Rheological Effects on Swelling of Polymer Membranes in Water

2020 ◽  
pp. 36-47
Author(s):  
N.F. Bunkin ◽  
S.V. Bashkin ◽  
Y.T. Juraev ◽  
R.S. Safronenkov ◽  
V.A. Kozlov
Keyword(s):  
Proton Exchange Membrane ◽  
Membrane Surface ◽  
Experimental Methods ◽  
Bulk Water ◽  
Proton Exchange ◽  
Polymer Fibers ◽  
Nafion Membrane ◽  
Deuterium Content ◽  
Infrared Spectrophotometry ◽  
Exchange Membrane

The study focuses on rheological effects which appear during swelling of the Nafion proton-exchange membrane in cuvettes of different thicknesses, and explains the effects by the appearance of the so-called excluded zone near the membrane surface. The excluded zone is the polymer fibers of the Nafion membrane, deployed towards bulk water. The depth of fiber penetration into the volume or the size of the excluded zone depends on the deuterium content in the water. It should be noted that in the process of swelling of the Nafion membrane plate in water it is structurally rearranged, which leads to a transition from a hydrophobic state to a hydrophilic one. By means of experimental methods based on Fourier transform infrared spectrophotometry, the study shows that the swelling of the Nafion membrane plate, which is initially hydrophobic, in ordinary water (deuterium content is 157 ppm) and in deuterium-depleted water (deuterium content is 1 ppm) in a cuvette of limited volume occurs differently. Small changes in the deuterium content in water turned out to lead to significant differences in the dynamics of swelling of the polymer membrane. For a 175-micron-thick Nafion membrane plate, this effect is most evident when the distance between the cuvette windows is L = 200 microns

Highly proton conductive membranes based on carboxylated cellulose nanofibres and their performance in proton exchange membrane fuel cells

2019 ◽  
Author(s):  
Valentina Guccini ◽  
Annika Carlson ◽  
Shun Yu ◽  
Göran Lindbergh ◽  
Rakel Wreland Lindström ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Surface Charge ◽  
Proton Exchange Membrane ◽  
Membrane Surface ◽  
Proton Exchange ◽  
Membrane Thickness ◽  
Fuel Cell Performance ◽  
Cellulose Nanofibres ◽  
Exchange Membrane

The performance of thin carboxylated cellulose nanofiber-based (CNF) membranes as proton exchange membranes in fuel cells has been measured in-situ as a function of CNF surface charge density (600 and 1550 µmol g<sup>-1</sup>), counterion (H<sup>+</sup>or Na<sup>+</sup>), membrane thickness and fuel cell relative humidity (RH 55 to 95 %). The structural evolution of the membranes as a function of RH as measured by Small Angle X-ray scattering shows that water channels are formed only above 75 % RH. The amount of absorbed water was shown to depend on the membrane surface charge and counter ions (Na<sup>+</sup>or H<sup>+</sup>). The high affinity of CNF for water and the high aspect ratio of the nanofibers, together with a well-defined and homogenous membrane structure, ensures a proton conductivity exceeding 1 mS cm<sup>-1</sup>at 30 °C between 65 and 95 % RH. This is two orders of magnitude larger than previously reported values for cellulose materials and only one order of magnitude lower than Nafion 212. Moreover, the CNF membranes are characterized by a lower hydrogen crossover than Nafion, despite being ≈ 30 % thinner. Thanks to their environmental compatibility and promising fuel cell performance the CNF membranes should be considered for new generation proton exchange membrane fuel cells.<br>

Design of a Climate Chamber to Study Transient Performance of a Proton Exchange Membrane Fuel Cell at Near Freezing Temperatures

2010 ◽  
Author(s):  
Daniel Cassar ◽  
Xia Wang
Keyword(s):  
Fuel Cells ◽  
Proton Exchange Membrane ◽  
Internal Heat ◽  
Proton Exchange ◽  
Operating Conditions ◽  
Nafion Membrane ◽  
Thermoelectric Device ◽  
Climate Chamber ◽  
Freezing Temperatures ◽  
Exchange Membrane

Freezing temperature startup of fuel cells is a serious issue for smaller applications such as auxiliary or backup power units. To accurately test and examine this problem, a laboratory climate chamber is required which can accurately represent possible environments. This research designed a climate chamber using thermoelectric (peltier) heat pumps to provide temperatures down up to −10 degrees Celsius. The internal heat absorption from air utilized forced convection while heat emitted by the thermoelectric device was removed by flowing water channels. A copper plate was used to provide separation between the heat absorbing plate and the thermoelectric heat pump. The unit showed accurate temperature control and successful operation at sub-zero temperatures. Two proton exchange membrane fuel cells with 117 Nafion membrane and 212 Nafion membrane were tested in the climate chamber under various operating conditions. The startup performance was examined under both freezing and non-freezing temperatures. Heated and humidified feed gasses were shown to greatly improve the steady state time of the 117 setup by over 30%.

scholarly journals Membrane Electrolyte Assembly Health Estimation Method for Proton Exchange Membrane Fuel Cells

2017 ◽  
Vol 14 (4) ◽  
Author(s):  
Alexander J. Headley ◽  
Martha Gross ◽  
Dongmei Chen
Keyword(s):  
Proton Exchange Membrane ◽  
Membrane Surface ◽  
Computational Cost ◽  
Estimation Method ◽  
Cell Voltage ◽  
Open Circuit ◽  
Proton Exchange ◽  
Normal Operation ◽  
Degradation Rates ◽  
Exchange Membrane

Membrane electrolyte assembly (MEA) aging is a major concern for deployed proton exchange membrane (PEM) fuel cell stacks. Studies have shown that working conditions, such as the operating temperature, humidity, and open circuit voltage (OCV), have a major effect on degradation rates and also vary significantly from cell to cell. Individual cell health estimations would be very beneficial to maintenance and control schemes. Ideally, estimations would occur in response to the applied load to avoid service interruptions. To this end, this paper presents the use of an extended Kalman filter (EKF) to estimate the effective membrane surface area (EMSA) of each cell using cell voltage measurements taken during operation. The EKF method has a low computational cost and can be applied in real time to estimate the EMSA of each cell in the stack. This yields quantifiable data regarding cell degradation. The EKF algorithm was applied to experimental data taken on a 23-cell stack. The load profiles for the experiments were based on the FTP-75 and highway fuel economy test (HWFET) standard drive cycle tests to test the ability of the algorithm to perform in realistic load scenarios. To confirm the results of the EKF method, low performing cells and an additional “healthy” cell were selected for scanning electron microscope (SEM) analysis. The images taken of the cells confirm that the EKF accurately identified problematic cells in the stack. The results of this study could be used to formulate online sate of health estimators for each cell in the stack that can operate during normal operation.

Synthesis of Platinum Nanoparticles and Then Self-Assembly on Nafion Membrane to Give a Catalyst Coated Membrane

2005 ◽  
Vol 2005 (7) ◽  
pp. 449-451 ◽  
Author(s):  
Haolin Tang ◽  
Zhiping Luo ◽  
Mu Pan ◽  
San Ping Jiang ◽  
Zhengcai Liu
Keyword(s):  
Self Assembly ◽  
Proton Exchange Membrane ◽  
Membrane Surface ◽  
Proton Exchange ◽  
The Self ◽  
Self Assembling ◽  
Self Assembled ◽  
Nanoparticle Structure ◽  
Exchange Membrane ◽  
Coated Membrane

A catalyst-coated membrane (CCM) for a proton exchange membrane fuel cell (PEMFC) with Pt loading of 2.8 μg/cm2 have been prepared by self-assembling charged Pt particles on a sulfonic acid function group, SO3-, on the membrane surface. Proton conductivity of the as-obtained CCM is 0.0932 S/cm. Half-cell polarisation showed that the self-assembled membrane is electrochemical active. Electrochemical characterisation of the self-assembled electrode showed that the Pt-PDDA nanoparticles were electrocatalytic active. The performance of self-assembled MEA with a Pt loading of 2.8 μg/cm2 achieved 2.3 mW/cm2. This corresponds to Pt utilisation of 821 W per 1 g Pt. The results demonstrated the feasibility of the formation of monolayered Pt nanoparticle structure on the membrane interface. Such a monolayered structure could offer a powerful tool in fundamental studies of polymer electrolyte systems.

Highly proton conductive membranes based on carboxylated cellulose nanofibres and their performance in proton exchange membrane fuel cells

2019 ◽  
Author(s):  
Valentina Guccini ◽  
Annika Carlson ◽  
Shun Yu ◽  
Göran Lindbergh ◽  
Rakel Wreland Lindström ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Surface Charge ◽  
Proton Exchange Membrane ◽  
Membrane Surface ◽  
Proton Exchange ◽  
Membrane Thickness ◽  
Fuel Cell Performance ◽  
Cellulose Nanofibres ◽  
Exchange Membrane

<p>The performance of thin carboxylated cellulose nanofiber-based (CNF) membranes as proton exchange membranes in fuel cells has been measured in-situ as a function of CNF surface charge density (600 and 1550 µmol g<sup>-1</sup>), counterion (H<sup>+</sup>or Na<sup>+</sup>), membrane thickness and fuel cell relative humidity (RH 55 to 95 %). The structural evolution of the membranes as a function of RH, as measured by Small Angle X-ray scattering, shows that water channels are formed only above 75 % RH. The amount of absorbed water was shown to depend on the membrane surface charge and counter ions (Na<sup>+</sup>or H<sup>+</sup>). The high affinity of CNF for water and the high aspect ratio of the nanofibers, together with a well-defined and homogenous membrane structure, ensures a proton conductivity exceeding 1 mS cm<sup>-1</sup>at 30 °C between 65 and 95 % RH. This is two orders of magnitude larger than previously reported values for cellulose materials and only one order of magnitude lower than Nafion 212. Moreover, the CNF membranes are characterized by a lower hydrogen crossover than Nafion, despite being ≈ 30 % thinner. Thanks to their environmental compatibility and promising fuel cell performance the CNF membranes should be considered for new generation proton exchange membrane fuel cells.</p>

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