Summary: Branched/crosslinked sulfonated polyimide membranes incorporating superior mechanical properties, high proton conductivity, and excellent fuel cell performance were successfully developed. The resulting polymer electrolytes displayed conductivity values of about 0.2 S · cm−1 at 120 °C and 100% relative humidity. In a single H2/O2 fuel cell system at 90 °C, they exhibited reasonably high fuel cell performances comparable to that of Nafion 112.
The structure of the branched/crosslinked sulfonated polyimide membranes studied here. 相似文献
A novel approach for effectively dispersing SiO2 nanoparticles in a sulfonated poly(arylene ether sulfone) ionomer (SPAES) matrix has been demonstrated. It is based on the application of wet-type milling process. Compared to a conventional mixing process such as sonication, wet-type milling allowed noticeable improvements in SiO2 nanoparticle dispersion, owing to the intensive impact of collisions between milling beads and nanoparticles. In terms of nanoparticle dispersion, the influence of wet-type milling on the direct methanol fuel cells (DMFC) membrane performance such as proton conductivity, methanol permeability, and selectivity was examined and compared with sonication process. This study underlines that nanoparticle dispersion in the composite membranes is crucial in determining DMFC membrane performance and can be substantially improved by employing a novel mixing process, i.e. wet-type milling. 相似文献
Phosphosilicate doped with a mixture of phosphotungstic acid and zirconium oxide (PWA/ZrO2–P2O2–SiO2) was investigated as potential glass composite membranes for use as H2/O2 fuel cell electrolytes. The glass membranes were studied with respect to their structural and thermal properties, proton conductivity, pore characteristics, hydrogen permeability, and performance in fuel cell tests. Thermal analysis including TG and DTA confirmed that the glass was thermally stable up to 400 °C. The dependence of the conductivity on the humidity was discussed based on the PWA content in the glass composite membranes. The proton transfer in the nanopores of the PWA/ZrO2–P2O5–SiO2 glasses was investigated and it was found that a glass with a pore size of ∼3 nm diameters was more appropriate for fast proton conduction. The hydrogen permeability rate was calculated at various temperatures, and was found to be comparatively higher than for membranes based on Nafion®. The performance of a membrane electrolyte assembly (MEA) was influenced by its PWA content; a power density of 43 mW/cm2 was obtained at 27 °C and 30% relative humidity for a PWA/ZrO2–P2O5–SiO2 glass membrane with a composition of 6–2–5–87 mol% and 0.2 mg/cm2 of Pt/C loaded on the electrode. 相似文献
A new sulfonated copolymers containing congo red groups were synthesized as a potential electrolyte for high temperature PEFCs. The resulting cross-linked sulfonated hybrid congo red membranes showed greatly improved water stability in comparison with the uncrosslinked ones while high proton conductivity was maintained. sulfonated membranes have been tested with respect to fuel cell performance. Short term fuel cell test for 100 hr gave a stable performance. These membranes are less expensive compared to Nafion. New sulfonated proton exchange composites membranes were used biological fuel cells. Molasses which is the waste of sugar factory, was used in anode as fuel and different bacteria species was sowing. Potential change was reported in biological fuel cells. 相似文献
semi-Interpenetrating polymer network (sIPN) composite membranes consisting of poly(styrenesuflonic) acid (PSSA) and poly(vinylidene fluoride) (PVDF) have been prepared and evaluated as proton exchange membrane electrolytes in direct methanol fuel cells (DMFCs). The membranes fabricated were evaluated in terms of their proton conductivity, methanol permeability, and their performance characteristics in direct methanol fuel cells (DMFCs). PSSA-PVDF membranes demonstrated decreased methanol crossover during operation of direct methanol fuel cells compared to state-of-art Nafion®-H membranes, yielding improved efficiency. PSSA-PVDF membranes have been demonstrated to operate efficiently in 1 in. × 1 in. and 2 in. × 2 in. direct methanol fuel cells. Fuel cells operating with PSSA-PVDF membranes were observed to have dramatically lower crossover rates compared to Nafion® 117 systems. Greater than 95% reduction in crossover was observed in some cases. These properties of PSSA-PVDF membranes resulted in improved fuel performance and fuel cell efficiencies for direct methanol fuel cells. It was also observed that the PSSA-PVDF membranes behave quite differently compared with Nafion®-based systems in terms water management characteristics at the cathode. The best performance with the new membranes was observed with very low oxygen or air flow rates at the cathode which is in contrast to Nafion®-based systems, which generally require higher flow rates due to excessive water accumulation at the cathode, resulting in flooding. 相似文献
Homogeneous, transparent and crack-free P2O5–ZrO2 and P2O5–ZrO2–SiO2 membranes have been synthesized by the sol–gel process. A first step has been oriented to the optimization of the synthesis and characterization of different compositions by TGA, FE-SEM, FTIR and EIS to choose the best inorganic composition in terms of chemical and mechanical stability, and proton conductivity. The addition of SiO2 improves the mechanical and chemical stability. On the other hand, compositions with higher content in P2O5 have demonstrated lower mechanical and chemical stability against water, but higher proton conductivity. The water retention and high porosity of inorganic membranes leads to high proton conductivity, 10−2 S/cm, at 140 °C and 100% relative humidity. The second step has been focused in the study of doped inorganic membranes of molar composition 99.65(40P2O5–20ZrO2–40SiO2)–0.35PWA. The high homogeneity, transparency and SEM-EDX analysis of these membranes indicates no phase separation suggesting that PWA is well dispersed in the inorganic structure. The incorporation of PWA in sol–gel oxides provides an increase of the proton conductivity at low relative humidity due to the adequate distribution of PWA in the inorganic network. Conductivity increases in two orders of magnitude at low humidity (10−4 S/cm at 50 °C and 62% RH) compared with undoped sol–gel oxide membranes. 相似文献
The transport properties and the swelling behaviour of NAFION and different sulfonated polyetherketones are explained in terms of distinct differences on the microstructures and in the pKa of the acidic functional groups. The less pronounced hydrophobic/hydrophilic separation of sulfonated polyetherketones compared to NAFION corresponds to narrower, less connected hydrophilic channels and to larger separations between less acidic sulfonic acid functional groups. At high water contents, this is shown to significantly reduce electroosmotic drag and water permeation whilst maintaining high proton conductivity. Blending of sulfonated polyetherketones with other polyaryls even further reduces the solvent permeation (a factor of 20 compared to NAFION), increases the membrane flexibility in the dry state and leads to an improved swelling behaviour. Therefore, polymers based on sulfonated polyetherketones are not only interesting low-cost alternative membrane material for hydrogen fuel cell applications, they may also help to reduce the problems associated with high water drag and high methanol cross-over in direct liquid methanol fuel cells (DMFC). The relatively high conductivities observed for oligomers containing imidazole as functional groups may be exploited in fully polymeric proton conducting systems with no volatile proton solvent operating at temperatures significantly beyond 100°C, where methanol vapour may be used as a fuel in DMFCs. 相似文献
A novel approach is proposed to prepare a proton-conductive nanochannel membrane based on polyvinylidene difluoride (PVDF) porous membrane with modified SiO2 nanospheres. The hydrophilic PVDF porous membrane with a 450-nm inner pore size was chosen as the supporting structure. Pristine SiO2 with a uniform particle size of 95–110 nm was synthesized and functionalized with –NH2 and –COOH, respectively. Through-plane channels of porous membrane and arranged functional nanoparticles in pores could contribute to constituting efficient proton transfer channels. The characteristics such as morphology, thermal stability, water uptake, dimensional swelling, proton conductivity and methanol permeability as proton exchange membranes, of the SiO2 nanospheres, and the composite membrane were investigated. The formation of ionic channels in membrane enhanced the water uptakes and proton conduction abilities of the composite membranes. PVDF/Nafion/SiO2–NH2 exhibited superior proton conductivities (0.21 S cm?1) over other samples due to several proton sites and the acid–base pairs formed between –NH2 and –SO3H. Furthermore, all the composite membranes exhibited improved methanol resistance compared with Nafion. Therefore, such a design based on porous membrane provided feasibility for high-performance proton exchange membrane in fuel cell applications. 相似文献
Nafion- and sulfonated polysulfone (SPS)- based composite membranes were prepared by incorporation of SnO2 nanoparticles in a wide range of loading (0 35 wt. %). The composites were investigated by differential scanning calorimetry, dynamic vapor sorption and electrochemical impedance spectroscopy to study the filler effect on water sorption, water mobility, and proton conductivity. A detrimental effect of the filler was observed on water mobility and proton conductivity of Nafion-based membranes. An increase in water mobility and proton conductivity was instead observed in SPS-based samples, particularly at low hydration degree. Analysis of the water sorption isotherms and states of water revealed that the presence of SnO2 in SPS enhances interconnectivity of hydrophilic domains, while not affecting the Nafion microstructure. These results enable the design of suitable electrolyte materials that operate in proton exchange membrane fuel cell conditions. 相似文献
We present a proton exchange membrane fuel cell (PEMFC) manufacturing route, in which a thin layer of polymer electrolyte solution is spray-coated on top of gas diffusion electrodes (GDEs) to work as a proton exchange membrane. Without the need for a pre-made membrane foil, this allows inexpensive, fast, large-scale fabrication of membrane-electrode assemblies (MEAs), with a spray-coater comprising the sole manufacturing device. In this work, a catalyst layer and a membrane layer are consecutively sprayed onto a fibrous gas diffusion layer with applied microporous layer as substrate. A fuel cell is then assembled by stacking anode and cathode half-cells with the membrane layers facing each other. The resultant fuel cell with a low catalyst loading of 0.1 mg Pt/cm2 on each anode and cathode side is tested with pure H2 and O2 supply at 80 °C cell temperature and 92% relative humidity at atmospheric pressure. The obtained peak power density is 1.29 W/cm2 at a current density of 3.25 A/cm2. By comparison, a lower peak power density of 0.93 W/cm2 at 2.2 A/cm2 is found for a Nafion NR211 catalyst coated membrane (CCM) reference, although equally thick membrane layers (approx. 25 μm), and identical catalyst layers and gas diffusion media were used. The superior performance of the fuel cell with spray-coated membrane can be explained by a decreased low frequency (mass transport) resistance, especially at high current densities, as determined by electrochemical impedance spectroscopy. 相似文献