Proton Conducting Polymer Electrolyte Research Articles

Effect of High Ammonium Salt Concentration and Temperature on the Structure, Morphology, and Ionic Conductivity of Proton-Conductor Solid Polymer Electrolytes Based PVA.

Polyvinyl alcohol (PVA) based proton-conducting solid polymer electrolyte was prepared with a high salt concentration of ammonium nitrate (NH4NO3) by the technique of solvent casting. From the X-ray diffraction studies, the semicrystalline nature of PVA with the inclusion of NH4NO3 was studied. XRD analysis indicates that the highest ion conductive sample exhibits the minimum crystalline nature. The decreasing trend of Jonscher-exponent with temperature rise reveals that the present system is insured by the correlated barrier hopping (CBH) model. The maximum room temperature conductivity was found to be 5.17 × 10−5 S/cm for PVA loaded 30 wt.% of NH4NO3. The ionic transport of the proton-conducting solid polymer electrolyte was studied at the temperature range of 303–353 K. The conductivity-temperature relationship of the systems was analyzed using both the Arrhenius and Vogel–Tammann–Fulcher (VTF) models to explain the ionic hopping mechanism for the system.

Substrate-dependent proton transport and nanostructural orientation of perfluorosulfonic acid polymer thin films on Pt and carbon substrate

The electrochemical reactions occur on the carbon-supported platinum covered by a proton conducting polymer electrolyte. Thus, it is important to clarify the correlation between proton conductivity and morphology of the polymer electrolyte on Pt or carbon. In this study, the properties of thin films (50–200 nm) of Nafion®, which is the typical polymer electrolyte, were investigated on platinum and carbon substrates. Grazing-incidence small/wide angle X-ray scattering and electrochemical impedance spectroscopy were used to extract morphological and proton transport information. Self-designed interdigitated array electrodes were utilized to test and compare the proton conductivity on the Pt and carbon substrates. Based on the results, the difference in anisotropic behavior of Nafion thin films on each substrate were explored, which exhibit that the proton conductivity of Pt-supported Nafion thin films has more well defined hydrophilic domain structure than that of carbon supported thin films along in-plane direction and while it showed the opposite trend in the out-of-plane direction. These datasets and analyses represented a thorough study of the behavior of Nafion thin films on model substrates of interest, i.e., Pt catalyst/carbon electrodes. These results are expected to further understanding the difference in term of proton transport pathway.

Electrochemical characteristics of solid state double-layer capacitor constructed from proton conducting chitosan-based polymer blend electrolytes

This research is about the preparation of polymer blend electrolytes based on chitosan using solution cast technique. Field emission scanning electron microscopy and Fourier transform infrared spectroscopy (FTIR) routes were utilized for studying morphological and structural properties, respectively. Electrical impedance spectroscopy (EIS) was engaged for determining the direct current electrical conductivity of the films. The ion association at the highest salt concentration was actually present as confirmed by EIS and FTIR achievements. The sample surface displays the protrude salts at the highest salt concentration. Proton conducting polymer electrolyte with NH4Br as H+ (proton) provider has been used in electric double-layer capacitor (EDLC) applications. The highest conducting sample was used to fabricate EDLC. The transference number measurement indicated that the sample is mostly includes ion charge carriers which are vital for application in electrochemical devices. The linear sweep voltammetry study revealed that the decomposition of the sample takes place above 1.54 V. The fabricated EDLC device was performed capacitive behavior, as it can be seen from the cyclic voltammetry (CV) plot. Since no redox peaks have appeared, it can be concluded that the EDLC did not undergo either oxidation or reduction. The acquired value of specific capacitance (132.5 Fg−1) is considered to be of great interest from the application viewpoints.

Role of protic ionic liquid concentration in proton conducting polymer electrolytes for improved electrical and thermal properties

Protic ionic liquids (PILs) in the acidic medium are known to show higher ionic conductivity than neat PIL or PIL in alkaline media. Hence, polymer electrolyte membranes (PEM) containing both PIL and acids are considered ideal for non-humidified intermediate temperature PEM fuel cells. Herein, we report non-aqueous proton conducting PEM made up of diethylmethylammonium trifluoromethanesulfonate; [dema][TfO] and neat phosphoric acid (H3PO4) with poly (vinylidene fluoride-co-hexafluoropropylene); PVDF-HFP as the host matrix. The presence of PIL significantly modified the structure and microstructure of the electrolyte films with the emergence of micropores in the PIL containing membranes. SEM images suggest leaching of PIL and phosphoric acid above 80 wt% of PIL in the electrolyte membranes. Thermogravimetric studies show that the dehydration in the PEM films due to phosphoric acid condensation at 100 °C–200 °C region is arrested by the presence of PIL. The maximum ionic conductivity at room temperature is ∼6.3 × 10−4 S cm−1 at 40 wt% of [dema][TfO] addition, which is two orders higher than that of the primary electrolyte (PE) containing only phosphoric acid in PVDF-HFP. This high conductivity in PEM films can be correlated to the increase in polar β and γ phases as well as a drop in the total crystallinity fraction in the film. The study using dielectric spectroscopy reveals a strong coupling of ionic conductivity with the structural or segmental relaxation of the PVDF-HFP due to the presence of [dema][TfO] in the PEMs.

Protonic ceramic electrolysis cells for fuel production: a brief review

Proton-conducting oxides exhibit significant hydrogen ion (proton) conductivity at intermediate temperatures around 300–600 °C. Owing to their distinguished features compared to high-temperature oxygen ion-conducting oxide electrolytes and low-temperature proton-conducting polymer electrolytes, diverse electrochemical applications based on the proton-conducting oxides have attracted great attention for efficient energy conversions. This review particularly aims to introduce protonic ceramic electrolysis cells (PCECs) and their extended applications. The constituent materials, recent developments, remaining issues in PCECs as well as the application integrated with PCEC for electrochemical ammonia synthesis will be presented. In addition, for each section, the relevant prospects and recommendations for future research directions will be discussed.

Electrochemical Impedance study of Proton Conducting Polymer Electrolytes based on PVC Doped with Thiocyanate and Plasticized with Glycerol

Solid polymer electrolyte (SPE) system based on poly (vinyl chloride) PVC doped with ammonium thiocyanate (NH4SCN) salt has been prepared by solution cast techniques using glycerol as a plasticizer and THF tetra-hydro furan as a solvent. To examine the electrical properties of the electrolyte films the electrochemical impedance spectroscopy (EIS) has been used. The effect of glycerol on electrical properties and structure of the plasticized PVC-based polymer electrolyte was examined, and the various weight ratio of glycerol plasticizer (%5, %10, %15, and % 20) of PVCNH4SCN weight is well correlated. Electrolytes are the heart of electrochemical devices and their conductivity investigation is crucial from the viewpoint of electrochemical device application. EIS electrode impedance spectroscopy was used to determine the bulk resistance Rb of the films at room temperature. The increase of the ionic conductivity with an increase in the amount of glycerol was observed through an impedance study, and the maximum ionic conductivity was 1.02512 x 10-6 S cm-1 obtained from (PVC-%20 NH4SCN-%20 glycerol) system. Dielectric relaxation studies of the polymer electrolyte film have been studied. The rise of the dielectric polarization of the films is proved by increases in a dielectric constant and dielectric loss. The peaks appeared in the imaginary part of the electric modulus reveals that ion conduction occurs through the viscoelastic relaxation dynamic. In the AC conductivity pattern plateau region ascribed to DC conductivity is appeared.

Impedance and ionic transport properties of proton-conducting electrolytes based on polyethylene oxide/methylcellulose blend polymers

Abstract Proton-conducting polymer electrolyte films were prepared by dissolving NH4I salt in polyethylene oxide/methylcellulose (PEO/MC) blend polymers using the solution cast technique. The semi-crystalline nature of the sample was identified from the X-ray diffraction (XRD) pattern. The surface morphology on the electrical conductivity was analyzed by scanning electron microscopy (SEM). The highest ionic conductivity of 7.62 × 10 − 5 S / c m was achieved at room temperature for the sample containing 30 wt. % of NH4I. The temperature dependence of the Jonscher's exponent shows that the conduction mechanism can be well represented by the overlapping large polaron tunneling (OLPT) model. The electrical conductivity enhancement was analyzed by the Rice and Roth model, which showed that the increase in the salt concentration caused an increment in the mobility and the diffusion coefficient of the ions. For all prepared samples, the highest value of conductivity was associated with the minimum value of activation energy. The dielectric data were analyzed for the highest ionic conducting sample at various temperatures to clarify an important factor of the ion conduction. The non-Debye behavior of the samples can be expressed from the electric modulus formalism and the dielectric properties of the electrolytes that have been proven by the incomplete semicircular arc of the Argand plots.

Review of the experimental study and prediction of Pt-based catalyst degradation during PEM fuel cell operation

Abstract The degradation of Pt-based catalyst severely limits the lifetime of a fuel cell with a proton-conductive polymer electrolyte membrane (PEM FC) operating with H2 as the fuel and O2 as the oxidant. In this paper, a review of recent progress in the description of degradation mechanisms by experimental techniques and a prediction of the extent of degradation by means of mathematical modelling are presented. Significant progress in the development of PEM FCs has been achieved both by basic research and advanced single-cell testing, often combining electrochemical and in situ analytical methods. The intensity of degradation processes is strongly dependent on operating conditions and, consequently, their experimental investigation requires a different scientific approach for each type of PEM FC. Mathematical modelling complements experimental studies to describe the individual degradation mechanisms.

Microstructural, dielectric, and transport properties of proton-conducting solid polymer electrolyte for battery applications

Poly (vinyl alcohol) (PVA) complexed with ammonium chloride (NH4Cl) solid polymer electrolyte films was prepared using solution casting technique. Complexation of dopant with polymer was studied using Fourier transform infrared spectroscopy (FTIR). X-ray diffraction (XRD) results reflect that degree of crystallinity of the polymer increases with doping level. Surface morphology and topology of the electrolyte were studied using Scanning electron microscopy (SEM) and atomic force microscopy (AFM). Thermogravimetric analysis (TGA) results accounts for the increase of thermal stability of PVA due to the incorporation of NH4Cl. Impedance analysis was carried out to understand relaxation phenomena of polymer electrolyte. Dielectric studies revealed that the mobility of charge carriers follows non-Debye nature of ionic relaxation. Electrical studies reveal that proton conduction occurs in this polymer electrolyte through Grotthus mechanism and maximum conductivity of the polymer electrolyte (7.5 wt% NH4Cl/PVA) has been observed to be 1.81 × 10−3 S/cm at 353 K. Transport parameters have been determined using Wagner’s polarization technique. The observed highest conductivity of polymer electrolyte indicates utilizing this electrolyte for the fabrication of proton battery applications, and accordingly, the cell parameters have been measured.

Structural and ionic conductivity characterization of PEO:MC-NH4I proton-conducting polymer blend electrolytes based films

In the present work, series of proton-conducting polymer electrolyte films based on polyethylene oxide/methylcellulose complexed with different concentrations of ammonium iodide (NH4I) as doping salt were prepared by solution cast technique. The produced films were characterized by X-ray diffraction (XRD), Polarized optical microscope (POM), Fourier transform infrared (FTIR), and electrical impedance spectroscopy (EIS). The XRD and POM results reveal that the sample with 30 wt% NH4I (PBE-30) has the lowest degree of crystallinity. The observed shift in the IR peak position of the N–H stretching band at regions 3000–3300 cm−1 as a function of NH4I concentration suggested clear evidence of an interaction between host polymers and NH4I. The highest value of electrical conductivity was found to be 7.62×10-5S.cm-1 at 303K for PBE-30. The temperature-dependent of electrical conductivity and ion transport properties was described using both the Arrhenius and Vogel-Tammann-Fulcher (VTF) relations. The activation energy values decrease with increasing DC conductivity and vice-versa.

Development of proton-exchange polymer nanocomposite membranes for fuel cell applications

The design and development of proton conducting polymer electrolyte membranes from a linear constituent, sulfonated poly (ether ether ketone) (SPEEK), and inorganic additive, niobium oxide (NBO), have been achieved. The degree of sulfonation of SPEEK was measured by back titration method and found to be 57%. The physicochemical properties such as water uptake ability, ion-exchange capacity, swelling ratio, proton conductivity, and thermal stability of the prepared polymer nanocomposite membranes were studied in detail. The distribution of NBO throughout the polymer matrix has been examined by scanning electron microscopic and X-ray diffraction analyses and found to be uniform. The SP-NBO-10 composite membrane shows 38.4% of water uptake, whereas the pristine membrane limits to 27.1%. The prepared electrolyte membranes exhibit good proton conductivity at temperature varying from 30°C to 90°C and possess less activation energy for the transportation of proton by the incorporation of NBO filler. The thermal studies demonstrated that the stability of the composite membranes was significantly enhanced by the impregnation of NBO. The filler NBO shows excellent improvements on the polymer nanocomposite, making it a very promising additive for other polymers and offers new roads for energy applications.

Al2O3-incorporated proton-conducting solid polymer electrolytes for electrochemical devices: a proficient method to achieve high electrochemical performance

A new series of proton-conducting solid polymer electrolytes with different compositions, comprising polyvinylpyrrolidone (PVPK40) and polymethylmethacrylate (PMMA) as host polymers, methanesulfonic acid (MSA) as a proton-conducting salt, and alumina (Al2O3) as the nanofiller, were prepared using solution casting. High proton-conducting samples were identified and utilized for the construction of primary proton batteries. The electrical properties of the prepared electrolytes were investigated through AC impedance analysis. The highest proton conductivity (2.51 × 10−5 S/cm) was achieved at room temperature by PMMA-PVPK40-MSA-based blended polymer electrolytes (BS3). The discharge characteristics of filler-dispersed solid polymer electrolytes were better than those of other solid polymer electrolytes. The estimated energy density of the constructed proton battery using solid polymer electrolytes with blended polymers and nanofillers was 0.66 and 3.25 Wh kg−1, respectively.

Synthesis and Physical Properties of Proton Conducting Polymer Electrolytes Comprising PAM Cross-Linked Flexible Spacers

The design of novel proton exchange membranes with high conductivity and better dimensional stability has become increasingly important due to the need for applications in different devices. The present work shows the acid-doped and crosslinked polyacrylamide (PAM) networks including flexible spaces. To this end PAM was modified with 1,4-butanediol diglycidyl ether (BG) to form PAM35BG and PAM50BG networks, which would afford more space for protonated solvents. The reaction of PAM with BG was monitored by FTIR and 13C CP-MAS NMR. The polymer electrolytes were produced by acid doping at several stoichiometric ratios with respect to the monomer repeat unit of a host polymer. The resulting materials exhibited better thermal, chemical, and electrochemical stabilities and had distinct Tg values. Additionally, the pores of the PAM-BG materials were filled with H3PO4 to get PAM35BG0.5H3PO4 and PAM50BG1.0H3PO4. The doping enhanced the proton conductivities of the membranes as high as 0.003 S/cm at 120 °C under an anhydrous atmosphere. The proton diffusion mechanism and the dielectric relaxation were further examined using the complex modulus formalism, M*.

FTIR, thermal and ionic conductivity studies of nanocomposite polymer electrolytes

In this study, proton-conducting nanocomposite plasticized polymer electrolytes based on poly(methyl methacrylate) (PMMA) complexed with trifluoromethanesulfonic acid (HCF3SO3) plasticized with propylene carbonate (PC) and dispersed with nanosized fumed silica (SiO2) have been prepared through the solution-casting technique. The ionic conductivity of electrolytes was measured as a function of acid, plasticizer and fumed silica concentrations. A maximum ionic conductivity of 3·31 × 10−4 S/cm for PMMA + 10 wt% trifluoromethanesulfonic acid polymer electrolytes and 5·37 × 10−3 S/cm for plasticized polymer electrolytes containing 50 wt% PC has been observed at room temperature. The viscosity percolation threshold for nanocomposite polymer electrolytes was observed at 3 wt% concentration of fumed silica with ionic conductivity of 8·84 × 10−3 S/cm at room temperature. Fourier transform infrared studies suggested the complexation of constituents of the electrolytes, formation of ion aggregates in unplasticized polymer electrolytes and dissociation of ion aggregates with the addition of the plasticizer in plasticized polymer electrolytes. Differential scanning calorimetry and thermogravimetric analysis studies proved that these electrolytes are thermally stable only up to 130°C. The conductivity shows negligible change with temperature from 30 to 130°C and time of 30 d, which is desirable for their use in practical applications such solid-state batteries, fuel cells, sensors and supercapacitors.

Studies of proton conducting polymer electrolyte based on PVA, amino acid proline and NH4SCN

Abstract Proton conducting polymer electrolytes based on PVA, amino acid proline and NH4SCN were prepared by the solution casting technique. An increase in the amorphous nature of the polymer electrolytes was confirmed by X-ray diffraction analysis. DSC measurements showed a decrease in Tg with increasing salt concentration. The complex formation of the PVA/Proline/NH4SCN was investigated by FTIR analysis. The highest ionic conductivity of 1.17 × 10-3 S/cm for the 75 Mwt% PVA: 25 Mwt% Proline: 0.5 Mwt% of NH4SCN polymer electrolyte at ambient temperature was obtained by using AC impedance technique. Transference number measurements revealed the nature of the charge transport species in the polymer electrolyte. Electrochemical stability window of 3.61 V was measured by using the linear sweep voltammetry for the highest ionic conducting (75 Mwt% PVA: 25 Mwt% Proline: 0.5 Mwt% of NH4SCN) polymer membrane. A primary proton battery was constructed using the 75 Mwt% PVA: 25 Mwt% Proline: 0.5 Mwt% of NH4SCN polymer membrane and its performance was tested.

Studies on proton conducting polymer electrolytes based on poly(ethylene oxide)/poly(vinyl pyrrolidone) with NH4 SCN

Studies on proton conducting polymer electrolytes based on poly(ethylene oxide)/poly(vinyl pyrrolidone) with NH4 SCN

Photoelectrochemical Gas-Electrolyte-Solid Phase Boundary for Hydrogen Production From Water Vapor.

Hydrogen production from humidity in the ambient air reduces the maintenance costs for sustainable solar-driven water splitting. We report a gas-diffusion porous photoelectrode consisting of tungsten trioxide (WO3) nanoparticles coated with a proton-conducting polymer electrolyte thin film for visible-light-driven photoelectrochemical water vapor splitting. The gas–electrolyte–solid triple phase boundary enhanced not only the incident photon-to-current conversion efficiency (IPCE) of the WO3 photoanode but also the Faraday efficiency (FE) of oxygen evolution in the gas-phase water oxidation process. The IPCE was 7.5% at an applied voltage of 1.2 V under 453 nm blue light irradiation. The FE of hydrogen evolution in the proton exchange membrane photoelectrochemical cell was close to 100%, and the produced hydrogen was separated from the photoanode reaction by the membrane. A comparison of the gas-phase photoelectrochemical reaction with that in liquid-phase aqueous media confirmed the importance of the triple phase boundary for realizing water vapor splitting.

Investigation on meta-polybenzimidazole blend with sulfonated PVdF-HFP proton conducting polymer electrolytes for HT-PEM fuel cell application

Sulfonated poly (Vinylidene Fluoride-co-hexafluoro propylene) (SPVdF-HFP) blended with varying concentrations of m-poly (Benzimidazole) (PBI) were prepared by solution casting techinque. The sulfonation of PVdF-HFP was carried out with fuming chlorosulfonic acid at 60 °C and the degree of sulfonation was found to be 2.48%. The addition of m-PBI into the hydrophilic sulfonated PVdF-HFP membrane has provided good chemical and thermal stability. And also the increases the physico-chemical characteristics such as the water uptake, ion exchange capacity and proton conductivity. An inter chain separation and specific interaction between the two polymers in the blends was observed by XRD and FT-IR analyses. The Fourier transform spectroscopy indicated the intense ionic bond between—SO3H and N-basic group. The 25% of m-PBI based blend polymer electrolyte gives high proton conductivity (5.72 × 10−3 S/cm) at 160 °C and also the thermal stability. The temperature dependent proton conductivity of the polymer electrolyte follows an Arrhenius relationship and Grotthuss mechanism and it shows hopping of ions in the polymer matrix. It is noticed that the addition of m-PBI in the sulfonated PVdF-HFP enhances the mechanical, thermal and proton conductivity, which are sufficiently better for the use in HT-PEM fuel cell applications.

(Invited) Biomimetic Proton Conductive Polymer Electrolyte

Proton conductive polymer electrolyte is one of the key components to fabricate an efficient fuel cell. Perfluorosulfonic acid polymers, such as Nafion are widely used because of their high proton conductivity. It has been considered that a strong acid is important for high proton conductivity therefore many group synthesized acid contain polymer from the viewpoint of how much strong acid can be added with keeping the polymer mechanical strength. On the other hand, living cell, mitochondria also used proton to produce energy. The difference in proton concentration across a membrane produce electrochemical potential energy, which drives the synthesis of ATP. Mitochondria does not contain strong acid and the protons are transferred using weak acid and base, whereas efficient proton conduction occurred at the bilayer membranes. Although the detailed mechanism for the proton conduction at the membrane is still controversial, several groups suggested that protons efficiently conduct through the membrane surface [1]. In this paper, we present a polymer proton conductive membrane which mimic the proton conduction at the bilayer membrane [2]. The polymer membrane was prepared by deposition of poly(N-dodecylacrylamide-co-acrylic acid) monolayer formed at an air-water interface using the Langmuir-Blodgett technique. The membrane was formed by multilayer film of the monolayer, in which formed a clear lamellar structure composed of hydrophobic alkyl side chains and hydrophilic amide and carboxylic acid regions. The hydrophilic region created 2D proton conductive nanospace, which resembles to the bilayer membrane surface. The proton conductivity in the 2D proton nanospace of the biomimetic polymer membrane reached to 5.9×10-2 S/cm, which is comparable to strong acid polymer electrolyte. The achievement of high proton conductivity even using weak acid as a proton source clearly indicates an efficient proton conduction in 2D nanospace. Moreover, we found that acrylic acid groups should be located in a proper distance to achieve the high proton conductivity. The mechanism of proton conduction at the 2D nanospace will be discussed using reported works of theoretical calculation.

Preparation and characterization of proton-conducting polymer electrolyte based on PVA, amino acid proline, and NH4Cl and its applications to electrochemical devices

Biodegradable solid polymer electrolytes based on PVA (polyvinyl alcohol) and amino acid (proline) with different molar mass percentages of ammonium chloride (NH4Cl) were prepared by solution-casting technique using distilled water as solvent. Their structural, thermal, vibrational, and electrical properties were studied. XRD analysis confirms the amorphous nature of the polymer electrolytes. DSC measurements show a decrease in Tg with increasing salt concentration. The FTIR analysis reveals the complex formation between the PVA, proline, and ammonium chloride. Transference numbers for the proton-conducting polymer electrolytes have been measured. The maximum ionic conductivity has been found to be 7.01 × 10−4 S/cm at ambient temperature for 75 Mwt% PVA;25 Mwt% proline:0.3 (m.m.%) of NH4Cl polymer electrolyte using AC impedance analyzer. The temperature-dependent conductivity of the polymer membranes obeys Arrhenius behavior. The highest ionic conductivity polymer electrolyte has low activation energy of 0.07 eV among the prepared polymer electrolytes. An electrochemical stability window of 3.10 V has been measured using linear sweep voltammetry for the highest ionic conducting membrane. The highest conductivity polymer electrolyte 75 Mwt% PVA:25 Mwt% proline:0.3 (m.m.%) NH4Cl has been used to construct a primary proton battery and fuel cell.