The influence of anion chemistry on the ionic conductivity and molecular dynamics in protic organic ionic plastic crystals

TY - JOUR

T1 - The influence of anion chemistry on the ionic conductivity and molecular dynamics in protic organic ionic plastic crystals

AU - Rao, Jun

AU - Vijayaraghavan, R.

AU - Zhou, Yundong

AU - Howlett, Patrick C.

AU - Macfarlane, Douglas R.

AU - Forsyth, Maria

AU - Zhu, Haijin

N1 - Publisher Copyright: © 2018 the Owner Societies.

PY - 2018

Y1 - 2018

N2 - 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.

AB - 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.

UR - http://www.scopus.com/inward/record.url?scp=85041749368&partnerID=8YFLogxK

U2 - 10.1039/c7cp07330e

DO - 10.1039/c7cp07330e

M3 - 文章

C2 - 29376537

AN - SCOPUS:85041749368

SN - 1463-9076

VL - 20

SP - 4579

EP - 4586

JO - Physical Chemistry Chemical Physics

JF - Physical Chemistry Chemical Physics

IS - 6

ER -