Molecular response of 1-butyl-3-methylimidazolium dicyanamide ionic liquid at the graphene electrode interface investigated by sum frequency generation spectroscopy and molecular dynamics simulations

Siyun Xu, Sirui Xing, Shin Shem Pei, Vladislav Ivaništšev, Ruth Lynden-Bell, Steven Baldelli

Research output: Contribution to journalArticle

33 Citations (Scopus)

Abstract

The ion distribution at the charged three layer graphene-ionic liquid (1-butyl-3-methylimidazolium dicyanamide, [BMIM][DCA]) interface is probed by sum frequency generation spectroscopy (SFG), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The SFG results show the presence of both [BMIM]+ cations and [DCA]- anions at the charged graphene surface, where the anion signal increased with the increasing external potential and the cation signal was little influenced by the external potential. The CV and EIS results suggest that ions form an electrically stable double layer at the charged graphene surface. Molecular dynamics simulations of [BMIM][DCA] near the charged graphene surface suggest that the interface consists of alternating layers of cations and anions that restructure with external potential variation. The experimental data can be interpreted by a double-layer model where the anionic and cationic layers interchange position with each other at the surface depending on the applied potential.

Original languageEnglish
Pages (from-to)26009-26019
Number of pages11
JournalJournal of Physical Chemistry C
Volume119
Issue number46
DOIs
Publication statusPublished - 10 Nov 2015

Keywords

  • graphene-based electrodes
  • room-temperature ionic liquids
  • supercapacitors

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