Proton Conducting Gel Electrolytes Research Articles

Conductivity of gel polymer electrolytes doped with solutions of phosphonic acid or protic ionic liquids

The proton-conducting gel electrolytes (PCGEs) based on PMMA, PVdF or PVdF-HFP doped with solutions of phosphonic acid or ammonium based protic ionic liquids (PILs) in DMF have been synthesized. Rather high values of the conductivity (10−4–10−3 S cm−1) have been reached at low dopant concentrations (up to 1 mol l−1). The influence of the nature of both polymeric matrix and dopant as well as dopant concentration on the conductivity values was discussed. It was established that the dependence of conductivity on the nature of dopant, but not the polymeric matrix, was more pronounced.

Highly proton conductive phosphoric acid-nonionic surfactant lyotropic liquid crystalline mesophases and application in graphene optical modulators.

Proton conducting gel electrolytes are very important components of clean energy devices. Phosphoric acid (PA, H(3)PO(4) · H2O) is one of the best proton conductors, but needs to be incorporated into some matrix for real device applications, such as into lyotropic liquid crystalline mesophases (LLCMs). Herein, we show that PA and nonionic surfactant (NS, C(12)H(25)(OCH(2)CH(2))(10)OH, C(12)E(10)) molecules self-assemble into PANS-LLCMs and display high proton conductivity. The content of the PANS-LLCM can be as high 75% H(3)PO(4) · H2O and 25% 10-lauryl ether (C(12)H(25)(OCH(2)CH(2))(10)OH, C(12)E(10)), and the mesophase follows the usual LLC trend, bicontinuous cubic (V1)-normal hexagonal (H1)-micelle cubic (I1), by increasing the PA concentration in the media. The PANS-LLCMs are stable under ambient conditions, as well as at high (up to 130 °C) and low (-100 °C) temperatures with a high proton conductivity, in the range of 10(-2) to 10(-6) S/cm. The mesophase becomes a mesostructured solid with decent proton conductivity below -100 °C. The mesophase can be used in many applications as a proton-conducting media as well as a phosphate source for the synthesis of various metal phosphates. As an application, we demonstrate a graphene-based optical modulator using supercapacitor structure formed by graphene electrodes and a PANS electrolyte. A PANS-LLC electrolyte-based supercapacitor enables efficient optical modulation of graphene electrodes over a range of wavelengths, from 500 nm to 2 μm, under ambient conditions.

Conductivity and thermal stability of proton-conducting electrolytes at confined geometry of polymeric gel

The proton-conducting gel electrolytes based on poly(methyl methacrylate) (PMMA) doped by acid solutions in aprotic solvents were synthesized and discussed in this work. The gel conductivity as a function on concentrations of acid and polymer as well as of molecular mass of PMMA has been analyzed. The thermal stability of electrolytes was estimated and discussed. Extreme dependence of the conductivity on concentration is found to be for the gel (at a concentration of PMMA from 5 to 15 wt.%). The increase of electrical conductivity in the concentration range from 5 to 10 wt.% of PMMA with an increase in viscosity of the system is discussed as an indication of an involvement of the polymer matrix in increasing the mobility of the charge carriers in frame of Grotthuss mechanism.

Synthesis and Study of PVA Based Gel Electrolyte

An attempt has been made to prepare polyvinyl alcohol (PVA) based proton conducting gel electrolytes in ammonium thiocyanate (NH 4SCN) solution and to characterize them. XRD studies revealed that the entire gel sample are amorphous in nature with a broad peak at nearly 2 �=22 0 . Variation of conductivity of gel electrolyte with loading concentration of PVA has also been studied. It has been observed, as loading of PVA in 0.2 M electrolyte of NH 4SCN+DMSO increases conductivity decreases. The conductivity of gel electrolytes exhibits liquid like nature at low polymer concentration while the behaviour is seen to be affected by the formation of PVA-NH 4SCN complexes upon increase in polymer content beyond 2 g. Temperature dependence of ionic conductivity exhibits VTF and Arrhenius behaviour. Keyword: PVA, Gel electrolyte, NH 4SCN+DMSO, X-RD, Ionic conductivity

Proton conducting gel electrolytes based on polymethylmethacrylate doped with sulfuric acid solutions in N,N-dimethylformamide

In the work presented time-stable proton conducting gel electrolytes based on polymethylmethacrylate doped with sulfuric acid solutions in N,N-dimethylformamide were synthesized. The dependences of gels conductivity on the acid concentration and the molecular mass of PMMA at 25–65 °C are studied. The thermal stability of electrolytes was estimated. The FT-IR (ATR) spectroscopy was used for understanding of mechanism of proton transfer.

Proton-conducting gel electrolytes based on poly(methyl methacrylate) doped with phosphoric acid in N,N-dimethylformamide

Time-stable proton-conducting gel electrolytes based on poly(methyl methacrylate) doped by o-phosphoric acid solutions of different concentrations in DMF are prepared. The dependences of the electrical conductivity of the gels on the concentrations of the acid and polymer and the molecular mass of PMMA at 25–65°C are studied. The thermal stability of electrolytes is estimated. It is found that an increase in the content of the polymer in gels changes the thermal behavior of the samples.

DSC and conductivity studies on PVA based proton conducting gel electrolytes

An attempt has been made in the present work to prepare polyvinyl alcohol (PVA) based proton conducting gel electrolytes in ammonium thiocyanate (NH4SCN) solution and characterize them. DSC studies affirm the formation of gels along with the presence of partial complexes. The cole-cole plots exhibit maximum ionic conductivity (2.58 × 10−3 S cm−1) for gel samples containing 6 wt% of PVA. The conductivity of gel electrolytes exhibit liquid like nature at low polymer concentrations while the behaviour is seen to be affected by the formation of PVA-NH4SCN complexes upon increase in polymer content beyond 5 wt%. Temperature dependence of ionic conductivity exhibits VTF behaviour.

Dynamics of the hydrogen and phosphate ions in proton conducting gel/D3PO4 electrolytes: A H2 and P31 nuclear magnetic resonance study

The synthesis and characterization of protonic conducting polymeric gels is motivated by their possible application in various electrochemical devices. Nonaqueous proton-conducting gel electrolytes are being developed for use in various sensors and electrochromic devices operating at ambient temperatures. The electrolyte must have a relatively high conductivity and chemical and physical stability. One method of producing nonaqueous conducting polymeric gel electrolytes is to entrap organic solutions of a strong acid such as H3PO4 in a polymer matrix. Results are reported on the system consisting of phosphoric acid dissolved in N,N-dimethyl formamide (DMF) within a gel network formed with poly(glycidyl methacrylate) (PGMA). Using selective deuteration, the diffusion coefficients for both the deuteron and phosphorus from the phosphoric acid and the DMF are measured by field gradient nuclear magnetic resonance (NMR) techniques. Combining the diffusion with conductivity measurements in the Nernst–Einstein equation leads to a better understanding of the number of charge carriers in the mixture and the temperature dependence of this number. Nuclear spin-lattice relaxation is used as a tool to probe the ion dynamics in these materials. In addition to NMR measurements, the samples have been characterized by electrical conductivity, differential scanning calorimetry, and viscosity measurements. The results show that the Grotthus mechanism involving the hopping of the proton from one molecular site to another, as well as the vehicular mechanism due to the motion of the D2PO4− and D4PO4+ ions are most responsible for the motion of the proton in these electrolytes. The variety of protonation sites in the PGMA/DMF/H3PO4 system is much more diverse that in the previously studied PMMA/PC/D3PO4 system. In the PGMA/DMF/H3PO4 system there are sites on the polymer, DMF and H3PO4.

A Proton Conductor Based on a Polymeric Complex of Poly(Ethylene Oxide)-Modified Poly(Methacrylate) with Anhydrous H3PO4

Nonaqueous proton-conducting gel electrolyte has been prepared by incorporating anhydrous H3PO4 in poly(ethylene oxide)-modified poly(methacrylate) (PEO−PMA) plasticized by poly(ethylene glycol) dimethyl ether (PEGDE). Optically transparent polymeric gel membranes were obtained in a wide range of the component ratio. The sample membranes have been characterized by AC conductivity, FTIR, and DSC measurements. High conductivity of 1.3 × 10-4 S cm-1 was obtained at room temperature for the composition of the (PEO−PMA)/PEGDE mass ratio 32:68. The ionic conductivity was enhanced by the addition of small amounts of the second plasticizer, dimethylformamide (DMF). The DC polarization experiments of the gel membranes with Pt blocking electrodes revealed that the charge transport in the gel was mainly ionic (tion > 0.99), where the type of the major mobile species was considered to be H+ cation with mobility μ = 2.5 × 10-4 cm2 V-1 s-1. The FTIR spectroscopy proved that hydrogen-bonding and protonic interactions exist between the dopant H3PO4 and the PEO−PMA matrix and/or entrapped plasticizer in the gel. In all cases, the Arrhenius plots of the conductivity showed linear relations in the temperature range of 22−90 °C. The mechanism of the ion transport in the nonaqueous gel is briefly discussed.

Proton-conducting gel electrolyte

Proton conduction in solid state xerogels and polymeric gels are reported. Xerogels, doped with known proton conductors, were prepared by “sol–gel” method starting either from inorganic precursor sodium metasilicate (termed as hydrogel) or organic precursor tetraethyl orthosilicate (termed as silica or SiO 2 alcogel). The dopants chosen for the former were NH 4BF 4, NH 4Cl, NH 4H 2PO 4 and N 2H 6SO 4, while for the latter, the dopants used were H 3PO 4, NH 4BF 4, NH 4H 2PO 4 and KH 2PO 4. The SiO 2:H 3PO 4 alcogel gave the highest room temperature conductivity (∼10 −3 S cm −1). Some of the xerogels studied by us were stable even up to 300 °C. Another interesting group of proton-conducting materials discussed in this paper is polymeric gel which was prepared by dispersing PMMA in the liquid electrolyte obtained by dissolving o-, m-, p-hydroxybenzoic acid; o-, m-, p-nitrobenzoic acid and three dicarboxylic acids, viz., oxalic, malonic and succinic acid, in a high-dielectric constant organic solvent. The role of the dissociation constants of the dissolved acids and the interaction of the polymer were discussed. The addition of polymer, inspite of the increasing viscosity, was found to sometimes lead to an increase in the conductivity of liquid electrolyte, which was explained on the basis of a breathing polymer chain model.

A basic investigation of anhydrous proton conducting gel electrolytes

The aim of this paper is to summarize recent trends in the studies on nonaqueous proton conducting gel electrolytes. The physical–chemical properties of these systems are described and their relation to the type and concentration of polymer matrix, proton donor as well as the solvent used is discussed. This analysis is performed on the basis of electrochemical (impedance spectroscopy, cyclic voltammetry), spectroscopic (NMR, PFG NMR, FT-IR), and thermogravimetric (DSC) experiments. The proton conduction mechanism is postulated and its dependence on the sample composition is discussed. The possibility of application of proton conducting gels in electrochromic devices is presented.

Characterization of perdeuterated H 3PO 4-doped nonaqueous gel electrolytes using 31P nuclear magnetic resonance spectroscopy

Proton conducting gel electrolytes based on a network of various polymer matrices such as methyl methacrylate (MMA) and glycidyl methacrylate (GMA) containing perdeuterated H 3PO 4 have been synthesized using propylene carbonate (PC), dimethylformamide (DMF) and dimethylacetamide (DMA) as entrapped solvents. These systems have ionic conductivities as high as 10 −4 S cm −1 at ambient temperatures. The operating range of these electrolytes is from 220 to 370 K. In an attempt to understand their structure and dynamic properties, we report 31P ( I=1/2) spectroscopic and self-diffusion coefficient ( D) measurements of mobile phosphorus species for these materials at room temperature, using pulsed field-gradient Hahn spin-echo techniques. The 31P NMR signal in some systems was found to have multiple peaks indicating the presence of o-phosphoric acid, charged dissociated species, and condensed phosphates. It is estimated that condensed phosphates comprise up to 40% of the phosphate species in GMA based electrolytes. As expected 31P diffusion coefficients of the different phosphate species present are determined to be dependent on the size of the moving phosphate species.

The effect of solvent and proton donor type on the conductivity and physico-chemical properties of poly(vinylidene fluoride)-based proton-conducting gel electrolytes

In the present work proton-conducting gels based on commercially available poly(vinylidene fluoride) (PVdF) system are studied. The polymer, H 3PO 4 and phosphoric acid organic esters (used as proton donors) are dissolved in dimethylformamide (DMF) or dimethyl acetate (DMA) at ambient temperatures and than cast on the flat glass substrate. Highly conducting (∼10 −3 S cm −1 at 20°C) colorless polymeric membranes are obtained in a relatively narrow PVdF and proton donor concentration ranges. The highest conductivities have been obtained when phosphoric acid esters are used as proton donors. Conductivities measured for systems containing DMF are slightly higher than for DMA-based derivatives. The gel electrolytes studied are thermally stable up 100°C as shown by the DSC experiments. The interactions between H 3PO 4 and solvents used are studied by means of FT-IR spectroscopy which shows the possibility of the protonation of solvent molecules by H 3PO 4. Therefore, the possibility of proton transportation via the Grotthus-type mechanism cannot be excluded.

Proton conducting polymer gel electrolytes

Novel proton conducting gel electrolytes from poly(vinylidene fluoride)-dimethylformamide-H3PO4 system are synthesized and characterized by impedance spectroscopy, infra-red spectroscopy and differential scanning calorimetry. Highly conducting (5×10−4 S/cm at 20°C) colorless polymeric membranes are obtained in a relatively narrow component concentration range. The gel electrolytes studied are thermally stable up to 70–120°C as shown by the DSC experiments.