Journal
JOURNAL OF MEMBRANE SCIENCE
Volume 630, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.memsci.2021.119325
Keywords
Fuel cells; Anion exchange membrane; Alkaline stability; Spirocyclic ionenes
Categories
Funding
- National Natural Science Foundation of China [21835005]
- Science and Technology Major Projects of Shanxi Province of China [20181102019]
- Hundred Talents Program of the Shanxi Province
- International Scientific & Technological Cooperation Project in Shanxi Province [201803D421075]
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By designing and preparing polymer based on different spirocyclic ionenes, their stability in alkaline and fuel cells was investigated. Blending membranes using spirocyclic ionenes with phenyl or biphenyl rings showed good performance at high temperature, but unexpected degradation was observed in fuel cell device durability testing.
A series of polymer based on spirocyclic quaternary ammonium (QA) cations having 5-/6- and 6-/6- membered rings were designed and prepared from tetrakis(bromomethyl) monomers to investigate the alkaline and fuel cell stability of spirocyclic ionenes. The alkaline stability testing of model compounds and DFT calculations showed that the spirocyclic QA having 5-/6-membered rings based on phenyl and biphenyl showed a better stability than that of the spirocyclic QA with naphthalene 6-/6-membered rings probably due to the strong electrowithdrawing effect of naphthalene rings. Although the high molecular weight polymer with naphthalene rings could not be obtained, the spirocyclic ionenes based on phenyl or biphenyl showed high molecular weight. Thus, the blending membrane with rigid NPBI have been fabricated to mitigate the water solubility of spirocyclic ionenes due to their high IEC values. The blending membrane showed a high ionic conductivity even at elevated temperature without any excessive swelling in spite of its high IEC value. Employing the spirocyclic ionenes as membrane, the H-2/O-2 single cell at 60 degrees C was firstly demonstrated. A peak power density of 135 mW cm(-2) was achieved for PP80N20 membrane. Surprisingly, the fuel cell device durability provided a counterintuitive data that showed that spirocyclic ionenes with excellent alkaline stability were not superior in device function assessment. A rapid ring-opening degradation as confirmed by NMR technique for the spirocyclic ionenes was observed in device testing. These results that stability investigation gives us new directions for polymer and cations designs for highly durable devices.
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