Synthesis and Characterization of a New Fluorine‐Containing Polybenzimidazole (PBI) for Proton‐Conducting Membranes in Fuel Cells

Abstract

A new type of fluorine‐containing polybenzimidazole, namely poly(2,2′‐(2,2′‐bis(trifluoromethyl)‐4,4′‐biphenylene)‐5,5′‐bibenzimidazole) (BTBP‐PBI), was developed as a candidate for proton‐conducting membranes in fuel cells. Polymerization conditions were experimentally investigated to achieve high molecular weight polymers with an inherent viscosity (IV) up to 1.60 dl g–1. The introduction of the highly twisted 2,2′‐disubstituted biphenyl moiety into the polymer backbone suppressed the polymer chain packing efficiency and improved polymer solubility in certain polar organic solvents. The polymer also exhibited excellent thermal and oxidative stability. Phosphoric acid (PA)‐doped BTBP‐PBI membranes were prepared by the conventional acid imbibing procedure and their corresponding properties such as mechanical properties and proton conductivity were carefully studied. The maximum membrane proton conductivity was approximately 0.02 S cm–1 at 180 °C with a PA doping level of 7.08 PA/RU. The fuel cell performance of BTBP‐PBI membranes was also evaluated in membrane electrode assemblies (MEA) in single cells at elevated temperatures. The testing results showed reliable performance at 180 °C and confirmed the material as a candidate for high‐temperature polymer electrolyte membrane fuel cell (PEMFC) applications.

Solution polymerization of polybenzimidazole

“…Since the early development, numerous variations of PBI derivatives have been reported . Of all the derivatives of polybenzimidazoles, aromatic PBIs have received the most attention due to their excellent thermal stabilities and chemical resistance …”

Fluorinated Polyazoles

“…The newly developed polymer, BTBP-PBI, membrane showed a proton conductivity of 0.02 S/cm at 180 °C at a doping level of 7.08 PA/RU, which is higher than fluorine-containing PBI membrane (6F-PBI, 1.70 × 10 −4 S/cm, 3.0 mol PA/RU, 160 °C) [35]. Under operation of oxidant gas H 2 /air and H 2 /O 2 , the cell voltage was 0.649 and 0.728 V, respectively [38]. Under operation of oxidant gas H 2 /air and H 2 /O 2 , the cell voltage was 0.649 and 0.728 V, respectively [38].…”

“…Reproduced with permission from Ref. This fluorinated diacid was used to prepare PBI, namely poly[2,2 ′ -{2,2 ′ -bis(trifluoromethyl)-4,4 ′ -biphenylene}-5,5 ′ -bibenzimidazole] (BTBP-PBI), by solution polymerization with DAB in Eaton's reagent (PPMA, phosphorous pentoxide:methanesulfonic acid = 1:10, w:w) [38]. In continuation of their work, Benicewicz et al synthesized a new fluorinated diacid monomer by a two-step method using 2,2 ′ -bis(trifluoromethyl)benzidine (1) as the starting material (Figure 5.8) [38].…”

“…At the first stage, the reaction between an aromatic dianhydride 6FDA and an aromatic tetraamine DAB resulted in PAI by the thermal cyclodehydration of the poly(amino amic acid) (PAAc) ( Figure 5.10). [38]. [38].…”

Polibenzimidazol (PBI) Lifleri

“…Yakıt enerjisini elektrokimyasal reaksiyon ile doğrudan elektrik enerjisine dönüştürme esasına dayanan yakıt hücreleri, bir cep telefonunun ihtiyacını karşılayacak kadar az ya da bir kente yetebilecek kadar çok güç üretebilecek bir kapasiteye sahiptir [132][133][134][135]. Yeni nesil çevre dostu enerji üretim mekanizması olan yakıt hücrelerinde, proton iletkenliğini sağlanmak amacı ile kuvvetli asitler ile yüklenerek proton iletken hale getirilen PBI kumaşlar ya da PBI proton değişim membranlar (PEM) kullanılabilmektedir (Şekil 11) [125,[136][137][138][139][140][141][142][143][144][145].…”