Trifluoromethylsulfonyl Amide Research Articles

Pressure-swing absorption and desorption behaviours of ammonia in bis(trifluoromethylsulfonyl)amide salts

The absorption and desorption behaviours of NH3 in bis(trifluoromethylsulfonyl)amide (TFSA) salts were investigated using the pressure-swing method.

(Digital Presentation) ORR Activities on Hydrophobic Phosphonium Ionic Liquid Modified Pt/C Catalysts

PEFCs have been attracted as one of the clean and efficient energy conversion systems. Platinum nanoparticles are commonly used as cathode catalysts in Polymer electrolyte fuel cells (PEFCs) due to their high activity for oxygen reduction reaction (ORR). However, platinum is rare and expensive, therefore it needs to improve the mass activity and durability for widespread fuel cells. Recently, ionic liquids (ILs) have been studied to enhance the ORR activity of platinum catalysts1). We try to improve the catalytic activity of Pt/C catalysts by using Ionic Liquids (ILs). RTILs are salts that melt at temperatures below 100 oC and generally consist of bulky cations and anions. It has been studied in a wide range of fields, including the energy sector because of its highly conductive and nonvolatile. Recently, it has been reported that ILs layer enhance the ORR catalytic activity on Pt surface, due to the suppress the coverage of OHad from water molecules1). However, the correlation between increased ORR activity and the structure of the ionic liquid has not been clarified. In this study, we focused on ILs quaternary phosphonium cations and a bis(trifluoromethylsulfonyl)amide (TFSA) anion. The phosphonium cations based ILs have been reported to have higher thermal stability than imidazolium or ammonium cations2). In addition, the phosphonium ILs show higher electrochemical stability, conductivity, and hydrophobicity than the ammonium ILs. The ORR activity was analyzed using the rotating disk electrode (RDE) method3). Commercially available 20 wt% Pt/C (Cabot, Vulcan XC-72R\U0001f12c) catalyst was used for bare Pt/C modified electrodes. The Pt/C electrodes were modified with phosphonium ILs (PXXXY+TFSA- [alkyl chain X= 4 Y= 1, 12, 16]). The thickness of the ILs layer was calculated by using the BET surface area of carbon supports. The electrochemical measurements were conducted under Ar or O2 saturated conditions, respectively. Electrochemical surface area (ECSA) was estimated from hydrogen adsorption wave in cyclic voltammograms (CVs). Mass activity (MA) and surface area specific activity (SA) of ORR at 0.9 V on Pt nanoparticles were calculated from the Koutecky-Levich equation. The ILs layer enhanced ORR activity. However, ORR activity decreased when the ILs layer was excessively thick. These results suggest that the ORR activity decreases in a thicker ILs layer due to increased resistance to oxygen mass transport or proton conductivity. Moreover, the ORR activity of the ILs modified Pt/C catalyst increased as the asymmetric part alkyl chains of the ILs became longer. Our previous reports show that as the size -is larger, both the molar volume and oxygen solubility increases. Our results show that these physicochemical properties originating from the structure of the cation affect ORR activities.[Reference]1) Gui-Rong Zhang, et al., ACS Catal., 8, 8244-8254 (2018).2) K. Tsunashima and M. Sugiya, Electrochem. Commun., 9, 2353, (2007).3) H. A. Gasteiger, S. S. Kocha, B. Sompalli, F. T. Wagner, Appl. Catal. B Environ. 56, 9. (2005).

Effect of β-Cyclodextrin on Physicochemical Properties of an Ionic Liquid Electrolyte Composed of N-Methyl-N-Propylpyrrolidinium bis(trifluoromethylsulfonyl)amide.

Ionic liquids (ILs) are promising electrolyte materials for developing next-generation rechargeable batteries. In order to improve their properties, several kinds of additives have been investigated. In this study, β-cyclodextrin (β-CD) was chosen as a new additive in IL electrolytes because it can form an inclusion complex with bis(trifluoromethylsulfonyl)amide (TFSA) anions. We prepared the composites by mixing N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)amide/LiTFSA and a given amount of triacetyl-β-cyclodextrin (Acβ-CD). The thermal behaviors and electrochemical properties of the composites were analyzed by several techniques. In addition, pulse field gradient NMR measurements were conducted to determine the self-diffusion coefficients of the component ions. The addition of Acβ-CD to the IL electrolytes results in the decrease in the conductivity value and the increase in the viscosity value. In contrast, the addition of Acβ-CD to the IL electrolytes induced an improvement in the anodic stability because of the formation of an inclusion complex between the Acβ-CD and TFSA anions. CDs are potential candidates as additives in IL electrolytes for electrochemical applications.

Anion amphiprotic ionic liquids as protic electrolyte matrices allowing sodium metal plating.

The sodium-ion battery (SIB) is proposed as a complementary technology to today's commercially dominant lithium-ion battery (LIB). While much know-how can be transferred from LIBs to SIBs, adjustments are still necessary, not the least for the electrolytes employed. Here the use of anion amphiprotic ionic liquid (AAIL) based electrolytes is proposed for SIB application. Two different AAILs, based on organic trifluoromethylsulfonylamide (TFSAm) and inorganic HSO4- anions, respectively, doped with NaTFSI salt have been studied, focusing on electrochemical stability and transport properties, complemented by studies of the ion-ion interactions, and final sodium-ion battery performance via stripping/plating vs. sodium metal electrodes.

Physical and Electrochemical Properties of Ionic Liquids Based on Quaternary Phosphonium Cations and Carboxylate Anions As Electrolytes

Ionic liquids (ILs) have been developed for a wide variety of electrochemical applications due to their unique physicochemical properties such as favorable solubility of organic and inorganic compounds, relatively high ionic conductivity, no measurable vapor pressure, high thermal stability, low flammability, etc. Another advantage of ILs is a designability of the ion structures. Although many kinds of ILs have been already investigated, phosphonium-based ILs have rarely been proposed. We have previously designed and synthesized the phosphonium ILs together with typical anion species such as bis(trifluoromethylsulfonyl)amide (TFSA) and bis(fluorosulfornyl)amide (FSA) anions.1,2 On the other hand, interests in ILs consisting of carboxylic acid based anions have been increasing in recent years. In this work, we synthesize the ILs based on quaternary phosphonium cations (tetraethylphosphonium, P2222 +, and tetrabutylphosphonium, P4444 +) in combination with carboxylate anions such as formate (HCO2 -), acetate (MeCO2 -) and propionate (EtCO2 -), characterizing the physicochemical and electrochemical properties of the ILs as a new family of IL-based electrolyte.The preparation of the phosphonium ILs was carried out by neutralization reactions of the precursor phosphonium hydroxides with the carboxylic acids. The obtained ILs were dried under high vacuum for at least 10 h at 60◦C. We also prepared the corresponding ammonium salts by the same procedure for comparison. The physicochemical and electrochemical properties such as conductivity (ac impedance method), viscosity (a cone-plate type viscometer), density, melting point (DSC), thermal decomposition temperature (TGA) and electrochemical window (linear sweep voltammetry using a conventional three-electrode cell) were measured under dry argon atmosphere. Table 1 summarizes the physicochemical properties of the ILs obtained in this work. The almost compounds were low-melting white solids; however only P4444-HCO2 became a liquid at ambient temperature. The conductivity and viscosity of P4444-HCO2 depended on temperature, showing the Arrhenius-type convex curve behaviors. This means a typical electrolyte behavior generally observed in IL media. P4444-HCO2 showed the lowest viscosity and highest conductivity in the three P4444-based phosphonium salts, which might be attributed to the anion sizes of the three phosphonium salts. It should be noted that the thermal decomposition temperatures of the phosphonium salts were much higher than those of the corresponding ammonium salts, revealing the high thermal stability of the carboxylic anion based phosphonium ILs (Fig. 1). In the electrochemical measurements, it was found that P4444-HCO2 had a high cathodic stability similar to those of the TFSA- and FSA-anion based phosphonium ILs. On the other hand, relatively low anodic potential window up to 0.7 V vs. Ag/Ag+ was observed, which seems likely to be due to the anodic oxidation of formate anion.

Removal of Iron and Boron by Solvent Extraction with Ionic Liquids and Recovery of Neodymium Metal by Direct Electrodeposition

ABSTRACTIn this study, the mechanism of Fe3+ ion extraction was investigated in the tri-n-butyl phosphate (TBP)/triethyl-pentyl-phosphonium (P2225) bis(trifluoromethyl-sulfonyl)amide (TFSA) system. According to the performed analysis, the Fe3+ extraction is based on cation exchange with ionic liquids:Moreover, the removal of Fe and B by continuous extraction was investigated. It was determined that nine extraction cycles led to the removal of all B and most of the Fe and increased the concentration of rare earth ions in the organic phase by a factor of 2.2.The electrochemical behavior of the extracted [Fe(III)(TBP)3(TFSA)3] complex was investigated at 373 K, and two reduction steps were detected:Based on these results, potentiostatic electrodeposition from an electrolytic bath was carried out at −1.75 V at 373 K after the ninth cycle of continuous extraction. Electrodeposits with 0.8–0.9 μm diameter were recovered on the Cu substrate, and metallic Fe in these deposits was identified by their energy dispersive X-ray spectrometry (EDX) spectra. Finally, the effectiveness of solvent extraction and direct electrodeposition in the recovery process was demonstrated in this study.

Extraction of Pr(III), Nd(III), and Dy(III) from HTFSA Aqueous Solution by TODGA/Phosphonium-Based Ionic Liquids

ABSTRACTThe extraction behavior of rare earth (RE) elements using N,N,N′,N′-tetraoctyl diglycolamide (TODGA) in an ionic liquid (IL) system was investigated by slope analyses. Metallic salts of Pr(III), Nd(III), and Dy(III) with bis(trifluoromethylsulfonyl)amide (TFSA) were synthesized and studied for their extraction mechanism. The selected concentration of TODGA was diluted with triethylpentylphosphonium bis(trifluoromethylsulfonyl)amide ([P2225][TFSA]) to prepare an extracting phase for the slope analyses. The stoichiometry of RE(III) was determined in order to estimate the extracted species. Furthermore, the complexation state of the extracted species was evaluated by spectroscopic analyses, including Fourier-transform infrared (FT-IR) spectroscopy, Raman spectroscopy, and ultraviolet–visible (UV–Vis) spectroscopy. The FT-IR and Raman spectra were estimated using density functional theory (DFT) calculations. Thorough analysis of the FT-IR spectrum was carried out in order to assign the TODGA group that mainly coordinated the metal ion. The solvation of the [TFSA]− anion in the coordination sphere of [Nd(TODGA)(2–3)]3+ was investigated by Raman spectroscopic analysis. The coordination ability of TODGA was investigated from the peak shift of the hypersensitive transition (4I9/2→2G7/2) in UV–Vis spectroscopic measurements. From electrochemical analysis, the extracted [Nd(TODGA)3]3+ complex in [P2225][TFSA] was found to be reduced as per the following reaction: [Nd(TODGA)3]3+ + 3e− → Nd(0) + 3[TODGA] at −3.0 V, and the diffusion coefficient of [Nd(TODGA)3]3+ was calculated to be 1.6 × 10−11 m2 s−1 at 373 K. The direct electrodeposition of the extracted [Nd(TODGA)3]3+ in [P2225][TFSA] at 373 K allowed us to conclude that the middle layer of Nd electrodeposits was the metallic state, while a part of the top surface was the oxidation state by XPS analysis.

Electrochemical Behavior of Magnesium Alloys in Alkali Metal-TFSA Ionic Liquid for Magnesium-Battery Negative Electrode

An investigation was made on the reduction of the passivation of Mg negative electrode in an intermediate temperature ionic liquid, alkali metal bis(trifluoromethylsulfonyl)amide (TFSA) mixture to facilitate anodic dissolution of magnesium. The anodic dissolution of pure Mg metal electrode proceeded at substantially high potential above 2.0 V vs. Li+/Lio due to passivation of the Mg surface with large hysteresis behavior in the cyclic voltammetry. In order to suppress/retard passivation of the electrode surface, several Mg alloys (ACM522, Mg-5 wt%Li, and Mg2Sn/Sn) were examined as the negative electrode materials. The magnesium dissolution from ACM522 including Al, Ca, and misch metals as additive elements occurred at a higher electrode potential than that from the pure Mg metal. These metal additives seem to facilitate the formation of a corrosion-resistant surface layer, which is inadequate for the anodic dissolution of magnesium. The anodic-dissolution potential of magnesium in the Mg2Sn/Sn electrode was 1.5 V vs. Li+/Lio, which showed the lowest potential of that in the other Mg-alloy electrodes. Owing to the redox potential of pure Sn element higher than 1.5 V vs. Li+/Lio in the alkali metal-TFSA ionic liquid, Sn is electrochemically stable in the electrolyte and solely worked as the element lowering the Mg activity in the Mg-alloy electrode. Thus, lowing of Mg activity is effective on the retardation of the electrode passivation.

Study of alkyl chain length dependent characteristics of imidazolium based ionic liquids [CnMIM]+[TFSA]− by Brillouin and dielectric loss spectroscopy

This study examined the acoustic phonon mode of ionic liquids consisting of 1-alkyl-3-methyl-imidazolium family (CnMIM) cations with n values ranging from 2 to 10 and bis(trifluoromethylsulfonyl)amide (TFSA) anion in the temperature range from 300 K to 100 K. [CnMIM]+[TFSA]− showed depolarized (VH) components of Brillouin peaks at temperatures below the glass transition temperature when n is larger than 4. On the other hand, in the case of ionic liquids with different anions, such as [C4MIM]+[BF4]−, [C4MIM]+[PF6]− and [C8MIM]+[BF4]−, the VH component of Brillouin peaks was not observed in the temperature range investigated. The dielectric loss spectra showed that the temperature dependence of alkyl chain domain relaxation of all ionic liquids followed the Arrhenius law and showed an increase in activation energy at the temperature where the VH component of Brillouin peak appeared. These results suggest that the observed depolarized component of Brillouin peak might originate from uniquely induced polarization in the 2nd domain composed of head groups of cations and anions.

Controlled self-assembly of amphiphiles in ionic liquids and the formation of ionogels by molecular tuning of cohesive energies

In this paper, the self-assembling characteristics of a series of L-glutamate-based ammonium amphiphiles are studied in ionic liquids (ILs). These cationic amphiphiles are dispersible in imidazolium ILs with bis((trifluoromethyl)sulfonyl)amide (TFSA) anion. Amphiphiles-containing didodecyl ester or short dioctyl amide groups were molecularly dispersed in conventional 1-butyl-3-methylimidazolium TFSA, whereas they formed bilayer membranes when they were dispersed in polar, ether linkage-introduced IL. Thus, the modification of ILs exerts a crucial influence on amphiphilic self-assembly. Enhancement of the intermolecular interactions of L-glutamate amphiphiles is achieved by introducing multiple amide bonds and longer alkyl chains, which leads to better self-assembling properties. These amide-enriched amphiphiles form fibrous bilayer assemblies even in conventional ILs with low cohesive energy densities. These observations confirm that the formation of bilayer membranes in ILs is a general phenomenon when the solute molecules have the appropriate ‘ionophilic/ionophobic’ nature. Molecular self-assembly in IL is promoted by controlling cohesive energies of amphiphiles and ILs.

Evidence for an influence of anodic decomposition products of ionic liquids on the electrodeposition of Si xGe 1 − x semiconductor

For the purpose of obtaining micrometer thick Si xGe 1 − x deposits, quite a long electrodeposition time was applied in ionic liquids containing GeCl 4 and SiCl 4. Surprisingly, it was observed that the deposit is dissolved with ongoing time, at room temperature, instead of getting thicker at a sufficiently negative electrode potential. The dissolution process was only observed in liquids with the bis(trifluoromethylsulfonyl)amide (TFSA) anion and not in liquids with the tris(pentafluoroethyl)trifluorophosphate (FAP) anion. Electrochemical and chemical experiments showed that the TFSA anion is subject to an anodic decomposition obviously promoted by the solutes SiCl 4 and GeCl 4. The decomposition products of the TFSA anion seem to oxidize the Si xGe 1 − x deposit chemically. These results, among others, show that the often reported superior chemical and electrochemical stability of some ionic liquids has to be handled with care: the stability limits can be significantly altered by e.g. the type of dissolved species.

Thermal properties of alkyloctamethylferrocenium salts with TFSA and TCNE (TFSA = bis(trifluoromethylsulfonyl)amide and TCNE = tetracyanoethylene)

Butyl- and hexyloctamethylferrocenium salts with bis(trifluoromethylsulfonyl)amide (TFSA) and tetracyanoethylene (TCNE) were prepared, and their thermal properties were investigated by differential scanning calorimetry (DSC) measurements. The TFSA salts were ionic liquids with melting points of 34.4°C and 27.7°C, respectively. The TCNE salts were prepared by annealing the mixture of alkyloctamethylferrocene and TCNE. These salts exhibited high melting points of 100.2°C and 80.9°C, respectively; they were thermally unstable at higher temperatures. A butyloctamethylferrocenium salt with PCNP (pentacyanopropenide), obtained by a reaction with TCNE under ambient conditions, was crystallographically characterized. The structure was severely disordered, consisting of alternately stacked cations and anions.

Unexpected decomposition of the bis (trifluoromethylsulfonyl) amide anion during electrochemical copper oxidation in an ionic liquid

In this letter we report on the decomposition of the bis (trifluoromethylsulfonyl) amide (TFSA) anion under quite mild electrochemical conditions. The results show clearly that the TFSA anion can easily be decomposed during anodic oxidation of copper in the ionic liquid 1-butyl-1-methylpyrrolidinium bis (trifluoromethylsulfonyl) amide [BMP] TFSA at 70 °C leading to the formation of CuF 2. At room temperature, however, no significant decomposition was obtained. Therefore, one has to be very careful in applying ionic liquids based on TFSA anions under anodic conditions at elevated temperature as the TFSA anion might decompose, depending on the anode material.

Surface Structural Study on Ionic Liquids Using Metastable Atom Electron Spectroscopy

The surface structures of ionic liquids 1-CnH2n+1-3-methylimidazolium tetrafluoroborate (BF4−), trifluoromethanesulfonate (OTf) and bis(trifluoromethylsulfonyl)amide (TFSA) with n = 4, 8, and 10 were investigated by ultraviolet photoemission spectroscopy (UPS) and metastable atom electron spectroscopy (MAES). The MAES spectra reveal that the anions and cations share the surface of the room-temperature ionic liquids (RTILs) with a shorter alkyl chain at n = 4 although the alkyl chain layer tends to cover the outermost surface in the case of RTILs with longer alkyl chains of n = 8 and 10. Comparison of UPS and MAES spectra demonstrates that the nonpolar groups such as the alkyl chain and the CF3 group point toward the vacuum side, while the polar groups such as the SO3 and SO2 groups face toward the bulk side. A double-layered structure at the surface, which consists of an alkyl chain layer and a polar layer containing anions and imidazolium rings, is proposed from these observations.

Über Phosphazene XXXVII

Sodium sulfonyl and phosphoryl amides together with dimethylchlorophosphine yielded PH-phosphine imines 4 instead of NH-aminophosphines 3. Sodium trifluoromethylsulfonyl amide did so even with diphenylchlorophosphine. In a second step biphosphine monoimines were formed in all cases. The dependency of δ31P, JPH and JPP is discussed.