How to calculate the theoretical Ion Exchange Capacity for recast Nafion membrane and Nafion composites?
See acid capacity in descriptions http://fuelcell.com/product-category/proton-exchange-membrane-pem/
Dear G. Rambabu ,
Int. J. Electrochem. Sci., 8 (2013) 9704 - 9713
Novel Bilayer Composite Membrane for Passive Direct
Methanol Fuel Cells with Pure Methanol
Li-Duan Tsai3
, Hung-Chung Chien2,3
, Wei-Han Huang2
, Chiu-Ping Huang2
, Chi-yun Kang2
Jiunn-Nan Lin2
, and Feng-Chih Chang1,3,
The bilayer composite membrane composed of the sulfonated graphene oxide (SGO)/Nafion and sulfonated activated carbon (SAC)/Nafion composite membrane is designed and prepared by repeatedly bar-coating. With the carefully chosen of solvent, the bilayer composite membrane has shown identical thickness on SEM observation. The SGO/Nafion side has a low methanol permeability ascribed to the unique selectivity of the SGO. Moreover, the SAC side has good water retention which can facilitate the back diffusion water produced by the cathode. The unique design of composite membranes confers low methanol crossover and high proton conductivity at the same time. The bilayer composite membrane shows better power density than Nafion 212 and Nafion 115 and the performance monitored for 24h to ensure the stable power density and the durability of the membrane.
Keywords: Nafion, sulfonated graphene oxide, sulfonated activated carbon, methanol crossover, direct methanol fuel cells
2.4 Manufacture of bilayer composite membranes
Nafion ionomers were transferred to N,N-dimethylacetamide (DMAc, Aldrich) by distilling a mixed solution of Nafion DE2020 and DMAc under reduced pressure until the solution temperature reached 70°C, to remove water and solvent. SGO/Nafion solution with 0.1 wt% SGO loading (compared to Nafion) in DMAc was prepared by adding well-dispersed SGO(aq) into the Nafion solution and mixing by mild ultrasonication. Then, the SGO/Nafion solutions were degassed and dispersed with a planetary mixer before casting. The composite membranes were obtained by bar coating with a gap of 300 um and drying at 50°C for 24 h, and post annealing at 140°C for 2 h. The SAC/Nafion solution was prepared by dispersing 10 wt% SAC (compared to Nafion) into Nafion solution (18% dispersion in aqueous alcohol). Then the SAC/Nafion mixture was bar-coating onto the SGO/Nafion film by a smaller bar with a controlled gap of 300 um and drying Nafion composite at 50°C for 24 h, and post annealing at 140°C for 2 h. Then, the membranes were cut into desired sizes and placed into 0.5 M H2SO4(aq) at 80°C for 1 h to activate the sulfonic acids of the Nafion. Then, the activated membranes were soaked at 80°C in DI water to remove excess acid on the membrane. The cross-section of the bilayer composite membrane was characterized by SEM (Field emission scanning electron microscopy, LEO 1530 FE-SEM).
2.5 Fabrication of membrane electrode assembly (MEA)
PtRu/C catalysts and Pt catalysts were obtained from Johnson Matthey, Inc. Anode ink was made by mixing the supported PtRu/C catalyst, deionized water, and Nafion dispersion. Meanwhile, the cathode ink was prepared by supported Pt catalysts, deionized water, and Nafion dispersion. The catalyst inks were ultrasonicated until the mixtures became homogenous pastes. The inks were coated onto gas diffusion layers and the loadings of the PtRu for the anode and the Pt for the cathode were 2
mg cm-2 each. Membrane electrode assemblies were prepared by hot pressing under a pressure of 25 kg cm-2 at 130°C for 3 min.
2.6 Proton conductivity
The impedance spectra of the membranes were measured by a four-point probe unit using a Bio-Logic SP-300 Analyser. The measurements were conducted at room temperature. Ultimately, the proton conductivity σ was calculated based on the equation:
σ = L/AR (1)
Where L is the sample thickness, A is the cross-sectional area, and R is the resistance of the membrane.
2.7 Water uptake and swelling ratio
The water uptakes of the membranes were calculated from the equation:
WU = (Wwet − Wdry)/Wdry (2)
Where Wwet and Wdry are the weights of the fully hydrated and the anhydrous membranes, respectively. In our protocol, the membranes were first immersed in deionized water (or methanol at 30°C) for 24 h, blotted with an absorbent paper, and then, Wwet was measured. Subsequently, the membranes were thoroughly dried in a vacuum oven at 70°C for 24 h; then, Wdry was measured. The
dimensions of the hydrated and dry membranes were measured by a micrometer (Mitutoyo) that was able to measure the membrane thickness with micrometer resolution. The volume swelling ratio was used instead of traditional swelling ratio in length. The volume changes according to the changes of the lengths and the thickness. The average thickness was measurement more than four times in different positions.
2.8 Ion exchange capacity and methanol permeability
Ion exchange capacity (IEC) titration was measured with the following procedure. Typically, 0.1g Nafion or AC/Nafion composite membrane was soaked into 50 mL 1M NaCl(aq) for 12 h. The membrane was taken out and titrated the NaCl(aq) with 0.01M NaOH(aq) until the pH value reached 7 (pH meter, Suntex SP-2200). The IEC value was calculated based on the equation.
IEC = VC/W (3)
Where V is the volume used for titration, C is the concentration of the NaOH(aq) and W is the sample weight. [13] The methanol permeability of the membrane was determined using a two-chamber liquid permeability cell with 20 v/v% MeOH(aq). The methanol permeability is based on methanol crossover the membrane for the concentration difference. The methanol permeability is calculated according to
the following equation:
CB (t) = (A/VB) D (K/L) CA (t - t0) (4)
Where C is concentration, VB is the volume of the solution in the methanol permeation side, A and L are the membrane area and thickness respectively; D and K, are respectively, the methanol diffusivity and partition coefficient. Assume that D inside the membrane is constant and K is independent to the concentration. The product DK is the membrane permeability. t0, referred as the time lag, is related to the diffusivity as t0=L2 /6D. CB has been monitored by density meter (Auton Paar,
DMA 4500). The methanol permeability was calculated from the slope of the straight line plot straight line plot obtained between CB(t) against time. [14]
2-Membranes (Basel). 2014 Mar; 4(1): 123–142.
Published online 2014 Mar 5. doi: 10.3390/membranes4010123
PMCID: PMC4021968
Preparation and Characterization of Nanocomposite Polymer Membranes Containing Functionalized SnO2 Additives
Roberto Scipioni,1 Delia Gazzoli,1 Francesca Teocoli,2 Oriele Palumbo,3 Annalisa Paolone,3 Neluta Ibris,4 Sergio Brutti,3,4 and Maria Assunta Navarra1,*
Author information ► Article notes ► Copyright and License information ►
Go to:
Abstract
In the research of new nanocomposite proton-conducting membranes, SnO2 ceramic powders with surface functionalization have been synthesized and adopted as additives in Nafion-based polymer systems. Different synthetic routes have been explored to obtain suitable, nanometer-sized sulphated tin oxide particles. Structural and morphological characteristics, as well as surface and bulk properties of the obtained oxide powders, have been determined by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform Infrared (FTIR) and Raman spectroscopies, N2 adsorption, and thermal gravimetric analysis (TGA). In addition, dynamic mechanical analysis (DMA), atomic force microscopy (AFM), thermal investigations, water uptake (WU) measurements, and ionic exchange capacity (IEC) tests have been used as characterization tools for the nanocomposite membranes. The nature of the tin oxide precursor, as well as the synthesis procedure, were found to play an important role in determining the morphology and the particle size distribution of the ceramic powder, this affecting the effective functionalization of the oxides. The incorporation of such particles, having sulphate groups on their surface, altered some peculiar properties of the resulting composite membrane, such as water content, thermo-mechanical, and morphological characteristics.
Keywords: functionalized metal oxides, nanocomposite polymer membranes, morphological, structural and spectroscopic characterizations, thermal and mechanical properties
3-Journal of Membrane Science 237 (2004) 145–161
A comparison of physical properties and fuel cell performance of
Nafion and zirconium phosphate/Nafion composite membranes
Chris Yang a,1, S. Srinivasan b, A.B. Bocarsly b, S. Tulyani c, J.B. Benziger c,∗
Abstract
The physiochemical properties of Nafion 115 and a composite Nafion 115/zirconium phosphate (∼25 wt.%) membranes are compared. The
composite membrane takes up more water than Nafion at the same water activity. However, the proton conductivity of the composite membrane
is slightly less than that for Nafion 115. Small angle X-ray scattering shows that the hydrophilic phase domains in the composite membrane
are spaced further apart than in Nafion 115, and the composite membrane shows less restructuring with water uptake. Despite the lower proton
conductivity of the composite membranes they display better fuel cell performance than Nafion 115 when the fuel cell is operated at reduced
humidity conditions. It is suggested that the composite membrane has a greater rigidity that accounts for its improved fuel cell performance.
© 2004 Elsevier B.V. All rights reserved.
Keywords: Composite membranes; Water sorption and diffusion; Fuel cell
4-ZIRCONIA BASED /NAFION COMPOSITE MEMBRANES FOR FUEL CELL APPLICATIONS
ABSTRACT
The nanoparticles of zirconium oxide, sulfated and phosphated zirconia were used to modify a Nafion membrane in order to improve its water retention, thermal stability, proton conductivity and methanol permeability so that it can be used at higher temperatures in fuel cell. These modified Nafion nanocomposite membrane with inorganic nanoparticles have been designed to run at operating temperatures between 120 o C and 140 o C because higher temperature operation reduces the impact of carbon monoxide poisoning, allows attainment of high power density and reduces cathode flooding as water is produced as vapor. The inorganic nanoparticles were incorporated within the Nafion matrix by recast, ion exchange and impregnation methods. The membrane properties were determined by ion exchange capacity (IEC), water uptake, methanol permeability and proton conductivity. The characterization of the inorganic nanoparticles within the nanocomposite membranes was determined by X-Ray diffraction (XRD), Brunau-Emmett-Teller (BET) surface area and Fourier transform infrared spectroscopy (FTIR) for structural properties. Thermal gravimetric analysis (TGA) and Differential scanning calorimetry (DSC) were used to determine the thermal properties, and the morphological properties were probed by Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM).
Pristine ZrO2, sulfated and phosphated ZrO2 nanoparticles were synthesized
successfully. The particle sizes ranged from 30 nm to 10 nm respectively. The resulted
particles were incorporated to a Nafion membrane with good dispersity. The
conductivity of the nanocomposite membrane were around 0.1037 S/cm at 25 o
C with iv a higher water uptake of 42 %. These results were confirmed by the highest IEC value of 1.42 meg.g-1 of Nafion/ S-ZrO2 nanocomposites membrane. These high IEC value may due to the incorporation of superacid S-ZrO2 nanoparticles which increased the membrane acid property for providing new strong acid site
Hoping this will be helpful,
Rafik
Dear G. Rambabu ,
Int. J. Electrochem. Sci., 8 (2013) 9704 - 9713
Novel Bilayer Composite Membrane for Passive Direct
Methanol Fuel Cells with Pure Methanol
Li-Duan Tsai3
, Hung-Chung Chien2,3
, Wei-Han Huang2
, Chiu-Ping Huang2
, Chi-yun Kang2
Jiunn-Nan Lin2
, and Feng-Chih Chang1,3,
The bilayer composite membrane composed of the sulfonated graphene oxide (SGO)/Nafion and sulfonated activated carbon (SAC)/Nafion composite membrane is designed and prepared by repeatedly bar-coating. With the carefully chosen of solvent, the bilayer composite membrane has shown identical thickness on SEM observation. The SGO/Nafion side has a low methanol permeability ascribed to the unique selectivity of the SGO. Moreover, the SAC side has good water retention which can facilitate the back diffusion water produced by the cathode. The unique design of composite membranes confers low methanol crossover and high proton conductivity at the same time. The bilayer composite membrane shows better power density than Nafion 212 and Nafion 115 and the performance monitored for 24h to ensure the stable power density and the durability of the membrane.
Keywords: Nafion, sulfonated graphene oxide, sulfonated activated carbon, methanol crossover, direct methanol fuel cells
2.4 Manufacture of bilayer composite membranes
Nafion ionomers were transferred to N,N-dimethylacetamide (DMAc, Aldrich) by distilling a mixed solution of Nafion DE2020 and DMAc under reduced pressure until the solution temperature reached 70°C, to remove water and solvent. SGO/Nafion solution with 0.1 wt% SGO loading (compared to Nafion) in DMAc was prepared by adding well-dispersed SGO(aq) into the Nafion solution and mixing by mild ultrasonication. Then, the SGO/Nafion solutions were degassed and dispersed with a planetary mixer before casting. The composite membranes were obtained by bar coating with a gap of 300 um and drying at 50°C for 24 h, and post annealing at 140°C for 2 h. The SAC/Nafion solution was prepared by dispersing 10 wt% SAC (compared to Nafion) into Nafion solution (18% dispersion in aqueous alcohol). Then the SAC/Nafion mixture was bar-coating onto the SGO/Nafion film by a smaller bar with a controlled gap of 300 um and drying Nafion composite at 50°C for 24 h, and post annealing at 140°C for 2 h. Then, the membranes were cut into desired sizes and placed into 0.5 M H2SO4(aq) at 80°C for 1 h to activate the sulfonic acids of the Nafion. Then, the activated membranes were soaked at 80°C in DI water to remove excess acid on the membrane. The cross-section of the bilayer composite membrane was characterized by SEM (Field emission scanning electron microscopy, LEO 1530 FE-SEM).
2.5 Fabrication of membrane electrode assembly (MEA)
PtRu/C catalysts and Pt catalysts were obtained from Johnson Matthey, Inc. Anode ink was made by mixing the supported PtRu/C catalyst, deionized water, and Nafion dispersion. Meanwhile, the cathode ink was prepared by supported Pt catalysts, deionized water, and Nafion dispersion. The catalyst inks were ultrasonicated until the mixtures became homogenous pastes. The inks were coated onto gas diffusion layers and the loadings of the PtRu for the anode and the Pt for the cathode were 2
mg cm-2 each. Membrane electrode assemblies were prepared by hot pressing under a pressure of 25 kg cm-2 at 130°C for 3 min.
2.6 Proton conductivity
The impedance spectra of the membranes were measured by a four-point probe unit using a Bio-Logic SP-300 Analyser. The measurements were conducted at room temperature. Ultimately, the proton conductivity σ was calculated based on the equation:
σ = L/AR (1)
Where L is the sample thickness, A is the cross-sectional area, and R is the resistance of the membrane.
2.7 Water uptake and swelling ratio
The water uptakes of the membranes were calculated from the equation:
WU = (Wwet − Wdry)/Wdry (2)
Where Wwet and Wdry are the weights of the fully hydrated and the anhydrous membranes, respectively. In our protocol, the membranes were first immersed in deionized water (or methanol at 30°C) for 24 h, blotted with an absorbent paper, and then, Wwet was measured. Subsequently, the membranes were thoroughly dried in a vacuum oven at 70°C for 24 h; then, Wdry was measured. The
dimensions of the hydrated and dry membranes were measured by a micrometer (Mitutoyo) that was able to measure the membrane thickness with micrometer resolution. The volume swelling ratio was used instead of traditional swelling ratio in length. The volume changes according to the changes of the lengths and the thickness. The average thickness was measurement more than four times in different positions.
2.8 Ion exchange capacity and methanol permeability
Ion exchange capacity (IEC) titration was measured with the following procedure. Typically, 0.1g Nafion or AC/Nafion composite membrane was soaked into 50 mL 1M NaCl(aq) for 12 h. The membrane was taken out and titrated the NaCl(aq) with 0.01M NaOH(aq) until the pH value reached 7 (pH meter, Suntex SP-2200). The IEC value was calculated based on the equation.
IEC = VC/W (3)
Where V is the volume used for titration, C is the concentration of the NaOH(aq) and W is the sample weight. [13] The methanol permeability of the membrane was determined using a two-chamber liquid permeability cell with 20 v/v% MeOH(aq). The methanol permeability is based on methanol crossover the membrane for the concentration difference. The methanol permeability is calculated according to
the following equation:
CB (t) = (A/VB) D (K/L) CA (t - t0) (4)
Where C is concentration, VB is the volume of the solution in the methanol permeation side, A and L are the membrane area and thickness respectively; D and K, are respectively, the methanol diffusivity and partition coefficient. Assume that D inside the membrane is constant and K is independent to the concentration. The product DK is the membrane permeability. t0, referred as the time lag, is related to the diffusivity as t0=L2 /6D. CB has been monitored by density meter (Auton Paar,
DMA 4500). The methanol permeability was calculated from the slope of the straight line plot straight line plot obtained between CB(t) against time. [14]
2-Membranes (Basel). 2014 Mar; 4(1): 123–142.
Published online 2014 Mar 5. doi: 10.3390/membranes4010123
PMCID: PMC4021968
Preparation and Characterization of Nanocomposite Polymer Membranes Containing Functionalized SnO2 Additives
Roberto Scipioni,1 Delia Gazzoli,1 Francesca Teocoli,2 Oriele Palumbo,3 Annalisa Paolone,3 Neluta Ibris,4 Sergio Brutti,3,4 and Maria Assunta Navarra1,*
Author information ► Article notes ► Copyright and License information ►
Go to:
Abstract
In the research of new nanocomposite proton-conducting membranes, SnO2 ceramic powders with surface functionalization have been synthesized and adopted as additives in Nafion-based polymer systems. Different synthetic routes have been explored to obtain suitable, nanometer-sized sulphated tin oxide particles. Structural and morphological characteristics, as well as surface and bulk properties of the obtained oxide powders, have been determined by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform Infrared (FTIR) and Raman spectroscopies, N2 adsorption, and thermal gravimetric analysis (TGA). In addition, dynamic mechanical analysis (DMA), atomic force microscopy (AFM), thermal investigations, water uptake (WU) measurements, and ionic exchange capacity (IEC) tests have been used as characterization tools for the nanocomposite membranes. The nature of the tin oxide precursor, as well as the synthesis procedure, were found to play an important role in determining the morphology and the particle size distribution of the ceramic powder, this affecting the effective functionalization of the oxides. The incorporation of such particles, having sulphate groups on their surface, altered some peculiar properties of the resulting composite membrane, such as water content, thermo-mechanical, and morphological characteristics.
Keywords: functionalized metal oxides, nanocomposite polymer membranes, morphological, structural and spectroscopic characterizations, thermal and mechanical properties
3-Journal of Membrane Science 237 (2004) 145–161
A comparison of physical properties and fuel cell performance of
Nafion and zirconium phosphate/Nafion composite membranes
Chris Yang a,1, S. Srinivasan b, A.B. Bocarsly b, S. Tulyani c, J.B. Benziger c,∗
Abstract
The physiochemical properties of Nafion 115 and a composite Nafion 115/zirconium phosphate (∼25 wt.%) membranes are compared. The
composite membrane takes up more water than Nafion at the same water activity. However, the proton conductivity of the composite membrane
is slightly less than that for Nafion 115. Small angle X-ray scattering shows that the hydrophilic phase domains in the composite membrane
are spaced further apart than in Nafion 115, and the composite membrane shows less restructuring with water uptake. Despite the lower proton
conductivity of the composite membranes they display better fuel cell performance than Nafion 115 when the fuel cell is operated at reduced
humidity conditions. It is suggested that the composite membrane has a greater rigidity that accounts for its improved fuel cell performance.
© 2004 Elsevier B.V. All rights reserved.
Keywords: Composite membranes; Water sorption and diffusion; Fuel cell
4-ZIRCONIA BASED /NAFION COMPOSITE MEMBRANES FOR FUEL CELL APPLICATIONS
ABSTRACT
The nanoparticles of zirconium oxide, sulfated and phosphated zirconia were used to modify a Nafion membrane in order to improve its water retention, thermal stability, proton conductivity and methanol permeability so that it can be used at higher temperatures in fuel cell. These modified Nafion nanocomposite membrane with inorganic nanoparticles have been designed to run at operating temperatures between 120 o C and 140 o C because higher temperature operation reduces the impact of carbon monoxide poisoning, allows attainment of high power density and reduces cathode flooding as water is produced as vapor. The inorganic nanoparticles were incorporated within the Nafion matrix by recast, ion exchange and impregnation methods. The membrane properties were determined by ion exchange capacity (IEC), water uptake, methanol permeability and proton conductivity. The characterization of the inorganic nanoparticles within the nanocomposite membranes was determined by X-Ray diffraction (XRD), Brunau-Emmett-Teller (BET) surface area and Fourier transform infrared spectroscopy (FTIR) for structural properties. Thermal gravimetric analysis (TGA) and Differential scanning calorimetry (DSC) were used to determine the thermal properties, and the morphological properties were probed by Transmission electron microscopy (TEM) and Scanning electron microscopy (SEM).
Pristine ZrO2, sulfated and phosphated ZrO2 nanoparticles were synthesized
successfully. The particle sizes ranged from 30 nm to 10 nm respectively. The resulted
particles were incorporated to a Nafion membrane with good dispersity. The
conductivity of the nanocomposite membrane were around 0.1037 S/cm at 25 o
C with iv a higher water uptake of 42 %. These results were confirmed by the highest IEC value of 1.42 meg.g-1 of Nafion/ S-ZrO2 nanocomposites membrane. These high IEC value may due to the incorporation of superacid S-ZrO2 nanoparticles which increased the membrane acid property for providing new strong acid site
Hoping this will be helpful,
Rafik
The Ion exchange capacity of the membrane can be determined using standard titration method. Initially, immerse the membranes in 2M NaCl solution for 24 hours, at 30 C in orbital shaker for the complete substitution of H+ by Na+. Further, titrate the remaining solution with 0.01 M NaOH solution using phenolpthalein indicator. Finally, the IEC can be otained using the following equation:
IEC(mmol/g) = ((0.01*1000*V of NaOH)/Wd)
where Volume of NaOH is "V" and "Wd" is the weight of the dry membrane
theoretical value of IEC can be calculated as follows,
IEC = contents of the quaternized element in %*10/molecular mass of the quaternized element in g/mol. the costs of quternized element can obtained from elemental analysis ( EDS
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