Reduction of methanol crossover and improved electrical efficiency in direct methanol fuel cell by the formation of a thin layer on Nafion 117 membrane: Effect of dip-coating of a blend of sulphonated PVdF-co-HFP and PBI (original) (raw)
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Electrochimica Acta, 2015
A B S T R A C T Sulfonation of PVdF was carried out in the presence of chlorosulfonic acid at 60 C. The presence of characteristic peaks of sulfonic acid in the FT-IR spectra confirmed the successful sulfonation of PVdF. X-ray diffraction was conducted to analyze the effect of sulfonation on the crystallinity of PVdF. On sulfonation for a period of 2 h, the maximum DS value achieved was 33%. This sulfonated PVdF resin was utilized as a laminate and/or coating material for the modification of Nafion-117. The laminated and coated Nafion-117 as polymer electrolyte membranes in direct methanol fuel cell (DMFC) exhibited significantly lower methanol crossover by magnitude of two orders, leading to their respective higher membrane selectivities and OCV (open circuit voltage) over prisine Nafion-117 membrane. By operating the DMFC with highly concentrated methanol (5 M), the cell efficiency (maximum power density) for the laminated and coated Nafion 117 membranes was found to be superior over that of pristine Nafion-117.
A coated Nafion membrane with a PVdF copolymer/Nafion blend for direct methanol fuel cells (DMFCs)
Solid State Ionics, 2005
To enhance the compatibility between electrode and membrane and also reduce methanol crossover from anode to cathode in direct methanol fuel cells, a Nafion membrane coated with a PVdF copolymer/Nafion blend has been prepared and characterized. This coated Nafion shows reduced methanol crossover and an enhancement in cell performance due to its improved compatibility with the electrode compared to that of native Nafion. D
Formation and evaluation of semi-IPN of nafion 117 membrane for direct methanol fuel cell
Journal of Power Sources, 2007
The in situ polymerization and crosslinking of sodium salt of sulfonated styrene in the pores of nafion 117 membrane has been studied for the evaluation of electrical performance of the resultant semi-IPN (semi-interpenetrating polymer network) membrane in direct methanol fuel cell (DMFC). The formation of semi-IPN is confirmed from the presence of aromatic characteristics peak in the FTIR spectra. Impedance results indicate that the semi-IPN sample with higher water uptake exhibits lower interfacial resistance compared to a sample with water uptake. This indicates that the semi-IPN formed in the pores of nafion 117 membrane has the ability to reduce methanol crossover by blocking the transportation. At higher temperatures (>110 • C) and lower current density (<25 mA cm −2), the electrical performance (power density) of a DMFC with a representative semi-IPN sample is observed to be higher than that with a nafion membrane.
Pd electroless plated Nafion® membrane for high concentration DMFCs
Journal of Membrane Science, 2005
A Pd layer was deposited on Nafion ® membrane by electroless plating in order to reduce methanol crossover. The composite membrane was characterized by using the following techniques of X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDXS) and transmission electron microscopy (TEM). Methanol crossover was determined by the electrochemical method. The experimental results indicated that Pd film was successfully deposited onto the Nafion ® membrane. The methanol permeability was effectively suppressed by the Pd layer, with methanol-related current decreasing from 64 mA/cm 2 (J lim ) to 57 mA/cm 2 for 1 M methanol and from 267 mA/cm 2 to 170 mA/cm 2 for 5 M methanol, respectively. Furthermore, by employing the novel Pd-Nafion ® composite electrolyte, the performance of single fuel cell was obviously improved with a high concentration of methanol such as 5 M, indicating that depositing Pd layer onto the Nafion ® membrane is an effective method to suppress the methanol crossover.
Membranes
Nafion, a perfluorosulfonic acid proton exchange membrane (PEM), has been widely used in direct methanol fuel cells (DMFCs) to serve as a proton carrier, methanol barrier, and separator for the anode and cathode. A significant drawback of Nafion in DMFC applications is the high anode-to-cathode methanol fuel permeability that results in over 40% fuel waste. Therefore, the development of a new membrane with lower permeability while retaining the high proton conductivity and other inherent properties of Nafion is greatly desired. In light of these considerations, this paper discusses the research findings on developing Nafion-based membranes for DMFC. Several aspects of the DMFC membrane are also presented, including functional requirements, transport mechanisms, and preparation strategies. More importantly, the effect of the various modification approaches on the performance of the Nafion membrane is highlighted. These include the incorporation of inorganic fillers, carbon nanomateri...
Applied Energy, 2014
Fabrication of low cost sulfonated polystyrene/PVdF-co-HFP/Nafion semi-IPN PEM. Enhancement of water uptake value and ion exchange capacity compared to Nafion-117. A maximum current density of 120 mA cm À2 at 0.2 V was obtained. A cell efficiency of 24 mW cm À2 at 60°C was obtained while using air at cathode. Enhanced proton conductivity over Nafion-117 was recorded. g r a p h i c a l a b s t r a c t a b s t r a c t Sodium salt of sulfonated styrene (SS) was polymerized in situ within the polymeric blend of PVdF-co-HFP/Nafion. The electrical efficiency of this cross-linked semi interpenetrating network membranes were evaluated for its potential application as a polymer electrolyte membrane in direct methanol fuel cell (DMFC). The characteristic aromatic peaks obtained in the FT-IR spectra confirmed the successful incorporation of SS within the polymeric blend. X-ray diffraction analyses were conducted to determine the presence of crystalline and amorphous domains within the structure of the blend membrane. Water uptake measurements at room temperature indicate that above a threshold value of 20 wt% of incorporated SS (S-20), water uptake of the semi-IPN membranes increases up to 24%, with an IEC value equal to Nafion, i.e. 0.8 meq g À1 . The maximum current density was recorded to be 120 mA cm À2 at 0.2 V, with a cell efficiency (power density) of 24 mW cm À2 at 60°C. In addition, proton conductivity and methanol permeability test results indicate that the prepared membrane S-20 is comparable to that of Nafion-117 membrane.
European Polymer Journal, 2008
Poly-(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP)/Nafion ionomer/aluminum oxy hydroxide nanocomposite membranes were prepared by phase inversion technique. The resultant membranes were subjected to protonic conductivity, methanol permeability, infra-red and thermogravimmetric analysis. The infra-red spectroscopic measurements revealed the presence of sulfonic acid groups in the composite membranes. The thermal stability and ionic conductivity of the polymer membranes have been greatly varied upon the addition of AlO[OH] n . Although the PVDF-HFP/Nafion/AlO[OH] n composite membranes have moderate protonic conductivity it has lower methanol permeability and may be considered as a candidate for DMFC applications.
RSC Adv., 2015
was incorporated into the blend of sulfonated-PVdF-co-HFP/Nafion using NMP (1-methyl-2pyrrolidone) as a common solvent with the aim to develop an alternate membrane to be used in a single cell direct methanol fuel cell (DMFC). Furthermore, the synthesized nano-composite membranes were subjected to different tests such as FTIR, XRD, water uptake, swelling, IEC (ion exchange capacity), proton conductivity and methanol crossover. The water uptake results indicated that with an increase in the nano-Al 2 O 3 content (up to 5% w/w) in the blend, the water uptake of the nanocomposite matrix rapidly increased up to 34.8%. Sample S-5 composed of 5% (w/w) Al 2 O 3 exhibited comparable proton conductivity/IEC, low methanol permeability and high membrane selectivity over the corresponding Nafion-117 membrane. In addition, the prospective nanocomposite membrane also exhibited comparable mechanical stability. Moreover, the maximum current density at 0.2 V in a single cell DMFC, which was operated with atmospheric air (without preheating/humidification) at the cathode, was recorded as 285 mA cm À2 and 270 mA cm À2 at 90 C and 110 C, respectively. Comparing the power densities of the single cell fitted with the membrane of Nafion-1 17 (28 mW cm À2 ) and blend of sulfonated-PVdF-co-HFP and Nafion (32 mW cm À2 ), the single cell with the composite membrane S-5 showed an optimum power density (57 mW cm À2 ) at +0.2 V at a high temperature of 90-110 C. These results indicate that the composite membrane could effectively reduce the anhydrous conditions at high operating temperatures.
Electrochimica Acta, 2005
TiO 2 nanometric powders were prepared via a sol-gel procedure and calcined at various temperatures to obtain different surface and bulk properties. The calcined powders were used as fillers in composite Nafion membranes for application in high temperature direct methanol fuel cells (DMFCs). The powder physico-chemical properties were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and pH measurements. The observed characteristics were correlated to the DMFC electrochemical behaviour. Analysis of the high temperature conductivity and DMFC performance reveals a significant influence of the surface characteristics of the ceramic oxide, such as oxygen functional groups and surface area, on the membrane electrochemical behaviour. A maximum DMFC power density of 350 mW cm −2 was achieved under oxygen feed at 145 • C in a pressurized DMFC (2.5 bar, anode and cathode) equipped with TiO 2 nano-particles based composite membranes.