Utilization of 1-butylpyrrolidinium Chloride Ionic Liquid as an Eco-friendly Corrosion Inhibitor and Biocide for Oilfield Equipment: Combined Weight Loss, Electrochemical and SEM Studies

With the help of the weight loss, and electrochemical techniques the suppressing action of the commercially available ionic liquid, 1-butylpyrrolidinium chloride [BPm1,1] Cl for carbon steel corrosion in 3.5% NaCl medium was scrutinized. It found that this compound acts as an excellent inhibitor with protection performance raised by an increase of its concentration and temperature. The adsorption behavior of the investigated ionic liquid was a mixed-type inhibitor subordinating Langmuir adsorption isotherm. To expounding adsorption and corrosion inhibition mechanisms, various thermodynamics and activation parameters such as adsorption constant (Kads), Gibb’s standard free energy ( Δ G ∗ $\Delta{{\text{G}}^{\ast}}$ ), activation energy (Ea), activation enthalpy ( Δ H ∗ $\Delta{{\text{H}}^{\ast}}$ ), and activation entropy ( Δ S ∗ $\Delta{{\text{S}}^{\ast}}$ ) were determined and debated. It has appeared that there is a strong interaction between the inhibitor molecules and the carbon steel surface in a predominantly chemisorptions manner. The presence of a protective inhibitor film on the metal surface was confirmed using a corroborative SEM tool. Moreover, the IL has screened for antibacterial activity against planktonic and sessile microorganisms. The obtained results emphasized that the utilized ionic liquid can be regarded as an efficacious biocide for both bacterial strains with a dissimilar efficiency.

Sonochemical Synthesis of Nanostructured ZnO/Ag Composites in an Ionic Liquid

In the present paper we show that nanocrystalline ZnO/Ag composites can be obtained via an ultrasonic-assisted approach in the ionic liquid 1-ethyl-3-methylimidazolium trifluoromethylsulfonate. Different techniques including, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and ultraviolet-visible spectroscopy (UV-vis) were utilized to characterize the synthesized materials. The XRD results revealed the formation of ZnO wurtzite structure along with metallic Ag in the ZnO/Ag composite. The particle size was estimated from the XRD results to be about 35 nm. The UV spectrum of ZnO/Ag showed the characteristic absorption band of wurtzite crystal structure of ZnO, and the presence of Ag in the ZnO/Ag composite led to a slight red shift. The employed ionic liquid acts as a template leading to the formation of nanoparticles of ZnO and of ZnO/Ag.

Corrosion Inhibition of Cast Iron in Arabian Gulf Seawater by Two Different Ionic Liquids

In this paper we report on the corrosion inhibition of cast iron in Arabian Gulf seawater by two different ionic liquids namely, 1-ethyl-3-methylimidazolium chloride ([EMIm]Cl) and 1-butyl-1-methylpyrrolidinium chloride ([Py1,4]Cl). The inhibiting influence of the employed ionic liquids was investigated by weight loss, open circuit potential electrochemical impedance spectroscopy, and cyclic potentiodynamic polarization. The results show the corrosion inhibition impact of the employed ionic liquids (ILs). Compared with [Py1,4]Cl, [EMIm]Cl shows a higher inhibition efficiency at a short immersion time, for the examined ILs concentrations. However, [Py1,4]Cl exhibits a higher efficiency upon increasing the immersion time indicating the persistence of the inhibiting influence. The corrosion inhibition of the employed ionic liquids is attributed to the adsorption of the cations of the ionic liquids onto the surface of cast iron forming a corrosion barrier.

Electrochemical and spectroscopic study of Zn(ii) coordination and Zn electrodeposition in three ionic liquids with the trifluoromethylsulfonate anion, different imidazolium ions and their mixtures with water

In this paper we report on the use of three ionic liquids, [MIm]TfO, [EMIm]TfO and [EMMIm]TfO containing Zn(TfO)₂ and their mixtures with water as electrolytes for zinc electrodeposition.

Effect of dissolved LiCl on the ionic liquid-Au(111) interface: an in situ STM study

The structure of the electrolyte/electrode interface plays a significant role in electrochemical processes. To date, most studies are focusing on understanding the interfacial structure in pure ionic liquids. In this paper in situ scanning tunnelling microscopy (STM) has been employed to elucidate the structure of the charged Au(111)-ionic liquid (1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate, [Py1,4]FAP) interface in the presence of 0.1 M LiCl. The addition of the Li salt to the ionic liquid has a strong influence on the interfacial structure. In the first STM scan in situ measurements reveal that Au(111) undergoes the (22 x √3) 'herringbone' reconstruction in a certain potential regime, and there is strong evidence that the gold surface dissolves at negative electrode potentials in [Py1,4]FAP containing LiCl. Bulk deposition of Li is obtained at -2.9 V in the second STM scan.

Synthesis of Silicon and Germanium Nanowire Assemblies by Template-Assisted Electrodeposition from an Ionic Liquid

We report on the template-assisted synthesis of silicon and germanium nanowires from the air- and water-stable ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide ([Py1,4] TFSA). The synthesis was done by electrochemical deposition in the pores of a commercial track-etched polycarbonate membrane. After chemical dissolution of the polycarbonate membrane in dichloromethane, nanowire assemblies with a regular arrangement were obtained. Different lengths of nanowires can be obtained by varying the applied potential and the time of deposition. The nanowire assemblies were characterised by scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDX). Our results show that the template-assisted electrochemical deposition approach in ionic liquids has the potential to easily synthesise germanium and silicon nanowire assemblies.

The interface ionic liquid(s)/electrode(s): in situ STM and AFM measurements

The structure of the interfacial layer(s) between the extremely pure air- and water-stable ionic liquid 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl) trifluorophosphate and Au(111) has been investigated using in situ scanning tunneling microscopy (STM) at electrode potentials more positive than the open circuit potential. The in situ STM measurements show that layers/islands form with increasing electrode potential. According to recently published atomic force microscopy (AFM) data the anion is adsorbed even at low anodic overvoltages and adsorption becomes slightly stronger with increasing electrode potential. Furthermore, the number of interfacial layers increases with increasing electrode potential. The present discussion paper shows that these layers are not uniform and have a structure on the nanoscale, supporting earlier results that the interface electrode/ionic liquid is highly complex. It is also shown that the addition of solutes changes this structure considerably. AFM results reveal that in the pure liquid, interfacial layers lead to a repulsive force but the addition of 10 wt% of LiCl leads to an attractive force close to the surface. These preliminary results show that solutes strongly alter the interfacial structure of the ionic liquid/ electrode interface.

Electrodeposition of Lithium in Polystyrene Sphere Opal Structures on Copper from an Ionic Liquid

In this paper we report on the electrodeposition of lithium on a polystyrene sphere modified electrode from an ionic liquid. By a simple dipping process, polystyrene (PS) spheres with an average diameter of 600 nm arrange in a hexagonal close packed structure onto an electrode surface. Surprisingly, lithium does not grow uniformly from the electrode surface to the electrolyte within the voids of the PS structure. Depending on the experimental conditions a more or less good inverse opal structure made of lithium, lithium spheres or hollow lithium half-spheres can be obtained showing that the growth of lithium in the employed ionic liquid is more complicated than expected. Somehow lithium tends to push away the PS spheres during growth. Applying a slight mechanical pressure on the PS spheres during deposition improves the growth within the voids of the opal structure. Despite this complicated behaviour the PS opal structure seems to suppress a vertical dendritic growth, thus, a lithium/PS composite electrode or other lithium/polymer composite electrodes might be of some interest in rechargeable lithium metal microbatteries where a dendritic vertical growth has to be avoided.

Aluminium Nanowire Electrodes for Lithium-Ion Batteries

In this paper, we report on the fabrication of mechanically stable aluminium nanowire electrodes for application in lithium-ion batteries. The electrochemical synthesis of the nanowire electrodes was performed in the chloroaluminate ionic liquid 1-ethyl-3-methylimidazolium chloride [EMIm]Cl/AlCl3 (40:60 mol %) using polycarbonate templates. The fabricated nanowire electrodes exhibit high mechanical stability after 50 cycles of lithium deposition/stripping without significant disintegration of the nanowire structure. The mechanical stability and strong adhesion of the Al-nanowires with the electrodeposited Al-electrode can lead to long cycling life. The fabricated Al-nanowire electrodes deliver a capacity of 790 mAh g–1 at 1C-rate.

In Situ Scanning Tunnelling Microscopy in Ionic Liquids: Prospects and Challenges

In this paper devoted to Professor Dieter Kolb's 65th birthday the prospects and challenges of ionic liquids for fundamental investigations at the interface electrode/electrolyte are discussed. Ionic liquids consist solely of mainly organic cations and anions and they have wide electrochemical windows of up to 6 V (approximately ± 3 V vs. NHE) combined with wide thermal windows of up to 300ºC and extremely low vapour pressures between 10-11 and 10-10 mbar around room temperature. Thus, thermodynamically they give access to many elements and compounds at variable temperature which due to their reactivity cannot be electrodeposited in aqueous solutions. Apart from a discussion of electrochemical windows examples to be covered in this paper are the local probe deposition of silicon, aluminium and tantalum on Au(111). There is an incredibly high number of possible liquids (between 1012 and 1018 liquids, binary and ternary mixtures have been predicted) but also one major challenge for fundamental physicochemical studies, especially with the in situ STM: purity. It is tough to purify ionic liquids as hitherto they can neither be distilled with considerable rates without decomposition nor recrystallized nor sublimed. It will be shortly discussed that even apparently ultrapure ionic liquids can contain low amounts of inorganic impurities leading to inexpected behaviour on the single crystalline surface of Au(111). Due to their importance this paper focuses soleley on the third generation of ionic liquids, i.e. air and water stable ones.

Surface Analysis of Nanoscale Aluminium and Silicon Films Made by Electrodeposition in Ionic Liquids

We present a spectroscopic and microscopic study of nanoscale Al and Si films electrodeposited in water- and air-stable ionic liquids. The choice of cations for such ionic liquids has previously been shown to have a significant effect on the crystallite size of electrodeposited Al or Si films. We found that the deposits are generally uniform, dense, metallic bright, and adherent with crystallite sizes in the nanometer range. The nanocrystalline films were characterized using X-ray Photoelectron Spectroscopy (XPS) and High-Resolution Scanning Electron Microscopy (HRSEM). The XPS results show that the surface of both films is oxidized although the deposition was done in an inert gas glove box. Furthermore our results suggest that as a consequence of oxygen attack the nanoparticles are composed of a metallic core surrounded by a thin oxidic shell. Our XPS study also shows that neither the cation nor the anion of the ionic liquid is entrapped in the deposit. Thus, electrodeposition in ionic liquids delivers pure materials.

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.

Ionic liquids: the link to high-temperature molten salts?

Due to their wide thermal windows, ionic liquids can be regarded as the missing link between aqueous/organic solutions and high-temperature molten salts. They can be employed efficiently for the coating of other metals with thin layers of tantalum, aluminum, and presumably many others at reasonable temperatures by electrochemical means. The development of ionic liquids, especially air and water stable ones, has opened the door for the electrodeposition of reactive elements such as, for example, Al, Ta, and Si, which in the past were only accessible using high-temperature molten salts or, in part, organic solvents.

AFM-Assisted Investigation of the Corrosion Behaviour of Magnesium and AZ91 Alloys in an Ionic Liquid with Varying Water Content

Atomic force microscopy (AFM)-assisted corrosion measurements of poly- and microcrystalline magnesium, of AZ91D magnesium alloys, and of AZ91D alloys with defined amounts of metallic impurities (Cu, Ni, and Si) in the ionic liquid 1-butyl-3-methylimidazolium trifluoromethylsulfonate with variable water contents is reported. Whereas both magnesium and the AZ91 alloys show a tremendous corrosion in aqueous solutions, they are practically inert in the water-free ionic liquid. The apparent electrochemical window of the water-free ionic liquid on magnesium and its alloys can reach values of 10 V and more. The low corrosion rate of AZ91 alloys with metallic impurities, in any case, follows the trend in aqueous solutions: in comparison to the base alloy, the addition of nickel and silicon leads to higher corrosion rates. Upon addition of water to the ionic liquid two effects are observed. The higher the water content in the ionic liquid, the lower the corrosion potential and the higher the corrosion rate. Poly- and microcrystalline magnesium shows a surprisingly complicated corrosion behaviour, which gives rise to different processes during electrochemical polarization. As a proof-of-principle, in-situ AFM measurements were performed on the corrosion of AZ91D alloy in the ionic liquid. No corrosion products are observed at the surface in the water-free ionic liquid by in-situ AFM, even after several hours at +3 V versus a saturated calomel electrode (SCE), which indicates surface passivation in the ionic liquid.

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.