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PBI‐type Polymers and Acidic Proton Conducting Ionic Liquids – Conductivity and Molecular Interactions
Author(s) -
Lin J.,
Korte C.
Publication year - 2020
Publication title -
fuel cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.485
H-Index - 69
eISSN - 1615-6854
pISSN - 1615-6846
DOI - 10.1002/fuce.201900201
Subject(s) - electrolyte , aqueous solution , chemistry , ionic liquid , trifluoromethanesulfonate , pulsed field gradient , protonation , ionic bonding , proton , conductivity , ionic conductivity , inorganic chemistry , proton transport , polymer , polymer chemistry , chemical engineering , molecule , organic chemistry , ion , catalysis , membrane , electrode , biochemistry , physics , quantum mechanics , engineering
Proton conducting ionic liquids (PILs) are discussed as new electrolytes for the use as non‐aqueous electrolytes at operation temperatures above 100 °C. During fuel cell operation the presence of significant amounts of residual water is unavoidable. The highly Brønsted‐acidic PIL 2‐Sulfoethylmethylammonum triflate [2‐Sema][TfO] is able to perform fast proton exchange processes with H 2 O, resulting from 1 H‐NMR and pulsed field gradient (PFG)/diffusion ordered spectroscopy (DOSY) self‐diffusion measurements. Proton conduction takes place by a vehicle mechanism via PIL cations or H 3 O + , but also by a cooperative mechanism involving both species. Thus, highly Brønsted‐acidic PILs are promising candidates for the use as non‐aqueous electrolytes. To use [2‐Sema][TfO] as electrolyte in a proton electrolyte fuel cell (PEFC) it has to be immobilized in a host polymer. There is a (slow) uptake of the PIL by polybenzimidazole (PBI) up to a weight increase of ∼130%, due to a swelling process. A protonation of the basic imidazole moieties takes place. NMR analysis was applied to elucidate the molecular interactions between PBI, PIL, and residual water. Proton exchange, respectively an interaction between the polar groups and water can be observed in spectra, indicating a network of H‐bonds in doped PBI. Therefore, highly acidic PILs are promising candidates for the use as non‐aqueous electrolytes.