Water Stable Ionic Liquid Research Articles

Probing Lithium and Alumina Impurities in Air- and Water Stable Ionic Liquids by Cyclic Voltammetry and In Situ Scanning Tunneling Microscopy

In this paper we report on some results on the electrochemical breakdown of ionic liquids at the cathodic limit of the electrochemical window and on the probing of inorganic impurities in ionic liquids (originating from the synthesis) at the interface electrode/electrolyte by in situ scanning tunneling microscopy on Au(111). It will be shown that the restructuring/reconstruction of Au(111) in ultrapure 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py1,4]Tf2N) leads to a transition from a wormlike surface structure to a surface with well defined terraces. Close to the cathodic decomposition of the liquid the quality of the STM pictures gets worse and at the onset of massive ionic liquid breakdown a film forms on the gold surface finally shielding completely the gold terraces. When the [Py1,4]Tf2N liquid, made by a metathesis reaction from [Py1,4]Cl and LiTf2N, is not thoroughly washed after the synthesis, the in situ STM pictures show in a wide potential range the same surface structures as with the ultrapure liquid, but in the cathodic regime the deposition of lithium in only a few monolayers is observed. In the respective cyclic voltammograms on Au(111) there is clear evidence for lithium deposition. We show furthermore that a spectroscopically ultrapure 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ionic liquid ([EMIm]Tf2N) can show unexpected behaviour at the electrode/electrolyte interface when after synthesis it is subject to an Al2O3 treatment with the aim to remove organic impurities. Al2O3 seems to be dissolved in the ionic liquid in low concentrations and deposited at the electrode surface. At lower electrode potentials the alumina seems to be reduced to metallic aluminium. Our results show that even ultrapure ionic liquids can contain inorganic impurities which are very difficult to probe with conventional analytical methods. Better synthesis routes will be necessary to make ultrapure ionic liquids for fundamental physicochemical studies.

Electrodeposition of Nano‐ and Microcrystalline Aluminium in Three Different Air and Water Stable Ionic Liquids

The present work shows, for the first time, a comparative experimental study on the electrodeposition of aluminium in three different water and air stable ionic liquids, namely 1-butyl-1-methylpyrrolidinium-bis(trifluoromethylsulfonyl)imide ([BMP]Tf2N), 1-ethyl-3-methylimidazolium-bis(trifluoromethylsulfonyl)imide ([EMIm] Tf2N), and trihexyl-tetradecyl-phosphoniumbis(trifluoromethylsulfonyl)imide (P(14,6,6,6) Tf2N). The ionic liquids [BMP]Tf2N and [EMIm]Tf2N show biphasic behaviour in the AlCl3 concentration range from 1.6 to 2.5 mol L(-1) and 2.5 to 5 mol L(-1), respectively. The biphasic mixtures become monophasic at temperatures >/=80 degrees C. It was found that nanocrystalline aluminium can be electrodeposited in the ionic liquid [BMP]Tf2N saturated with AlCl3. The deposits obtained are generally uniform, dense, shining, and adherent with very fine crystallites in the nanometer size regime. However, coarse cubic-shaped aluminium particles in the micrometer range are obtained in the ionic liquid [EMIm]Tf2N. In this liquid the particle size significantly increases as the temperature rises. A very thin, mirrorlike aluminium film containing very fine crystallites of about 20 nm is obtained in the ionic liquid [trihexyl-tetradecyl-phosphonium]Tf(2)N at room temperature. At 150 degrees C, the average grain size is found to be 35 nm.

Electrodeposition of Metals and Semiconductors in Air‐ and Water‐Stable Ionic Liquids

In addition to their stability, the advantages of air- and water-stable ionic liquids over chloroaluminate ionic liquids, which were intensively investigated in the past, are that they are easy to dry, purify, and handle. Moreover, some of these ionic liquids have an extremely large electrochemical window of more than 5 V, and hence they give access to the electrodeposition of many metals and semiconductors, such as Ta, Ti, Si, and Ge. The results to date for the electrodeposition of metals and semiconductors in the most popular air- and water-stable ionic liquids are presented.

Air and water stable ionic liquids in physical chemistry

Ionic liquids are defined today as liquids which solely consist of cations and anions and which by definition must have a melting point of 100 degrees C or below. Originating from electrochemistry in AlCl(3) based liquids an enormous progress was made during the recent 10 years to synthesize ionic liquids that can be handled under ambient conditions, and today about 300 ionic liquids are already commercially available. Whereas the main interest is still focussed on organic and technical chemistry, various aspects of physical chemistry in ionic liquids are discussed now in literature. In this review article we give a short overview on physicochemical aspects of ionic liquids, such as physical properties of ionic liquids, nanoparticles, nanotubes, batteries, spectroscopy, thermodynamics and catalysis of/in ionic liquids. The focus is set on air and water stable ionic liquids as they will presumably dominate various fields of chemistry in future.

High-pressure phase behavior of systems with ionic liquids: measurements and modeling of the binary system fluoroform+1-ethyl-3-methylimidazolium hexafluorophosphate

In order to gain insight into the phase behavior of ionic liquids+supercritical fluids, the phase boundaries of a binary mixture of an air- and water-stable ionic liquid and a supercritical fluid has been studied experimentally. For this purpose, fluoroform (CHF 3) was considered as the supercritical fluid and 1-ethyl-3-methylimidazolium hexafluorophosphate ([emim][PF 6]) was selected as the ionic liquid. A synthetic method was used to measure vapor–liquid and solid–liquid boundaries. Results are reported for CHF 3 concentrations ranging from 10.1 to 99.0 mol%, and within temperature and pressure ranges of 309.3–367.5 K and 1.6–51.6 MPa, respectively. The Peng–Robinson equation of state is used to model this binary system.