 at 100 °C for 120 h), (ii) the oxidative stability (Fenton's test, FT) and (iii) the organic solvent stability (extraction in N,N-Dimethylacetamide). Membranes were characterized in terms of the percentage weight, the ion exchange capacity (IEC) and the thermal stability (TGA-FTIR) changes, before and after the various treatments. Although all blended membrane types were sufficiently stable during H2SO4 treatment, proton conductivity measurements indicated that the blends containing only partially fluorinated blend components displayed superior stability (better compatibility) as well as conductivity. Cell voltages showed an improvement of up to 190 mV for operations at 120 °C compared to earlier studies conducted at 80 °C for similar PBI-blended membranes. It was established that both chemically stable and conductive PBI-blended membranes, suitable for SO2 electrolysis above 100 °C, could be obtained by varying the composition of selected polymer components.

CHS-WSiA doped hexafluoropropylidene-containing polybenzimidazole composite membranes for medium temperature dry fuel cells

Various loadings (0, 5, 10, 20 wt%) of wet-mechanochemically prepared CsHSO4–H4SiW12O40 (CHS-WSiA) composite were incorporated into polymer electrolyte membranes (PEM) based on commercial polybenzimidazole (PBI) and synthesized fluorine-containing PBI (F6PBI). The membranes thus obtained were evaluated by thermal analysis, Fenton's test, acid leaching test, proton conductivity and fuel cell performance. The addition of CHS-WSiA inorganic composite improved acid retention ability and proton conductivity. F6PBI composite membrane exhibited enhanced chemical stability against hydroxyl radical attack, while improving acid doping characteristics and acid retention ability significantly. With 8 mol phosphoric acid doping level (PADL) (173 wt% phosphoric acid uptake), F6PBI with 10 wt% CHS-WSiA, namely F6PBI(10), exhibited the highest conductivity of 2.14 mScm−1 at 150 °C under dry conditions. Under similar conditions as for fuel cell performance, F6PBI(10) achieved a maximum power density of 498 mWcm−2 with a stable voltage of 0.614 V under a constant current 0.2 Acm−2 durability test over 24 h.

Chemical stability of sulfonated poly(benzimidazole)s in proton exchange membrane fuel cells: A comprehensive Ab initio mechanistical study

Electrochemical reactions in fuel cells produce various radical species which lead to degradation of membranes. Desulfonation of membranes is the most important factor in reducing cell performance in the long term. The present study theoretically investigated the chemical stability of sulfonated poly(benzimidazole)s. Possible degradation mechanisms for two sulfonated poly(benzimidazole)s with different sulfonating agents (sPBI1 and sPBI2) was studied to provide valuable data. For sPBI1, H radical is the main destructive agent and desulfonation occurs by the addition of H radical to the imidazole ring and hemolytic CS cleavage. While the desulfonation of the imidazole ring in the presence of OH radical is unfavorable in sPBI1, in the sPBI2, both H and OH radicals play important roles through different mechanisms. Desulfonation by H radical occurs by addition to the imidazole ring and CN bond cleavage, but desulfonation by OH radical proceeds from an elimination reaction and CC formation. The results for model compounds were in agreement with experimental data from Fenton's test. Also, backbone degradation for both sPBI1 and sPBI2 were thermodynamically unfavorable, exhibits good chemical stability in the presence of active radicals.

Influence of doping level in Yttria-Stabilised-Zirconia (YSZ) based-fillers as degradation inhibitors for proton exchange membranes fuel cells (PEMFCs) in drastic conditions

Yttria-Stabilized-Zirconia fillers with different Y2O3 loadings are used to prepare composite Nafion membranes for PEMFCs. XRD and BET demonstrate the formation of a c-ZrO2 mesoporous structure. SEM reveals a size reduction of the agglomerates increasing the ZrO2 doping level. A good mechanical resistance, no variation into the water retention, swelling restraint and an increased Ion Exchange Capacity (IEC) of the membranes are found respect to reference membrane, above all for highly doped membranes, indicating an acidic properties enhancement. Proton conductivity (PC) at 100%RH (80–100 °C) is unchanged for composite membranes compared to reference. At 75%RH, PC is positively affected by the highest YSZ loadings. Fenton's test on membranes evidences a higher oxidative chemical stability for composite membranes. This improved stability is confirmed by accelerated stress test in drastic conditions: composite highly doped membranes work for more than 110 cycles with a good performance and lower H2-crossover against 95 cycles and higher H2-crossover than reference membrane.

Improved proton conductive membranes from poly(phenylenebenzophenone)s with pendant sulfonyl imide acid groups for fuel cells

Super gas-phase acidity of the sulfonyl imide groups have become the attractive materials for polymer electrolyte membranes. Therefore, sulfonyl imide functionalized proton exchange membranes (SI-PPBP) have been prepared from poly(phenylene)s by carbon-carbon coupling polymerization. Initially, fully aromatic poly(phenylenebenzophenone)s backbones (PPBP) have been synthesized from newly synthesized symmetrical 1,4-dichloro-2,5-diphenylene methoxy benzophenone (PMBP) and 1,4-dichloro-2,5-dibenzoyl benzene (PBP) monomers using Ni (0) catalyst. Afterward, the incorporation of the sulfonyl imide groups onto the PPBP polymer backbones has been carried by post-modification process. The synthesized sulfonyl imide based PPBP polymers (SI-PPBP) membranes exhibit a rational ion exchange capacity from 1.00 to 1.76 meq/g., water uptake from 28.7 to 62.7% and proton conductivity from 74.9 to 142.85 mS/cm. Noticeably, SI-PBP- 40 shows higher conductivity (142.85 mS/cm) compare to Nafion 117® (84.73 mS/cm). The thermogravimetric analysis (TGA), tensile strength and Fenton test have been used to evaluate the thermal, mechanical and chemical stability of the synthesized SI-PPBP membranes, respectively. The hydrophilic/hydrophobic phase separation of the polymer membranes have been investigated by the atomic force microscopic (AFM). All the results support the potential features of the synthesized SI-PPBP membranes to be used an alternative material to Nafions for fuel cells.

Xantomatosis cerebrotendinosa. Reporte de un caso en el Perú: Evaluación clínica integral y estudios de neuroimágenes.

Se presenta el caso de una paciente de 73 años de edad que, a los 30 años aproximadamente, comenzó a quejarse de dolor al caminar, localizando la molestia a nivel de las regiones aquilianas, con subsecuente aumento de volumen; al paso del tiempo, estas molestias la obligaron a efectuar consulta médica. Los análisis de laboratorio mostraron severa dislipidemia mixta. Al lado de información de significativa declinación cognitiva, provista por familiares (vgr., (i.e., olvidos frecuentes, desorientación, atención disminuida, concentración pobre), hubo evidencia de ánimo fluctuante, labilidad emocional, crisis ansiosas evolucionando hacia ataques de pánico. El test minicognitivo de Folstein, mostró severo estado demencial y en el examen neurológico se constataron ataxia cerebelosa y signos de piramidalismo parcial. El examen oftalmológico puso en evidencia xantelasmas, cataratas y un denso arco senil. El estudio del cerebro con resonancia magnética (RM) mostró el daño encefálico y signos sugestivos de depósitos del colastenol en el SNC. La presencia de xantomas , los hallazgos oftalmológicos, la demencia definidamente progresiva y la ataxia cerebelosa fueron hallazgos clínicos que permitieron establecer el diagnóstico de xantomatosis cerebrotendinosa.

Polybenzimidazole as proton conducting filler in polydimethylsiloxane: Enhanced oxidative stability and membrane properties

ABSTRACTIn this work, pyridine‐based low‐molecular‐weight polybenzimidazole (LMP) was synthesized (inherent viscosity: 0.52 dL g−1) by controlling the reaction time. The synthesized LMP was incorporated into polydimethylsiloxane (PDMS) matrix to impart proton conductivity. The composite membrane containing 30 wt % of LMP exhibited proton conductivity of 16 mS cm−1 at 100–120 °C. The LMP chains were bundled and formed clusters (aggregates) in the PDMS matrix as observed in field emission scanning electron microscopy. This is attributed to nonpolar (siloxane)–polar (polybenzimidazole) repulsion. An impressive weight loss of 8.6% was observed after 120 h Fenton's test that indicates the high oxidative stability of composite membranes. However, elongation of composite membranes was decreased compared to that of pristine PDMS, which is attributed to the incorporation of rigid LMP chains. The resultant composite membranes exhibited moderate proton conductivity, low moisture absorption, and good thermal stability. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 48151.

Bisphenol A based carbon-carbon coupled poly(arylene)s from dibenzoyl-dichlorobenzene via Ni(II) catalyzed and condensation polymerization for PEMFC

The major challenges experienced by the researchers till now are to synthesis the chemically and mechanically stable proton exchange membranes. However, Ni catalyzed CC coupling polymerization together with condensation reaction assist to get the high molecular weight polymer membranes as well as thermally and chemically stable PEMs. In this study, bisphenol A-based sulfonated poly (arylene)s copolymers (bis A-SPAs) have been successfully synthesized by the carbon-carbon coupling polymerization using Ni (0) catalyst from sulfonated 1,4-dibenzoyl-2,5-dichlorobenzene (SDBDCB) monomer and subsequently condensation reaction with bisphenol A. The (bis A-SPAs) membranes were flexible in nature and attained high molecular weight. The synthesized (bis A-SPAs) membranes exhibited water uptake from 7.42 to 56.4%, ion exchange capacity ranging from 0.73 to 1.67 meq/g, and proton conductivity from 48.8 to 96.4 mS/cm (at 90 °C) with maximum power density of 0.48–0.60 W/cm2. Membrane with high-sulfonated degree (bis A-SPAs-50) showed almost analogous conductivity (96.4 mS/cm) to Nafion® 117 membrane (98.92 mS/cm) at 90 °C and 90% humidity. The synthesized sulfonated polymer membranes displayed well phase separation that increased the proton conductivity. The TGA and Fenton's test results confirmed that the synthesized membranes possessed admirable thermal stability and mechanical stability. Therefore, the new synthesized (bis A-SPAs) membranes have the promising suitable properties as a proton exchange membrane in the fuel cell applications.

Electrodeposition of Pt/CeO2/MWCNT as Hydrogen Peroxide Scavenger for Chemical Degradation Mitigation of Nafion Membrane

Pt/CeO2 electrocatalysts were coated on the multi-walled carbon nanotube (MWCNT) substrate using a facile electrochemical deposition technique. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) were used for characterization the Pt/CeO2/MWCNT catalyst. The electrochemical behavior of prepared electrocatalysts was studied in acidic pH using cyclic voltammetry measurement at ambient temperature. Next, Fenton test was carried out as an ex-situ accelerated experiment for 96 h to investigate the performance Pt/CeO2/MWCNT electrocatalysts in chemical degradation mitigation of Nafion membrane. The impact of adding CeO2 on chemical degradation mitigation of the Nafion was investigated using Fourier-transform infrared spectroscopy (FTIR), fluoride emission rate, weight loss, and SEM tests. Achieved outcomes showed that CeO2 nanoparticles could considerably enhance the chemical degradation mitigation of the Nafion membrane in proton exchange membrane fuel cells (PEMFCs).

Anion Exchange Membranes Based on Sulfonated Poly(ether ether ketone) Crosslinked Methylpyrrolidinium Functionalized Poly (vinyl benzyl chloride) with High Chemical Stability

Developing anion exchange membranes (AEMs) with superior chemical stability and high conductivity is a considerable challenge for the practical application in AEM fuel cells. Herein, novel ionic crosslinked AEMs from methylpyrrolidinium functionalized poly (vinyl benzyl chloride) (PVBC-MPy) and sulfonated poly(ether ether ketone) (sPEEK) were fabricated through a facile and gentle method. The PVBC-MPy ionomer with a superior alkaline stability is used as the hydroxide conductor, while the sPEEK polymer plays the role as a macromolecular crosslinker. The PVBC-MPy exhibited good compatibility with sPEEK without phase separation. The obtained PVBC-MPy/x%sPEEK membranes displayed excellent oxidative resistance toward the attack of radicals as demonstrated by Fenton test. Meanwhile, AEMs also exhibited low dimensional swellings, improved mechanical strength, high conductivity and superior alkaline stability simultaneously. The PVBC-MPy/10%sPEEK membrane exhibited a weight retention rate of 86% after the Fenton test for 180 h, a volume swelling of 45%, a tensile strength of 25.6 MPa at room temperature, an anion conductivity of 28 mS cm−1 at 80°C, and retained its initial conductivity of 86.4% after immersing in 1 M KOH at 80°C for 410 h.

Perfluorinated composite membranes with organic antioxidants for chemically durable fuel cells

A perfluorinated composite membrane incorporating an organic antioxidant was prepared to improve the chemical durability of a polymer electrolyte fuel cell. Bipyridine and benzoquinone (BQ) were added as organic antioxidants, and the oxidative stability of the composite electrolyte membranes containing them was evaluated via accelerated aging tests, i.e., an ex situ Fenton's test and in situ open-circuit voltage (OCV)-holding test. The effects of the antioxidants in the Fenton's test were verified using scanning electron microscopy, fluorine ion detection, Fourier-transform infrared spectroscopy, and tensile strength measurements. Moreover, a commercial membrane, NRE211, and a composite membrane, Nafion-BQ, were incorporated into a membrane electrode assembly (MEA) that then underwent an OCV-holding test for 500 h. The change in the MEA state over time was analyzed using cyclic voltammetry and linear sweep voltammetry. While NRE 211 showed a significant reduction in OCV from 300 h, Nafion-BQ maintained a stable OCV for 500 h. Hence, the organic antioxidants added to the electrolyte membrane effectively improved the oxidative stability of the proton exchange membrane fuel cell without sacrificing the ionic conductivity of the perfluorinated electrolyte membrane.