A classical density functional theory for interfacial layering of ionic liquids

Ionic liquids have attracted much recent theoretical interest for broad applications as environmentally-friendly solvents in separation and electrochemical processes. Because of the intrinsic complexity of organic ions and strong electrostatic correlations, the electrochemical properties of ionic liquids often defy the descriptions of conventional mean-field methods including the venerable, and over-used, Gouy–Chapman–Stern (GCS) theory. Classical density functional theory (DFT) has proven to be useful in previous studies of the electrostatic properties of aqueous electrolytes but until recently it has not been applied to ionic liquids. Here we report predictions from the DFT on the interfacial properties of ionic liquids near neutral or charged surfaces. By considering the molecular size, topology, and electrostatic correlations, we have examined major factors responsible for the unique features of electric-double layers of ionic-liquid including formation of long-range and alternating structures of cations and anions at charged surfaces.

[1]  R. H. Amirov,et al.  Influence of temperature on the structure and dynamics of the [BMIM][PF(6)] ionic liquid/graphite interface. , 2010, Physical chemistry chemical physics : PCCP.

[2]  F. Leermakers,et al.  Room-temperature ionic liquids: excluded volume and ion polarizability effects in the electrical double-layer structure and capacitance. , 2009, Physical review letters.

[3]  Haiping Fang,et al.  Double-layer formation of [Bmim][PF6] ionic liquid triggered by surface negative charge. , 2010, Langmuir : the ACS journal of surfaces and colloids.

[4]  S. Baldelli,et al.  Gas-liquid interface of room-temperature ionic liquids. , 2010, Chemical Society reviews.

[5]  A. Van Itterbeek,et al.  Mesures sur la viscosit de l'oxygne dans un champ magntique et pour des trs basses pressions , 1938 .

[6]  L. Scriven,et al.  Non-local free-energy density-functional theory applied to the electrical double layer , 1990 .

[7]  H. Steinrück,et al.  Liquid/solid interface of ultrathin ionic liquid films: [C1C1Im][Tf2N] and [C8C1Im][Tf2N] on Au(111). , 2011, Langmuir : the ACS journal of surfaces and colloids.

[8]  A. Kornyshev,et al.  Double layer in ionic liquids: overscreening versus crowding. , 2010, Physical review letters.

[9]  L. Blum,et al.  Mean spherical model for asymmetric electrolytes , 1975 .

[10]  Alexei A Kornyshev,et al.  Double-layer in ionic liquids: paradigm change? , 2007, The journal of physical chemistry. B.

[11]  Jianzhong Wu,et al.  Density-functional theory of spherical electric double layers and zeta potentials of colloidal particles in restricted-primitive-model electrolyte solutions. , 2004, The Journal of chemical physics.

[12]  P. Milani,et al.  Nanometric ionic-liquid films on silica: a joint experimental and computational study , 2009, Journal of physics. Condensed matter : an Institute of Physics journal.

[13]  C. W. Outhwaite.  Modified Poisson–Boltzmann equation in electric double layer theory based on the Bogoliubov–Born–Green–Yvon integral equations , 1978 .

[14]  K. Fukui,et al.  Direct observation of layered structures at ionic liquid/solid interfaces by using frequency-modulation atomic force microscopy. , 2010, Chemical communications.

[15]  Oleg Borodin,et al.  Molecular insights into the potential and temperature dependences of the differential capacitance of a room-temperature ionic liquid at graphite electrodes. , 2010, Journal of the American Chemical Society.

[16]  De-en Jiang,et al.  Density functional theory for differential capacitance of planar electric double layers in ionic liquids , 2011 .

[17]  Stanislaw Lamperski,et al.  The electric double-layer differential capacitance at and near zero surface charge for a restricted primitive model electrolyte. , 2009, The journal of physical chemistry. B.

[18]  Kenneth R. Seddon,et al.  Ionic liquids. Green solvents for the future , 2000 .

[19]  R. Lynden-Bell.  Gas—liquid interfaces of room temperature ionic liquids , 2003 .

[20]  D. Wasan,et al.  LOW TEMPERATURE ANOMALIES IN THE PROPERTIES OF THE ELECTROCHEMICAL INTERFACE , 1999 .

[21]  W. Fawcett,et al.  Monte Carlo, density functional theory, and Poisson–Boltzmann theory study of the structure of an electrolyte near an electrode , 2002 .

[22]  H. Davis,et al.  Simulations of solvent effects on confined electrolytes , 1993 .

[23]  G. Wipff,et al.  Ordering of Imidazolium-Based Ionic Liquids at the α-Quartz(001) Surface: A Molecular Dynamics Study , 2008 .

[24]  Jianzhong Wu,et al.  Density-functional theory for complex fluids. , 2007, Annual review of physical chemistry.

[25]  E. Maginn,et al.  Molecular Dynamics Study of the Ionic Liquid 1-n-Butyl-3-methylimidazolium Hexafluorophosphate , 2002 .

[26]  A. Kornyshev,et al.  F ¨ Ur Mathematik in Den Naturwissenschaften Leipzig towards Understanding the Structure and Capacitance of Electrical Double Layer in Ionic Liquids towards Understanding the Structure and Capacitance of Electrical Double Layer in Ionic Liquids , 2022 .

[27]  A. Kornyshev,et al.  Double layer in ionic liquids: the nature of the camel shape of capacitance , 2010 .

[28]  J. Torrecilla,et al.  Density and Molar Volume Predictions Using COSMO-RS for Ionic Liquids. An Approach to Solvent Design , 2007 .

[29]  J. P. Valleau,et al.  Electrical double layers. 4. Limitations of the Gouy-Chapman theory , 1982 .

[30]  R. Penfold,et al.  Classical Density Functional Theory of Ionic Liquids , 2017 .

[31]  Jianzhong Wu,et al.  Density-functional theory for the structures and thermodynamic properties of highly asymmetric electrolyte and neutral component mixtures. , 2004, Physical review. E, Statistical, nonlinear, and soft matter physics.

[32]  S. Lamperski,et al.  A modified Poisson-Boltzmann analysis of the solvent primitive model electrical double layer , 1996 .

[33]  Jiawei Yan,et al.  The electrode/ionic liquid interface: electric double layer and metal electrodeposition. , 2010, Chemphyschem : a European journal of chemical physics and physical chemistry.

[34]  V. Lockett,et al.  Orientation and mutual location of ions at the surface of ionic liquids. , 2010, Physical chemistry chemical physics : PCCP.

[35]  D. Henderson,et al.  Some exact results and the application of the mean spherical approximation to charged hard spheres near a charged hard wall , 1978 .

[36]  Thierry Biben,et al.  Generic density functional for electric double layers in a molecular solvent , 1998 .

[37]  R. Lynden-Bell.  Screening of pairs of ions dissolved in ionic liquids. , 2010, Physical chemistry chemical physics : PCCP.

[38]  Jianzhong Wu,et al.  Density functional theory for polyelectrolytes near oppositely charged surfaces. , 2006, Physical review letters.

[39]  F. Kremer,et al.  Measurement of Forces across Room Temperature Ionic Liquids between Mica Surfaces , 2009 .

[40]  T. Uruga,et al.  Ionic multilayers at the free surface of an ionic liquid, trioctylmethylammonium bis(nonafluorobutanesulfonyl)amide, probed by x-ray reflectivity measurements. , 2010, The Journal of chemical physics.

[41]  Zhen Cao,et al.  Molecular Dynamic Simulations of Ionic Liquids at Graphite Surface , 2010 .

[42]  O. Borodin,et al.  Molecular simulations of the electric double layer structure, differential capacitance, and charging kinetics for N-methyl-N-propylpyrrolidinium bis(fluorosulfonyl)imide at graphite electrodes. , 2011, The journal of physical chemistry. B.

[43]  J. P. Valleau,et al.  Electrical double layers. I. Monte Carlo study of a uniformly charged surface , 1980 .

[44]  Matthew K. Tam,et al.  Double Layer Structure of Ionic Liquids at the Au(111) Electrode Interface: An Atomic Force Microscopy Investigation , 2011 .

[45]  John Ralston,et al.  Differential capacitance of the double layer at the electrode/ionic liquids interface. , 2010, Physical chemistry chemical physics : PCCP.

[46]  T. Albrecht,et al.  Layering and shear properties of an ionic liquid, 1-ethyl-3-methylimidazolium ethylsulfate, confined to nano-films between mica surfaces. , 2010, Physical chemistry chemical physics : PCCP.

[47]  R. L. Rowley,et al.  Simulation and density functional study of a simple membrane separating two restricted primitive model electrolytes , 1999 .

[48]  S. Lamperski,et al.  Monte Carlo study of the electrode|solvent primitive model electrolyte interface , 2007 .

[49]  Q. Dou,et al.  Molecular dynamics simulation of the interfacial structure of [Cnmim][PF6] adsorbed on a graphite surface: effects of temperature and alkyl chain length , 2011, Journal of physics. Condensed matter : an Institute of Physics journal.

[50]  D. Chapman,et al.  LI. A contribution to the theory of electrocapillarity , 1913 .

[51]  D. F. Evans,et al.  Double-layer and solvation forces measured in a molten salt and its mixtures with water , 1988 .

[52]  L. Scriven,et al.  Interactions between primitive electrical double layers , 1992 .

[53]  D. Henderson,et al.  Insights from theory and simulation on the electrical double layer. , 2009, Physical chemistry chemical physics : PCCP.

[54]  M. Lozada-Cassou,et al.  The application of the hypernetted chain approximation to the electrical double layer: Comparison with Monte Carlo results for symmetric salts , 1982 .

[55]  Simulations of ionic liquids, solutions, and surfaces. , 2007, Accounts of chemical research.

[56]  B. Ocko,et al.  Molecular Layering of Fluorinated Ionic Liquids at a Charged Sapphire (0001) Surface , 2008, Science.

[57]  Jianzhong Wu,et al.  Density functional theory for inhomogeneous mixtures of polymeric fluids , 2002 .

[58]  Gerhard Kahl,et al.  Fundamental measure theory for hard-sphere mixtures revisited: the White Bear version , 2002 .

[59]  A. A. Kornyshev,et al.  The anatomy of the double layer and capacitance in ionic liquids with anisotropic ions: Electrostriction vs. lattice saturation , 2010 .

[60]  D. Gillespie.  Free-Energy Density Functional of Ions at a Dielectric Interface. , 2011, The journal of physical chemistry letters.

[61]  B. Ocko,et al.  Surface layering in ionic liquids: an X-ray reflectivity study. , 2005, Journal of the American Chemical Society.

[62]  Jianzhong Wu,et al.  A hybrid method for predicting the microstructure of polymers with complex architecture: combination of single-chain simulation with density functional theory. , 2006, The Journal of chemical physics.

[63]  Rosenfeld,et al.  Free-energy model for the inhomogeneous hard-sphere fluid mixture and density-functional theory of freezing. , 1989, Physical review letters.

[64]  Communication: Density-functional theory for inhomogeneous hyperbranched polymeric fluids: polydisperse effect of degree of branching. , 2010, The Journal of chemical physics.

[65]  S. Marčelja,et al.  Double layer interactions in mono‐ and divalent electrolytes: A comparison of the anisotropic HNC theory and Monte Carlo simulations , 1992 .

[66]  D. Henderson,et al.  Application of the hypernetted chain approximation to the electric double layer at a charged planar interface , 1979 .

[67]  Jianzhong Wu,et al.  Structures of hard-sphere fluids from a modified fundamental-measure theory , 2002 .

[68]  D. Morikis,et al.  Molecular thermodynamics for charged biomacromolecules , 2006 .