Vibrational Spectrum of 1-Ethyl-3-Methylimidazolium Tetrafluoroborate on Graphene Surface

Published in Journal of Molecular Liquids, 2020

Jiao Zhang1, Yongii Guan1, Jinyuan Wang, Fulong Yang, Huanwang Jing, Xiaoping Zhang, Youquan Deng. Journal of Molecular Liquids, 2020, 311, 113340.

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Abstract

Ionic liquids (ILs) are promising novel solvents for energy harvesting and understanding the graphene/ILs interface structural characteristics is required. In this study, we calculate the vibrational spectrum (VS) of 1-ethyl-3-methylimidazolium tetrafluoroborate ([Emim][BF4]) pair on graphene surface in the range from 10 to 3500 cm-1 and systemically investigate the influence of the graphene on the VS of [Emim][BF4] using density functional theory. The results show 24 vibrational bands (VBs) with obvious shifting. The VBs at 3170.26 and 3033.51 cm-1 show a redshift of 59.46 and 14.95 cm-1 respectively which was mainly caused by the enhanced hydrogen bond strength of C2H···F and F atoms with the CH on the ethyl chain. The VBs at 101.49 and 1417.43 cm-1 show a blueshift of 62.43 and 23.86 cm-1 due to the enhancement of induction effect of [Emim][BF4] on graphene surface (from −44.68 to −45.42 kJ mol-1). The VB at 86.91 cm-1 shows a redshift of 59.43 cm-1 which can be ascribed to the reduction of the whole interaction energy between the cation and anion of [Emim][BF4] on graphene surface (from −367.06 to −356.06 kJ·mol-1). Overall, these shifts of the VS are mainly attributed to the attraction between graphene and anion [BF4]-, which is dominated by the induction and dispersion interaction accounting for 63.43% and 34.37% of the attraction interaction respectively. Due to this attraction, the anion [BF4]- move closer to the surface of graphene.

Jiao Zhang1, Yongii Guan1, Jinyuan Wang, Fulong Yang, Huanwang Jing, Xiaoping Zhang, Youquan Deng. Vibrational Spectrum of 1-Ethyl-3-Methylimidazolium Tetrafluoroborate on Graphene Surface. Journal of Molecular Liquids, 2020, 311, 113340.