The influence of anion chemistry on the ionic conductivity and molecular dynamics in protic organic ionic plastic crystals. Issue 6 (29th January 2018)

• Record Type: Journal Article
• Authors: Rao, Jun; Vijayaraghavan, R.; Zhou, Yundong; Howlett, Patrick C.; MacFarlane, Douglas R.; Forsyth, Maria; Zhu, Haijin
• Is Part Of: Physical chemistry chemical physics. Volume 20:Issue 6(2018)
• Page Start: 4579
• Page End: 4586
• Publication Date: 2018-01-29
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c7cp07330e
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Protic organic ionic plastic crystals based on different anions exhibit more than two orders of magnitude difference in conductivity. Abstract : Proton conductors are widely used in different electrochemical devices including fuel cells and redox flow batteries. Compared to conventional proton conducting polymer membranes, protic organic ionic plastic crystal (POIPC) is a novel solid-state proton conductor with high proton conductivity even under anhydrous conditions. In this work, different organic protic salts based on the same parent di-functional cation with different anions were synthesized and characterized. It is found that the di-protonated cation plays an important role in defining the thermal properties, leading to stronger plastic crystal behavior and a higher melting point. Static solid-state NMR and the synchrotron XRD results show that the di-protonated cation allows greater dynamics in the crystal in contrast to the mono-protonated counterparts. The 1-( N, N -dimethylammonium)-2-(ammonium)ethane triflate ([DMEDAH2 ][Tf]2 ) has the highest ionic conductivity of 1.1 × 10 −4 S cm −1 at 50 °C, whereas the bis(trifluoromethanesulfonyl)amide counterpart [DMEDAH2 ][TFSA]2 has the lowest ionic conductivity (2.8 × 10 −7 S cm −1 at 50 °C) with no measureable mobile ion component at this temperature. The fraction of mobile species is significantly suppressed in the TFSA containing salts as against the Tf systems.