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Title: Tunable High Performance Cross-Linked Alkaline Anion Exchange Membranes for Fuel Cell Applications

Abstract

Fuel cells are energy conversion devices that show great potential in numerous applications ranging from automobiles to portable electronics. However, further development of fuel cell components is necessary for them to become commercially viable. One component critical to their performance is the polymer electrolyte membrane, which is an ion conductive medium separating the two electrodes. While proton conducting membranes are well established (e.g., Nafion), hydroxide conducting membranes (alkaline anion exchange membranes, AAEMs) have been relatively unexplored by comparison. Operating under alkaline conditions offers significant efficiency benefits, especially for the oxygen reduction reaction; therefore, effective AAEMs could significantly advance fuel cell technologies. Here we demonstrate the use of ring-opening metathesis polymerization to generate new cross-linked membrane materials exhibiting high hydroxide ion conductivity and good mechanical properties. Cross-linking allows for increased ion incorporation, which, in turn supports high conductivities. This facile synthetic approach enables the preparation of cross-linked materials with the potential to meet the demands of hydrogen-powered fuel cells as well as direct methanol fuel cells.

Authors:
 [1];  [1];  [1];  [1];  [1];  [1]
  1. Cornell Univ., Ithaca, NY (United States)
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC); Energy Materials Center at Cornell (EMC2)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1064853
DOE Contract Number:
SC0001086
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society; Journal Volume: 132; Journal Issue: 10; Related Information: Emc2 partners with Cornell University (lead); Lawrence Berkeley National Laboratory
Country of Publication:
United States
Language:
English
Subject:
30 DIRECT ENERGY CONVERSION; catalysis (homogeneous); catalysis (heterogeneous); energy storage (including batteries and capacitors); hydrogen and fuel cells; defects; charge transport; membrane; materials and chemistry by design; synthesis (novel materials); synthesis (self-assembly); synthesis (scalable processing)

Citation Formats

Robertson, Nicholas J., Kostalik, IV, Henry A., Clark, Timothy J., Mutolo, Paul F., Abruña, Héctor D., and Coates, Geoffrey W.. Tunable High Performance Cross-Linked Alkaline Anion Exchange Membranes for Fuel Cell Applications. United States: N. p., 2010. Web. doi:10.1021/ja908638d.
Robertson, Nicholas J., Kostalik, IV, Henry A., Clark, Timothy J., Mutolo, Paul F., Abruña, Héctor D., & Coates, Geoffrey W.. Tunable High Performance Cross-Linked Alkaline Anion Exchange Membranes for Fuel Cell Applications. United States. doi:10.1021/ja908638d.
Robertson, Nicholas J., Kostalik, IV, Henry A., Clark, Timothy J., Mutolo, Paul F., Abruña, Héctor D., and Coates, Geoffrey W.. Tue . "Tunable High Performance Cross-Linked Alkaline Anion Exchange Membranes for Fuel Cell Applications". United States. doi:10.1021/ja908638d.
@article{osti_1064853,
title = {Tunable High Performance Cross-Linked Alkaline Anion Exchange Membranes for Fuel Cell Applications},
author = {Robertson, Nicholas J. and Kostalik, IV, Henry A. and Clark, Timothy J. and Mutolo, Paul F. and Abruña, Héctor D. and Coates, Geoffrey W.},
abstractNote = {Fuel cells are energy conversion devices that show great potential in numerous applications ranging from automobiles to portable electronics. However, further development of fuel cell components is necessary for them to become commercially viable. One component critical to their performance is the polymer electrolyte membrane, which is an ion conductive medium separating the two electrodes. While proton conducting membranes are well established (e.g., Nafion), hydroxide conducting membranes (alkaline anion exchange membranes, AAEMs) have been relatively unexplored by comparison. Operating under alkaline conditions offers significant efficiency benefits, especially for the oxygen reduction reaction; therefore, effective AAEMs could significantly advance fuel cell technologies. Here we demonstrate the use of ring-opening metathesis polymerization to generate new cross-linked membrane materials exhibiting high hydroxide ion conductivity and good mechanical properties. Cross-linking allows for increased ion incorporation, which, in turn supports high conductivities. This facile synthetic approach enables the preparation of cross-linked materials with the potential to meet the demands of hydrogen-powered fuel cells as well as direct methanol fuel cells.},
doi = {10.1021/ja908638d},
journal = {Journal of the American Chemical Society},
number = 10,
volume = 132,
place = {United States},
year = {Tue Feb 23 00:00:00 EST 2010},
month = {Tue Feb 23 00:00:00 EST 2010}
}
  • A unique one-step cross-linking strategy that connects quaternary ammonium centers using Grubbs II-catalyzed olefin metathesis was developed. The cross-linked anion exchange membranes showed swelling ratios of less than 10% and hydroxide conductivities of 18 to 40 mS cm(- 1). Cross-linking improved the membranes' stability to hydroxide degradation compared to their non-cross-linked analogues.
  • A series of differently cross-linked FEP-g-polystyrene proton exchange membranes has been synthesized by the preirradiation grafting method [FEP: poly(tetrafluoroethylene-co-hexafluoropropylene)]. Divinylbenzene (DVB) and/or triallyl cyanurate (TAC) were used as cross-linkers in the membranes. It was found that the physical properties of the membranes, such as water-uptake and specific resistance, are strongly influenced by the nature of the cross-linker. Generally it can be stated that DVB decreases water-uptake and increases specific resistance; on the other hand TAC increases swelling and decreases specific resistance to values as low as 5.0 {Omega} cm at 60 C. The membranes were tested in H{sub 2}/O{sub 2}more » fuel cells for stability and performance. It was found that thick (170 {micro}m) DVB cross-linked membranes showed stable operation for 1,400 h at temperatures up to 80 C. The highest power density in the fuel cell was found for the DVB and TAC double-cross-linked membrane; it exceeded the value of a cell with a Nafion{reg_sign} 117 membrane by more than 60%.« less
  • Random copolymers of isoprene and 4-vinylbenzyl chloride (VBCl) with varying compositions were synthesized via nitroxide-mediated polymerization. Subsequent quaternization afforded solvent processable and cross-linkable ionomers with a wide range of ion exchange capacities (IECs). Solution cast membranes were thermally cross-linked to form anion exchange membranes. Cross-linking was achieved by taking advantage of the unsaturations on the polyisoprene backbone, without added cross-linkers. A strong correlation was found between water uptake and ion conductivity of the membranes: conductivities of the membranes with IECs beyond a critical value were found to be constant related to their high water absorption. Environmentally controlled small-angle X-ray scatteringmore » experiments revealed a correlation between the average distance between ionic clusters and the ion conductivity, indicating that a well-connected network of ion clusters is necessary for efficient ion conduction and high ion conductivity.« less
  • Robust, cross-linked anion exchange membranes (AEMs) were prepared from solvent-processable polyisoprene- ran -poly(vinylbenzyltrimethylammonium chloride) (PI- ran -P- [VBTMA][Cl]) ionomers via photoinitiated thiol - ene chem- istry. Two series of membranes were prepared choosing two dithiol cross-linkers, 1,10-decanedithiol and 2,2 ' - (ethylenedioxy)diethanethiol, selected for their di ff erent hydro- phobicities. A strong correlation was found between the choice of dithiol cross-linker, water uptake, morphology, and the ion conductivity of the membranes. Results were compared with previous fi ndings of thermally cross-linked AEMs from analogous random copolymers. Comparably high chloride ion conductivities were obtained at low to moderate ion exchange capacitiesmore » (IECs) with signi fi cantly low water uptake values. It was shown that by choosing a hydrophilic cross-linker ion cluster formation may be suppressed and ion conduction improved. This study highlights that it is possible to promote ion conductivities for low IEC membranes (<1 mmol/g) by forming well- connected, ion conducting network morphology. This observation paves the way for mechanically robust ion conducting membranes with enhanced conductivities and better water management.« less