A Classical Density Functional Theory of Ionic Liquids

Jan Forsman,Clifford E Woodward,Martin Trulsson

doi:10.1021/jp111747w

Jan Forsman, Clifford E Woodward + Show 1 more

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https://doi.org/10.1021/jp111747w

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Abstract

We present a simple, classical density functional approach to the study of simple models of room temperature ionic liquids. Dispersion attractions as well as ion correlation effects and excluded volume packing are taken into account. The oligomeric structure, common to many ionic liquid molecules, is handled by a polymer density functional treatment. The theory is evaluated by comparisons with simulations, with an emphasis on the differential capacitance, an experimentally measurable quantity of significant practical interest.

Highlights

The current technological revolution based on ionic liquids (ILs) is driven by their unique properties
In this chapter we describe an alternative theoretical approach that aims to play a similar role for ILs as the Poisson-Boltzmann Approximation (PBA) does for traditional electrolytes
6.1 Performance of the density functional theory (DFT) for the full IL model In our previous publication (Forsman et al, 2011), we demonstrated that our DFT is able to reproduce simulated differential capacitance curves qualitatively, and with a semi-quantitative accuracy

Summary

Introduction

The current technological revolution based on ionic liquids (ILs) is driven by their unique properties. Some actual and potential uses of ILs include: specific solvents for heterogeneous and homogeneous catalysis; selective solvents for removal of heavy metal contaminants; electrolytes in various electrochemical processes and devices; and as dispersive agents for stabilization of nanoparticles In all of these applications, the structural properties of ILs and their mixtures in the bulk phase and at interfaces are crucial to their performance (Maier et al , 2010). In electrowinning processes, such as aluminium refining, metal ion speciation is a crucial consideration in determining the population of electroactive components (Rocher et al , 2009) and influences the pertinent dynamical processes that lead to oxidation and reduction. As emphasized by Kornyshev in a recent review article (Kornyshev , 2007), applications of ILs at electrified interfaces to energy-storage systems, electrowetting devices or nanojunction gating media will be strongly promoted by a deeper understanding of the structure and properties of the interfacial double layer

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