DMFC Membrane Research Articles

Synthesis and Characterization of Chitosan/Alginate/Mesoporous Phosphotungstic Acid Electrolyte Membranes for Direct Methanol Fuel Cell Applications

In this study, chitosan (Chi), alginate (Alg), and mesoporous phosphotungstic acid (mPTA) were used as electrolyte membrane materials for DMFC. Chi and Alg will be crosslinked with mPTA filler to improve the performance of the electrolyte membrane. Characterizations carried out include tensile tests, methanol permeability, and proton conductivity. The results of the tensile test showed that the Chi-Alg(3:1) membrane had a higher tensile strength value (26.64 N/mm2) than the pure chitosan membrane (11.97 N/mm2). The results of methanol permeability show that the Chi-Alg(3:1)/mPTA(2.0%) membrane has a lower methanol permeability value (8.17 × 10-6 cm2 s-1) and a relatively high proton conductivity value, (45.8 × 10-3 S cm-1). Chi-Alg/mPTA membrane, simplicity of the used simple preparation method and the cost reduction can be applied as an electrolyte membrane for DMFC.

Membran Polieugenol Tersulfonasi (PET) Sebagai Potensi Sel Bahan Bakar Metanol Langsung

Nafion is a type of perfluorosulfonic acid membranes, are widely used in fuel cell technology and exhibit several disadvantages such as expensive, have a limited working temperature range and high methanol crossover. This study aims to produce an electrolyte new polymer membrane from polyeugenol sulfonated (PET) and a review of the membrane properties was carried out on the basis of Water Contact Angle (°), Water Uptake (%), Methanol Uptake (%), Swelling ratio (%), IEC (ion exchange capacity). Analysis of DMFC membrane performance has an optimal proton conductivity of 0.0009 S.cm-1 and methanol permeability of 23.5.10-7 cm2.s-1 with a PET composition of 27% (w/w).

Synthesis of (Si-PWA)-PVA/PTFE high-temperature proton-conducting composite membrane for DMFC

The inorganic silica immobilized PWA based (Si-PWA)-PVA/PTFE composite membrane was developed by an amalgamation of pore filling and layer by layer (LBL) casting. The composition of the top layer was optimized to be 0.3 M PWA: 0.2 M TEOS: 0.15PVA concerning to proton-conductivity and methanol permeability of the membrane. Surface morphological studies and elemental analysis were carried out by using SEM-EDX. The FT-IR and XRD analysis had confirmed the intercalation of sol with PTFE. Thermal deformation of the membrane was studied by TGA and it is stable up to 180 °C. Ion exchange capacity and water uptake were determined to be 2.38 meq per gram and 21.7%. The membrane has exhibited maximum proton conductivity of 41.2 mS cm−1 at 100 °C. The membrane has significantly lower methanol permeability of 3.2 × 10−7 cm2 S−1 compared to that of Nafion117 (7.9 × 10−7 cm2 S−1) at 28 °C and the same trend was observed at 40, 60, and 80 °C. The (Si-PWA)-PVA/PTFE composite membrane is showed enhanced proton conductivity and lower methanol permeability at elevated temperatures.

Modification of Chitosan-Chitosan Phtalate Anhydrides Matrices

Chitin and chitosan are natural biopolymers on shrimp shells. Chitosan is used extensively as a raw material in various industries. The study aimed to extract chitin and chitosan from fanami shrimp skin through deproteinization, demineralization, and deastilation reactions and to modify the matrix to improve the physical properties. The results of the analysis of the FTIR chitin spectrum shows several major peaks at wave number 3446.91 cm-1 which showed the vibrations of bending secondary amide and amine (NH) secondary amides at 1654.98 cm-1 indicating the presence of vibration stretching CH. The results of the chitosan FTIR spectrum analysis shows symmetrical stretching vibrations at 3433.41 cm-1 due to overlapping OH and amines (NH), stretching vibrations of 1653.05 cm-1 caused by the propagation of C = O stretching and stretching vibrations of 1587.47 cm-1 indicating secondary amide. The results of the characterization with XRD shows that the extracted compounds were chitin and chitosan. In modifying the chitosan matrix, the spectra result show peak at 1656.91 - 1564.32 cm-1 indicating the presence of an amide group. New aromatic group peak found in the area of 1631.83 cm-1 which not found in chitosan. Diffract gram XRD from pure chitosan shows three highest peak peaks at 2θ equal to 609.2; 609.88 and 550 while chitosan-anhydrous modification shows a peak at 2θ equal to 609.8. The addition of anhydrous phthalates to chitosan has reduced its crystallinity which results in an increase in the hydrophilic characteristics of the membrane. The results of this study are expected to be one of the references in further research regarding the manufacture of phthalate chitosan-anhydrous based composite membranes for DMFC

Preparation and Characterization of Nano Titania modified PVA-Pectin polymer electrolyte membranes for DMFC

In this study, poly vinyl alcohol and pectin are in situ cross-linked using dual cross-linker comprising a mixture of sulfosuccinic acid and glutaraldehyde followed by solvent casting.Titanium dioxide nanoparticles are incorporated into polymer solutions that controls alignment and disentanglement of polymer chains at molecular level. It is shown that rational design of membrane microstructure with proper arrangement of hydrophobic and hydrophilic domains has been formulated by blending PVA with PC. Water sorption through nanocomposite membrane enhanced when optimum quantity of titanium dioxide particles are present. In addition, titanium dioxide nanoparticles help to provide more inter-connected proton conducting pathways and acts as reinforcing units. Through the hydrogen bonds formed between surface functional groups of titanium oxide nanoparticles and polymer chains, protons are transferred through the membrane both by hopping and vehicular mechanisms. Titanium dioxide nanoparticles also act as fillers and effectively prevent the methanol permeation. Polymer voids are occupied by the presence of Titanium dioxide nanoparticles that selectively allow protons to pass through form anode to cathode side. Both improved proton conductance and lower methanol permeability, electrochemical selectivity of nano Titanium dioxide modified PVA-Pectin polymer electrolyte membrane is enhanced. With further enriched proton conductivity by the presence of titanium dioxide nanoparticles, fabricated pectin polyvinyl alcohol hybrid nanocomposite membrane exhibit higher electrochemical selective factor.

Effect of pore-directing agents in SBA-15 nanoparticles on the performance of Nafion®/SBA-15n composite membranes for DMFC

Nanoparticles of 2D hexagonal mesoporous SBA-15 silica were prepared for the first time and mixed in Nafion® to form composite membranes by solvent casting method. The SBA-15 nanoparticles containing P123 surfactant (S-SBA-15n) and that extracted with ethanol (Ex-SBA-15n) were used as the inorganic fillers in order to see the effect of pore-directing agent on the performance of resultant composite membranes. The physico-chemical properties of SBA-15 nanoparticles were examined with powder XRD, N2 sorption, TGA and SEM. The methanol permeability, proton conductivity, and cell performance of the resultant composite membranes were compared in terms of the content of SBA-15 nanoparticles and whether the pore-directing agent was removed. The optimal proton conductivities were obtained for the composite membranes with 5wt% loading of SBA-15 nano-particles. Moreover, the P123 pore-directing agent present inside the pores of S-SBA-15n was found to effectively resist methanol permeation from anode to cathode and also assist the proton transferring. The single cell assembled with 5wt% S-SBA-15n/Nafion composite membrane gave the highest power density of 117mWcm−2 at 60°C, which was about 80% higher than the cell with recast Nafion membrane and also 23% higher than that with commercial membrane of Nafion® 117.

Preparation and properties of DMFC membranes from polymer-brush nanoparticles

We describe a novel approach for the preparation of proton-conducting membranes using polymer brush nanoparticles (PBNPs). PBNPs can be assembled into the membranes directly, or the membranes can be prepared by first assembling porous scaffolds from unmodified NPs followed by surface modification with polymer brushes. In both cases, proton-conducting channels are formed in the interstitial spaces between the nanoparticles. First, proton-conducting membranes were prepared using silica nanoparticles (SNPs) surface-grafted with 40–400nm sulfonated polymer brushes, poly(3-sulfopropylmethacrylate), pSPM, and poly(4-styrenesulfonic acid), pSSA, grown via surface-initiated atom transfer radical polymerization (SI-ATRP). The membranes prepared from the NPs carrying longer polymer chains possessed polymer-like characteristics, compared to the stiffer membranes made with shorter polymer brushes. All these membranes showed comparable proton conductivities, with a maximum value of ~0.06S/cm at 98°C and 70% R. H. Second, we prepared proton-conducting pore-filled membranes. In this case, nanoporous colloidal crystals were first assembled from unmodified SNPs, followed by filling the pores with pSPM or pSSA brushes covalently attached to the pore surface using SI-ATRP. The membranes could be hydrated almost completely and did not swell. The proton conductivity was similar for both polymer-filled membranes, with a maximum value of ~0.02S/cm achieved at 30°C and 94% R. H. A sigmoidal dependence of the proton conductivity on the amount of sulfonic acid groups was found for pSPM pore-filled membranes. The proton conductivity remained relatively low at low degrees of sulfonation, increased rapidly around 50% sulfonic acid group content, and did not increase significantly after reaching ca. 75% sulfonic acid group content. We found that OCV for DMFC MEAs built using these membranes reached its maximum at 65% sulfonic group and decreased after that. We attribute this effect to the increased methanol cross-over, which was confirmed by methanol uptake measurements for the membranes.

Blue membranes: Sulfonated copper(II) phthalocyanine tetrasulfonic acid based composite membranes for DMFC and low relative humidity PEMFC

Polymer electrolyte membranes (PEMs) consisting of copper(II)phthalocyanine tetrasulfonic acid tetrasodium salt (CuPCSA) and disulfonated poly(arylene ether sulfone) (SES0005) are prepared. The TEM analysis results prove the incorporation of CuPCSA as nanoparticles into the composite membranes. Catalytic activity of CuPCSA towards peroxide degradation is shown by CV. Addition of CuPCSA increases the dimensional stability in contact with water (18% vs. 43% linear swelling for pristine SES0005). Addition of 10wt% CuPCSA (SES0005-IM10) increases the proton conductivity four fold to 16.8mScm−1 at 120°C and 50% relative humidity (rh). Activation energy decreases with CuPCSA content, reducing the conductivity's temperature dependence. Membranes were tested in low and medium temperature PEM fuel cells at 65 and 120°C, respectively, at 50% rh. In the LT-PEMFC, 40µm thick SES0005-IM10 and Nafion 212 based MEAs exhibited current densities of 470 and 454mAcm−2 at 0.7V, respectively. In the MT-PEMFC, SES0005-IM10 based MEAs demonstrated a current density of 405mAcm−2 at 0.5V, 2.4 folds more than pristine membrane based MEAs. In the DMFC, SES0005-IM10 enabled a peak power density of 153mWcm−2 at 70°C and 1M methanol feed, 20% higher than Nafion 212, 38% higher than mPES60.

Synthesis and Characterization of Chitosan/Phosphotungstic Acid-Montmorillonite Modified by Silane for DMFC Membrane

Montmorillonite was functionalized by (3-glycidyloxypropyl) trimethoxy silane (GPTMS). Subsequently, chitosan (CS) membranes filled by GPTMS-modified montmorillonite particles were prepared and characterized by FTIR. The result of FTIR obtained the peak wavenumber of 2940, 1471 and 1390 cm-1 referring to vibration stretching of CH2, bending of CH2 and CH3 form epoxy groups in silane, respectively which indicated modification of montmorillonite by silane. Compared with the pure CS and CS/PWA-MMT membrane, these CS/PWA-MMT/Silane hybrid membranes show apparently high proton conductivity and the lower methanol permeability, which could be assigned to the better interfacial morphology and compatibility between chitosan matrix and GPTMS-modified montmorillonite. In all the prepared CS/PWA-MMT/Silane hybrid membranes, the CS membrane filled by 10% GPTMS-modified montmorillonite particles exhibits the highest proton conductivity and the lowest methanol permeability, which is 19.15 x 10-3 S.cm-1 at 80 °C and 4.33 x 10-8 cm2.s-1, respectively. The results imply that CS/PWA-MMT silane 10% membrane has better interaction of interfacial morphology and compatibility between chitosan matrix and GPTMS-modified montmorillonite particles.

An approach of balancing the ionic conductivity and mechanical properties of PVA based nanocomposite membrane for DMFC by various crosslinking agents with ionic liquid

Nano composite membranes of polyvinyl alcohol (PVA) have been synthesized to investigate their applicability as a proton conducting membrane for direct methanol fuel cell. These membranes consist of PVA, sulfonated organic modified montmorillonite nanoclay (SMMt) and 1-butyl-3-methylimidazolium bis (trifluoromethyl sulfonyl) imide (BMIM TFSI) with different crosslinking agents such as sulfosuccinic acid (SSA), 4-sulfophthalic acid (SPA) and dodecanedioic acid (DDA). FTIR spectroscopy, scanning electron microscope (SEM) and thermogravimetric analysis (TGA) have been used to investigate the structure property relationship. The water uptake behavior of the membranes shows variation with the dosage of SMMt. The good dispersion of the nanoclay in the PVA matrix is detected by using ionic liquid. The improved tensile strength of the membrane comprising 3 wt% of SMMt is achieved. The proton conductivities of the membranes are dependant on the compositions and are in the range of 0.003–0.008 Scm−1 at room temperature and 100% relative humidity. A maximum proton conductivity of 0.017 Scm−1 has been obtained for the membrane comprising of 3 wt% SMMt at 80 °C. Furthermore, the peak power density of the direct methanol fuel cell fabricated with 3 wt% SMMt based membrane in 2 M methanol is 7.02 mW cm−2 at 70 °C.

New bio-polymeric membranes composed of alginate-carrageenan to be applied as polymer electrolyte membranes for DMFC

Novel polyelectrolyte membranes were prepared from pure solutions of alginate (Alg), carrageenan (Car) and their mixtures. The films were crosslinked and sulfonated and then, characterized by several techniques: ionic exchange capacity (IEC), water uptake, mechanical thermal properties, and also functional properties such as methanol permeability and proton conductivity. The results show that Alg/Car membranes have a ductile behavior. Low carrageenan concentrations have a weak thermoprotective effect, which slightly delays both Tg and Tm of prepared membranes. The methanol permeability of Alg/Car membranes increase with the carrageenan content varying from 0.55 × 10−6 cm2 s−1 for Alg/Car 100/00 to 4.89 × 10−6 cm2 s−1 for Alg/Car 80/20. The Proton conductivities of the membranes increase with the carrageenan content from 9.79 × 10−3 S cm−1 for Alg/Car 100/00 until 3.16 × 10−2 S cm−1 for Alg/Car 80/20 at 90 °C. Finally the proton transfer mechanism is discussed in terms of the conductivity activation energy and the dependence of the proton diffusion coefficient with the temperature has been studied.

Polycyclotriphosphazene Derivative Grafted and NanometerY2O3Doped SPEEK Composite Membrane for DMFC

A type of polycyclotriphosphazene derivative (PCTPD), hexasulfanilic acid polycyclotriphosphazene (HSACP) and HSACP grafting SPEEK, sulfonated poly[2-(petachloropolycyclotriphosphazene-oxy)] etheretherketone (SPPSACPEEK) were synthesized, which were characterized by FTIR and <TEX>$^{31}P$</TEX> NMR. Then three types of composite membranes such as HSACP grafting SPEEK, HSACP blending SPEEK, and nano <TEX>$Y_2O_3$</TEX> doping and HSACP grafting SPEEK, respectively, were continuously prepared by solution-casting method. Comparing to SPEEK membranes with different amount of HSACP grafted or blended, grafting 15 wt% HSACP and doping 10 wt% nano <TEX>$Y_2O_3$</TEX> SPEEK membrane conducted outstanding overall behavior of proton conductivity reaching <TEX>$3.18 {\times}10^{-2}$</TEX> S/cm at <TEX>$90^{\circ}C$</TEX> which was merely junior to SPEEK with 15 wt% HSACP grafted, methanol permeability coefficient getting <TEX>$9.46{\times}10^{-8}cm^2{\cdot}s^{-1}$</TEX>, swelling degree of 20.9% and solid residue of 98.98% which was superior to all specimen.

Performance of SPEEK based polymer–nanoclay inorganic membrane for DMFC

Sulfonated poly (ether ether ketone) (SPEEK) membrane with degree of sulfonation (DS) of 63% was modified by adding various amounts of Cloisite15A ® clay. The effect of clay loading on the physical properties of SPEEK nanocomposite membranes was investigated. SPEEK mixed with 2.5 wt.% of Cloisite15A ® (SP63/2.5Cl) has been identified as the best composite formulation in this study. Subsequently, various amounts of 2,4,6-triaminopyrimidine (TAP) were further incorporated into SP63/2.5Cl formulation. The effect of TAP incorporation on the physical and performance properties of the membranes was studied. Nanometer scale distribution of Cloisite15A ® in the SPEEK polymer matrix has been achieved by the assistance of TAP, as observed by the field emission scanning electron microscopy (FESEM). A complete exfoliated nanocomposite structure of SP63/2.5Cl/5.0TAP was confirmed by X-ray diffraction (XRD). The increase of Cloisite15A ® content in the SPEEK membrane has dramatically improved the swelling behavior and barrier properties towards methanol. The SP63/2.5Cl/5.0TAP polymer–clay nanocomposite membrane served as a promising alternative proton exchange membrane (PEM) for DMFC applications with superior DMFC performance compared to commercial Nafion ®112.

Analysis of states of water in poly (vinyl alcohol) based DMFC membranes using FTIR and DSC

The microstructural modifications associated with the lowering of hydrophilic/hydrophobic phase separation can reduce the molecular permeation in an ionomer without compensating the ionic conductivity significantly. This idea has been investigated by selecting poly (vinyl alcohol) PVA as the polymer matrix of proton exchange membranes. 4-Formyl-1,3-benzenedisulfonic acid disodium salt (DSDSBA) molecules, with two protogenic groups tethered to the rigid aromatic ring are introduced to the polymer chains as ion carriers. With a view to improve the morphological stability, glutaraldehyde is used as the cross-linking agent. The molecular chemistry such as flexible backbone, short and rigid side chains and dense acid functionalities improved the selective proton conduction through the membranes. The ionomers show up to eight times selectivity as that of Nafion for protons over methanol. The XRD, DSC and FTIR results are employed to establish the microstructural features of hydrated membranes. Large sorption of nonfreezing water is identified as the main reason for the attractive DMFC membrane characteristics of the prepared membranes. A detailed analysis of the state of water in the prepared membranes reveals that well connected system of narrow water channels allowed for low methanol permeation along with high mobility of protonic charge carriers.

Synthesis and characterization of sulfonated poly(arylene ether sulfone) ionomers incorporating perfluorohexylene units for DMFC membranes

A new, sulfonated poly(arylene ether sulfone) ionomer with partially fluorinated groups (F-SPAES) was synthesized by the direct polymerization of 1,6-bis(4-fluororphenyl)-perfluorohexane (FPPFH) and 6F-bisphenol A (6F-BPA) with 3,3′-disulfonated 4,4′-difluorodiphenyl sulfone (SDFDPS). The effect of fluorination on the membrane properties and membrane-electrode assembly (MEA) performance for DMFC applications were investigated comprehensively and compared with the pristine SPAES sample. Deliberate control of the hydrophobicity as well as the degree of sulfonation in the F-SPAES membranes allows the effective suppression of water uptake and methanol permeability, while barely affecting the proton conductivity and IEC value. Such an improvement in the membrane properties contributes to the superior single cell performance of the F-SPAES compared to pristine SPAES and Nafion®.

A Covalently Cross-linked Polyetheretherketone Proton Exchange Membrane for DMFC

The proton exchange membrane was prepared by covalent cross-linking sulfonated-sulfinated polyetheretherketone. The cross-linked membrane showed high proton conductivity (0.04 S/cm) with suitable water uptake, low methanol permeability (2.21 × 10-7 cm2/s) and good electrochemical stability. The results suggested that cross-linked polyetheretherketone membrane is particularly promising to be used as proton exchange membrane for the direct methanol fuel cell application.

Simultaneous Measurement of Proton Conductivity and Methanol Permeability for the Development of Direct Methanol Fuel Cell Membranes

DMFC membrane development is complicated by the fact that the two most important transport properties, methanol crossover and proton conductivity, are coupled, thus strategies that improve one property will almost invariably have an undesirable effect upon the other. Each measurement is usually done in separate experiments, even under different conditions. These measurements can be carried out in fuel cells and are indeed simultaneous, however, many complicating factors can interfere with the derived properties. This paper presents a methodology for the simultaneous measurement of membrane conductivity and methanol permeability. The equipment and method will be presented, and examples discussed including a comparison to analogous in-fuel cell results as well as examination of a series of experimental DMFC membranes. Further, a graphical means of viewing transport results as well as the derived benefits in rapid analysis and comparison of candidate membranes will be presented.

Control of water-channel structure and state of water in sulfonated poly(arylene ether sulfone)/diethoxydimethylsilane in situ hybridized proton conductors and its influence on transport properties for DMFC membranes

A new approach for noticeably improving the DMFC membrane transport properties of sulfonated poly(arylene ether sulfone) copolymers (SPAES) has been demonstrated, which is based on controlling the water-channel structure and the state of water by in situ hybridization of ORMOSIL (Organically Modified SILicates). Diethoxydimethylsilane (DEDMS) was employed as a functional ORMOSIL precursor. Its hydrophobic nature made it possible to adjust the hydrophilicity of the resulting hybrid membranes. An increase of DEDMS uptake into SPAES membranes allowed the water uptake to decrease and the water channels to become narrow and tortuous. The influence of DEDMS uptake on the state of water was investigated by measuring the characteristic melting peak of water at 0 °C. Based on this investigation, the dependence of water uptake on the state of water was quantitatively identified. A noteworthy observation is that the incorporation of DEDMS into SPAES was effective in suppressing the methanol crossover with slightly sacrificing the proton conductivity, resulting in the higher selectivity. This improvement in DFMC membrane transport properties was discussed in terms of the water-channel structure and the state of water.

A Covalently Cross-linked Polyetheretherketone Proton Exchange Membrane for DMFC

not Available.

Improvement of Nanoparticle Dispersion in SPAES/SiO2 Composite Proton Conductors and Its Influence on DMFC Membrane Performances

not Available.