Enhancement of ‘dry’ proton conductivity by self-assembled nanochannels in all-solid polyelectrolytes

Abstract

Nanoscale proton-channels endow a polyelectrolyte membrane with exciting anhydrous proton conductivity, making it attractive for high-temperature PEMFC applications.

Proton Conducting Membranes Based on Poly(Ionic Liquids) Having Phosphonium Counter‐Cations

“…The ionic conductivity recorded at 30 °C was around 5 × 10 −7 S cm −1 and gradually increases with increasing temperature as expected. The recorded value at 150 °C was around 2 × 10 −4 S cm −1 , which is similar to the ammonium analog PSTFSI HN + 122 reported earlier making it a potential useful candidate for intermediate temperature applications . Interestingly, even a small amount of water in this polymer produces more than an order of magnitude higher conductivity (compare Figure c,d) which suggests the likely importance of water for encouraging proton hopping in these systems as has been suggested before for ammonium analogs …”

“…The materials prepared with the PSTFSI backbone displayed moderate conductivities in comparison to PAMPS and PSS analogs even though the samples contained significantly less water due to their high hydrophobicity. This enhanced ionic conductivity can be attributed to the delocalized negative charge center of the TFSI anion as reported in the literature, hence enhancing the dissociation of the counter ions. The sample PSTFSI HP + 444 displayed the best membrane properties in terms of its elasticity and thermal stability.…”

“…Subsequently, the few reported protic poly(ionic liquids) typically consist of a cationic polymerized ammonium or imidazolium (with a labile proton on it) backbone and a free carboxylate anion which have been investigated as proton conductors and for CO 2 absorption . More recently, Zhu and co‐workers developed a protic poly(ionic liquid) having an anionic polymeric backbone based on polystyrene sulfonamide having a free ammonium counter‐cations . This polymer showed very interesting anhydrous proton conductivity of 3 × 10 −4 S cm −1 at 120 °C, making it an attractive candidate proton conducting membrane for intermediate temperature operation.…”

New Insights into Decoupled Cation and Anion Transport and Dynamic Heterogeneity in a Diethyl(methyl)(isobutyl)phosphonium Hexafluorophosphate Organic Ionic Plastic Crystal

“…Unusual Cation and Anion Diff usion Behavior in [P 122i4 ][PF 6 ] OIPC. The purity of the compound is confirmed by multinuclear ( 1 H, 13 C, 31 19 F PFG and 50 ms for 1 H PFG. The gradient amplitude was varied between 0.1 and 2500 Gauss/cm in 32 steps (log scale) for both nuclei.…”

“…30 This restricted diffusion is manifested by a decrease in the measured diffusion coefficient with increasing diffusion time. 24,30,31 Figure 2 shows the diffusion time dependency of the fast-and slow-PF 6 anions as well as the P 122i4 cation. Clearly, the fast anion species exhibits a sudden decrease in the diffusion coefficient at a relatively long diffusion time of 1000 ms or longer.…”