An NMR study on the molecular dynamic and exchange effects in composite Nafion/sulfated titania membranes for PEMFCs (original) (raw)
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2008
Nafion-Silica oxide (SiO2)-Phosphotungstic acid (PWA) composite membrane have been synthesized using solution phase sol-gel method. The effect of the weight ratio of Nafion:SiO2:PWA to the electrochemical properties of composite membrane when applies as electrolyte in the PEMFC was investigated using Fuel Cell Test System (FCTS) at temperature of range of 80 – 90 oC and 40% relative humidity (RH). The weight ratio of the composite membrane samples varied in the range of 100:2.88:1.15, 100:4.33:1.73 and 100:5.76:2.30 and designated as NS10W, NS15W and NS20W, respectively. The aim of the experiment was to insert the inorganic hygroscopic and high conductivity filler like PWA and SiO2 in the Nafion matrix to order to improve the water retention, proton conductivity (σ), hydrogen crossover (β), and thermal stability in addition to increase PEMFC performance at elevated temperature and low RH condition. The result showed when appropriately embeded in the Nafion cluster, the hydrated PWA ...
Nafion/PTFE/silicate membranes for high-temperature proton exchange membrane fuel cells
International journal of …, 2008
Fuel cell performance of membrane electrode assemblies (MEAs) prepared from poly (tetrafluoroethylene)/Nafion/silicate (PNS) membrane and Nafion-112 membrane were investigated. Due to the low conductivity of PTFE and silicate, PNS had a higher proton resistance than Nafion-112. However, in this work we show that PNS performs better than Nafion-112 for a high current density i4500 mA=cm 2 operation with a low inlet gas humidity. As the PEMFCs were operated at 60 C with 100% RH, the results showed the maximum power density ðPD max Þ of PNS was: PD max ¼ 717 mW=cm 2 at i ¼ 1452 mA=cm 2 with both H 2 and O 2 flow rates of 300 ml/min, and PD max ¼ 1042 mW=cm 2 at i ¼ 2785 mA=cm 2 with H 2 flow rate of 360 ml/min and O 2 flow rate of 600 ml/min, which were much higher than the PD max ¼ 4677 mW=cm 2 at i ¼ 1130 mA=cm 2 of Nafion-112 with both H 2 and O 2 flow rates of 300 ml/min. The PD max of PNS was: 700 mW=cm 2 , 656 mW=cm 2 , and 577 mW=cm 2 at i ¼ 1400 mA=cm 2 as the operating temperature and inlet gas humidity were set at 90 C with 67.7% RH, 100 C with 46.8% RH, and 110 C with 33.1% RH, respectively. However, no output power was detected for Nafion-112 MEA when the cell was operated at a temperature higher than 90 C and an inlet gas humidity lower than 67.7% RH. The high PEMFC performance of PNS at high current density and low humidity is attributed to the presence of silicate in the PNS membrane, which enhances water uptake and reduces electro-osmosis water loss at a high current density.
2008
Investigation of the single cell Proton Exchange Membrane Fuel Cell (SCPEMFC) using a series of Nafion-SiO2-PWA composite membranes as electrolyte have been carried out using the Arbin Fuel Cell Test System (FCTS). PEMFC performance and proton conductivity of the composite membrane have been determined over a temperature range of 30-90 o C at pressure 1-1.7 atm at 40% RH. Analysis with FCTS showed that higher current density was yielded by composite membrane (82 mAcm -2 at 0.6 V for NS15W) than with the Nafion membrane (30 mAcm -2 at 0.2 V) at 90 o C. Hence the composite is potentially a good candidate to substitute Nafion membrane especially for the electrolyte of PEMFC operating at higher temperature range and lower RH.
International Journal of Hydrogen Energy, 2012
Polymer electrolyte membrane fuel cells Water uptake Thermogravimetric measurements Fabrication and testing of membraneelectrode assemblies a b s t r a c t This work reports the preparation, characterization and test in a single fuel cell of two families of hybrid inorganic-organic proton-conducting membranes, each based on Nafion and a different "core-shell" nanofiller. Nanofillers, based on either a ZrO 2 "core" covered with a HfO 2 "shell" (ZrHf) or a HfO 2 "core" solvated by a "shell" of SiO 2 nanoparticles (SiHf), are considered. The two families of membranes are labelled [Nafion/(ZrHf) x ] and [Nafion/ (SiHf) x ], respectively. The morphology of the nanofillers is investigated with high-resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray spectroscopy (EDX) and electron diffraction (ED) measurements. The mass fractions of nanofiller x used for both families are 0.05, 0.10 or 0.15. The proton exchange capacity (PEC) and the water uptake (WU) of the hybrid membranes are determined. The thermal stability is investigated by high-resolution thermogravimetric measurements (TGA). Each membrane is used in the fabrication of a membrane-electrode assembly (MEA) that is tested in single-cell configuration under operating conditions. The polarization curves are determined by varying the activity of the water vapour (a H2O ) and the back pressure of the reagent streams. A coherent model is proposed to correlate the water uptake and proton conduction of the hybrid membranes with the microscopic interactions between the Nafion host polymer and the particles of the different "coreeshell" nanofillers.
Nafion–Titanate Nanotube Composite Membranes for PEMFC Operating at High Temperature
Journal of The Electrochemical Society, 2007
Nafion-titanate nanotube composites were investigated as electrolytes for proton exchange membrane fuel cells ͑PEMFCs͒ operating at high temperature T. With the addition of 5-15 wt % of nanotubes to the ionomer, PEMFC performance can be significantly sustained for T up to 130°C. The polarization curves of PEMFCs using the composite electrolytes reflect a competing effect between an increase in water uptake due to the extremely large surface area of the nanotubes and a decrease in proton conductivity of the composites.
Journal of Power Sources, 2002
Composite polymer electrolyte membranes were prepared by impregnating Nafion solution into the porous expanded PTFE (ePTFE) films as a substrate and their single cell performance, gas permeability, water flux, and water uptake were investigated. Although the nitrogen permeability of the composite membrane was higher than that of Nafion 112, there was not the serious cross-over of gases to diminish cell performance and it was seen that the cell performance could be improved by reduced thickness of the composite membrane. It was also seen that water uptake and water flux of the composite membrane were dependent on the Nafion loading amount on the substrate and, therefore, the thickness of the membrane. The water uptake as well as the water flux of the composite membrane increased as the Nafion loading amount increased and the increase rate of water uptake with temperature for the composite membranes was found to be larger than Nafion 112. #
Journal of Power Sources, 2006
Composite membranes were prepared by impregnation of porous PTFE membrane with 2.5% Nafion ® solution prepared in various solvents. The solvents chosen were based on their solubility parameters to effectively wet the substrate for obtaining membranes with lower resistances. Earlier studies on composite membrane preparation did not take the solubility parameter of the solvent to wet the substrate into account. Membrane conductivity was dependent on the solvent type and its solubility parameter. Solvents with solubility parameter close to Nafion ® backbone/PTFE showed lower charge transfer resistance and the solvents with solubility parameter close to ionic groups showed higher conductivity. The effect of other parameters like compaction pressure, humidity and incorporation of Pt particles on the membrane resistance have also been investigated.
Nafion/Analcime and Nafion/Faujasite composite membranes for polymer electrolyte membrane fuel cells
Chemical Engineering Research & Design, 2010
The Nafion/zeolite composite membranes were synthesized for polymer electrolyte fuel cells (PEMFCs) by adding zeolite in the matrix of Nafion polymer. Two kinds of zeolites, Analcime and Faujasite, having different Si/Al ratio were used. The physico-chemical properties of the composite membranes such as water uptake, ion-exchange capacity, hydrogen permeability, and proton conductivity were determined. The fabricated composite membranes showed the significant improvement of all tested properties compared to that of pure Nafion membrane. The maximum proton conductivity of 0.4373 S cm−1 was obtained from Nafion/Analcime (15%) at 80 °C which was 6.8 times of pure Nafion (0.0642 S cm−1 at 80 °C). Conclusively, Analcime exhibited higher improvement than Faujasite.
Composite Nafion-CaTiO3-δ Membranes as Electrolyte Component for PEM Fuel Cells
Polymers, 2020
Manufacturing new electrolytes with high ionic conductivity has been a crucial challenge in the development and large-scale distribution of fuel cell devices. In this work, we present two Nafion composite membranes containing a non-stoichiometric calcium titanate perovskite (CaTiO3−δ) as a filler. These membranes are proposed as a proton exchange electrolyte for Polymer Electrolyte Membrane (PEM) fuel cell devices. More precisely, two different perovskite concentrations of 5 wt% and 10 wt%, with respect to Nafion, are considered. The structural, morphological, and chemical properties of the composite membranes are studied, revealing an inhomogeneous distribution of the filler within the polymer matrix. Direct methanol fuel cell (DMFC) tests, at 110 °C and 2 M methanol concentration, were also performed. It was observed that the membrane containing 5 wt% of the additive allows the highest cell performance in comparison to the other samples, with a maximum power density of about 70 mW...