Polybenzimidazoles direct methanol fuel cells

Polybenzimidazole films doped with phosphoric acid have also been investigated for direct methanol fuel cells. These membranes, however, only display the requisite conductivities at high temperatures and have only been demonstrated in vapor feed systems operated at 150-200 C. Thus, although these novel membrane applications have been demonstrated to have decreased methanol permeability in fuel cells, none of the systems have been successful in being applied to low temperature liquid-feed direct methanol fuel cells. 

Hou H, Sun G, He R, Wu Z, Sun B (2008) Alkali doped polybenzimidazole membrane for high performance alkaline direct methanol fuel cell. J Power Sources 182 95-99... 

Wycisk R, Chisholm J, Lee J, Lin J, Pintauro PN (2006) Direct methanol fuel cell membranes from Nafion-polybenzimidazole blends. J Power Sources 163 9-17... 

Gubler L, Kramer D, Belack J, Unsal O, Schmidt TJ, Scherer GG (2007) Celtec-V. A polybenzimidazole-based membrane for the direct methanol fuel cell. J Electrochem Soc... 

Wang J-T, Wainright JS, Savinell RF, Lilt M (1996) A direct methanol fuel cell using acid-doped polybenzimidazole as polymCT electrolyte. J Appl Electrochem 26 751-756... 

Chuang SW, Hsu LC, Hsu CL (2007) Synthesis and proptuties of fluorine-containing polybenzimidazole/montmmillonite nanocomposite membranes for direct methanol fuel cell applications. J Power Sources 168 172-177... 

Lobato J, Canizares P, Rodrigo MA et al (2008) Performance of a vapor-fed polybenzimidazole (PBI)-based direct methanol fuel cell. Energy Fuels 22 3335-3345... 

Wu J-F, Lo C-F, Li L-Y et al (2014) Thermally stable polybenzimidazole/carbon nano-tube composites for alkaline direct methanol fuel cell applications. J Power Sources 246 39 8... 

Membrane prepared by blending sulfonated polybenzimidazole (PBI) with Nafion polymer showed a conductivity of 0.032 S cm The methanol permeability of the composite membrane was found to be 0.82 x 10 cm s as compared to Nafion, which is around 2.21 x 10 cm s [22]. Addressing the problem of methanol permeation, a composite membrane of Nafion with polyvinyl alcohol (PVA) for direct methanol fuel cell has been reported. It is concluded that at the weight ratio of 1 1 in PVA and Nafion, the thin film-coated Nafion membrane exhibited low methanol crossover, and the membrane protonic conductivity could be improved by the sulfonation treatment [23]. Recently, Zaidi et al. [24] prepared composite membranes of PFSA ionomer with boron phosphate and showed the conductivity of 6.2 X 10-2 S cm-i at 120°C. 

Abstract There have been numerous studies on modifying DuPont s Nafion (a perfluorosulfonic acid polymer) in order to improve the performance of this membrane material in a direct methanol fuel cell. Modifications focused on making Nafion a better methanol barrier, without sacrificing proton conductivity, so that methanol crossover during fuel cell operation is minimized. In this chapter, a brief literature survey of such modifications is presented, along with recent experimental results (membrane properties and fuel cell performance curves) for (1) thick Nafion films, (2) Nafion blended with Teflon-FEP or Teflon-PFA, and (3) Nafion doped with polybenzimidazole. 

There has been considerable research on modifying Nafion, so as to improve its properties for use in a direct methanol fuel cell. In this chapter, a review of Nafion-based DMFC membranes is presented, including a literature survey followed by recent results by the present authors on improving Nafion by (1) using thick stacked Nafion membranes, (2) blending Nafion with Teflon-FEP or Teflon-PFA, and (3) doping Nafion with polybenzimidazole. 

A number of other interesting uses have been foimd for polybenzimidazole membranes, including a propane fueled fuel cell, an alkaline based fuel ceU, a trimethoxymethane based fuel cell, and a quasi-direct methanol fuel cell. Wang et al. investigated trimethoxymethane (TMM) as an alternative fuel for a m-PBI direct oxidation fuel cell [77]. The oxidation of TMM was analyzed by an online mass spectrometer and onhne FTIR spectroscopy. The PBI membranes used in the TMM study were doped with 5 moles PA/PRU. The TMM was hydrolyzed to form a mixture of methylformate, methanol, and formic acid. At temperatures at or above 120 °C, the TMM hydrolyzed in the presence of water without an acid catalyst. The anode performance of the different fuels increased in the order of methanol < TMM < formic acid/methanol < methylformate. The improved performance of TMM over just methanol was most likely due to the electrochemical activity of formic acid. 

J.-T. Wang, J. S. Wainright, R. F. SavineU, and M. Litt, A Direct Methanol Fuel Cell Using Acid-Doped Polybenzimidazole as Polymer Electrolyte, J. Appl. Electrochem, Vol. 26, p. 751, 1996. 

Wycisk, R., Lee, J. K., and Pintauro, P. N. (2005). Sulfonated polyphosphazene-polybenzimidazole membranes for direct methanol fuel cells. J. Electrochem Soc. 152, A892. 

Chuang, S. W., Chung, S. L., and Hsu, H. C. L. (2007). Synthesis and Properties of Fluorine-Containing Polybenzimidazole/Montmorillonite Nanocomposite Membranes for Direct Methanol Fuel Cell Applications. Journal Power Sources. 168 172-177. 

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