Protic ionic liquid and ionic melts prepared from methanesulfonic acid and 1H-1,2,4-triazole as high temperature PEMFC electrolytes

Abstract

Protic ionic liquid and ionic melts were prepared from the combination of methanesulfonic acid (CH 3 SO 3 H) and 1H-1,2,4-triazole (C 2 H 3 N 3) at various molar ratios. The thermal properties, crystal structure, acid-base interactions, ionic conductivity, proton conduction behavior and electrochemical stability of the system were studied. The equimolar composition, 1,2,4-triazolium methanesulfonate (C 2 H 4 N 3 + $CH 3 SO 3 À (1)), was a proton transfer salt with a melting point of around 134 C. Single crystal and powder XRD data, as well as TGA results, revealed that the base-rich region was a mixture of 1 and 1H-1,2,4-triazole. Infrared analysis and single crystal data suggested that the C 2 H 3 N 3-CH 3 SO 3 H system exists in a strongly hydrogen-bonded network. Systematic investigation of the ionic conductivity showed that the ionic conductivity reached local maxima at the compositions of [C 2 H 3 N 3 ]/[CH 3 SO 3 H] ¼ 10/90 and 80/20, respectively, while it exhibited a local minimum at the equimolar composition. The temperature dependence of the ionic conductivity was found to obey the Vogel-Fulcher-Tamman (VFT) equation. The fitting of the conductivity data to the VFT equation showed that the carrier ion concentration versus the mole fraction of 1H-1,2,4-triazole exhibited a volcano shape. In addition, the C 2 H 3 N 3-CH 3 SO 3 H system showed adequate electrochemical stability under PEMFC conditions as measured by linear sweep voltammetry. The relatively high ionic conductivity, wide electrochemical window and good thermal stability demonstrated that the C 2 H 3 N 3-CH 3 SO 3 H system is a suitable candidate for high temperature PEMFC electrolytes.

Improving the Conductivity of Sulfonated Polyimides as Proton Exchange Membranes by Doping of a Protic Ionic Liquid

“…SPI/IL composite membranes exhibited two sharp absorption peaks at 1023 and 1086 cm −1 , which were due to the aromatic -SO3H symmetric and asymmetric stretching vibrations of SPI, respectively, and characteristic aromatic C-H stretching of the imidazolium cation near 3165 cm −1 [28]. The absorption at 1547 cm −1 was attributed to cationic C=N in ionic liquid [24]; while a peak at 1660 cm [29]. The FTIR spectra shown in Figure 3 further indicated the formation of SPI/IL composite membranes.…”

“…ILs are molten salts that have attracted much attention in recent years because of their exceptional properties, including high ionic conductivity, a wide liquid temperature range, high thermal and chemical stability, low vapor pressure and high polarity [24,25]. PILs have even higher ionic conductivity than common ILs (which are usually aprotic), and most importantly, PILs are desired due to their intrinsic proton conductivity.…”

“…PILs have even higher ionic conductivity than common ILs (which are usually aprotic), and most importantly, PILs are desired due to their intrinsic proton conductivity. Aprotic ILs usually have no proton conductivity unless they are Brønsted acidic [24]. PILs can be tuned by varying the combination of various cations and anions.…”

Ionic association and conductance of ionic liquids in dichloromethane at temperatures from 278.15 to 303.15 K

“…The transport properties of the mixtures of ionic liquids (conductance, viscosity, and transference numbers) are important because the values provide useful and sensitive information about ion-solvent interaction, ionic association, and solvent structure. A survey of literature indicates that most studies report only the specific conductivity data for pure ionic liquids or binary and ternary mixtures of ILs with various solvents at 298.15 K. The conductance studies of dilute solutions of ionic liquids in a wide temperature range allow the determination of the values of association constants and thermodynamic functions of association, which consequently allows the better understanding of the behavior of ILs in various solvents [1][2][3]. This paper is both a continuation and an extension of our and other authors' works on association of imidazolium-based ionic liquids, i.e., [ 4 ] in water [4], 1-propanol [5], N,N-dimethylformamide [6], acetonitrile [7,8], dimethylsulfoxide [9], and methanol [9,10].…”

Current Developments in the Syntheses of 1,2,4-Triazole Compounds

“…In chemical aspects, as corrosion inhibitors, triazole-derived compounds may easily form -coordination bonds with various metal ions to inhibit the corrosion of metals [20,21]; as light stabilizers, triazole derivatives with low volatility and high thermostability have been widespreadly applied in paints, food packages as well as sunscreen agents [11]. As a new type of ionic liquids (ILs), triazoles have exhibited conspicuous advantages with nonvolatile, wide applicable temperatures and environmentally friendly properties [22,23]. In supramolecular chemistry, the specific 1,2,4-triazole ring as good building block has been frequently employed to construct various artificial cation, anion and molecular receptors [3,24], enzyme models and supramolecular catalysts [25,26] as well as nanometer materials [3,27], especially in supramolecular recognization, assembly [28,29] and in the development of supramolecular drugs [30][31][32].…”