Proton Exchange Capacity Research Articles

Ultrafast Proton Conduction in an Aqueous Electrolyte Confined in Adamantane-like Micropores of a Sulfonated, Aromatic Framework.

Sulfonated, cross-linked porous polymers are promising frameworks for aqueous high-performance electrolyte-host systems for electrochemical energy storage and conversion. The systems offer high proton conductivities, excellent chemical and mechanical stabilities, and straightforward water management. However, little is known about mass transport mechanisms in such nanostructured hosts. We report on the synthesis and postsynthetic sulfonation of an aromatic framework (SPAF-2) with a 3D-interconnected nanoporosity and varying sulfonation degrees. Water adsorption produces the system SPAF-2H20. It features proton exchange capacities up to 6 mequiv g-1 and exceptional proton conductivities of about 1 S cm-1. Two contributions are essential for the highly efficient transport. First, the nanometer-sized pores link the charge transport to the diffusion of adsorbed water molecules, which is almost as fast as bulk water. Second, continuous exchange between interface-bound and mobile species enhances the conductivities at elevated temperatures. SPAF-2H20 showcases how to tailor nanostructured electrolyte-host systems with liquid-like conductivities.

Current status and future perspectives of proton exchange membranes for hydrogen fuel cells

The world is on the lookout for sustainable and environmentally benign energy generating systems. Fuel cells (FCs) are regarded as environmentally friendly technology since they address a variety of environmental issues, such as hazardous levels of local pollutants, while also delivering economic advantages owing to their high efficiency. A fuel cell is a device that changes chemical energy contained in fuels (such as hydrogen and methanol) into electrical energy. A wide variety of FCs are commercially available; however, proton exchange membranes for hydrogen fuel cells (PEMFCs) have received overwhelming attention owing to their potential to significantly reduce our energy consumption, pollution emissions, and reliance on fossil fuels. The proton exchange membrane (PEM) is a critical element; it is made of semipermeable polymer and serves as a barrier between the cathode and anode during fuel cell construction. Additionally, membranes function as an insulator between the cathode and anode, facilitating proton exchange and inhibiting electron exchange between the electrodes. Due to the excellent features such as durability and proton conductivity, Nafion membranes are commercially viable and have been in use for a long time. However, Nafion membranes are costly, and their proton exchange capacities degrade over time at higher temperatures and low relative humidity. Other types of membranes have been considered in addition to Nafion membranes. This article discusses the problems connected with several types of PEMs, as well as the strategies adopted to improve their characteristics and performance.

Proton-based solid acids for ammonia absorption in ammonia water

Ammonia absorption behavior of insoluble proton-based solid acids such as proton-exchanged montmorillonite, proton-exchanged zeolites α-zirconium phosphate and acid impregnated activated carbon in the water solution, was studied by ammonia and pH meters. The ammonia absorption capacity of α-zirconium phosphate was 10.2 wt%, which was highest among those acids. The ammonia absorption capacities corresponded to the proton exchange capacities, indicating that NH3 reacts with H+ to form NH4+ in the solid acids. The nitrogen concentration in the solution (NH3, NH4+) about 2500 ppm decreased with time, approaching about 50 ppm by addition of α-zirconium phosphate which is also useful to suppress the water pollution. Simulated leaked ammonia gas about 1000 ppm was removed by addition of aqueous dispersion of α-zirconium phosphate.

Effect of the Sulfonation on the Swollen State Morphology of Styrenic Cross-Linked Polymers.

The chemical structure and morphology of a set of sulfonic gel-type poly(styrene-divinylbenzene) resins (2 mol% DVB) prepared with different synthetic approaches were investigated by solid state NMR, Inverse Size Exclusion Chromatography (ISEC), FT-IR and elemental analysis to compare their swollen state structure. FT-IR and solid state NMR clearly show that the sulfonation mainly occurs in the para- position with respect the main polymer chain. Sensible proportions of sulfone bridges were found in the materials obtained with oleum and chlorosulfonic acid. With oleum, the presence of the sulfone bridges is clearly associated to a reduced ability to swell in the water medium relative to the proton exchange capacity. This highlights the cross-linking action of the sulfone bridges according to ISEC results, showing a high proportion of a dense polymer fraction in the swollen material. An even higher degree of sulfone-bridging, lower swelling ability, and a high proportion of a dense polymer fraction in the swollen material are found in the resin obtained with chlorosulfonic acid. As a matter of fact, Cross Polarization Magic Angle Spinning Nuclear Magnetic Resonance (CP-MAS 13C-NMR), elemental analysis, and ion exchange capacity, show that oleum and chlorosulfonic acid produced resins with remarkably smaller pores and lower swollen gel volume in polar solvents, with respect to concentrated sulfuric acid.

Phosphate-Solubilizing Microbes and Biocontrol Agent for Plant Nutrition and Protection: Current Perspective

ABSTRACTPhosphate-solubilizing microbes (PSM) are widely distributed in the rhizosphere and helps plant to acquire phosphates from soil. The availability of phosphates in soil are governed by several factors among which the proton exchange capacity has been regarded to be the most important factor involved in cation complex formations with soluble phosphates making them unavailable to plants, thereby disturbing the phosphorus cycling events found in arable soils. PSM solubilizes the cation complexes and thereby improves the functioning of phosphorus cycle in soil. In addition to involvement in biogeochemical cycling events, PSM have been also found to have antagonistic potential against several plant phytopathogens. These biocontrol microbes represent the most abundant groups of soil microflora. Among which some nutrient solubilizers have been used for effective biocontrol of important plant diseases. This review article shows contributions of different plant growth promoters used in nutrient and disease management practices in agriculture.Abbreviations: P (phosphorus), PSM (phosphate-solubilizing microbes), PSB (phosphate-solubilizing bacteria), PSF (phosphate-solubilizing fungi), PGPM (plant growth-promoting microbes), PGPB (plant growth-promoting bacteria), SAR (systemic acquired resistance), ISR (induced systemic resistance), TCP (tri-calcium phosphate), HCN (hydrogen cyanide), IAA (indole-3-acetic acid), aPhosphorus [(SSP) single super phosphate, RP (rock phosphate), PM (poultry manure) and FYM (farm yard manure)], PAL (phenylalanine ammonia lyase), ESI-MS (electrospray ionization mass spectrometry), DAPG (2,4-diacetylphloroglucinol) and NMR (1H nuclear magnetic resonance).

Highly stable graphene oxide composite proton exchange membrane for electro-chemical energy application

Proton exchange membrane is a basic element for any redox flow battery. Nafion is the only commercial available proton exchange membrane used in different electro-chemical energy systems. High cost restrict it's used for energy generation devices. In present work, we synthesised styrene divinylbenzene based composite proton exchange membranes (PEMs) with varying sulfonated graphene oxide (sGO) content for redox flow battery (RFB). Synthesized copolymer PEMs were analyzed in terms of their chemical structure with the help of FT-IR spectroscopy to confirm desired functional groups at appropriate position. Electrochemical characterization was performed in terms proton-exchange capacity, protonic conductivity and water uptake. Membrane shows adequate proton exchange capacity with good proton conductivity. Vanadium ion permeability was also tested for the prepared membrane to assess capability for vanadium redox flow battery (VRFB) in contrast with commercially available Nafion 117 PEM. Higher VO+2 ion cross-over resistance was found for CEM-4 with 7.17 × 10−7 cm2 min−1 permeability, which is about half of the CEM-1. Further CEM-4 was also evaluated for charging-discharging phenomenon for single cell VRFB. The values of columbic, voltage and energy efficiency for VRFB confirms prepared membrane as a good candidate for redox flow battery. Composite PEM also shows better mechanical and thermal stability. Results indicates that synthesized composite membrane can be used in vanadium redox flow battery.

Effect of the preparation method on the morphology and proton conductivity of membranes based on sulfonated ABA triblock copolymers

Sulfonated ABA triblock copolymers were synthesized based on ionomers with a hydrophilic block such as sulfonated poly(ether ether sulfone) (sPEES) and hydrophobic blocks such as poly(methyl methacrylate) (PMMA) and poly(pentafluorostyrene) (PPFS). The formation of these copolymers was evidenced by Fourier transform infrared (FTIR), proton nuclear magnetic resonance (1H NMR), and gel permeation chromatography (GPC) analyses. The copolymers were used to prepare membranes by two approaches: direct self-assembly and infiltration of the polymers into anodized aluminum oxide (AAO) templates. The effect of the copolymer chemical structure (fluorinated and non-fluorinated) and preparation method on the properties of the membranes, such as morphology, thermal stability, water uptake, ion exchange capacity (IEC), and proton conductivity, was evaluated. Both methods used to obtain membranes from ABA copolymers synthesized were successful. Morphological characterization showed that the fluorinated membranes prepared by self-assembly exhibited phase separation. This phase-segregated morphology of partially fluorinated block copolymer structures and high density of sulfonic acid groups had a positive impact on proton exchange capacity and proton conductivity. Moreover, methanol permeability was improved in comparison with Nafion® 117. Otherwise, the morphology of AAO membranes pores filled by infiltration was verified, and the proton conductivity was low due to an increase in the tortuosity which affected proton transport. The present study shows that the membranes prepared by self-assembly of sulfonated ABA block copolymers presented the best properties to be applied as proton exchange membranes.

Synthesis and electrochemical properties of blend membranes of polysulfone and poly (acrylic acid-co-2-(2-(piperazin-1-yl) ethylamino)-2-hydroxyethyl methacrylate) for proton exchange membrane fuel cell

In this work, new piperazine containing copolymer membrane was developed from acrylic acid and 2-(2-(piperazin-1-yl)ethylamino)-2-hydroxyethyl methacrylate through free radical polymerization method by means of AIBN as an initiator, in bulk. The monomer feed ratio was varied to obtain various copolymers having a different composition. The developed copolymer was blended in polysulfone (PSF) at 3 and 6 wt% using N,N′-Dimethylformamide solvent. The FTIR spectra and 1H NMR spectral data have proved the presence of copolymer that has hydrophilic functional group which influences the better proton conductivity. The membranes were characterized by their morphology using scanning electron microscope and x-ray diffraction analysis. The hydrophilic nature of the membranes is proved through high water uptake ratio. The exchangeable proton at the carboxylic acid group has enhanced the high ion exchange capacity. The blend membranes have higher water uptake, low swelling rate and higher ion exchange capacity than that of neat PSF membrane. The fabrication of fuel cell and studies on proton exchange capacity indicates that the prepared membranes have proton conductivity of as high as 8.77 × 10−4 S cm−1. Low methanol crossover was obtained about 2.112 × 10−6 cm2s−1 when compared to the pristine membrane.

Sodium Styrene Sulfonate-co-Methyl Methacrylate-Based Proton Conducting Membranes for Electrochemical Energy Applications

ABSTRACTThe present investigation reports one-pot synthetic approach to develop cation exchange membranes (CEMs) via free radical polymerization which avoids the post functionalization step that involves use of hazardous chemicals. The CEM is composed of sodium styrene sulfonate (StSO3Na), methyl methacrylate, divinyl benzene, and polyvinyl chloride which is prepared by varying relative amount of vinyl monomers. The membranes shown improved ion-exchange capacity, water uptake, ionic conductivity, and stabilities (mechanical, chemical, and thermal). Among different CEMs, CEM-1 has shown significantly improved performance with 8.54 × 10−2S.cm−1 proton conductivity and 2.71 meq. g−1 proton exchange capacity.

Electrochemical methanol reformation (ECMR) using low-cost sulfonated PVDF/ZrP membrane for hydrogen production

Polymer electrolyte membrane (PEM)-based electrochemical methanol reformation has gained interest as a practical way to produce hydrogen than water electrolysis due to its low operating voltages. Development of alternative PEM for this application is of considerable interest in order to reduce the cost as well as increase the system efficiency. Presently, a novel SPVDF/ZrP composite membrane was synthesized as proton exchange membrane for hydrogen production using electrochemical methanol reformation (ECMR). PVDF-co-HFP granules were defluorinated by alkali treatment followed by sulfonation using chlorosulfonic acid to prepare sulfonated polymer. Inorganic zirconium phosphate (ZrP) was further added to increase proton conductivity. The membranes were characterized for their physicochemical properties, mechanical strength, and thermal stability. The enhancement in proton exchange capacity and water uptake with adequate dimensional stability was observed with dehydrofluorination and impregnation of ZrP. A novel electrolyzer consisting of Pt-Ru/C as anode electrode, same format as anode as cathode electrode and the SPVDF/ZrP composite membrane was assembled and its performance was tested for hydrogen production. It was found that SPVDF/ZrP composite membrane showed good electrochemical cell performance of 0.65 V at 0.15 A cm−2 current density at ambient temperature and gives scope for operating ECMR cell at higher current densities for to increase the hydrogen production rate which is comparable to the performance of commercial Nafion® 117 membrane.

Present understanding of the stability of Li-stuffed garnets with moisture, carbon dioxide, and metallic lithium

Fast lithium-ion conducting garnet-type metal oxides are promising membranes for next-generation all-solid-state Li batteries and beyond Li-ion batteries, including Li-air and Li-S batteries, due to their high total Li-ion conductivity and excellent chemical stability against reaction with elemental Li. Several studies have been reported on structure-chemical composition-ionic conductivity property in Li-stuffed garnet-type metal oxides. Here, an overview of the chemical and electrochemical stability of lithium-based garnets against moisture/humidity, aqueous solutions, carbon dioxide, sulfur, and metallic lithium are analyzed. Moisture and aqueous stability studies focus on understanding the crystal structure stability, the proton exchange capacity as a function of Li content in Li-stuffed garnets, and how the protonated species affect the crystal structure and mass transport properties. H+/Li+ exchange was found to be in the range of 2–100%. Stability concerning Li-ion conductivity and morphology under carbon dioxide are discussed. Interfacial chemical stability with lithium metal characterized by electrochemical stability window, Li dendrite formation and area specific resistance (ASR) for the reaction Li⇌Li++e− are presented. Recent attempts to suppress dendrite formation and to reduce ASR via surface modification are also highlighted. Li and Li-stuffed garnet interface ASR values are shown to be as high as >2000 Ω cm2 and as low as 1 Ω cm2 at room temperature for surface modified Li-stuffed samples. Furthermore, recent studies on Li-S battery utilizing chemically stable Li – garnet electrolyte are also discussed.

Nanoporous composite proton exchange membranes: High conductivity and thermal stability

Nanoporous composite proton exchange membranes of sulfonated poly ether sulfone (SPES) and sulfonated mesoporous silica (S-MCM-41) have been prepared for energy based applications. Various weight % of Sulfonated MCM-41 has been incorporated in SPES matrix. The presence of surface functionalized MCM-41 as inorganic fillers in the SPES matrix, subsequently led to significant enhancement in the proton exchange capacity and proton conductivity of the nanoporous membranes. Nanoporous composite membranes have been subjected to various structural, thermal and mechanical techniques. Further developed membranes have been analyzed, for methanol permeability to evaluate membrane performance for fuel cell application. Methanol permeability of SM-2 is found to be 2.34 × 10−8 cm2 s−1 which is very less than SPES revealing the suitability of composite membranes for fuel cell.

One Pot Synthesis of PVDF Based Copolymer Proton Conducting Membrane by Free Radical Polymerization for Electro-Chemical Energy Applications

We report one pot synthesis of Poly (vinylidene difluoride) based proton conducting membranes (PCM) by free radical polymerization instead of post functionalization that uses hazardous sulfonating agents via electrophilic substitution reaction. PCM synthesised by copolymerization reaction among the three monomers viz Poly (vinylidene difluoride), 1-vinylimidazole and styrene sodium sulfonate. The enhancement in proton conductivity, proton exchange capacity and mechanical stability has been recorded by varying the amount of 1-vinyl imidazole and sodium styrene sulfonate alternatively. The membrane shows the enhancement in water uptake with adequate dimensional stability. PVDF-5 PCM shows the better performance among the membranes with 4.82*10−2S/cm proton conductivity and 2.19meq/g proton exchange capacity. Membranes also shows better oxidative stability as well as mechanical stability.

Polymer electrolyte membranes prepared by pre-irradiation induced graft copolymerization on ETFE for vanadium redox flow battery applications

The application of grafted membranes based on modified poly(ethylene-alt-tetrafluoroethylene) (ETFE) in redox flow-batteries is reported. In analogy to commercial Nafion® 117 based membranes ETFE backbone material provides chemical, thermal, and mechanical stability. Side chains composed of 2-hydroxyethyl methacrylate (HEMA) and glycidyl methacrylate (GMA) grafted to ETFE were sulfonated to achieve the required proton exchange capacity. Application in a vanadium based redox flow-battery demonstrates the applicability of this kind of membranes for energy storage systems. The degree of grafting was identified as the key parameter to tune the membrane properties.

Polyhedral oligomeric silsesquioxane (POSS) containing sulfonic acid groups as a metal-free catalyst to prepare polycaprolactone

Organic-inorganic hybrid nano-building block of polyhedral oligomeric silsesquioxane (POSS) containing hyperbranched sulfonic acid groups was easily prepared within a day through oxidation reaction at room temperature. The desired product was fully characterized by 1H, 13C{1H} NMR, 29Si CP/MAS NMR, FT-IR spectroscopy, and TGA-DSC analysis, confirming the complete formation of sulphonic acids while retaining the cubic structure of silsesquioxanes cage. Furthermore, the proton exchange capacities of POSS catalyst were determined to be 5.39 meq of H+/g, much greater than any previous silicon-based materials, leading to the catalytic preparation of polycaprolactone with well-controlled polymerization under the metal-free system and without the addition of any co-catalysts and solvents.

Proton conducting blend membranes: physical, morphological and electronic properties

Blend membranes of sulfonated poly(ether ether ketone) (SPEEK) and sulfonated polyetherimide (SPEI) have been prepared and investigated as a potential polymer electrolyte membrane (PEM) for direct methanol fuel cell (DMFC). Polymers were dissolved in N-methyl-2-pyrrolidone (NMP) in different mixing ratios and membranes were casted using a semi-automatic casting machine on a pre-cleaned glass plate. The influence of SPEI percentage on ion exchange capacity (IEC), water uptake, methanol permeability and proton exchange capacity have been investigated. Blend membranes showed slightly better IEC, water uptake and methanol crossover properties as compare to pure SPEEK; but proton conductivity was slightly lower than that of pure SPEEK membrane. Membrane morphology was investigated by FESEM, TGA and AFM. Overall, a homogeneous surface was observed for most of the blend membranes, with minor phase separation at higher SPEI contents samples. AFM image of the membrane surface shows nanoscale surface roughness.

Review on Modification of Sulfonated Poly (-ether-ether-ketone) Membranes Used as Proton Exchange Membranes

The proton exchange membrane fuel cell (PEMFC) is a type of modern power, but the traditional proton exchange membranes (PEM) of PEMFC are limited by high methanol permeability and water uptake. Poly-ether-ether-ketone (PEEK) is a widely used thermoplastic with good cost-effective property. Sulfonated poly (-ether-ether-ketone) (SPEEK) has high electric conductivity and low methanol permeability, as well as comprehensive property, which is expected to be used as PEMs. However, the proton exchange ability, methanol resistance, mechanical property and thermal stability of SPEEK are closely related to the degree of sulfonation (DS) of SPEEK membranes. Additionally, the proton conductivity, methanol permeability, and stability of SPEEK membranes applied in various conditions need to be further improved. In this paper, the research into modification of SPEEK membranes made by SPEEK and other polymers, inorganic materials are introduced. The properties and modification situation of the SPEEK and the composite membranes, as well as the advantages and disadvantages of membranes prepared by different materials are summarized. From the results we know that, the methanol permeability of SPEEK/PES-C membranes is within the order of magnitude, 10-7cm2/s. The proton conductivity of the SPPESK/SPEEK blend membrane reaches 0.212 S cm-1 at 80 °C. The cross-linked SPEEK membranes have raised thermal and dimensional stability. The non-solvent caused aggregation of the SPEEK ionomers. The proton conductivity of SPEEK/50%BMIMPF6/4.6PA membrane maintains stable as 2.0 x 10-2S cm-1 after 600 h at 160 °C. Incorporation of aligned CNT into SPEEK increases the proton conductivity and reduces the methanol permeability of the composite membranes. The PANI improves the hydrothermal stability. More proton transfer sites lead to a more compact structure in the composite membranes. According to the results, the proton exchange capacity, water uptake, and conductivity of the SPEEK membranes are closely related to the structure, stability, mechanical and electrochemical property and methanol permeation of the PEMFC. The modification of SPEEK membranes will improve their applications in aviation, military and other industries. Some proposals for further research are put forward.DOI: http://dx.doi.org/10.5755/j01.ms.21.4.9712

Preparation and Characterization of sPDVB/SPPO Composite Proton Exchange Membrane for Fuel Cell

In this study, a series of composite proton exchange membranes are prepared from sulfonated polydivinyl benzene (sPDVB) microspheres and sulfonated polyphenyl ether (SPPO). The PDVB microsphers and PPO are functionalized by direct sulfonation. The synthesis products are characterized by Fourier Transform Infrared Spectroscopy technique (FT-IR), thermogravimetry analysis (TGA), scanning electron microscope (SEM). The incorporation of sPDVB decreases the water uptake and proton exchange capacity, so the proton conductivity is lower than that of blank SPPO membrane. But the composite membranes still have the excellent conductivity range from 4.88×10-2 to 6.99×10-2 Scm-1.

Synthesis and characterisation of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) Zr(IV) monothiophosphate composite cation exchanger: analytical application as lead ion selective membrane electrode

A Pb2+ ion selective membrane electrode based on poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) Zr(IV) monothiophosphate composite cation exchange material was fabricated using solution casting method. The effect of membrane composition on the proton exchange capacity was investigated by using varying amounts of electroactive material. The membrane with 250 mg of electroactive material and 10 µL of plasticiser exhibited higher proton conductivity. The optimised membrane composition was used for the fabrication of ion selective membrane electrode which exhibited typical Nernstian response towards Pb2+ ions in the concentration range 20.70 gL−1–20.7 µgL−1 (1 × 10–1–1 × 10–7 mol L−1) with a sub-Nernstian slope of 27.429 mV per decade change in Pb2+ ion concentration. The response time of the electrode under study for Pb2+ ions was found to be 11 s and the electrode can be used for 120 days without any considerable divergence in response potential. It can also be successfully used in the pH range from 3.0 to 6.5. It was found selective for Pb2+ ions in the presence of various monovalent, divalent and trivalent interfering metal ions. It was also employed as an indicator electrode in the potentiometric titration of Pb2+ ions using ethylenediaminetetraacetic acid, disodium salt, as a titrant.

Biosorption of Neodymium by Selected Photoautotrophic and Heterotrophic Species

In a search for alternative methods for isolation of rare earth elements from diluted solutions, a possibility of their preconcentration on biomass of mainly phototrophic species, that can be easily cultivated in open or closed systems, was investigated in this study. A screening of 19 biological species, consisting of 17 microalgae, one yeast and one moss, in regard to the biosorption of neodymium (Nd) on their lyophilized biomass was performed. Maximum sorption capacity (qM) was determined after incubation for 3 h at room temperature and centrifugation through measuring the Nd content in the supernatant via a spectrophotometric assay. The obtained qM values ranged from 0.26 mmol*g-1 for Chlamydomonas reinhardtii to 0.48 mmol*g-1 for Calothrix brevissima and up to 0.74 mmol*g-1 for Physcomitrella patens. Kinetic measurements show the reaching of qM after 30 min for C. reinhardtii and 180 min for P. patens. Based on titration studies the proton exchange capacity was found to be 0.39 mmol*g-1 for C. reinhardtii and 0.44 mmol*g-1 for P. patens leading to a conclusion that proton exchange was mainly responsible for the biosorption mechanism. To our knowledge it is the first report of screening regarding such a wide scope of microalgae for a sorption of Nd.