Screening of Ion–Graphene Electrode Interactions by Ionic Liquids: The Effects of Liquid Structure

Abstract

We have investigated the screening of solute ion−electrode interactions in two ionic liquids (1-butyl 3-methylimidazolium tetrafluoroborate [BMIm][BF 4 ] and 1,3dimethylimidazolium chloride [MMIm]Cl) by constructing free energy profiles for dissolved charged probes as a function of distance from a charged surface (graphene). The free energy profiles for three types of mutual interactions (surface and solute with opposite charges, solute and uncharged surface, and surface and solute with the same charges) differ from each other, but are remarkably similar in the two ionic liquids. They all show oscillations rather than the monotonic behavior predicted by Debye-type screening models. In both ionic liquids, there are high barriers impeding the motion of charged probes to the oppositely charged surface. We examined the local liquid structure around the probes and found that the free energy minima correspond to positions in which the solvation layers induced by the surface charge and the solvation shells around the probes enhance each other while barriers occur where they perturb each other.

Poly(a)morphic portrait of the electrical double layer in ionic liquids

“…The simulation setups (equilibration, length of simulations, system parameters and computational methods) were overall the same to the ones used in our previous works: Ref. [20] (fully atomistic model of [BMIm][BF 4 ]) and Refs. [11] (coarse-grained models).…”

“…The OPLS-AA force field was used together with partial charges taken from [22] for the IL. The charges were screened by a factor of 0.79 to account for the highfrequency electronic polarisability [20].…”

Improved Electrochemical Performance of a ZnFe2O4 Nanoflake‐Based Supercapacitor Electrode by Using Thiocyanate‐Functionalized Ionic Liquid Electrolytes

“…It is known that the performance of supercapacitors with ILs as the electrolyte depends on the IL functional group, and the selection of the cations and anions by varying the alkyl chain length 17,18. Various synthetic strategies have been reported for tailoring of the chemical structures of the IL cation or anion with different functional groups 19. Shaikh et al reported a simple Brønsted acidic ionic liquid as an electrolyte with Ru‐doped CuO thin‐film electrode, which demonstrated a potential window of 1.0 V, specific capacitance of 406 F g –1 , and retained this with cycle stability up to 2000 cycles 20.…”

Potential‐Dependent Adlayer Structure and Dynamics at the Ionic Liquid/Au(111) Interface: A Molecular‐Scale In Situ Video‐STM Study

“…For a deeper insight into the structure–reactivity correlation, detailed data on the molecular‐scale interface structure and dynamics at metal/RTILs interfaces is necessary, which is a subject of substantial current research 2d. 3 Recent experimental4 and theoretical studies3c, 5 revealed a multilayer architecture that exhibits fundamental differences compared to the electrochemical double layers found in aqueous and organic electrolytes.…”