Domain Size Manipulation of Perflouorinated Polymer Electrolytes by Sulfonic Acid-Functionalized MWCNTs To Enhance Fuel Cell Performance (original) (raw)
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Nafion and carbon nanotube nanocomposites for mixed proton and electron conduction
Journal of Membrane Science, 2010
Carbon nanotubes (CNTs) exhibit extraordinary mechanical, electronic and thermal properties, because of which they have been used in several applications like mechanical reinforcement of polymers, electrocatalysis, sensors, electronics, batteries, etc. Nafion is a sulfonated fluoropolymer that has become standard material in fuel cell applications for its excellent proton conducting property, and for its thermal and mechanical stability.
Journal of Membrane Science, 2007
Multi-walled carbon nanotubes (MWCNTs) were dispersed by melt-extrusion within Nafion® membranes in order to decrease the methanol permeability without deleterious effect on the ionic conductivity. The risk of short-circuits was minimized by keeping the carbon nanotubes content lower than the percolation threshold. Two series of carbon nanotubes grafted by carboxylic acid groups were used, i.e., commercially available carbon nanotubes and MWCNTs home-grafted by carboxylic acid containing alkyl radicals. The second series of nanotubes were more resistant to break-up during melt-processing. Methanol permeability was decreased by approximately 60% without any decrease in the ionic conductivity. In parallel, the Young's modulus was increased by 140% and 160% as compared to pure Nafion® at MWCNT contents of 1 and 2 wt%, respectively.
Journal of Nanoscience and Nanotechnology, 2014
Multi-walled carbon nanotubes (MWCNTs) are regarded as ideal fillers for Nafion ® polymer electrolyte membranes (PEMs) for fuel cell applications. The highly aggregated properties of MWC-NTs can be overcome by the successful cross-linking with polyvinyl alcohol (PVA) into the MWCNTs/Nafion ® membrane. In this study, a series of nanocomposite membranes were fabricated with the PVA-influenced functionalized MWCNTs reinforced into the Nafion ® polymer matrix by a solution casting method. Several different PVA contents were blended to f-MWCNTs/Nafion ® nanocomposite membranes followed by successful cross-linking by annealing. The surface morphologies and the inner structures of the resulting PVA-MWCNTs/Nafion ® nanocomposite membranes were then observed by optical microscopy and scanning electron microscopy (SEM) to investigate the dispersion of MWCNTs into the PVA/Nafion ® composite membranes. After that, the nanocomposite membranes were characterized by thermo-gravimetric analysis (TGA) to observe the thermal enhancement caused by effective cross-linking between the f-MWCNTs with the composite polymer matrixes. Improved water uptake with reduced methanol uptake revealed the successful fabrication of PVA-blended f-MWCNTs/Nafion ® membranes. In addition, the ion exchange capacity (IEC) was evaluated for PEM fuel cell (PEMFC) applications.
2017
A novel Nafion®-based nanocomposite membrane was synthesized to be applied as direct methanol fuel cells (DMFCs). Carbon nanotubes (CNTs) were coated with a layer of silica and then reacted by chlorosulfonic acid to produce sulfonate-functionalized silicon dioxide coated carbon nanotubes (CNT@SiO2-SO3H). The functionalized CNTs were then introduced to Nafion®, and subsequently, methanol permeability, proton conductivity, ion exchange capacity (IEC) and water uptake properties of the prepared membranes were investigated. The experimental results showed that the water uptake and IEC of the Nafion®/CNT@SiO2-SO3H (1 wt%) membrane increased in comparison with the recast Nafion®. IEC was enhanced from 0.9 meq/g for the recast Nafion® to 0.946 meq/g for Nafion® /CNT@SiO2-SO3H, which could be attributed to the presence of sulfonate groups on the surface of CNTs. In addition, the proton conductivity of the sulfonate modified CNT/Nafion® composite was enhanced in a wide range of temperatures....
Carbon Nanotubes Based Nafion Composite Membranes for Fuel Cell Applications
Fuel Cells, 2010
Carbon nanotubes (CNTs) containing Nafion composite membranes were prepared via melt-blending at 250°C. Using three different types of CNTs such as pure CNTs (pCNTs), oxidised CNTs (oCNTs) and amine functionalised CNTs (fCNTs); the effect of CNTs surface oxidation as well as functionalisation in composite membranes was investigated by focussing on three aspects: thermo-mechanical sta-bility, thermal degradation and proton conductivity. The oCNTs-containing Nafion composite membrane exhibited concurrent improvement in most of the properties as compared to that of pure Nafion or other CNTs-containing Nafion composite membranes.
International Journal of Hydrogen Energy, 2011
The Nafion loading in multi-walled carbon nanotube (MWCNT) composites with Nafion used as Pt support in the oxygen reduction reaction (ORR) has been studied. We varied the amount of Nafion in these composites and added a Pt loading of 0.3 mg cm À2 to the catalyst layer. The performance of these electrodes in the ORR was measured with linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), chronoamperometry, inductive coupled plasma (ICP), X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). In addition, we compared the performance of the MWCNTs as Pt supports with those of the composites. Our results indicate that the composites are better Pt supports in comparison with MWCNT.
Journal of Membrane Science, 2018
In the present work, three kinds of sulfonated poly(arylene ether ketones) (SPAEKs) with different structures are introduced into Nafion as blending modifiers to enhance the properties of Nafion, especially methanol resistance. Characterizations such as transmission electron microscope (TEM), proton conductivity, methanol crossover, and single cell performance, are carried out to evaluate these composite membranes (SPAEK@Nafion) as prepared. Besides, recast Nafion membrane is prepared and characterized for comparison via the same method. By investigating the microstructure of SPAEK@Nafion membranes, p-BPAF@Nafion membrane is found to have the most homogeneous distribution and Nafion-like phase separation among these membranes. The pendent sulfobutyl side-chain and fluorinated main chain of p-BPAF make it most similar structure with Nafion among three modifiers, and such Nafion-liked structure provides p-BPAF a good compatibility with Nafion, which can facilitate its enhancement for Nafion. Consequently,
The Journal of Physical Chemistry C, 2016
Sulfonic acid-functionalized graphene (S-graphene) is employed as a promising inorganic filler as well as a solid acid proton conducting medium to realize a composite membrane with Nafion for polymer electrolyte fuel cell (PEFC) applications under reduced relative humidity (RH). The functionalization of graphene is performed by sulfonic acid-containing aryl radicals to increase the number of sulfonate groups per unit volume of a domain. A Nafion-S-graphene composite membrane is obtained by embedding S-graphene in Nafion, which provides high absorption of water and fast proton-transport across the electrolyte membrane under low RH values. The proton conductivity of the Nafion-S-graphene (1%) composite membrane at 20% RH is 17 mS cm-1 , which is five times higher than that of a pristine recast Nafion membrane. PEFCs incorporating the Nafion-S-graphene composite membrane deliver a peak power density of 300 mW cm-2 at a load current density of 760 mA cm-2 while operating at optimum temperature of 70 °C under 20% RH and ambient pressure. By contrast, operating under identical conditions, a peak power density of 220 mW cm-2 is achieved with the pristine recast Nafion membrane. The Nafion-S-graphene composite membrane could be used to address many critical problems associated with commercial Nafion membranes in fuel cell applications.
Polymers, 2019
Nafion composite membranes, containing different amounts of mesoporous sulfated titanium oxide (TiO2-SO4) were prepared by solvent-casting and tested in proton exchange membrane fuel cells (PEMFCs), operating at very low humidification levels. The TiO2-SO4 additive was originally synthesized by a sol-gel method and characterized through x-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and ion exchange capacity (IEC). Peculiar properties of the composite membranes, such as the thermal transitions and ion exchange capacity, were investigated and here discussed. When used as an electrolyte in the fuel cell, the composite membrane guaranteed an improvement with respect to bare Nafion systems at 30% relative humidity and 110 °C, exhibiting higher power and current densities.