Methanol Permeability Of Membranes Research Articles

Self-Assembly DBS Nanofibrils on Solution-Blown Nanofibers as Hierarchical Ion-Conducting Pathway for Direct Methanol Fuel Cells.

In this work, we reported a novel proton exchange membrane (PEM) with an ion-conducting pathway. The hierarchical nanofiber structure was prepared via in situ self-assembling 1,3:2,4-dibenzylidene-d-sorbitol (DBS) supramolecular fibrils on solution-blown, sulfonated poly (ether sulfone) (SPES) nanofiber, after which the composite PEM was prepared by incorporating hierarchical nanofiber into the chitosan polymer matrix. Then, the effects of incorporating the hierarchical nanofiber structure on the thermal stability, water uptake, dimensional stability, proton conductivity, and methanol permeability of the composite membranes were investigated. The results show that incorporation of hierarchical nanofiber improves the water uptake, proton conductivity, and methanol permeability of the membranes. Furthermore, the composite membrane with 50% hierarchical nanofibers exhibited the highest proton conductivity of 0.115 S cm−1 (80 °C), which was 69.12% higher than the values of pure chitosan membrane. The self-assembly allows us to generate hierarchical nanofiber among the interfiber voids, and this structure can provide potential benefits for the preparation of high-performance PEMs.

Azide-assisted crosslinked quaternized polysulfone with reduced graphene oxide for highly stable anion exchange membranes

As an important component for anion exchange membrane fuel cells (AEMFCs), anion exchange membranes (AEMs) should possess good mechanical strength and relatively high stability in alkaline environment. Besides, fuel permeation as a serious issue which may lead to the potential decrease and catalyst poisoning could also affect the application for AEMs. Herein, we prepared a series of crosslinked composite membranes which using reduced graphene (rGO) as both inorganic nanofillers and crosslinkers. During a simple thermal crosslinking at 160°C, a covalently cross-linked structure was formed between side chains with azide groups and rGO with alkenyl groups without sacrificing ionic groups. Properties such as water uptake (WU) and swelling ratio were significantly decreased after crosslinking, which caused the decline of ion conductivity for the membranes. However, it was found that when only a small amount of rGO (less than 0.5wt%) was incorporated into QPSU to induced crosslinking, the methanol permeability of membranes obviously decreased by two orders of magnitude, and the mechanical strength and thermal stability of the composite membranes were enhanced. Moreover, the crosslinked membrane maintained stable in Fenton's reagent and exhibited high alkaline resistance in 1M of KOH at 60°C for more than 500h. Therefore, the crosslinked membranes with rGO demonstrate great potential as anion exchange membrane for fuel cell.

Solution‐blown SPEEK/POSS nanofiber–nafion hybrid composite membranes for direct methanol fuel cells

ABSTRACTThis study aims to develop novel hybrid composite membranes (NHMs) by impregnating Nafion solution into the porous sulfonated poly(ether ether ketone)/polyhedral oligomeric silsesquioxanes (SPEEK/POSS) nanofibers (NFs). The composite membrane was prepared by solution blowing of a mixture of SPEEK/POSS solution. The characteristics of the SPEEK/POSS NFs and the NHMs, including morphology, thermal stability, and performance of membrane as PEMs, were investigated. The performance of NHMs was compared with that of Nafion117 and SPEEK/Nafion composite membranes. Results showed that the introduction of POSS improved the proton conductivity, water swelling, and methanol permeability of membranes. A maximum proton conductivity of 0.163 S cm−1was obtained when the POSS content was 6 wt % at 80°C, which was higher than that of Nafion117 and SPEEK/Nafion. NHMs could be used as proton exchange membranes (PEMs) for fuel cell applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2015,132, 42843.

Highly conductive proton exchange membranes based on sulfonated poly(phthalazinone ether sulfone) and cerium sulfophenyl phosphate

Polymer composite membranes based on sulfonated poly(phthalazinone ether sulfone) (SPPES) and cerium sulfophenyl phosphate (CeSPP) are prepared. Three CeSPP concentrations are used: 10, 20, and 30wt.%. The membranes are characterised by infrared spectroscopy (IR), X-ray diffraction spectroscopy, thermal gravimetric analysis, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The IR results indicate the formation of intense hydrogen bonds between CeSPP and SPPES molecules. The SEM micrographs show that CeSPP well dispersed in composite membrane. The properties of the membranes are evaluated by their water uptake, ionic exchange capacity, proton conductivity and methanol permeability. The proton conductivity of the SPPES (DS 91%)/CeSPP (30wt.%) composite membrane (I) reaches 0.384S/cm at 130°C and 100% relative humidity, which is three times more than Nafion®117. CeSPP improves the conductivity of composite membranes at a low humidity. At 105°C and 70% RH, the proton conductivity of membrane (I) is 9.1×10−2S/cm, while Nafion®117 8.8×10−3S/cm. The methanol permeability of membrane (I) is 10−8cm2/s. That is much lower than Nafion®117.

Proton-Conductive Nanochannel Membrane for Fuel-Cell Applications

Novel design of proton conductive membrane for direct methanol fuel cells is based on proton conductivity of nanochannels, which is acquired due to the electric double layer overlap. Proton conductivity and methanol permeability of an array of nanochannels were studied. Anodic aluminum oxide with pore diameter of 20 nm was used as nanochannel matrix. Channel surfaces of an AAO template were functionalized with sulfonic groups to increase proton conductivity of nanochannels. This was done in two steps; at first -SH groups were attached to walls of nanochannels using (3-Mercaptopropyl)-trimethyloxysilane and then they were converted to -SO3H groups using hydrogen peroxide. Treatment steps were analyzed by Fourier Transform Infrared spectroscopy and X-ray Photoelectron Spectroscopy. Proton conductivity and methanol permeability were measured. The data show methanol permeability of membrane to be an order of magnitude lower, than that measured of Nafion. Ion conductivity of functionalized AAO membrane was measured by an impedance analyzer at frequencies ranging from 1 Hz to 100 kHz and voltage 50 mV to be 0.15 Scm(-1). Measured ion conductivity of Nafion membrane was 0.05 Scm(-1). Obtained data show better results in comparison with commonly used commercial available proton conductive membrane Nafion, thus making nanochannel membrane very promising for use in fuel cell applications.

Morphology and transport properties of protons and methanol through partially sulfonated block copolymers

The morphological changes with different compositions of casting solvents in the membranes of sulfonated polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) were investigated with small-angle X-ray scattering (SAXS) and transmission electron microscope (TEM). Using the single solvent of tetrahydrofuran (THF) and the solvent mixtures of methanol/THF with different compositions, the casting polymer solutions were prepared for the membrane fabrication. The proton conductivity and the methanol permeability of membranes were measured, and the effect of morphological changes on the casting solvents was discussed through Flory–Huggins theory. It was found that the sulfonated SEBS membranes were transformed from well ordered lamellar to disordered co-continuous structure and the morphological difference caused abrupt enhancement in the proton conductivity and the methanol permeability as the concentration of methanol in the mixed solvents (MeOH/THF) increased.

설폰화된 폴리설폰/PPSQ 유-무기 복합 전해질막의 수소이온 전도도 및 메탄올 투과 특성

설폰화된 폴리설폰 (sulfonated polysulfone, SPSF)과 Poly(phenylmethyl silsequioxane) (PPSQ)의 유무기 복합 전해 질막을 제조하여 이온전도도와 메탄을 투과 특성을 조사하였다 클로로트리메틸실란과 클로로설폰산의 반응 몰비와 반응시간를 변화시켜 설폰화도가 <TEX>$37\~75\%$</TEX>인 SPSF를 합성하였다. SPSF/PPSQ복합 전해막은 SPSF와 PPSQ를 DMF에 용해하여 캐스팅하는 방법으로 제조하였다 이 복합 전해질막의 수소 이온 전도도는 상온에서 <TEX>$2.8\times10^{-3}\~4.9\times10^{-2}S/cm$</TEX>이었으며 설폰화도가 증가할수록 전도도는 증가하였다. 제조된 설폰화된 폴리설폰 복합 전해질막의 메탄을 투과도는 이온전도도와 설폰화도에 비례하여 증가하였으며, PPSQ의 함량이 커질수록 메탄을 투과도가 비례적으로 감소하는 것을 확인할 수 있었다. 약 <TEX>$5wt\%$</TEX> PPSO론 포함한 복합 전해질막의 이온전도도 및 메탄을 투과도는 SPSF에 비교하여 거의 동일하지만 함수율을 크게 감소시키는데 효과적이었다. Sulfonated polysulfone (SPSF) with poly(phenylmethyl silsesquioxane, PPSQ) composite polymer electrolyte membranes were prepared and their proton conductivity, water uptake and methanol permeability of membranes were characterized. By controlling the ratio of <TEX>$(CH_3)_3SCI\;and\;CISO_3H$</TEX> and reaction time, SPSF with <TEX>$37\~75\%$</TEX> degree of sulfonation were synthesized. The increase of sulfonate groups in the base polymer resulted in the increase of the water uptake in the membranes as well as methanol permeability. Composite membranes were prepared by casting of DMF solution of SPSF and PPSQ. The proton conductivity of the composite membrane at room temperature was <TEX>$2.8\times10^{-3}\~4.9\times10^{-2}S/cm.$</TEX> The increase of PPSQ contents in composite membranes resulted in a decrease in water uptake and methanol permeability. Composite membranes containing <TEX>$5\%$</TEX> PPSQ did not make a significant effect on the proton conductivity nO methanol permeability compared with that of pristine SPSF, but a significant decrease of water uptake was observed.

燃料電池用プロトン伝導膜 直接メタノール燃料電池用電解質膜の現状と新展開

To develop a high performance direct methanol fuel cell (DMFC), a novel electrolyte membrane is needed. This electrolyte membrane should be durable up to 130t to improve the catalytic reaction, and the methanol crossover should be reduced. Reported membranes are reviewed in this article, and our own approach is shown. Our approach is to design a pore-filling type polyelectrolyte membrane, where the polyelectrolyte is filled into the pores of a porous substrate, and the membrane swelling is suppressed by the substrate matrix. Proton conductivity was achieved through the filling electrolyte polymer. Methanol permeation was controlled by the swelling of the electrolyte polymer, and the mechanical strength at high temperature was maintained by the substrate. From this concept, a high proton conductivity was shown to exist with reduced membrane methanol permeability, and in addition, a heat-resistance was also achieved.