Conducting Polymer Membranes Research Articles

(ECS Edward Goodrich Acheson Award) Improvements in Anion Exchange Membrane Water Electrolysis Materials and Devices

Green hydrogen is a critical energy carrier for the future net-zero carbon emission by 2050. Anion exchange polymer electrolytes enable the use earth-abundant catalysts, non-fluorinated solid polymer electrolytes, and low-cost cell components for sustainable, low-temperature water electrolysis to produce green hydrogen. However, long-term durability of the anion exchange membrane water electrolysis (AEMWE) needs to be demonstrated at high current density (i.e., > 1 A/cm2). AEMWE can be operated with a more gentle (i.e., lower) hydroxide anolyte feed for improved chemical durability, however, the cell overpotential has shown to increase at lower pH.New materials and operating conditions have been demonstrated which contribute to improved durability and energy-efficiency by the use of (i) stable ion conductive polymer membranes, (ii) self-adhesive electrode ionomers, and (ii) a high ionic strength anolyte without raising the pH. The increase in cathode hydration (where water is reduced to hydrogen) is critical to achieving durable, higher current performance. The cathode hydration level was improved in several ways including the use of hydrophilic ion conducting polymer in the membrane and cathode. A self-adhesive poly(norbornene) terpolymer ionomer has been developed for durable electrode fabrication where the hydrophilicity of the electrode environment was adjusted for each electrode. The ionomer was covalently bonded to a catalyst and the gas diffusion layer to achieve stable electrolysis under vigorous gas evolution. The rate of water transport through the AEM was improved by use of a lower pH, higher ionic strength anolyte. It has been shown that increasing the ionic strength of the anolyte, without increasing the pH, assists in water delivery to the cathode. The uptake of alkali cations within the AEM plasticizes the AEM (i.e., increases ion diffusivity) and migration of the hydrated cations to the cathode increases the overall water transport. Finally, improvements in the anion exchange membrane synthesis and fabrication have been found which can lower the overall electrolysis cost. Long-term AEMWE durability with the optimized electrodes and low pH/high ionic strength anolyte is demonstrated.

Tamarind gum based magnesium ion conducting polymer membrane for energy storage applications

A solid bio polymer electrolyte (SPE) based on tamarind gum (TG) and magnesium nitrate was synthesized by a solution casting technique. The amorphous behavior is observed by X-ray diffraction (XRD) analysis, and the degree of crystallinity is calculated from the XRD deconvolution spectra. The interaction between the polymer and the salt was confirmed by Fourier transform infrared (FTIR) analysis. Using FTIR deconvolution spectra, the percentage of free ions can be calculated. The glass transition temperature (Tg) was determined via differential scanning calorimetry (DSC). A higher ionic conductivity (σ) of 1.97 × 10−4 S/cm is observed for the sample with 1 g of tamarind gum and 0.5 g of magnesium nitrate (4 TMN). The conduction mechanism shows that sample 4 TMN obeys the quantum mechanical tunneling model (QMT) at low frequency. The prepared SPEs follow the Arrhenius behavior, and the minimum activation energy (Ea) of 0.207 eV is observed for sample 4 TMN. The lowest relaxation time (τ) was 3.46 × 10−7 s for 4-TMN according to the tangent spectra. The transference number of ions (tion) is calculated by Wagner’s polarization method. The electrochemical stability window observed by linear sweep voltammetry (LSV) is 2.25 V. The primary battery is fabricated by using sample 4TMN, and an open circuit voltage (OCV) of 2.01 V is observed.

Operando Raman Spectroscopy Reveals Degradation Byproducts from Ionomer Oxidation in Anion Exchange Membrane Water Electrolyzers.

This work showcases the discovery of degradation mechanisms for nonplatinum group metal catalyst (PGM free) based anion exchange membrane water electrolyzers (AEMWE) that utilize hydroxide ion conductive polymer ionomers and membranes in a zero gap configuration. An entirely unique and customized test cell was designed from the ground up for the purposes of obtaining Raman spectra during potentiostatic operation. These results represent some of the first operando Raman spectroscopy explorations into the breakdown products that are generated from high oxidative potential conditions with carbonate electrolytes. We provide a unique design and fabrication method for three-dimensional (3D) printable flow cells that enable spatially resolved Raman spectra collection from the electrode surface into the bulk electrolyte. It is proposed that the generation of breakdown products from the hydroxide-conductive ionomers and membranes originates from a multistep, free radical reaction pathway resulting in chain scission of the poly aryl backbone. This hypothesis is backed by the detection of carboxylic and aromatic functional group Raman signals from small molecules that had dissolved and diffused into the bulk electrolyte.

Performance and Durability of Poly(norbornene) Anion-Conducting Membranes and Ionomers

Low-temperature, polymer-based water electrolyzers using anion conductive polymers have several potential advantages over acid-based polymer electrolyzers. However, the long-term durability of the anion conducting polymer membrane and ionomer remains to be demonstrated.In this study, a family of norbornene-based copolymers and terpolymers have been used in fuel cells and electrolyzers to provide high conductivity (>200 mS/cm at 80oC) and superior mechanical properties. The factors affecting the voltage and durability of alkaline electrolyzers will be reported.

Polybenzimidazole-based polymers of intrinsic microporosity membrane for high-temperature proton conduction

Anhydrous proton conducting polymer membrane materials have raised much attention in the application of high-temperature proton-exchange membranes (HT-PEMs) fuel cells, which convert chemical energy into electrical energy. Polybenzimidazole-based polymers, as typical materials for HT-PEMs, their compact structures result in small fractional free volumes (FFV), which is not conducive to the adsorption and retention of proton carriers. Herein, a series of polybenzimidazole-based polymers of intrinsic microporosity (PIM-PBIs) were synthesized. PIM-PBIs possess the benzimidazole units and porous structures, and have good thermal stability and large specific surface area (100 ∼ 400 m2/g). PIM-PBIs are further embedded in polyvinylidene fluoride (PVDF) to form mixed matrix membranes for high-temperature proton conduction. The resulting membranes exhibit high proton conductivity up to 90.11 mS cm−1 at 140 ℃ and high phosphoric acid (PA) retention rate of 90.0 %. This work provides a facile method for the precise design and preparation of proton-conducting porous materials.

Durable underwater super-oleophobic/super-hydrophilic conductive polymer membrane for oil-water separation.

Oily sewage has made serious impact on environment and people's life, and its treatment has become a global problem to be urgently solved. Oil-water separation has been considered to be an effective method to treat oily sewage at present. In this work, an underwater super-oleophobic/super-hydrophilic membrane with oil-water separation and self-cleaning properties was fabricated by electrochemical oxidation of sodium lignosulfonate doped polypyrrole. The membrane showed super-hydrophilicity for water-removal in air and super-hydrophilicity for oil-removal underwater in both oxidation and reduction states. The oil-water separation efficiency of the membranes for different organics exceeded 98.44%, no matter in oxidation or reduction state. Moreover, the membrane still exhibited excellent performance in terms of the oil-water separation efficiency and flux after 70 cycles, which were greater than 97.18% and 70.14 L·m-2·h-1, respectively. Simultaneously, through exploration of the mechanism, it was found that the larger anion kept intact in the membrane during the redox process, which made the stability of composition and performance. Thus, the membrane with advantageous properties, including underwater super-oleophobic/super-hydrophilicity, high oil-water separation efficiency, high circulating rate and stability, has significant potential in separation and collection of oily sewage.

Toward Understanding Interfacial Phenomena of Anion Exchange Membrane Water Electrolyzers: Investigating the Role of Electrolyte pH Gradient with Operando Raman Spectroscopy

There is growing industrial appeal of anion exchange membrane water electrolyzers (AEMWEs) to produce hydrogen. A significant challenge remains that AEMWE durability testing is not standardized, and more minute interfacial degradation mechanisms between ionomer, catalyst, membrane, and electrolyte are not well characterized. Of particular interest is the impact of electrolyte selection on the polarization performance. There is a general desire to achieve reliable operation with environmentally obtained saltwater as the electrolyte, although this presents numerous challenges manifesting in typically poor long-term durability. Saltwater presents complexities in determining electrolyzer component interfacial phenomena.Performance of AEMWEs is typically benchmarked with hydroxide or carbonate solutions, therefore providing more direct opportunities to study fundamental mechanisms with regards to interactions between surfaces. Of particular interest is the presence of electrolyte anion concentration gradients that depend on the polarization state of the oxygen evolution reaction electrode (OER). We demonstrated in our early work with operando Raman probing of a custom designed spectroelectrochemical cell that there is initial evidence of spatially resolved anion gradients from the OER electrode surface into bulk electrolyte in a half cell configuration. We hypothesize that local pH changes near an electrode surface may impact the polarization via transport limited ion exchange and the relative overpotential of the overall cell, ultimately leading to an iterative and long-term contribution to decaying cell durability.We continue our work with a series of in-situ Raman experiments with a full cell configuration: OER electrode with PGM free catalyst, hydrogen evolution reaction (HER) electrode with PGM free catalyst, and anion conductive polymer membrane. Both electrodes also contain an ionically conductive polymer, or ionomer, that serves as a binder. By increasing the complexity of the system to match that of an industrially relevant configuration, we aim to probe the spatially resolved pH gradient with both potassium hydroxide and potassium carbonate solutions of varying concentrations. We utilized a custom, 3D printed, flow cell design comprising a sapphire observation window and isolated electrolyte flow chambers.Operando Raman spectroscopy measurements were conducted primarily with potassium carbonate solutions by tracking the spatially resolved changes in relative peak intensity of carbonate and bicarbonate signatures. With regards to the carbonate-bicarbonate equilibrium, we calculate changes in pH as the probe approaches the surface of an electrode. We finally connect our findings to a proposed mechanism for the interfacial phenomena relative to cell durability as a function of concentration changes and operating voltages.

Fabrication of Poly (Trans-3-(3-Pyridyl)Acrylic Acid)/Multi-Walled Carbon Nanotubes Membrane for Electrochemically Simultaneously Detecting Catechol and Hydroquinone.

Herein, conductive polymer membrane with excellent performance was successfully fabricated by integrating carboxylated multi-walled carbon nanotubes (MWCNTs) and poly (trans-3-(3-pyridyl) acrylic acid) (PPAA) film. The drop-casting method was employed to coated MWCNTs on the glassy carbon electrode (GCE) surface, and PPAA was then electropolymerized onto the surface of the MWCNTs/GCE in order to form PPAA-MWCNTs membrane. This enables the verification of the excellent performances of proposed membrane by electrochemically determining catechol (CC) and hydroquinone (HQ) as the model. Cyclic voltammetry experiments showed that the proposed membrane exhibited an obvious electrocatalytic effect on CC and HQ, owing to the synergistic effect of PPAA and MWCNTs. Differential pulse voltammetry was adopted for simultaneous detection purposes, and an increased electrochemical responded to CC and HQ. A concentration increase was found in the range of 1.0 × 10-6 mol/L~1.0 × 10-4 mol/L, and it exhibited a good linear relationship with satisfactory detection limits of 3.17 × 10-7 mol/L for CC and 2.03 × 10-7 mol/L for HQ (S/N = 3). Additionally, this constructed membrane showed good reproducibility and stability. The final electrode was successfully applied to analyze CC and HQ in actual water samples, and it obtained robust recovery for CC with 95.2% and 98.5%, and for HQ with 97.0% and 97.3%. Overall, the constructed membrane can potentially be a good candidate for constructing electrochemical sensors in environmental analysis.

Polymer-based Electrochemical Sensor: Fast, Accurate, and Simple Insulin Diagnostics Tool

Study of the use of polymers with higher conductivity like polypyrrole, and polyaniline in the electrochemical insulin sensors can overcome the drawbacks arising from the ongoing use of non-conductive polymer membrane. Conductive polymer membranes maintain the positive properties of polymers, like improved stability, reproducibility, and even increase the current response of the prepared sensor toward insulin oxidation. Three different screen-printed electrodes modified with polyaniline, polypyrrole, or chitosan with electrochemically deposited nickel nanoparticles ensuring insulin oxidation were prepared. The electrode morphology was examined via SEM with EDX analysis. Also, the electroactive surface area and stability were determined by voltammetric methods. Based on the results, the SPCEs modified by polypyrrole and nickel nanoparticles were determined as the most appropriate for the insulin determination. The NiNPs-PPy-SPCE exhibited a linear range (500 nM–5 µM), a low-down limit of detection (38 nM), high sensitivity (3.98 µA/µM), and excellent result from insulin determination in real samples (human blood serum). The results confirmed the high potential of developed sensor for future research focused on detection of insulin via electrochemistry methods in clinical samples.Graphical

(Invited) Operando EPR Study on Radicals in Anion-Exchange Membrane Fuel Cells

In the rapidly developing modern society, there is an urgent need for the wide-ranging availability of advanced and eco-friendly energy sources. One of the possible alternatives is the application of anion exchange membrane fuel cells (AEMFCs) with a catalyst reducing dioxygen efficiently. These promising devices can revolutionize the energy sector since they practically produce no pollution. However, to make them more widely used, several obstacles must be overcome. As a result, vast-ranging investigations focus on improving the properties of conductive polymer membranes [1] and catalysts for the oxygen reduction reaction (ORR) [2]. The durability of the membrane electrode assembly (MEA) is one of the critical requirements for the successful commercialization of anion exchange membrane fuel cells (AEMFCs). Despite significant impacts of nucleophilic degradation on ion-exchange capability and the anionic conductivity of investigated membranes, it is believed to affect only cationic sites of membrane polymers and thus cannot explain the reported loss in the mechanical strength of degraded AEMs. Such a phenomenon might be related to polymer backbone degradation caused by free radicals. This was widely described in the literature in the case of fuel cells using proton-conducting membranes [3] but barely mentioned for AEMFCs [4]. Since the oxidative degradation of hydrocarbon polymers is very well known, we aimed to comprehensively investigate the formation of the short-lived species generated during the operation of AEMFCs as well as stable radicals present in the polymer membranes.We investigated the LDPE-base membranes with Pt black, Pd black, PdAg, and Ag as the ORR catalysts, whereas for HOR the Pt black, Pd black, and NiFe catalysts were used. The in-situ measurements are performed with a micro-AEMFC inserted into a resonator of an electron paramagnetic resonance (EPR) spectrometer, which enables separate monitoring of radicals formed on the anode and cathode sides. The creation of radicals was monitored by the EPR spin trapping technique. In Figure 1 the EPR spectra of DMPO spin adducts trapped during operation of micro-fuel cell placed in EPR spectrometer cavity are presented. In this experiment, the LDPE-base membrane with platinum catalysts on both sides was used. The main detected adducts during the operation of the micro-AEMFC were DMPO-OOH and DMPO-OH on the cathode side and DMPO-H on the anode side. Additionally, we clearly show the formation and presence of stable radicals in AEMs during and after long-term AEMFC operation [5]. Preliminary results suggest that the creation of the short-living radicals during AEMFCs operation is independent of the used membrane. However, the applied catalysts determine the number of detected radicals. The EPR investigations indicate that, in addition to the known chemical degradation mechanisms of the cationic ammonium groups of the membrane, oxidative degradation, including radical reactions, has to be taken into account when the stability of an anion conductive polymer for AEMFCs is investigated. The formation of stable radicals in AEMs was proven for the first time in this study. All short-living radicals formed during the AEMFC operation were fully identified. The presence of radicals in the AEM after AEMFC testing indicates that reactive oxygen species may play a very important role in the degradation mechanism of the anion conducting polymers. Results from this study shed light on the understanding of radical formation and presence in the membranes during AEMFC tests, which in turn may help to solve the challenge of anion exchange membrane stability. Acknowledgments. This work was supported by the Polish National Science Centre (NCN) project OPUS-14, No. 2017/27/B/ST5/01004.

Development and characterization of eco-friendly biopolymer gellan gum based electrolyte for electrochemical application

Abstract Magnesium ion conducting eco-friendly biopolymer electrolyte based on gellan gum has been developed by solution casting technique and characterized by XRD, FTIR, DSC, AC impedance analysis and LSV. Amorphous nature of the polymer electrolyte has been confirmed by XRD analysis. FTIR analysis confirms the complex formation between gellan gum and magnesium nitrate salt. Glass transition temperature of the polymer electrolytes have been found in DSC analysis. Ionic conductivity of polymer electrolyte membrane has been analysized by AC impedance studies, polymer electrolyte 1.0 g gellan gum with 0.7 wt% Mg (NO3)2 has highest ionic conductivity 1.392 × 10−2 S/cm at room temperature. Evan’s polarization method attributes Mg+ cationic transference number as 0.342 for high conducting polymer electrolyte. The high conducting polymer membrane has electrochemical stability 3.58 V. Using this high conducting polymer electrolyte, magnesium ion battery is constructed and the battery performance was studied. The open circuit voltage is found as 1.99 V.

Decoupling polymer, water and ion transport dynamics in ion-selective membranes for fuel cell applications

Ion conducting polymer membranes are designed for applications ranging from separation and dialysis, to energy conversion and storage technologies. A key application is in fuel cells, where the semi-permeable polymer membrane plays several roles. In a fuel cell, electrical power is generated from the electrochemical reaction between oxygen and hydrogen, catalysed by metal nanoparticles at the cathode and anode sites. The polymer membrane permits the selective transport of H + or OH − to enable completion of the electrode half-reactions, plays a major role in the management of water that is necessary for the conduction process and is a product in the reactions, and provides a physical barrier against leakage across the cell. All of these functions must be optimised to enable high conduction efficiency under operational conditions, including high temperatures and aggressive chemical environments, while ensuring a long lifetime of the fuel cell. Polymer electrolyte membranes used in current devices only partially meet these stringent requirements, with ongoing research to assess and develop improved membranes for a more efficient operation and to help realise the transition to a hydrogen-fuelled energy economy. A key fundamental issue to achieving these goals is the need to understand and control the nature of the strongly coupled dynamical processes involving the polymer, water and ions, and their relationship to the conductivity, as a function of temperature and other environmental conditions. This can be achieved by using techniques that give access to information across a wide range of timescales. Given the complexity of the dynamical map in these systems, unravelling and disentangling the various processes involved can be accessed by applying the “serial decoupling” approach introduced by Angell and co -workers for ion-conducting glasses and polymers. Here we introduce this concept and propose how it can be applied to proton- and anion-conducting fuel cell membranes using two main classes of these materials as examples. • The serial decoupling approach is a powerful way of disentangling coupled dynamics in polymers. • It is now been extended to disentangle relaxation and diffusional processes. • We demonstrate how it provides a useful approach for decoding the membrane function and performance.

Light‐Powered Ion Pumping in a Cation‐Selective Conducting Polymer Membrane

AbstractThe simulation of the ion pumping against a proton gradient energized by light in photosynthesis is of significant importance for the energy conversion in a non‐biological environment. Herein, we report light‐powered ion pumping in a polystyrene sulfonate anion (PSS) doped polypyrrole (PPy) conducting polymer membrane (PSS‐PPy) with a symmetric geometry. This PSS‐PPy conducting polymer membrane exhibits a cationic selectivity and a light‐responsive surface‐charge‐governed ion transport attributed to the negatively charged PSS groups. An asymmetric visible irradiation on one side of the PSS‐PPy membrane induces a built‐in electric field across the membrane due to the intrinsic photoelectronic property of PPy, which drives the cationic transport against the concentration gradient, demonstrating an ion‐pumping effect. This work is a prototype that uses a geometry‐symmetric conducting polymer membrane as a light‐powered artificial ion pump for active ion transport, which exhibits potential applications in nanofluidic energy conversion.

Light-Powered Ion Pumping in a Cation-Selective Conducting Polymer Membrane.

The simulation of the ion pumping against a proton gradient energized by light in photosynthesis is of significant importance for the energy conversion in a non-biological environment. Herein, we report light-powered ion pumping in a polystyrene sulfonate anion (PSS) doped polypyrrole (PPy) conducting polymer membrane (PSS-PPy) with a symmetric geometry. This PSS-PPy conducting polymer membrane exhibits a cationic selectivity and a light-responsive surface-charge-governed ion transport attributed to the negatively charged PSS groups. An asymmetric visible irradiation on one side of the PSS-PPy membrane induces a built-in electric field across the membrane due to the intrinsic photoelectronic property of PPy, which drives the cationic transport against the concentration gradient, demonstrating an ion-pumping effect. This work is a prototype that uses a geometry-symmetric conducting polymer membrane as a light-powered artificial ion pump for active ion transport, which exhibits potential applications in nanofluidic energy conversion.

Fabrication of biocompatible and conductive polypropylene micromembrane as a soft and porous electrode

BackgroundWe adopt a biomimic approach to fabricate a biocompatible and conductive polypropylene micromembrane (PPMM). It usefulness as a soft electrode is validated via its large electrochemical active surface area for in-vivo and in-vitro glucose sensing. MethodsWe conduct the conformal coating of Au on polypropylene (PP) fibers of PPMM using polydopamine (PDA) and polyvinyl alcohol (PVA) as the adhesive, wetting, and reducing agent, simultaneously. The uniform coverage of PDA/PVA on individual PP fibers of PPMM renders the latter to be hydrophilic for subsequent electroless Au deposition in thickness of 150 nm encapsulating every single PP fiber. SignificantFindings The metalized PPMM exhibits impressive conductivity in both X (10.04 S/cm) and Z (1.23 × 10−2 S/cm) directions. In addition, its tensile strength and strain are similar to those of pristine PPMM. After 10,000 bending cycles, the metalized PPMM reveals negligible physical delamination. Thermogravimetric analysis shows a thermal stability of 400 °C and an effective Au loading of 5.32 mg/cm2. Electrochemical analysis indicates a large electrochemical active surface area with for enhanced glucose sensing performance. Our strategy of using the PDA/PVA for their multifunctional roles could be adopted to fabricate alternative conductive polymer membranes for many possible applications.

Electrospun Composite Gel Polymer Electrolytes with High Thermal Conductivity toward Wide Temperature Lithium Metal Batteries

Herein, the thermally conductive composite polymer membranes (CPMs) with silica-coated silver nanowires (AgNWs@SiO2) and poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) are first fabricated by an electrospinning technique. Various composite gel polymer electrolytes (CGPEs) are investigated with different weight percentages of AgNWs@SiO2 with respect to PVDF-HFP in the presence of liquid electrolytes. The CPMs display high thermal conductivity and thermal stability, good mechanical strength, and high electrolyte uptake. The thermal conduction property of CPMs was analyzed by a bidirectional asymmetric heat transfer model. Moreover, the CGPEs with the electrospun CPM as the matrix and AgNWs@SiO2 as fillers (es-CGPEs) possess the high ionic conductivity and excellent electrochemical performance compared to the Celgard separator system. The Li/es-CGPEs/LiFePO4 cell shows an enlarged excellent cycling life and better rate performance at 25 and 60 °C, in comparison to the one without AgNWs@SiO2 fillers. Interestingly, the Li/es-CGPEs/LiFePO4 cell in the presence of 5 wt % of AgNWs@SiO2 still delivers an excellent rate capability at 0 °C. The es-CGPE with AgNWs@SiO2 would be a promising candidate as the electrolyte material toward wide temperature lithium metal batteries.

Synthesis and characterization of Dextran, poly (vinyl alcohol) blend biopolymer electrolytes with NH4NO3, for electrochemical applications

ABSTRACT New biocompatible biopolymer membranes have been synthesized from naturally occurring bacterial polysaccharide Dextran, which is efficacious versatile polymer known for medicinal applications. In the present study, biodegradable solid polymer electrolytes based on Dextran:Poly vinyl alcohol (PVA) with different composition of ammonium nitrate (NH4NO3) are prepared by solution casting technique with double distilled water as a solvent. The prepared polymer membranes have been characterized by various techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetric (DSC), AC impedance, linear sweep voltammetry (LSV), and transference number measurement. The amorphous nature of the polymer membrane is enhanced due to the addition of ammonium nitrate has been confirmed by X-ray diffraction analysis. The complex formation between the host polymer and the salt has been studied by Fourier transform infrared spectroscopy. The highest ionic conductivity of 1.66 × 10−3 S/cm for the composition 700 mgDextran:300 mgPVA:450 mgNH4NO3 has been observed by AC impedance spectroscopy at room temperature. The electrochemical stability of the highest conducting polymer electrolyte (700 mgDextran:300 mgPVA:450 mgNH4NO3) has been observed as 3.32 V by Linear sweep voltammetry. From Wagner’s polarization method transference number of highest conducting polymer electrolyte has been calculated as 0.99. Finally primary proton battery has been constructed using the highest conducting polymer membrane of 700 mgDextran:300 mgPVA:450 mgNH4NO3. Its open circuit voltage is measured as 1.51 V and its performance is studied.

Study on novel biopolymer electrolyte Moringa oleifera gum with ammonium nitrate

A new class of environmental friendly bio-based electrolytes has been synthesized from natural tree gum of Moringa oleifera by solution casting technique. An ionic salt of ammonium nitrate (NH4NO3) of varying compositions from 0.2 to 0.6 wt % has been used as an additive to optimize the ionic conductivity of Moringa gum (MG) based biopolymer membranes. X-ray diffractograms affirm the enhancement in amorphous nature of the membranes with the addition of salt, and the high degree of amorphous nature is exhibited by the composition of MG (1 g) with 0.5 wt % NH4NO3. Complex formation between MG and salt has been studied by Fourier transform infra-red (FTIR). Thermal behavioural study by differential scanning calorimetry (DSC) authenticates the flexibility of the prepared MG-based membrane with NH4NO3 by low glass transition temperature. The obtained solid polymer electrolyte MG (1 g) with 0.5 wt % NH4NO3 achieved an ionic conductivity as high as 2.66 × 10−3 S cm−1 at room temperature and the high ionic transference number of 0.98 is observed for the same. Primary proton cell has been fabricated with the optimum conducting polymer membrane (with a configuration Zn: ZnSO4.7H2O:C|| MG :0.5 wt % NH4NO3 Membrane || PbO2: V2O5 ) exhibits an open cell potential of 2.19 V and 1.88 V when shunted through the load resistance of 100 KΩ. Natural tree gum of Moringa oleifera as an electrolyte in the primary proton cell has provided a considerable open cell potential of 2.19 V which authenticates the utility of MG as a successful electrolytic material.

Effect of Structure and Hydration Level on Water Diffusion in Chitosan Membranes

AbstractBioprotonic devices show promise for medicinal/therapeutic treatments because of their ability to deliver a controlled flow of small molecules and ions to living organisms. These devices rely on biocompatible, conductive polymer membranes to facilitate molecular/ionic transport. Herein, ab initio molecular dynamics simulations are used to probe the effects structure and hydration level on water diffusion in chitosan‐based polymer membranes. The diffusion coefficient of water is shown to be highest in membranes with low overall densities and weak non‐covalent interactions. Insight from these results may aid in optimizing the molecular/ionic transport properties of polymer membranes for bioprotonic applications.

Enhancing Proton Conduction of Poly(benzimidazole) with Sulfonated Titania Nano Composite Membrane for PEM Fuel Cell Applications

Polybenzimidazole (PBI)-sulfonated nano titania (S-TiO2) polymer composite membranes have been prepared by solvent casting technique for high temperature polymer electrolyte membrane (HT-PEM) fuel cells. X-Ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy was used to characterize the polymer structure and confirm the complexation of the sulfonated titania inside the polymer matrix. The highest proton conductivity obtained was 0.091 S cm−1 at 160 °C. The temperature dependent proton conductivity of the phosphoric acid doped proton conducting polymer electrolyte exhibits an Arrhenius relation and Grotthuss mechanism. Thermal gravimetric analysis (TGA) showed that all the prepared proton conducting polymer membrane exhibit good thermal stability. The morphological behaviors of the prepared proton conducting polymer electrolytes were depicted by scanning electron microscope (SEM) micrograph. The prepared composite membranes were characterized by proton conductivity, durability and mechanical strength. The acid uptake of the PBI-sulfonated titania blended membrane was found to be higher than that of the pristine PBI. The fabricated composite membrane with the highest conductivity exhibited a maximum current density of 0.89 A cm−2 through the high proton conductivity.