In this study, we examined the thickness of the electrical double layer (EDL) in ionic liquids using density functional theory (DFT) calculations and molecular dynamics (MD) simulations. We focused on BF4- anion adsorption from the 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) ionic liquid on the Au(111) surface. At both DFT and MD levels, we evaluated the capacitance-potential dependence for the Helmholtz model of the interface. Using MD simulations, we also explored a more realistic, multilayer EDL model accounting for the ion layering. Concurrent analysis of the DFT and MD results provides a ground for thinking whether the electrical double layer in ionic liquids is one- or multi-ionic-layer thick.

Ionic liquids (IL) are promising electrolytes for electrochemical applications due to their remarkable stability and high charge density. Molecular dynamics simulations are essential for better understanding the complex phenomena occurring at the electrode-IL interface. In this work, we have studied the interface between graphene and 1-ethyl-3-methyl-imidazolium tetrafluoroborate IL, using density functional theory-based molecular dynamics simulations at variable surface charge densities. We have disassembled the electrical double layer poten-1 tial drop into two main components: one involving atomic charges and the other -dipoles.The latter component arises due to the electronic polarisation of the surface and is related to concepts hotly debated in the literature, such as the Thomas-Fermi screening length, effective surface charge plane, and quantum capacitance.

Carbon materials have a range of properties such as high electrical conductivity, high specific surface area, and mechanical flexibility are relevant for electrochemical applications. Carbon materials are utilised in energy conversion-and-storage devices along with electrolytes of complementary properties. In this work, we study the interaction of highly concentrated electrolytes (ionic liquids) at a model carbon surface (circumcoronene) using density functional theory methods. Our results indicate the decisive role of the dispersion interactions that noticeably strengthen the circumcoronene-ion interaction. Also, we focus on the adsorption of halide anions as the electrolytes containing these ions are promising for practical use in supercapacitors and solar cells.

Electrochemical characterization of the interface between Bi(111) surface and ionic liquid mixtures of 1-ethyl-3-methylimidazolium tetrafluoroborate with 1-ethyl-3-methylimidazolium bromide (EMImBF 4 + x% EMImBr) has been evaluated by using the electrochemical impedance spectroscopy, cyclic voltammetry methods and density functional theory calculations. Dependence of the experimental data on the bromide concentration and on the electrode potential has been analyzed. Comparison of adsorption data with Bi(111) | EMImBF 4 + x% EMImI interface shows that adsorption activity of halide ions from EMImBF 4 follows a similar trend as from the aqueous and organic electrolyte solutions. The adsorption activity of anions increases in order Cl − < Br − < I − , despite the fact that the solvation properties of relevant media are significantly different. We discuss this trend in the light of a possible application of the RTIL mixtures as an electrolyte for electrochemical energy storage devices like supercapacitors. The ionic liquids as electrolytes have been studied since the early 20 th century, but there is still much to be understood regarding some fundamental aspects. [1][2][3][4][5][6] Theoretical models that explain the dependence of the differential capacitance values on the electrode potentials have been worked out for the aqueous and non-aqueous electrolytes and molten salts. 7,8 However, in the case of the specific adsorption, there are no detailed models for the electrical double layer capacitance, that analyze the influence of the surface-active anion concentration and electrode potential on the specific interaction energy (including charge transfer) and on the distance of the closest approach of anions onto the metal electrode surface.5,9,10 Therefore, the detailed analysis and characterization of these complex electrode | ionic liquid interfaces (with the addition of ions that might have strong chemical interactions and high interaction energies with electrode surface layer atoms, demonstrating very negative Gibbs adsorption energy values, so-called strong specific adsorption properties) is considered our high priority. Bismuth, as an electrode material, has been studied widely and has shown good electrochemical stability and high reproducibility of the data. The properties are inevitable for detailed investigation of interfacial adsorption and faradaic charge transfer processes. The amount of previously measured adsorption data from different electrolytes (including electrochemical impedance spectroscopy and in situ STM methods) enables to develop more realistic, i.e. complex models for the electrical double layer capacitance, that analyze the influence of the surface-active anion addition on the inner layer structure, dielectric permittivity, effective dipoles moment for dipole created at metal|RTIL interface, etc. 7,[11][12][13][14] To continue with the systematic research of halide ions, 1-ethyl-3-methylimidazolium bromide (EMImBr) was selected for the source of bromide ions. There are some theoretical and e...

On the example of 40 ion pairs (5 cations times 8 anions), this study demonstrates how the core-level binding energy values can be calculated and used to plot theoretical spectra at low computational cost using density functional theory methods. Three approaches for obtaining the binding energy values are based on delta Kohn-Sham (ΔKS) calculations, 1s KS orbital energies, and atomic charges. The ΔKS results show reasonable agreement with the available experimental X-ray photoelectron data. The 1s KS orbital energies correlate well with the ΔKS results. Atomic charge correlation with ΔKS is improved by accounting for the charges of neighboring atoms. Assignment of binding energies to atoms and the applicability of the mentioned methods to model systems of ionic liquids are discussed. K E Y W O R D S core-level binding energy, delta Kohn-Sham, Green function, ionic liquid, X-ray photoelectron spectra