| Intermediate temperature proton conductors for PEM fuel cells based on phosphonic acid as protogenic group: a progress report. | |
| | |
MedLine Citation:
|
PMID: 17415487 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
|
The melting behaviour and transport properties of straight chain alkanes mono- and difunctionalized with phosphonic acid groups have been investigated as a function of their length. The increase of melting temperature and decrease of proton conductivity with increasing chain length is suggested to be the consequence of an increasing ordering of the alkane segments which constrains the free aggregation of the phosphonic acid groups. However, the proton mobility is reduced to a greater extent than the proton diffusion coefficient indicating an increasing cooperativity of proton transport with increasing length of the alkane segment. The results clearly indicate that the "spacer concept", which had been proven successful in the optimization of the proton conductivity of heterocycle based systems, fails in the case of phosphonic acid functionalized polymers. Instead, a very high concentration of phosphonic acid functional groups forming "bulky" hydrogen bonded aggregates is suggested to be essential for obtaining very high proton conductivity. Aggregation is also suggested to reduce condensation reactions generally observed in phosphonic acid containing systems. On the basis of this understanding, the proton conductivities of poly(vinyl phosphonic acid) and poly(meta-phenylene phosphonic acid) are discussed. Though both polymers exhibit a substantial concentration of phosphonic acid groups, aggregation seems to be constrained to such an extent that intrinsic proton conductivity is limited to values below sigma = 10(-3) S cm(-1) at T = 150 degrees C. The results suggest that different immobilization concepts have to be developed in order to minimize the conductivity reduction compared to the very high intrinsic proton conductivity of neat phosphonic acid under quasi dry conditions. In the presence of high water activities, however, (as usually present in PEM fuel cells) the very high ion exchange capacities (IEC) possible for phosphonic acid functionalized ionomers (IEC >10 meq g(-1)) may allow for high proton conductivities in the intermediate temperature range (T approximately 120 -160 degrees C). |
| | |
Authors:
|
H Steininger; M Schuster; K D Kreuer; A Kaltbeitzel; B Bingöl; W H Meyer; S Schauff; G Brunklaus; J Maier; H W Spiess |
Related Documents
:
|
12322987 - Covalent immobilization of chitosan/heparin complex with a photosensitive hetero-bifunc... 9185047 - Surface treatment of indirect resin composite surfaces before cementation. 15997437 - Poly(lactide) stereocomplexes: formation, structure, properties, degradation, and appli... 8593197 - Antimicrobial effects of a stabilized stannous fluoride dentifrice in reducing plaque a... 15527317 - A straightforward synthesis of (-)-phaseolinic acid. 7759147 - Amino acid metabolism by hepatocytes in a hybrid liver support bioreactor. |
Publication Detail:
|
Type: Journal Article; Research Support, Non-U.S. Gov't; Review Date: 2007-02-27 |
Journal Detail:
|
Title: Physical chemistry chemical physics : PCCP Volume: 9 ISSN: 1463-9076 ISO Abbreviation: Phys Chem Chem Phys Publication Date: 2007 Apr |
Date Detail:
|
Created Date: 2007-04-06 Completed Date: 2007-06-07 Revised Date: - |
Medline Journal Info:
|
Nlm Unique ID: 100888160 Medline TA: Phys Chem Chem Phys Country: England |
Other Details:
|
Languages: eng Pagination: 1764-73 Citation Subset: IM |
Affiliation:
|
Max-Planck-Institut für Festkörperforschung, Heisenbergstrasse 1, 70569 Stuttgart, Germany. |
Export Citation:
|
APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
|
Computer Simulation Electric Conductivity Electric Power Supplies / trends* Electrochemistry / methods*, trends Electrolytes / chemistry* Electromagnetic Fields Membranes, Artificial* Models, Chemical* Phosphonic Acids / chemistry* Polymers / chemistry* Temperature |
| Chemical | |
Reg. No./Substance:
|
0/Electrolytes; 0/Membranes, Artificial; 0/Phosphonic Acids; 0/Polymers |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
Previous Document: Effect of hypoxia during early organogenesis on cardiac activity and noradrenergic regulation in the...
Next Document: Carbon materials for supercapacitor application.