Double Layer at [BuMeIm][Tf₂N] Ionic Liquid–Pt or −C Material Interfaces

Abstract

The interface [BuMeIm][Tf2N]/electrode, where [BuMeIm][Tf2N] stands for the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, was characterized by electrochemical impedance spectroscopy at different temperatures and for different electrode materials: platinum (Pt, metallic), glassy carbon (GC, high conductivity), carbon nitride (a-CNx, mean conductivity), and boron-doped diamond (BDD, semiconducting with a quasimetallic character). For Pt, GC, and a-CNx, the behavior of the interface could be described by the same equivalent electrical circuit. In the case of BDD, a parallel combination of Rsc and Csc was introduced into the circuit to take into account the potential drop due to the development of a space charge region within the material. The Mott-Schottky plots have confirmed the polycrystalline semiconductor character of the BDD material, and the boron concentration estimated is fully consistent with the B amount introduced for the synthesis. The variations of the double-layer capacitance as a function of potential were found to be camel shaped for all electrode materials at the highest studied temperature. This is consistent with the prediction of Kornyshev's theory as low values of the packing parameter γ were estimated by simulation (lower than 0.33). An increase of the double-layer capacitance is found with the temperature similarly to most of the results obtained for molten salts.

Fundamental measure theory for the electric double layer: implications for blue-energy harvesting and water desalination

“…For low concentrations it has a local minimum at Ψ = 0V, which turns into a global maximum at higher packing fractions. This transition from the so-called bell to camel shape occurs when the packing parameter within mPB theory becomes γ = 1 3 and both camel and bell shape have been found experimentally [73,74]. Obviously, in the confining geometry of our model supercapacitor, both mPB and FMT-type theories reproduce decaying tails of C diff for increasing electrode potentials, as shown in figure 4.…”

Non-Faradaic Energy Storage by Room Temperature Ionic Liquids in Nanoporous Electrodes

“…The open structure for the slit and nanotube pores is a flat surface, and recent experiments 114,115 and chemically realistic simulations 116À118 showed that RTIL based electrolytes on atomically flat surfaces generate capacitance between 4 and 6 μF/cm 2 . The simulations presented here show that the enhancement of the capacitance due to nanoconfinement in the subnanometer wide slits and cylinders accounts for ∼30À50% increase in capacitance relative to the corresponding open structure and, hence, these pores are only capable to enhance the capacitance up to ∼6À8 μF/cm 2 .…”

The interface between Au(100) and 1-butyl-3-methyl-imidazolium-bis(trifluoromethylsulfonyl)imide

“…Apart from BMIPF 6 , we made experiments also with a home-made guanidinium-based IL [20]; while the results reported in this paper were obtained with an ionic liquid comprising the same imidazoliumbased cation as in BMIPF 6 , but in combination with the bis(trifluoromethylsulfonyl)imide, Tf 2 N − anion (Figure 1). The first report on the double layer property measurements on BMITf 2 N have appeared just recently [21]. Unfortunately, this study was done not on Au, but on other electrode materials, Pt and carbon materials.…”