Proton Conduction Mechanism for Anhydrous Imidazolium Hydrogen Succinate Based on Local Structures and Molecular Dynamics

Abstract

Anhydrous organic crystalline materials incorporating imidazolium hydrogen succinate (Im-Suc), which exhibit high proton conduction even at temperatures above 100 °C, are attractive for elucidating proton conduction mechanisms toward the development of solid electrolytes for fuel cells. Herein, quantum chemical calculations were used to investigate the proton conduction mechanism in terms of hydrogenbonding (H-bonding) changes and restricted molecular rotation in Im-Suc. The local H-bond structures for proton conduction were characterized by vibrational frequency analysis and compared with corresponding experimental data. The calculated potential energy surface involving proton transfer (PT) and imidazole (Im) rotational motion showed that PT between Im and succinic acid was a rate-limiting step for proton transport in Im-Suc and that proton conduction proceeded via the successive coupling of PT and Im rotational motion based on a Grotthusstype mechanism. These findings provide molecular-level insights into proton conduction mechanisms for Im-based (or -incorporated) H-bonding organic proton conductors.

Design of Novel Solid-State Electrolytes Based on Plastic Crystals of Quinuclidinolium Methanesulfonate for Proton Conduction

“…17,20,85,86 The Arrhenius plots of three heating and cooling cycles of R-[QH]MS (see Figure S12) compared with those of [QHrac]-MS, and [QHco]MS (see Figure S13) are drawn not only to show reproducibility but also to calculate the activation energies before and after the phase transition regions by using the Arrhenius equation: of R-[QH]MS are found to be 151, 143, and 146 kJ mol −1 , respectively. As a typical behavior of OIPCs, after the plastic phase transition, the E a is decreased to 92 kJ mol −1 , indicating point defect-mediated conduction through bulk plastic phase in the case of enantiopure R-[QH]MS. 60,61,87 ■ CONCLUSIONS…”

Proton Conductive Mononuclear Hydrogen-Bonded Cobalt(II) Spin Crossover Complex

“…The proton-conducting mechanism for hydrogen-bonding in confined spaces, such as that presented for 1 ·4H 2 O, follows the Grotthuss-type mechanism, , as reported by Kitagawa et al , A similar phenomenon has been discovered in several previously reported compounds with an activation energy value of 0.37–0.48 eV. ,, Proton migration in these compounds follows a Grotthuss-type mechanism. In addition, E a , sometimes, includes a proton-conduction mechanism that changes hydrogen-bonding and restricts molecular rotation. , The observed relatively high E a values suggest that proton conduction in 1 ·4H 2 O includes other molecular motions, such as molecular rotation. Based on the crystal structural analysis, we can conclude that intermolecular hydrogen-bonding could be expanded to 1D networks through proton migration based on the disorder of the ClO 4 – counteranions and rotation of carboxy group of COOH-terpy, leading to the creation of good proton-conduction pathways (Figure ).…”

“…In addition, E a , sometimes, includes a protonconduction mechanism that changes hydrogen-bonding and restricts molecular rotation. 45,46 The observed relatively high E a values suggest that proton conduction in 1•4H 2 O includes other molecular motions, such as molecular rotation. Based on the crystal structural analysis, we can conclude that intermolecular hydrogen-bonding could be expanded to 1D networks through proton migration based on the disorder of the ClO 4 − counteranions and rotation of carboxy group of COOH-terpy, leading to the creation of good proton-conduction pathways (Figure 6).…”

Construction of a unique 2-D layered vanadoborate with water-assisted proton conductivity

“…For the Grotthuss-type mechanism, it is related to the proton hopping from one proton carrier site to a neighboring one through H-bonds. 50 In compound 1 , the presence of [V 12 B 18 O 54 (OH) 6 (H 2 O)] 10− and H 2 en 2+ could not only provide more mobile protons but also administer a smooth proton transfer pathway. And the existence of Na + ions may have a distinct effect on the water dynamics.…”