Phosphoric-acid-doped polybenzimidazole

Li, Q., Hjuler, H.A., and Bjerrum, N.J., Phosphoric acid doped polybenzimidazole membranes physiochemical characterization and fuel cell applications, J. Appl. Electrochem., 31, 773, 2001. 

A. Schechter and R.F. Savinell. Imidazole and 1-methyl imidazole in phosphoric acid doped polybenzimidazole, electrolyte for fuel cells. Solid State Ionics 147, 181-187 2002. 

R.H. He, Q.F. Li, G. Xiao, and N.J. Bjerrum. Proton conductivity of phosphoric acid doped polybenzimidazole and its composites with inorganic proton conductors. Journal of Membrane Science 226, 169-184 2003. 

To prepare new and inexpensive membranes, various trials have been made 196 sulfonated aromatic polyether membrane such as polyether ketones (PEEK),197 sulfonated polysulfone198 and membranes from sulfonated polyphenylene sulfide,199 phosphoric acid-doped polybenzimidazole, (PBI),200 polybenzimidazole having sulfonic acid groups,201 polybenzimidazole with phosphonic acid groups,202 a blend membrane of polybenzimidazole and sulfonated polysulfone,203 sulfonated phosphazene polymer.204... 

Figure 17.3.16 Results for oxidation of formic acid (dotted curves) and methanol (solid curves) at a fuel-cell anode (Pt/Ru) with phosphoric-acid-doped polybenzimidazole polymer electrolyte, 170°C. (a) current density and (b) mass signal for CO2 at a scan rate of 1 mV/s. [From M. Weber, J.-T. Wang, S. Wasmus, and R. F. Savinell, J. Electrochem. Soc., 143, L158 (1996), reprinted by permission of the publisher. The Electrochemical Society, Inc.]...

Normal PEFC operating temperatures using PFSA or polyaryl membranes are in the range of 80 °C with new developments aiming at temperatures up to 120 °C [3, 4]. Higher operating temperatures up to 180 °C can be achieved with phosphoric acid doped polybenzimidazole membranes [5]. 

Nores-Pondal FJ, Buera MP, Corti HR (2010) Thermal properties of phosphoric acid-doped polybenzimidazole membranes in water and methanol-water mixtures. J Power Sources 195 6389-6397... 

Copolymers with benzimidazole and benzoxazole units have been prepared and used as a polymer electrolyte material [30,11]. The polymer electrolyte material has both high proton conductivity and excellent mechanical properties even when it is obtained by in situ phosphoric acid doping. The polymer electrolyte material may substitute for the conventional phosphoric acid doped polybenzimidazole in a polymer electrolyte membrane fuel cell, particularly in a high-temperature polymer electrolyte membrane fuel cell. 

Chen, C.Y. and Lai, W.H. (2010) Effects of temperature and humidity on the cell performance and resistance of a phosphoric acid doped polybenzimidazole fuel cell. J. Power Sources, 195, 7152. 

Jiao, K. and Li, X. (2010) A three-dimensional non-isothermal model of high temperature proton exchange membrane fuel cells with phosphoric acid doped polybenzimidazole membranes. Fuel Cells, 10, 351. 

In a cost comparison by Gebert et al. [42], it is concluded that sulfonated Polyether ether ketone (S-PEEK) and phosphoric acid-doped polybenzimidazole (H3PO4-PBI) could be a factor of five cheaper than Nafion. As discussed earlier, this cost advantage is only helpful when not offset by lower MEA power density. 

Fig. 11.12 Relationship between proton conductivity and adjoining gas stream humidity at various temperatures for Nafion (1100 EW) [5] and phosphoric acid-doped polybenzimidazole (FBI) [54]. The data clearly demonstrate that the increase in temperature from 80°C to 120°C has little effect on the conductivity of Nafion but a significant effect on the PBI systeans. A curve is also shown for a material exhibiting the desired conductivity as a function of the relative humidity that would be ideal for system simpUiication (The figure is reproduced from Gasteiger and Mathias [5] with permission from The Electrochemical Society)...

Phosphoric acid-doped polybenzimidazole (PA-PBl) membrane is the most common type for HT-PEMFCs. It was also introduced in the catalyst layer as an ionomer to improve proton conductivity [8, 80-83]. Similar to die apphcation of Nafion ionomer in the catalyst layer, polybenzimidazole (PBl) solution was incorporated into the catalyst layer by an impregnation method (die electrode was soaked in a PBI solution), by a gluing method (the PBl membrane was coated by PBI solution), or by a brushing method (the PBl solution was brushed onto the electrode) [80]. 

Li Q, Hjuler HA, Bjerrum NJ. Phosphoric acid doped polybenzimidazole membranes Physicochemical characterization and fuel cell apphcations. J Appl Electrochem... 

For phosphoric acid-doped polybenzimidazole membranes with an intermediate Ap Ta (3.5), hydrogen bonds are likely formed as shown by infrared spectroscopy [61, 62] and molecular dynamic simulation [63]. The overall proton conductivity of the acid-doped membranes is at least an order of magnitude lower than that of pure phosphoric acid due to the presence of the solid polymer phase. The polymer does not seem to interrupt the extensive hydrogen bond network of the phosphoric acid, though it does decrease the percolation within the liqmd-like part of the phosphoric acid domain. As a result, the proton conducting mechanism remains the same, i.e., primarily via the Grotthuss... 

Schechter A, Savinell RF, Wainright JS et al (2009) H and P NMR study of phosphoric acid-doped polybenzimidazole under controlled water activity. J Electrochem Soc 156 B283-B290... 

He R, Li Q, Bach A et al (2006) Physicochemical properties of phosphoric acid doped polybenzimidazole membranes for fuel cells. J Membr Sci 277 38 5... 

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