There is a huge demand especially for polyvinylidene fluoride (PVDF) and its copolymers to provide high performance solid polymer electrolytes for use as an electrolyte in energy supply systems. In this regard, the blending approach was used to prepare PVDF‐based proton exchange membranes and focused on the study of factor affecting the ir proton conductivity behavior. Thus, a series of copolymers consisting of poly (methyl methacrylate) (PMMA), polyacrylonitrile (PAN), and poly(2‐acrylamido‐2‐methyl‐l‐propanesulfonic acid) (PAMPS) as sulfonated segments were synthesized and blended with PVDF matrix in order to create proton transport sites in PVDF matrix. It was found that addition of PMMA‐co‐PAMPS and PAN‐co‐PAMPS copolymers resulted in a significant increase in porosity, which favored the water uptake and proton transport at ambient temperature. Furthermore, crystallinity degree of the PVDF‐based blend membranes was increased by addition of the related copolymers, which is mainly attributed to formation of hydrogen bonding interaction between PVDF matrix and the synthesized copolymers, and led to a slight decrease in proton conductivity behavior of blend membranes. From impedance data, the proton conductivity of the PVDF/PMMA‐co‐PAMPS and PVDF/PAN‐co‐PAMPS blend membranes increases to 10 and 8.4 mS cm−1 by adding only 50% of the related copolymer (at 25°C), respectively. Also, the blend membranes containing 30% sulfonated copolymers showed a power density as high as 34.30 and 30.10 mW cm−2 at peak current density of 140 and 79.45 mA cm−2 for the PVDF/PMMA‐co‐PAMPS and PVDF/PAN‐co‐PAMPS blend membranes, respectively. A reduction in the tensile strength was observed by the addition of amphiphilic copolymer, whereas the elongation at break of all blend membranes was raised. 相似文献
This paper reports proton and methanol transport behavior of composite membranes prepared for use in the direct methanol fuel cell (DMFC). The composite membranes were prepared by embedding various proportions (10–30 wt.%) of inorganic proton conducting material (tungstophosphoric acid (TPA)/MCM-41) into sulfonated poly(ether ether ketone) (SPEEK) polymer matrix. The results indicate that the proton conductivity of the membranes increases with increasing loading of solid proton conducting material. The highest conductivity value of 2.75 mS/cm was obtained for the SPEEK composite membrane containing 30 wt.% solid proton conducting material (50 wt.% TPA in MCM-41). The methanol permeability and crossover flux were also found to increase with increasing loading of the solid proton conducting material. Lowest permeability value of 5.7 × 10−9 cm2 s−1 was obtained for composite membrane with 10 wt.% of the solid proton conducting material (40 wt.% TPA in MCM-41). However, all the composite membranes showed higher selectivity (ratio between the proton conductivity and the methanol permeability) compared to the pure SPEEK membrane. In addition, the membranes are thermally stable up to 160 °C. Thus, these membranes have potential to be considered for use in direct methanol fuel cell. 相似文献
Hybrid dual-network membranes comprising chitosan (CS)–polyvinyl alcohol (PVA) networks crosslinked with sulfosuccinic acid
(SSA) and glutaraldehyde (GA) and modified with stabilized silicotungstic acid (SWA) are reported for their application in
direct methanol fuel cells (DMFCs). Physico-chemical properties of these membranes are evaluated using thermo-gravimetric
analysis and scanning electron microscopy in conjunction with their mechanical properties. Based on water sorption and proton
conductivity measurements for the membranes, the optimum content of 10 wt.% SWA in the membrane is established. The methanol
crossover for these membranes are studied by measuring the mass balance of methanol using density meter and are found to be
lower compared to Nafion-117 membrane. The membrane–electrode assembly with 10 wt.% stabilized SWA–CS–PVA hybrid membrane
with SSA and GA as crosslinking agent delivers a peak power density of 156 mW cm−2 at a load current density of 400 mA cm−2 and 88 mW cm−2 at a load current density of 300 mA cm−2, respectively, in DMFC at 70 °C. 相似文献
The main goal of the present work is the development of partially fluorinated, low‐cost proton exchange membranes. The styrene grafted onto commercial ethylene chlorotrifluoroethylene (ECTFE) membranes using solution grafting technique, and after that the membranes were sulfonated. Diluting styrene on ECTFE with a solvent mixture of methanol plus methylene chloride (1:1) was highly effective in promoting the grafting reaction as indicated by the increase in the degree of grafting (DG) to 21.3% compared to other solvents. The DG in ECTFE membranes increased with an increase in the monomer concentration up to 60% and then declined. Fourier transform infrared spectroscopic analysis confirmed grafting and sulfonation onto ECTFE films. The maximum value of proton conductivity for ECTFE‐g‐PSSA film with DG = 21.3% was observed to be 141 mS cm−1, which is also higher than those of Nafion 212 membrane. Furthermore, the activation energy of ECTFE‐g‐PSSA membranes was obtained ranging from 8.27 to 9.726 kJ mol−1. So both proton transport mechanisms (hopping and vehicle) have been commonly accepted. The mobility of the charge carriers calculated from proton conductivity data has robust dependence on the grafting yield and temperature. Moreover, the tensile strength and elongation at break ratio decreases with the increase in DG. The water and methanol uptakes increase up to 0.97% and 30%, respectively, for the highest DG value. Finally, the ECTFE‐g‐PSSA has lower cost and higher conductivity they could be better used instead of Nafion in direct methanol fuel cells. 相似文献
Sulfonated poly (vinylidene fluoride-co-hexafluoropropylene) (SPVDF-co-HFP) based nanocomposite proton exchange membranes (PEM) are fabricated by simple solution casting method using polydopamine coated exfoliated molybdenum disulfide (PDA-MoS2) nanosheets as an alternative for Nafion® in vanadium redox flow batteries (VRFBs). PDA-MoS2 is synthesized by the etching of exfoliated MoS2 nanosheets with dopamine molecule by self-polymerization method. Various characteristic results clearly demonstrated that the incorporated PDA-MoS2 nanosheets homogeneously distributed into the SPVDF-co-HFP matrix and the presence of NH/NH2 group electrostatically interacts with SPVDF-co-HFP to form a strong acid-base pair and thus enhances the proton transport via Grotthuss type mechanism. Besides, the improvement in surface hydrophilicity provides the vehicle type conduction also. As a result, SPVDF-co-HFP/PM nanocomposite membranes showed higher proton conductivity in comparison with the pristine membrane. Especially SPVDF-co-HFP/PM-1 membrane demonstrated the excellent proton conductivity of 5.24 × 10−3 Scm−1 at 25 °C, lower vanadium-ion permeability of 1.05 × 10−8 cm2min−1 and highest membrane selectivity of 49.9 × 104 Scm−3min. On the other hand, vanadium-ion stability of the membrane increased by adding the PD-MoS2 content is attributed to their strong electrostatic attraction towards the polymer matrix. Overall results suggested that the SPVDF-co-HFP/PM-1 nanocomposite membrane is found to be a better alternative for commercially costly Nafion in VRFB applications. 相似文献
In this work, we prepared amino-modified halloysite nanotubes (PEI-DHNTs) via the co-deposition of self-polymerized dopamine and polyethylenimine (PEI) on the surface of nanotubes, which was confirmed by X-ray photoelectron spectroscopy (XPS) and Thermogravimetric analysis (TGA). A series of composite proton exchange membranes (PEMs) were prepared by incorporating PEI-DHNTs and phosphotungstic acid (HPW) into sulfonated poly(ether ether ketone) (SPEEK). It was found that both PEI-DHNTs and HPW were well dispersed in the polymer matrix, exhibiting excellent filler-matrix compatibility. The composite membranes demonstrated enhanced proton conductivity, reaching as high as 0.078 S cm−1 with 33.3 wt.% HPW loading, which was ~90% higher than that of SPEEK control membrane. Such improvement was mainly attributed to the strong acid–base pairs formed by PEI-DHNT with both SPEEK and HPW, which shortened proton hopping distance and created more continuous proton conduction pathways. Furthermore, the membrane conductivity remained almost constant after 1 year's immersion in liquid water, indicating the successful immobilization of HPW in the composite membranes. 相似文献
Summary: A simple and mass‐producible method was developed to densely assemble multiwalled carbon nanotubes (MWNTs) onto electrospun nylon 6 nanofibrous membranes. The process consists of dispersing the acid‐treated MWNTs in surfactant solutions or organic solvents, and dipping the nanofibrous membranes in the resulting dispersion for only 60 seconds, followed by the extraction of the surfactants in pure water and drying. The conductivity of the MWNT‐adsorbed nanofibrous membranes ranges from 2.2 × 10−2 to 1.5 × 10−1 S · cm−1, as determined by the four probe method, which implies that the MWNTs are adsorbed uniformly and densely along the nanofibrous membranes. Furthermore, the results suggest that there is a strong interaction between the acid‐treated MWNTs and nylon 6. We also investigate the amount of MWNTs present in the membranes using thermogravimetric analysis.
Solid conducting biodegradable composite membranes have shown to enhance nerve regeneration. However, few efforts have been directed toward porous conducting biodegradable composite membranes for the same purpose. In this study, we have fabricated some porous conducting poly(dl-lactide) composite membranes which can be used for the biodegradable nerve conduits. The porous poly(dl-lactide) membranes were first prepared through a phase separation method, and then they were incorporated with polypyrrole to produce porous conducting composite membranes by polymerizing pyrrole monomer in gas phase using FeCl3 as oxidant. The preparation conditions were optimized to obtain membranes with controlled pore size and porosity. The direct current conductivity of composite membrane was investigated using standard four-point technique. The effects of polymerization time and the concentration of oxidant on the conductivity of the composite membrane were examined. Under optimized polymerization conditions, some composite membranes showed a conductivity close to 10−3 S cm−1 with a lower polypyrrole loading between 2 and 3 wt.%. A consecutive degradation in Ringer's solution at 37 °C indicated that the conductivity of composite membrane did not exhibit significant changes until 9 weeks although a noticeable weight loss of the composite membrane could be seen since the end of the second week. 相似文献
Biofouling of anion exchange membranes is a matter of concern in microbial fuel cell. In the present study, we have attempted to improve the antibiofouling potential of anion exchange membrane by using quaternized poly(ether ether ketone) (QPEEK) with surface modification by polydopamine. It is well known that the antiadhesion test tops the list in measuring the antibiofouling potential of the membrane and hence studied. In addition, the effect of dopamine concentration on membrane hydrophilicity and surface roughness was also discussed. From the data, it was clear that power density in all microbial fuel cells showed the highest in the sixth batch and thereafter declined, although at a varying rate. As predicted, QPEEK‐1.0 registered the least. The power density suffered a loss of 918 to 897 mW m−2 in the case of QPEEK‐1.0, which is the minimum and the same for QPEEK; QPEEK‐0.5 and AMI‐7001 were 918 to 869 mW m−2, 917 to 885 mW m−2, and 578 to 537 mW m−2, respectively. A least value of protein content was obtained for QPEEK‐1.0 (0.21 ± 0.05 g cm−2), and the same for QPEEK‐0.5, QPEEK, and AMI 7001 were found to be 0.37 ± 0.05 g cm−2, 0.78 ± 0.09 g cm−2, and 1.4 ± 0.11 g cm−2, respectively. In comparison, the antibiofouling potential of modified membranes was found to be higher than that of unmodified QPEEK and commercially available AMI 7001. The internal resistance values also confirmed that modification with PDA prevents bacteria adhesion leading to high antibiofouling potential. 相似文献
In this study, a unique multi-scale nanofiber membrane prepared by electrospinning with adding the tetrabutylammonium chloride (TBAC) was applied to proton exchange membrane for direct methanol fuel cell. Three types of multi-scale nanofiber membranes of cellulose acetate (CA), nylon 6 (PA6) and poly-m-phenyleneisophthalamide (PMIA) were carefully selected as effective conductive fillers to be incorporated into Nafion as composite membranes (T-CA-Nafion, T-PA6-Nafion and T-PMIA-Nafion). At 80 °C, the proton conductivity of the multi-scale nanofiber composite membranes could reach 0.192 S cm?1 (T-CA-Nafion), 0.287 S cm?1 (T-PA6-Nafion) and 0.225 S cm?1 (T-PMIA-Nafion), which were higher than that of the ordinary nanofiber composite membrane. At the same time, the methanol permeability was also significantly reduced. The above superiorities could be attributed to the following aspects: Firstly, the unique multi-scale nanofiber structure could provide hierarchically consecutive long-range channels for proton conducting. Meanwhile, the hydrophilicity of TBAC additives made the membrane with high water-absorbing capacity, which could be beneficial to provide more water molecule carriers for proton conduction via the Vehicle mechanism. Moreover, the cross-linked nanofiber network can be acted as barriers to further hinder methanol penetration. Specifically, the –NH (amido bonds in the PA6 and PMIA) groups could be interconnected with –SO3H groups in Nafion matrix via electrostatic attractions, leading to the formation of effective –NH…–SO3H pairs in the composite membrane. The effective acid–base pairs can facilitate the proton hopping through Grotthuss mechanism, which also well illustrated the better proton conducting behavior of the T-PA6-Nafion and T-PMIA-Nafion membranes.
The possibility of developing low‐cost commercial grafted and sulfonated Poly(vinylidene fluoride) (PVDF‐g‐PSSA) membranes as proton exchange membranes for fuel cell applications have been investigated. PVDF‐g‐PSSA membranes were systematically prepared and examined with the focus of understanding how the polymer microstructure (degree of grafting and sulfonation, ion‐exchange capacity, etc) affects their methanol permeability, water uptake, and proton conductivity. Fourier transform infrared spectroscopy was used to characterize the changes of the membrane's microstructure after grafting and sulfonation. The results showed that the PVDF‐g‐PSSA membranes exhibited good thermal stability and lower methanol permeability. The proton conductivity of PVDF‐g‐PSSA membranes was also measured by the electrochemical impedance spectroscopy method. It was found that the proton conductivity of PVDF‐g‐PSSA membranes depends on the degree of sulfonation. All the sulfonated membranes show high proton conductivity at 92°C, in the range of 27 to 235 mScm−1, which is much higher than that of Nafion212 (102 mScm−1 at 80°C). The results indicated that the PVDF‐g‐PSSA membranes are particularly promising membranes to be used as polymer electrolyte membranes due to their excellent stability, low methanol permeability, and high proton conductivity. 相似文献
A series of ionically crosslinked composite membranes were prepared from sulfonated poly(arylene ether sulfone) (SPAES) and polybenzimidazole (PBI) via in situ polymerization method. The structure of the pristine polymer and the composite membranes were characterized by FT-IR. The performance of the composite membranes was characterized. The study showed that the introduction of PBI led to the reduction of methanol swelling ratio and the increase of mechanical properties due to the acid–base interaction between the sulfonic acid groups and benzimidazole groups. Moreover, the oxidative stability and thermal stability of the composite membranes were improved greatly. With the increase of PBI content, the methanol permeability coefficient of the composite membranes gradually decreased from 1.59 × 10−6 cm2/s to 1.28 × 10−8 cm2/s at 30 °C. Despite the fact that the proton conductivity decreased to some extent as a result of the addition of PBI, the composite membrane with PBI content of 5 wt.% still showed a proton conductivity of 0.201 S/cm at 80 °C which could actually meet the requirement of proton exchange fuel cell application. Furthermore, the composite membranes with PBI content of 2.5–7.5 wt.% showed better selectivity than Nafion117 taking into consideration the methanol swelling ratio and proton conductivity comprehensively. 相似文献