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A Novel Method for Humidity-Dependent Through-Plane Impedance Measurement for Proton Conducting Polymer Membranes.

ABSTRACT: In this study, we introduce a through-plane electrochemical measurement cell for proton conducting polymer membranes (PEM) with the ability to vary temperature and humidity. Model Nafion and 3M membranes, as well as anisotropic composite membranes, were used to compare through plane and in plane conductivity. Electrochemical impedance spectroscopy (EIS) was applied to evaluate the proton conductivity of bare proton exchange membranes. In the Nyquist plots, all membranes showed a straight line with an angle of 60-70 degrees to the Z'-axis. Equivalent circuit modeling and linear extrapolation of the impedance data were compared to extract the membrane resistance. System and cell parameters such as high frequency inductance, contact resistance and pressure, interfacial capacitance were observed and instrumentally minimized. Material-related effects, such as swelling of the membranes and indentation of the platinum mesh electrodes were examined thoroughly to receive a reliable through-plane conductivity. The received data for model Nafion and 3M membranes were in accordance with literature values for in-plane and through-plane conductivity of membrane electrode assemblies. Anisotropic composite membranes underlined the importance of a sophisticated measurement technique that is able to separate the in-plane and through-plane effects in polymer electrolytes.

SUBMITTER: Heimerdinger P

PROVIDER: S-EPMC6571940 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Conducting Polymer-Based Cantilever Sensors for Detection Humidity.

Project description:This paper describes the use of different conducting polymers (polyaniline, poly(o-ethoxyaniline), and polypyrrole) as a sensitive layer on a silicon cantilever sensor. The mechanical response (deflection) of the bimaterial (the coated cantilever) was investigated under the influence of relative humidity. The variations in the deflection of the coated cantilevers when exposed to relative humidity were evaluated. The results indicated a linear sensitivity in ranges, where the high value was obtained for a polypyrrole-sensitive layer between 20 and 45% of humidity. Furthermore, the sensor shows excellent performance along with rapid response and recovery times, relatively low hysteresis, and excellent stability. The sensors developed are potentially excellent materials for sensing low humidity for long time.

| S-EPMC6008807 | biostudies-literature

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| S-EPMC5551730 | biostudies-other

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| S-EPMC6223772 | biostudies-literature

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| S-EPMC5764980 | biostudies-literature

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| S-EPMC7176501 | biostudies-literature

Structural, Morphological, Electrical and Electrochemical Properties of PVA: CS-Based Proton-Conducting Polymer Blend Electrolytes.

Project description:Polymer blend electrolytes based on poly(vinyl alcohol):chitosan (PVA:CS) incorporated with various quantities of ammonium iodide were prepared and characterized using a range of electrochemical, structural and microscopic techniques. In the structural analysis, X-ray diffraction (XRD) was used to confirm the buildup of the amorphous phase. To reveal the effect of dopant addition on structural changes, field-emission scanning electron microscope (FESEM) was used. The protrusions of salt aggregates with large quantity were seen at the surface of the formed films at 50 wt.% of the added salt. The nature of the relationship between conductivity and dielectric properties was shown using electrochemical impedance spectroscopy (EIS). The EIS spectra were fitted with electrical equivalent circuits (EECs). It was observed that both dielectric constant and dielectric loss were high in the low-frequency region. For all samples, loss tangent and electric modulus plots were analyzed to become familiar with the relaxation behavior. Linear sweep voltammetry (LSV) and transference number measurement (TNM) were recorded. A relatively high cut-off potential for the polymer electrolyte was obtained at 1.33 V and both values of the transference number for ion (tion) and electronic (telec) showed the ion dominant as charge carrier species. The TNM and LSV measurements indicate the suitability of the samples for energy storage application if their conductivity can be more enhanced.

| S-EPMC7231387 | biostudies-literature

Rocking-Chair Proton Batteries with Conducting Redox Polymer Active Materials and Protic Ionic Liquid Electrolytes.

Project description:Rechargeable batteries that use redox-active organic compounds are currently considered an energy storage technology for the future. Functionalizing redox-active groups onto conducting polymers to make conducting redox polymers (CRPs) can effectively solve the low conductivity and dissolution problems of redox-active compounds. Here, we employ a solution-processable postdeposition polymerization (PDP) method, where the rearrangements ensured by partial dissolution of intermediated trimer during polymerization were found significant to produce high-performance CRPs. We show that quinizarin (Qz)- and naphthoquinone (NQ)-based CRPs can reach their theoretical capacity through optimization of the polymerization conditions. Combining the two CRPs, with the Qz-CRP as a cathode, the NQ-CRP as an anode, and a protic ionic liquid electrolyte, yields a 0.8 V proton rocking-chair battery. The conducting additive-free all-organic proton battery exhibits a capacity of 62 mAh/g and a capacity retention of 80% after 500 cycles using rapid potentiostatic charging and galvanostatic discharge at 4.5 C.

| S-EPMC8153541 | biostudies-literature

Positive impedance humidity sensors via single-component materials.

Project description:Resistivity-type humidity sensors have been investigated with great interest due to the increasing demands in industry, agriculture and daily life. To date, most of the available humidity sensors have been fabricated based on negative humidity impedance, in which the electrical resistance decreases as the humidity increases, and only several carbon composites have been reported to present positive humidity impedance. However, here we fabricate positive impedance humidity sensors only via single-component WO3-x crystals. The resistance of WO3-x crystal sensors in response to relative humidity could be tuned from a negative to positive one by increasing the compositional x. And it was revealed that the positive humidity impedance was driven by the defects of oxygen vacancy. This result will extend the application field of humidity sensors, because the positive humidity impedance sensors would be more energy-efficient, easier to be miniaturized and electrically safer than their negative counterparts for their lower operation voltages. And we believe that constructing vacancies in semiconducting materials is a universal way to fabricate positive impedance humidity sensors.

| S-EPMC4858685 | biostudies-literature

Solid-State NMR and Impedance Spectroscopy Study of Spin Dynamics in Proton-Conducting Polymers: An Application of Anisotropic Relaxing Model.

Project description:The 1H-13C cross-polarization (CP) kinetics in poly[2-(methacryloyloxy)ethyltrimethylammonium chloride] (PMETAC) was studied under moderate (10 kHz) magic-angle spinning (MAS). To elucidate the role of adsorbed water in spin diffusion and proton conductivity, PMETAC was degassed under vacuum. The CP MAS results were processed by applying the anisotropic Naito and McDowell spin dynamics model, which includes the complete scheme of the rotating frame spin-lattice relaxation pathways. Some earlier studied proton-conducting and nonconducting polymers were added to the analysis in order to prove the capability of the used approach and to get more general conclusions. The spin-diffusion rate constant, which describes the damping of the coherences, was found to be strongly depending on the dipolar I-S coupling constant (DIS). The spin diffusion, associated with the incoherent thermal equilibration with the bath, was found to be most probably independent of DIS. It was deduced that the drying scarcely influences the spin-diffusion rates; however, it significantly (1 order of magnitude) reduces the rotating frame spin-lattice relaxation times. The drying causes the polymer hardening that reflects the changes of the local order parameters. The impedance spectroscopy was applied to study proton conductivity. The activation energies for dielectric relaxation and proton conductivity were determined, and the vehicle-type conductivity mechanism was accepted. The spin-diffusion processes occur on the microsecond scale and are one order faster than the dielectric relaxation. The possibility to determine the proton location in the H-bonded structures in powders using CP MAS technique is discussed.

| S-EPMC8607415 | biostudies-literature

Spectroelectrochemical Evidence of Interconnected Charge and Ion Transfer in Ultrathin Membranes Modulated by a Redox Conducting Polymer.

Project description:Previous publications have demonstrated the tuning of ion-transfer (IT) processes across ion-selective membranes (ISMs) with thicknesses in the nanometer order by modulating the oxidation state of a film of a conducting polymer, such as poly(3-octylthiophene) [POT], that is in back-side contact. Attempts on the theoretical description of this charge transfer (CT)-IT system have considered the Nernst equation for the CT, while there is no empirical evidence confirming this behavior. We present herein the first experimental characterization of the CT in POT films involved in different CT-IT systems. We take advantage of the absorbance change in the POT film while being oxidized, to monitor the CT linked to nonassisted and assisted ITs at the sample-ISM interface, from one to three ionophores, therefore promoting a change in the nature and number of the ITs. The CT is visualized as an independent sigmoid in different potential ranges according to the assigned IT. Herein, we have proposed a simple calculation of the empirical CT utilizing the mathematical Sigmoidal-Boltzmann model. The identification of the physical meaning of the mathematical definition of CT opens up new possibilities for the design of sensors with superior analytical features (mainly in terms of selectivity) and the calculation of apparent binding constants in the ISM.

| S-EPMC7584340 | biostudies-literature

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