Proton conducting behavior in non-crosslinked and crosslinked polyethylenimine with excess phosphoric acid

The state-of-the-art of polymer electrolyte membrane fuel cell (PEMFC) technology is based on perfluorosulfonic acid (PFSA) polymer membranes operating at a typical temperature of 80°C. Some of the key issues and shortcomings of the PFSA-based PEMFC technology are briefly discussed. These include water management, CO poisoning, hydrogen, reformate and methanol as fuels, cooling, and heat recovery. As a means to solve these shortcomings, hightemperature polymer electrolyte membranes for operation above 100°C are under active development. This treatise is devoted to a review of the area encompassing modified PFSA membranes, alternative sulfonated polymer and their composite membranes, and acidbase complex membranes. PFSA membranes have been modified by swelling with nonvolatile solvents and preparing composites with hydrophilic oxides and solid proton conductors. DMFC and H 2 /O 2 (air) cells based on modified PFSA membranes have been successfully operated at temperatures up to 120°C under ambient pressure and up to 150°C under 3-5 atm. Alternative polymers are selected from silicon-and fluorine-containing inorganic polymers or aromatic hydrocarbon polymers and functionalized by sulfonation. The sulfonated hydrocarbons and their inorganic composites are potentially promising for high-temperature operation. High conductivities have been obtained at temperatures up to 180°C. Acid-base complex membranes constitute another class of electrolyte membranes. A high-temperature PEMFC based on H 3 PO 4 -doped PBI has been demonstrated for operation at temperatures up to 200°C under ambient pressure. The advanced features include high CO tolerance, simple thermal and water management, and possible integration with the fuel processing unit.

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“…263 Recently Nylon 264 and poly(diallyldimethylammonium-dihydrogen phosphate, PAMA + -H 2 PO4 -) 265 have also been investigated.…”

Section: Acid-base Polymer Membranes In Generalmentioning

confidence: 99%

Approaches and Recent Development of Polymer Electrolyte Membranes for Fuel Cells Operating above 100 °C

et al. 2003

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“…The resulting acid-base complex systems constitute a new class of proton conducting polymer membranes. The polymers studied include: polyethylene oxides (PEO) [42,43], polyvinyl acetate (PVA) [44], polyacrylamide (PAAM) [45±47], polyethyleneimine (PEI) [48] and others. Among the inorganic acids, phosphoric acid (H 3 PO 4 ) is of special interest due to its thermal stability and high proton conductivity, even in the anhydrous form (100%) and at high temperatures.…”

Section: Acid-base Polymer Membranesmentioning

confidence: 99%

“…High acid contents result in high conductivity but sacrifice mechanical stability, especially at temperatures above 100 C. Recently, attempts have been made to improve the high temperature strength of the acid-base polymer membranes. These efforts include (i) crosslinking of polymers, e.g., PEI [48], (ii) using inorganic fillers, e.g., micro-sized SiO 2 , and (iii) using high T g (glass transition temperature) polymers such as PBI and polyoxadiazole (POD) [49]. Chemically, a solid polycation is formed when combining the acid with the polymer.…”

Section: Acid-base Polymer Membranesmentioning

confidence: 99%

PBI‐Based Polymer Membranes for High Temperature Fuel Cells – Preparation, Characterization and Fuel Cell Demonstration

et al. 2004

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Proton exchange membrane fuel cell (PEMFC) technology based on perfluorosulfonic acid (PFSA) polymer membranes is briefly reviewed. The newest development in alternative polymer electrolytes for operation above 100 °C is summarized and discussed. As one of the successful approaches to high operational temperatures, the development and evaluation of acid doped polybenzimidazole (PBI) membranes are reviewed, covering polymer synthesis, membrane casting, acid doping, physicochemical characterization and fuel cell testing. A high temperature PEMFC system, operational at up to 200 °C based on phosphoric acid‐doped PBI membranes, is demonstrated. It requires little or no gas humidification and has a CO tolerance of up to several percent. The direct use of reformed hydrogen from a simple methanol reformer, without the need for any further CO removal, has been demonstrated. A lifetime of continuous operation, for over 5000 h at 150 °C, and shutdown‐restart thermal cycle testing for 47 cycles has been achieved. Other issues such as cooling, heat recovery, possible integration with fuel processing units, associated problems and further development are discussed.

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“…Typically, the polymer backbone has a strong basic site such as an ether, alcohol, imine, amide or imide group and can react strongly with acids. Among the polymers investigated were poly(ethylene oxide) (PEO) [26], poly(vinyl acetate) (PVA) [27], polyacrylamide (PAAM) [28][29][30], poly(ethyleneimine) (PEI) [31] and polybenzimidazole (PBI) [32][33][34][35][36][37][38][39][40][41]. In these cases, phosphoric acid (PA) is typically used as the proton conductor due to its thermal stability and high-proton conductivity at high temperature.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Properties of Segmented Block Copolymers of Functionalised Polybenzimidazoles for High‐Temperature PEM Fuel Cells

Mader

Benicewicz

2011

Fuel Cells

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A series of novel segmented block copolymers of sulphonated polybenzimidazole (PBI) (s‐PBI) and p‐PBI were prepared with various polymer ratios (10–90 mol% s‐PBI; 90‐10 mol% p‐PBI). A two‐step synthesis of oligomeric species, followed by combination and further polymerisation was used via the polyphosphoric acid (PPA) process. The membranes showed improved high‐temperature proton conductivities and fuel cell performance over previous literature reports, with moderate incorporation of s‐PBI into the copolymer showing the best results. The non‐humidified fuel cell performance was extensively studied with various fuels and oxidants and showed excellent properties. Block copolymers that incorporated 40, 50 or 60 mol% s‐PBI and the corresponding 60, 50 or 40 mol% p‐PBI, at 0.2 A cm–2 and 160 °C, had hydrogen–air performances of 0.661–0.666 V, depending on composition. The performance was improved using hydrogen–oxygen, with voltages between 0.734 and 0.742 V at 0.2 A cm–2 and 160 °C. Fuel cells operating on a reformed hydrocarbon gas showed decreased performance (0.622–0.627 V, same conditions), especially at lower temperatures, but was significantly improved over previous literature reports of sulphonated PBI membranes operating at high temperatures.

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Proton conducting behavior in non-crosslinked and crosslinked polyethylenimine with excess phosphoric acid

Cited by 57 publications

References 6 publications

Approaches and Recent Development of Polymer Electrolyte Membranes for Fuel Cells Operating above 100 °C

Approaches and Recent Development of Polymer Electrolyte Membranes for Fuel Cells Operating above 100 °C

PBI‐Based Polymer Membranes for High Temperature Fuel Cells – Preparation, Characterization and Fuel Cell Demonstration

Synthesis and Properties of Segmented Block Copolymers of Functionalised Polybenzimidazoles for High‐Temperature PEM Fuel Cells

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