Alkaline solid polymer electrolyte membranes based on structurally modified PVA/PVP with improved alkali stability

Novel alkaline solid polymer electrolyte membranes that can conduct anions (OH⁻) have been prepared from poly(vinyl alcohol)/poly(vinylpyrrolidone) (PVA/PVP) by blending and chemical cross-linking, followed by doping in aqueous KOH solution. The physicochemical properties of these membranes have been studied in detail by FTIR, TG, and SEM analyses. The ionic conductivity was found to be greatly dependent on the concentration of KOH and the interpenetrated PVP in the PVA matrix. A maximum conductivity of up to 0.53 S cm⁻¹ at room temperature was achieved for PVA/PVP in a mass ratio of 1:0.5 after doping in 8 m aqueous KOH solution. The membrane showed perfect alkaline stability without losing its integrity even upon exposure to 10 m KOH solution at up to 120 °C. Scanning electron micrographs revealed a highly ordered microvoid structure uniformly dispersed on the membrane surface with a pore size of ca. 200 nm after heat-curing, which imparted the membrane with good liquid electrolyte (KOH) retention ability. FTIR spectra showed that these high ionic conductivities may be attributed to the presence of excess free KOH in the polymer matrix in addition to KOH bound to the polymer. Almost constant, highly stable, ionic conductivity while maintaining mechanical integrity was retained at room temperature for more than one month.     

Facile Fabrication of Poly(vinyl alcohol)/Polyquaternium-10 (PVA/PQ-10) Anion Exchange Membrane with Semi-Interpenetrating Network

Anion exchange membranes (AEMs) are one of the core components of AEM fuel cells. A series of poly(vinyl alcohol)/polyquaternium-10 (PVA/PQ-10) AEMs with semi-interpenetrating networks (s-IPNs) are prepared by a simple solution-casting method using glutaraldehyde (GA) as a cross-linking agent. Subsequently, the prepared PVA/PQ-10 cross-linked membranes are characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, mechanical analysis, water uptake and swelling ratio tests, ion exchange capacity (IEC) tests, ionic conductivity measurements, and oxidative/alkaline stability tests. The effects of the mass ratio of PVA and PQ-10 and the amount of cross-linking agent GA on the performance of the PVA/PQ-10 cross-linked membranes are systematically explored. The results show that the cross-linked PVA/PQ-10 AEMs have high IEC and low water uptake and swelling ratio, and its maximum ionic conductivity can reach 79.37 mS cm^–1 at 80 °C. In addition, the PVA/PQ-10 cross-linked membrane has good oxidative and alkaline stability under optimal preparation conditions. These results may provide valuable insights toward more effective scheme designs and new, simple preparation methods for AEMs with s-IPN structures.     

Imidazolium functionalized poly(vinyl alcohol) membranes for direct methanol alkaline fuel cell applications

In this study, imidazolium functionalized poly(vinyl alcohol) (PVA) was synthesized by acetalization and direct quaternization reaction. Afterwards, composite anion exchange membranes based on imidazolium‐ and quaternary ammonium‐ functionalized PVA were used for direct methanol alkaline fuel cell applications. ¹H NMR and Fourier transform infrared spectroscopy data indicated that imidazole functionalized PVA was successfully synthesized. Inductively coupled plasma mass spectrometry data demonstrated that the imidazolium structure was efficiently obtained by direct quaternization of the imidazole group. Composite anion exchange membranes were fabricated by application of the functionalized PVA solution on the surface of porous polycarbonate (PC) membranes. Fuel cell related properties of all prepared membranes were investigated systematically. The imidazolium functionalized composite membrane (PVA‐Im/PC) exhibited higher ionic conductivity (7.8 mS cm^?1 at 30 °C) despite a lower water uptake and ion exchange capacity value compared to that of quaternary ammonium. In addition, PVA‐Im/PC showed the lowest methanol permeation rate and the highest membrane selectivity as well as high alkaline and oxidative stability. Dynamic mechanical analysis results reveal that both composite membranes were mechanically resistant up to 10⁷ Pa at 140 °C. The superior performance of imidazolium functionalized PVA composite membrane compared to quaternary ammonium functionalized membrane makes it a promising candidate for direct methanol alkaline fuel cell applications. © 2020 Society of Chemical Industry     

Poly(vinyl alcohol)/Cu(II) complex anion exchange membranes prepared using chemical fiber for direct methanol fuel cells

PVA/Cu (II) complex anion exchange membranes (AEMs) were prepared for direct methanol fuel cells. The complex was for the first time used as membrane material of AEMs. Glutaraldehyde as a crosslinking agent was introduced to control water uptake and swelling of the membranes. The membranes with thickness of 1 μm were fabricated using chemical fibers based on the solution surface tension. The complex membranes show good ionic conductivity and low methanol permeability in the magnitude of 10^?2 S · cm^?1 and 10^?7 cm^?2 · S^?1, respectively. This is a facile, efficient, green, and fast way to prepare new AEMs for direct methanol fuel cells. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1172‐1178, 2013     

Polystyrene‐based anion exchange membranes via click chemistry: improved properties and AEM performance

Polystyrene‐based anion exchange membranes (AEMs) have been fabricated using in situ click chemistry between azide and alkyne moieties introduced as side groups on functionalized polymers. The membrane properties such as water uptake, swelling ratio and conductivity were affected by the number of cations and the degree of crosslinking. The membranes containing a larger amount of trimethylammonium cationic groups (i.e. higher ion exchange capacity) showed high hydroxide conductivity when immersed in KOH solution, exhibiting a peak in conductivity (156 mS cm^?1) in 3 mol L^–1 KOH solution. A higher degree of crosslinking tended to decrease conductivity. These membranes demonstrated relatively good stability in 8 mol L^–1 KOH at 60 °C and maintained 33%–62% of initial conductivity after 49 days with most of the loss in conductivity occurring in early stages of the test. In an alkaline fuel cell, the areal specific resistance was constant indicating good stability of the membranes. The observed peak power density (157 mW cm^?2) was comparable to that of other AEM‐based fuel cells reported. © 2018 Society of Chemical Industry     

Shape stability enhancement of PVDF electrospun polymer electrolyte membranes blended with poly(2-acrylamido-2-methylpropanesulfonic acid lithium)

The purpose of this study is to overcome the poor dimensional stability of poly(vinylidene fluoride) (PVDF)-based electrospun membranes for polymer electrolytes, a new type of composite fibrous membranes based on PVDF/poly(2-acrylamido-2-methylpropanesulfonic acid lithium) (PAMPSLi) blend systems with different blend ratios were fabricated by electrospinning method. Morphology of the composite fibrous membranes was evaluated by scanning electron microscopy. Average diameters of the membranes were less than 250 nm, which were far less than that of pure PVDF fibrous membrane (400 nm). Fourier transform infrared spectroscopy and Raman scattering were used to characterize the interactions of two polymers. Wide-angle X-ray diffraction and differential scanning calorimetry techniques were applied to investigate the crystal structure of composite fibrous membranes. Owning to the good miscibility between PVDF and PAMPSLi, no phase-separated microstructure was observed in composite fibrous membranes. The membranes possessed a good wettability by liquid electrolytes and exhibited an excellent dimensional stability even at high loading of electrolytes. The polymer electrolyte showed the ionic conductivity of 3.45 × 10^?3 S/cm at room temperature and electrochemical stability up to 5.4 V for the blend ratio of 5/1. PVDF/PAMPSLi (5/1)-based polymer electrolyte was observed much more suitable than polymer electrolytes with other ratios of PVDF/PAMPSLi for application in high-performance lithium rechargeable batteries.     

Synthesis and characterization of poly(benzimidazolium) membranes for anion exchange membrane fuel cells

Poly(dimethyl benzimidazolium) iodides were synthesized from polybenzimidazole derivatives by permethylation. They were easily changed to OH^?, CO₃ ^2? and HCO₃ ^? ion conducting electrolytes by immersing in 1 M of KOH, K₂CO₃ and KHCO₃. Properties of polymers were changed by the ion exchange process. The anion conducting membranes showed tough and flexible properties. The water uptake, ion exchange capacity and conductivity varied depending on the counter anions. One of the poly(dimethyl benzimidazolium) carbonate membranes, Me-DAB-OBBA-carbonate showed the highest water uptake (59 %) as well as ion conductivity (33.74 mS/cm at 80 °C), and could be a good candidate for an anion exchange membrane for anion exchange membrane fuel cells.     

Preparation Polyelectrolyte Complexes of Chitosan-Polyacrylic Acid-Modified Iron Sand Leachate for Proton Exchange Membranes

ABSTRACT

Polyelectrolyte complex (PEC) of chitosan (Chi) and poly (acrylic acid) (PAA)-modified iron sand leachate were prepared and considered for applicability as a proton exchange membrane in fuel cells. Chi-PAA-hematite blended in different weight ratios and the resulting membranes were treated to enable the formation of the polyelectrolyte. The membranes of Chi-PAA polyblend were treated using iron sand leachate and reveal high ion exchange capacity (IEC), proton conductivity, water uptake, and good mechanical stability. The result of research indicated that the membrane with 40 wt% of Chi and 60 wt% of PAA blend which its conductivity of 6.10 × 10^?2 S cm^?1 was potentially for a proton exchange membrane in fuel cell applications.     

Chitosan-Modified Poly(2,6-dimethyl-1,4-phenylene Oxide) for Anion-Exchange Membrane in Fuel Cell Technology

A series of cross-linking chitosan-modified quaternary ammonium poly(2,6-dimethyl-1,4-phenylene oxide)s membranes (CS-QAPPO) were prepared by the Menshutkin reaction. The mechanical property, dimensional stability, and alkaline stability of the CS-QAPPO membrane have been impressively improved by introducing CS into PPO backbone. Even the hydroxide conductivity of CS-QAPPO membranes is higher than that of the pristine QAPPO membrane. The 20% chitosan-modified QAPPO membrane shows the best performance, and the hydroxide conductivity is 32 mS cm^?1 at 90°C. The alkaline stability measurements demonstrated excellent chemical stability of the CS-QAPPO membrane in 2?M NaOH solution at room temperature after 2,000?h.     

Synthesis of Low Methanol Permeation Polymer Electrolyte Membrane from Polystyrene-Butadiene Rubber

In order to find a low cost polymer electrolyte membrane with low methanol cross-over, the development of novel polymer electrolytes have been actively carried out in recent time as alternatives to Nafion®, which is the state-of-the art membrane. The problems associated with these alternative membranes are higher permeability to the fuel, lower proton attraction and thermal stability. This work therefore was focused on synthesizing low methanol permeable membrane with good proton conductvity and thermal stability from locally available polymer (Polystyrene-butadiene rubber). Results obtained revealed that the synthesized membrane exhibited methanol permeation in the ranges of 2.13 × 10^?7 to 7.58 × 10^?7 mol/cm²s which was lower than that of Nafion® (3.15 × 10^?6 cm²/s). The proton conductivity of the synthesized membrane is in the order of 10^?2 S/cm. The results also show that water and solvent uptake of the synthesized membrane are moderate as compared to that of Nafion®. These results are influenced by the degree of sulphonation and membrane thickness ranging from 0.112 mm?0.420 mm.     

Novel polymer electrolyte membranes based on semi‐interpenetrating blends of poly(vinyl alcohol) and sulfonated poly(ether ether ketone)

In this work, the properties of novel ionic polymer blends of crosslinked and sulfonated poly(vinyl alcohol) (PVA) and sulfonated poly(ether ether ketone) (SPEEK) are investigated. Crosslinking and sulfonation of PVA were carried out using sulfosuccinic acid (SSA) in the presence of dispersed SPEEK to obtain semi‐interpenetrating network blends. PVA–SSA/SPEEK blend membranes of different compositions were studied for their ion‐exchange capacity, proton conductivity, water uptake, and thermal and mechanical properties. The hydrated blend membranes show good proton conductivities in the range of 10^?3 to 10^?2 S/cm. When compared with pure component membranes, the PVA–SSA/SPEEK blend membranes also exhibit improvement in tensile strength, tensile modulus, and delay in the onset of thermal and chemical degradation. Semi‐interpenetrating nature of the blends is established from morphology and dynamic mechanical analysis. Morphology of the membranes was studied using scanning electron microscopy after selective chemical treatment. The dynamic mechanical properties of the membranes are examined to understand the miscibility characteristics of the blends. The relative proportions of PVA and SPEEK and the degree of crosslinking of PVA–SSA are important factors in determining the optimum properties for the blend. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Poly(vinyl alcohol) modified by KE reactive dyes as a novel proton‐exchange membrane for potential fuel‐cell applications

A new type of proton‐exchange membrane based on poly(vinyl alcohol) (PVA) modified KE reactive dyes (KE‐4BD) was prepared and evaluated as H⁺‐conducting polymer electrolytes. The effects of the content of KE‐4BD on the membrane H⁺ conductivity and water uptake were studied with an alternating‐current impedance technique and the method of weighing, respectively. Fourier transform infrared and scanning electron microscopy were used for the chemical and structural characterization of these membranes. With all of these properties, the optimal mass ratio between PVA and KE‐4BD was 1:0.5, and the resulting membrane exhibited a high proton conductivity (0.109 S/cm) at room temperature; this afforded a power density of 83.9 mW/cm² at 210.4 mA/cm² and an open‐circuit voltage of 810.8 mV. The PVA/KE‐4BD membranes showed a high oxidative stability in Fenton's reagent (3% H₂O₂ v/v, 2 ppm FeSO₄). Thermal analysis also showed that the membranes exhibited a significant improvement in thermal stability. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43019.     

Novel imidazole‐grafted hybrid anion exchange membranes based on poly(2,6‐dimethyl‐1,4‐phenylene oxide) for fuel cell applications

Novel organic–inorganic hybrid membranes, based on poly(2,6‐dimethyl‐1,4‐phenylene oxide), have been prepared through 1,2‐dimethylimidazole functional groups and double crosslinking agents including 3‐glycidyloxypropyltrimethoxysilane and tetraethyl orthosilicate by sol–gel process for the purpose of improving the conductivity and alkaline resistance. The structure of membranes was characterized using Fourier‐transform infrared spectra, ¹H NMR, and X‐ray diffraction. The physico‐chemical properties of all membranes were shown in ion exchange capacity, water uptake, stability, and conductivity. Membranes with OH^– conductivity up to 0.022 at 25 °C and 0.036 S cm^?1 at 80 °C. Promisingly, the chemical stability of the resulting membranes remains unchanged after storage in 2 mol dm^?3 KOH at 25 °C over at least 10 days. The tensile strength can be higher than 30 MPa, and the elongation at break (Eb) is in the range 6.68–10.84%. Hence, this hybrid membrane can be potentially applied in alkaline fuel cells. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46034.     

Enhancing the Anhydrous Proton Conductivity of Sulfonated Polysulfone/Polyvinyl Phosphonic Acid Composite Membranes With Hexagonal Boron Nitride

Hexagonal boron nitride (h-BN) particles have attracted increasing interest due to mechanical properties, chemical stability, electrical features, thermal stability, and good lubrication property. In this work hexagonal boron nitride were used as inorganic fillers, which increase the mechanical and thermal stabilities of the membrane. The proton conducting polymer membranes were prepared by blending of sulfonated polysulfone, polyvinyl phosphonic acid, and boron nitride. Scanning electron microscopy indicated the homogeneous distribution of hBN nanoparticles in the polymer matrix. hBN increased the proton conductivity and in the anhydrous state the maximum proton conductivity was determined as 7.9 × 10^?3 S/cm at 150°C for PVPA-SPSU-5hBN.     

An easy method for the preparation of anion exchange membranes: Graft‐polymerization of ionic liquids in porous supports

A novel way for anion exchange membrane (AEM) preparation has been investigated, avoiding the use of expensive and toxic chemicals. This new synthetic approach to prepare AEMs was based on the use of a porous polybenzylimidazole membrane as support in which functionalized ILs were introduced and subsequently grafted on the polymer backbone. These new AEMs were prepared and their chemical structures and properties including morphology, thermal stability, and ionic conductivity were characterized. The hydroxyl ionic conductivity of the synthesized membranes can reach values upto 6.62 × 10^?3 S cm^?1 at 20°C. Although the ionic conductivity is not very high yet, the work shows the strength of the concept. Membrane properties can be easily tailored toward specific applications by choosing the proper chemistry, i.e., porous polymer support, ionic liquid, and method of initiation and polymerization. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Improved proton conductivity and methanol permeability of PVA-based proton exchange membranes using diphenylamine-4-sulfonic acid sodium salt and silica nanoparticles

ABSTRACT

A novel series of PVA/DPA-4-SASS/SiO₂ composite membranes were fabricated and characterized in the present study. Compared to the neat PVA, water uptake, proton conductivity, and ion exchange capacity of the membranes were enhanced. The membrane containing 5 Wt. % of SiO₂ nanoparticles and 80 Wt. % of the DPA-4-SASS showed the highest values of water uptake, proton conductivity (1.5 × 10^?1 S/cm) and ion exchange capacity (1.47 mmol/g). The results also indicated that methanol permeability was decreased by increasing the DPA-4-SASS content in the hybrid membranes. Thermal stability and mechanical properties of the cross-linked membranes were also improved.     

Dynamic Mechanical,DSC, and Electrical Investigations on Nano Al2O3 Filled PVA:NH4SCN:DMSO Polymer Composite Dried Gel Electrolytes

This paper reports the dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and ionic conductivity studies on nanosized Al₂O₃(aluminium oxide) filled PVA:NH₄SCN:DMSO polymer composite dried gel electrolytes prepared by the wet chemistry route. Better mechanical stability and thermal behavior are noticed in the composite system. Multiple relaxation peaks seen in tangent loss measurements (in DMA studies) have been suitably correlated. Enhancement in ionic conductivity has been noticed with an optimum value of 4.02 × 10^?3 Scm^?1 for 4 wt% nano Al₂O₃ filled composite electrolytes. Temperature dependence of ionic conductivity shows a combination of Arrhenius and VTF (Vogel-Tamman-Fulcher) behavior.     

Proton‐conducting blend membranes of crosslinked poly(vinyl alcohol)–sulfosuccinic acid ester and poly(1‐vinyl‐1,2,4‐triazole) for high temperature fuel cells

New type of composite membranes were synthesized by crosslinking of poly(vinyl alcohol) (PVA) with sulfosuccinic acid (SSA) and intercalating poly(1‐vinyl‐1,2,4‐triazole) (PVTri) into the resulting matrix. The complexed structure of the membranes was confirmed by Fourier transform infrared (FTIR) spectroscopy. The resulting hybrid membranes were transparent, flexible, and showed good thermal stability up to ～200°C. The proton conductivities of the membranes were investigated as a function of PVTri and SSA and operating temperature. The water/methanol uptake was measured and the results showed that solvent absorption of the materials increased with increasing PVTri content in the matrix. The proton conductivity of the membranes continuously increased with increasing SO₃H content, PVTri content, and the temperature. In the anhydrous state, the maximum proton conductivity is 7.7 × 10^?5 S/cm for PVA–SSA–PVTri‐1 and for PVA–SSA–PVTri‐3 is 1.6 × 10^?5 S/cm at 150°C. After humidification (RH = 100%), PVA–SSA–PVTri‐4 showed a maximum proton conductivity of 0.0028 S/cm at 60°C. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Phosphonic acid functionalized siloxane crosslinked with 3‐glycidoxyproyltrimethoxysilane grafted polybenzimidazole high temperature proton exchange membranes

Phosphonic acid functionalized siloxane crosslinked with 3‐glycidoxypropyltrimethoxysilane (GPTMS) grafted polybenzimidazole (PBI) membranes are prepared by sol–gel process. The structure of the membranes is characterized by Fourier‐transform infrared spectroscopy and X‐ray diffraction spectroscopy. SEM images of the membranes show that the membranes are homogeneous and compact. The crosslinked membranes exhibit excellent thermal stability, chemical stability and mechanical property. The proton conductivity of the crosslinked membranes increases by an order of magnitude over range of 20 °C to 160 °C under anhydrous condition, which can reach 3.15 × 10^?2 S cm^?1 at 160 °C under anhydrous condition. The activation energy of proton conductivity for membranes decreases with increase of PBI, because the formation of hydrogen bond network between the phosphonic acid and the imidazole ring can enhance the continuity of hydrogen bond in the membrane. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44818.     

Electrically conductive polyaniline/polyimide microfiber membrane prepared via a combination of solution blowing and subsequent in situ polymerization growth

Dodecylbenzene sulfonic acid (DBSA) doped-polyaniline (PANI) coated conductive polyimide (PI) microfiber membrane was prepared by chemical oxidation polymerization. PI nanofiber membrane was prepared by solution blowing. Fourier transform infrared spectra (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM) proved that the successful preparation of composite microfiber membrane with core-shell structures. At the same time, the PANI had an effect of protection on PI nanofiber, which was detected by thermal gravimetric analysis (TGA). The orthogonal experiments were designed to determine the optimal reaction conditions for the conductivity of PANI/PI microfiber membranes as following: ANI concentration (0.15 mol L^?1), APS concentration (0.1 mol L^?1) and DBSA concentration (0.3 mol L^?1). The conductivity of PANI/PI microfiber membranes could arrive to 3.83 × 10^?2 S cm^?1. Moreover, the PANI/PI microfiber membranes had a superior hexavalent chromium (Cr (VI)) adsorption performance. The factors affecting the performance of hexavalent chromium (Cr (VI)) removal from the aqueous solutions were investigated.