Proton conducting polymer blend electrolytes based on MC: FTIR,ion transport and electrochemical studies

In this work, the free-standing plasticized solid polymer electrolyte films were made utilizing methylcellulose (MC) and dextran (DN) doped with ammonium fluoride (NH₄F) and plasticized with glycerol by a typical solution casting approach. Based on the characterizations, MC-DN-NH₄F electrolyte has been shown to improve the structural, electrical, and electrochemical properties resulting from the dispersion of glycerol plasticizer. The electrochemical impedance spectroscopy (EIS) measurement for the highest inclusion of plasticizer revealed a conductivity of 2.25 × 10^-3 S/cm. The electrical equivalent circuit (EEC) model has established the circuit elements for each electrolyte. The variation trend of dielectric constant and DC conductivity was matched and confirmed by the EIS data. The fourier transform infrared (FTIR) analysis displayed credible confirmation of polymers-ion-plasticizer interactions. The dielectric study is extra highlighted the conductivity behavior. The dielectric constant and loss (ε′ and ε″) quantities were reported to be high at low frequencies. On the other hand, the irregular shape of the imaginary part of modulus (M“) spectra denotes the non-Debye behaviors of relaxation. The ion transference number (t_ion) value for the maximum plasticized system is 0.944, where the ions are the primary components for the charge transfer process. Stability of the highest conducting sample is determined to be 1.6 V, using linear sweep voltammetry (LSV).     

The study of ion transport parameters associated with dissociated cation using EIS model in solid polymer electrolytes (SPEs) based on PVA host polymer: XRD,FTIR, and dielectric properties

Electrical impedance spectroscopy (EIS) model is used to determine ion transport parameters. The transport parameters such as mobility, carrier density and diffusion coefficient of ions are the subject of great interest. The solution cast method is used to fabricate SPEs using polyvinyl alcohol (PVA) loaded with different amounts of sodium iodide (NaI). XRD deconvolution is used to separate the crystalline phase from amorphous phase. The degree of crystallinity is reduced with an increased amount of NaI. FTIR is used to investigate the polymer/salt interactions. To find out the circuit element, the Nyquist plots of impedance results are fitted with EEC modeling. The bulk resistance obtained from the EEC modeling is used to determine DC conductivity. At room temperature the maximum conductivity of $2.41\times {10}^{-4}\mathrm{S}/\mathrm{c}\mathrm{m}$ is measured. The regions belong to the electrode polarization (EP) effect are distinguished form the spectra of dielectric constant and dielectric loss. Due to the buildup of charge carriers, the dielectric constant and loss are observed to be high at the low-frequency region. Obvious peaks are appeared in the tanδ and M“ spectra at high salt concentrations. Shifting of the tanδ peaks to the high frequency region are detected. The incomplete circular arc of the argand plot is shown the non-Debye relaxation. It is found that with increasing frequency, AC conductivity increased. The regions belong to the EP and DC contributions are differentiated in the AC spectra.     

Structural,ion transport parameter and electrochemical properties of plasticized polymer composite electrolyte based on PVA: A novel approach to fabricate high performance EDLC devices

In this study a novel polymer composite electrolytes (PCEs) based on poly (vinyl alcohol) (PVA): Ce(III)-complex:NH₄SCN plasticized with glycerol are prepared by solution cast technique. XRD and FTIR routes are used to study the film structure. The crystalline and amorphous areas are determined through the deconvolution of XRD spectra and their values were used to calculate the degree of crystallinity. The deconvolutions of the FTIR of asymmetric C≡N stretching mode are carried out to establish the bands coupled with free ions, contact ion pairs and ion aggregates. The maximum ambient temperature DC conductivity of 2.07 × 10⁻³ S cm⁻¹ is recorded for the sample with the lowest degree of crystallinity. It was found that the number density (n), mobility (μ) and diffusion coefficient (D) of ions are increased with the glycerol concentration. Field emission scanning electron microscopy (FESEM) is used to examine the effect of plasticizer on film morphology. The DC conductivity trend is interpreted in detail with the help of dielectric properties. It is found that the transference numbers of ions (t_ion) and electrons (t_el) are 0.965 and 0.035, respectively. It is shown by the linear sweep voltammetry (LSV) that the potential window of the PCE is 2.1 V. A shape, which is nearly rectangular at lower scan rates, is identified from cyclic voltammetry (CV). Specific capacitance and energy density are exhibited by EDLC with average of 161.5 F/g and 18.17 Wh/kg, respectively within 400 cycles. The initial power density is shown by EDLC to be 2.825 × 10³ W/kg.     

The effect of polyvinyl alcohol (PVA) on the optical,electrical and solid state properties of copper zinc tin sulfide (CZTS) deposited by sensitive spray pyrolysis (SSP)

Recently, the use of CZTS as the basis for other generation of low cost thin films solar cells has stimulated further researches. Its excellent p-type absorber nature, relatively high absorption coefficient and ideal energy band-gap of 1.5eV motivated these efforts. Additionally, CZTS consist of earth-abundant, cheap and non-toxic elements with very low manufacturing cost. Initially, copper indium gallium selenide (CIGS) solar cell device emerged but suffered limitations in further development because of rare indium and gallium in the device structure therefore, CZTS is recently preferred as an alternative to CIGS commercial solar cell absorber layer. In this work, solution mixture of CZTS and PVA was deposited on a substrate at temperature of 150 °C. Sensitive spray pyrolysis was used to grow the thin films where calculated amount of the precursor mixture was allowed to fall and be deposited on a heated substrate to form CZTS/PVA thin films. Subsequently, the thin film samples were annealed at a temperature of 200^oCfor 1 h to achieving pure crystalline thin film formation. SEM, XRD analysis, Optical, Solid State properties and Raman analysis were studied. The XRD analysis showed that the thin films fell into the pure kesterite structure of CZTS. Results show that produced thin films exhibited higher absorption coefficient and optical conductivity than pure CZTS, 10⁶ m^?1 and 10¹⁴(S^?1) against 10⁴cm^?1 and 10¹²(S^?1) respectively. The band-gap is between 1.53eV and 1.73eV. Using a PVA concentration of 0.05 M yielded highest absorbance and optical conductivity with lowest real dielectric constant and transmittance. These improved optical, electrical and solid state properties suitably qualify these thin films as absorber layer material for solar cell applications.     

Pervaporation dehydration of ethylene glycol with chitosan–poly(vinyl alcohol) blend membranes: Effect of CS–PVA blending ratios

Chitosan–poly(vinyl alcohol), CS–PVA, blended membranes were prepared by solution casting of varying proportions of CS and PVA. The blend membranes were then crosslinked interfacially with trimesoyl chloride (TMC)/hexane. The physiochemical properties of the blend membranes were determined using Attenuated Total Reflection-Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), tensile test and contact angle measurements. Results from ATR-FTIR show that TMC has crosslinked the blend membranes successfully, and results of XRD and DSC show a corresponding decrease in crystallinity and increase in melting point, respectively. The crosslinked CS–PVA blend membranes also show improved mechanical strength but lower flexibility in tensile testing as compared to uncrosslinked membranes. Contact angle results show that crosslinking has decreased the surface hydrophilicity of the blend membranes. The blend membrane properties, including contact angle, melting point and tensile strength, change with a variation in the blending ratio. They appear to reach a maximum when the CS content is at 75 wt%. In general, the crosslinked blend membranes show excellent stability during the pervaporation (PV) dehydration of ethylene glycol–water mixtures (10–90 wt% EG) at different temperatures (25–70 °C). At 70 °C, for 90 wt% EG in the feed mixture, the crosslinked blend membrane with 75 wt% CS shows the highest total flux of 0.46 kg/(m² h) and best selectivity of 986. The blending ratio of 75 wt% CS is recommended as the optimized ratio in the preparation of CS–PVA blend membranes for pervaporation dehydration of ethylene glycol.     

Structural changes of silver polymer electrolytes: Comparison between poly(2‐ethyl‐2‐oxazoline) and poly(N‐vinyl pyrrolidone) complexes with silver salt

The difference between the polymer matrices of poly(2‐ethyl‐2‐oxazoline) (POZ) and poly(N‐vinyl pyrrolidone) (PVP) does not have a significant effect on the facilitated propylene transport and propylene solubility in 1:1 polymer/silver salt complex membranes, according to our previous work. In this article, its origin is investigated in terms of both microstructures of silver polymer electrolytes and the coordinative interaction of silver ion with polymer and with the counteranion. Initially different microstructures of POZ and PVP become similar to each other upon dissolving a large amount of silver salt, as evidenced by propane transport properties, specific volume, and Bragg d‐spacing. The dissolution of the silver salt in the polymer solvent strongly depends on the coordinative interaction between silver ion and carbonyl oxygen of POZ and PVP. Thus, the structural similarity upon dissolving silver salts in POZ and PVP is primarily determined by the coordinative interaction between silver ion and carbonyl oxygen, which was confirmed by theoretical structure calculation based on density functional theory and by IR and Raman spectroscopy. Therefore, facilitated olefin transport for silver polymer electrolyte membranes does not strongly depend on the polymeric matrix at high silver concentrations. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 232–237, 2004