High-Resolution Solid-State NMR Studies of Poly(vinyl phosphonic acid) Proton-Conducting Polymer:  Molecular Structure and Proton Dynamics

Lee, Young Joo; Bingöl, Bahar; Murakhtina, Tatiana; Sebastiani, Daniel; Meyer, Wolfgang; Wegner, Gerhard; Spiess, Hans Wolfgang

doi:10.1021/jp072112j

Cited by 148 publications

(193 citation statements)

References 46 publications

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“…Based on this type of membranes BASF-PEMEAS has developed an MEA product under the trade mark Celtec ® -V. Being the simplest polymeric diprotic acids with highest density of immobilized phosphonic acid, PVPA has been considered for PEMFC applications [134,135] and more interest has arisen recently [18]. Synthesis [136] and characterizations with respect to water content, selfcondensation and proton conductivity as a function of relative humidity has recently been investigated [137].…”

Section: Acid Dopingmentioning

confidence: 99%

High temperature proton exchange membranes based on polybenzimidazoles for fuel cells

Jensen

Savinell

et al. 2009

Progress in Polymer Science

1,243

852

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This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. To achieve high temperature operation of proton exchange membrane fuel cells (PEMFC), preferably under ambient pressure, acid-base polymer membranes represent an effective approach. The phosphoric acid-doped polybenzimidazole membrane seems so far the most successful system in the field. It has in recent years motivated extensive research activities with great progress. This treatise is devoted to updating the development, covering polymer synthesis, membrane casting, physicochemical characterizations and fuel cell technologies. To optimize the membrane properties, high molecular weight polymers with synthetically modified or N-substituted structures have been synthesized. Techniques for membrane casting from organic solutions and directly from acid solutions have been developed. Ionic and covalent cross-linking as well as inorganic-organic composites has been explored. Membrane characterizations have been made including spectroscopy, water uptake and acid doping, thermal and oxidative stability, conductivity, electro-osmotic water drag, methanol crossover, solubility and permeability of gases, and oxygen reduction kinetics. Related fuel cell technologies such as electrode and MEA fabrication have been developed and high temperature PEMFC has been successfully demonstrated at temperatures of up to 200• C under ambient pressure. No gas humidification is mandatory, which enables the elimination of the complicated humidification system, compared with Nafion cells. Other operating features of the PBI cell include easy control of air flow rate, cell temperature and cooling. The PBI cell operating at above 150• C can tolerate up to 1% CO and 10 ppm SO 2 in the fuel stream, allowing for simplification of the fuel processing system and possible integration of the fuel cell stack with fuel processing units. Long-term durability with a degradation rate of 5 V h −1 has been achieved under continuous operation with hydrogen and air at 150-160• C. With load or thermal cycling, a performance loss of 300 V per cycle or 40 V h −1 per operating hour was observed. Further improvement should be done by, e.g. optimizing the thermal and chemical stability of the polymer, acid-base interaction and acid management, activity and stability of catalyst and more importantly the catalyst support, as well as the integral interface between electrode and membrane.

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Section: Acid Dopingmentioning

confidence: 99%

High temperature proton exchange membranes based on polybenzimidazoles for fuel cells

Jensen

Savinell

et al. 2009

Progress in Polymer Science

1,243

852

View full text Add to dashboard Cite

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“…[9] In addition, PVPA forms a strong hydrogen-bonding network through the pendant neighboring phosphonic acid groups on the polymer; [10] thus, it is expected that it forms an effective proton pathway after blending with PBI to enable a proton conduction in the absence of the mobile acid. In our previous study, we used carbon nanotubes (CNTs) [11] as the catalyst support.…”

Section: Introductionmentioning

confidence: 99%

High‐Temperature Polymer Electrolyte Fuel Cell Using Poly(vinylphosphonic acid) as an Electrolyte Shows a Remarkable Durability

2014

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The development of a high‐performance, durable, and less expensive membrane electrode assembly (MEA) composed of a polymer electrolyte membrane and electrocatalysts is important for developing fuel cells. Herein, we described the design and fabrication of an electrocatalyst with carbon black, polybenzimidazole doped with poly(vinylphosphonic acid) (PVPA), and platinum nanoparticles as an electron‐conducting support material, an electrolyte, and a metal catalyst, respectively. Most importantly, we used PVPA in place of phosphoric acid, which is a widely used acid dopant, as the acid dopant for both the electrocatalyst and the polymer electrolyte membrane. We reported that the use of PVPA is crucial for the high performance of the MEA because it prevented the leaching of acid molecules from the MEA, which led to high durability compared to that of the phosphoric acid‐doped MEAs.

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“…While the chemical shifts give information about the chemical environments, the line widths of the signals at different temperatures often provided mobility information on the molecular level. 30 During this study, the interaction between PBI and phosphoric acid was characterized by 1 H MAS and 31 P CP/MAS NMR spectroscopy. CP/MAS NMR technique is used to obtain 31 P spectra in order to enhance signal to noise at a much shorter experimental time.…”

Section: Journal Of Thementioning

confidence: 99%

12-Silicotungstic Acid Doped Phosphoric Acid Imbibed Polybenzimidazole for Enhanced Protonic Conductivity for High Temperature Fuel Cell Applications

Nguyen

Ziolo

Yang

et al. 2017

J. Electrochem. Soc.

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12-Silicotungstic acid, a heteropoly acid (HPA) -was incorporated into phosphoric acid (PA) doped polybenzimidazole (PBI) membrane that exhibited strong mechanical stability, excellent proton conductivity, and can be used for high temperature proton exchange membrane fuel cells (PEMFCs). At 160 • C, an electrochemical impedance spectroscopy (EIS) fitting of the fuel cells data showed the membrane electrode assemblies (MEAs) made of PBI/20%HPA/PA had three times lower ohmic resistance (0.057 ± 0.002 Ohm * cm 2 ) as compared to the control reference of PBI/PA (0.160 Ohm * cm 2 ). In addition, the ohmic resistance of the composite MEA remained unchanged while the charge transfer resistance decreased after 313 hours conditioning. Fourier transform infrared spectroscopy (FTIR), magic angle spinning -nuclear magnetic resonance (MAS-NMR), and thermogravimetric analysis (TGA) showed 12-silicotungstic acid inhibits water from escaping the membrane at elevated temperatures and adds more acid sites, providing additional paths for proton transport. Scanning electron microscope (SEM), transmission electron microscopy (TEM), and small angle X-ray scattering (SAXS) were used to confirm the structure and morphology of PBI/20%HPA/PA membrane prior making the MEAs. Fuel cell technologies have the potential to reduce our dependence on fossil fuels and to reduce associated emissions of pollutants as the global population continues to grow. Polymer electrolyte membrane fuel cells (PEMFCs) have the advantage of being fully scalable for stationary power generation than other types of fuel cells. PEMFCs have outstanding power density, rapid start-up, and high efficiency. 1In addition, the operation of PEMFCs is straightforward and does not generate any additional pollutants. Despite several advantages, current PEMFCs are not yet widely used or commercialized, because they remain too expensive, do not have enough durability, and require very pure hydrogen as a fuel.2 At the moment, PEMFCs generally operate below 100• C due to the need to fully humidify commonly used perfluorosulfonic acid electrolytes such as Nafion. At low operating temperatures, a small concentration of CO or SO 2 impurities in the fuel could poison the catalysts and lower the fuel cell performance. Therefore, current PEMFCs require high purity hydrogen that can only be cost-effectively produced from natural gas at this time. Furthermore, the humidification of fuel and oxidant in low temperature PEMFCs requires a complicated humidification system. These technical challenges can be addressed by increasing operating temperatures above 120• C. High temperature operation is a promising way to improve PEMFC performance; it has been shown that higher operating temperatures would increase chemical kinetics at the anode and dramatically enhance the electrode tolerance to fuel impurities, which allows for the use of lower-cost hydrogen.3 In addition, fuel cell operation above 120• C can tolerate up to 1% CO and 10 ppm SO 2 . Operating at elevated temperatures would also provid...

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High-Resolution Solid-State NMR Studies of Poly(vinyl phosphonic acid) Proton-Conducting Polymer: Molecular Structure and Proton Dynamics

Cited by 148 publications

References 46 publications

High temperature proton exchange membranes based on polybenzimidazoles for fuel cells

High temperature proton exchange membranes based on polybenzimidazoles for fuel cells

High‐Temperature Polymer Electrolyte Fuel Cell Using Poly(vinylphosphonic acid) as an Electrolyte Shows a Remarkable Durability

12-Silicotungstic Acid Doped Phosphoric Acid Imbibed Polybenzimidazole for Enhanced Protonic Conductivity for High Temperature Fuel Cell Applications

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