Synthesis, characterization and electrochemistry of triethyl ammonium sulphate ionic liquid

Abstract

Protic ionic liquids (PILs) being intrinsic proton conducting ionic species are considered as potential green electrolytes for study of electrocatalytic reactions and for fabrication of IL-based fuel cells (FCs) and batteries. We have prepared a sulfate anion based protic ionic liquid (PIL), triethylammonium sulfate (TEAS) through a reaction involving transfer of proton from H2SO4 to triethylamine (TEA). 1H NMR and FT-IR spectroscopic techniques were employed for confirmation of the synthesis of TEAS and water content of the PIL was quantified using coulometric Karl–Fischer (KF) titration. 1H NMR and FT-IR analysis confirm the synthesis of the PILs and KF-titration analysis shows that TEAS contains 1.43 w/w % water. Electrical conductivity of TEAS was determined at different temperatures showing that the PIL has excellent ionic conductivity that enhances with rise in temperature of the medium. The temperature dependence of the conductivity of the PIL follows the Arrhenius equation as the logσ versus 1/T plot is linear. The electrochemical windows (EWs) of the electrolyte were found using cyclic voltammetry at Pt and Au working electrodes and found to decrease with increase in temperature of the medium. The data revealed that the surfaces of the electrodes are covered with oxide layers due to oxidation of trace water (1.43 w/w %) present in the PIL. The oxide layers growth increase and their onset potential moves to less positive values as the temperature of the PILs is increased. The data was compared with the literature and would be helpful in understanding of the surface electrochemistry in this neoteric medium for being used as potential electrolyte in industry for various electrochemical applications.

Assessment of The Hygroscopic Behaviour of Proton-Conducting Ionic Liquids: Kinetics, Conductivity and Electrochemical Analysis

“…The high water contents in the PCILs may partly result from the water content present in the precursor reagents as TEA and TEOA were 99% pure, and H 2 SO 4 , H 3 PO 4 , and HNO 3 were 95%-98%, 85%, and 60% pure, respectively or they may absorb moisture from the atmosphere during synthesis process. 8 Each of the PCIL samples was then exposed for different time intervals (24,48, and 72 h) to air under the ambient laboratory conditions as mentioned and a plot of % water absorbed vs different time intervals is plotted and shown in Fig. 2.…”

“…triethanolamine, TEOA, and triethylamine, TEA with the appropriate acids i.e. H 2 SO 4 , H 3 PO 4 , and HNO 3 , 3,8,12,21,22 shown in the reaction schemes. For the synthesis of the PCILs, the bases were measured into a threenecked round bottom flask placed in an ice bath.…”

“…These are attributed to the formation of an oxide layer on the surface of Pt (PtOH/PtO/PtO 2 ) due to trace water oxidation in the protic ionic liquid electrolytes and the thickness of the oxide layers increases with the increase of positive potential limit. 3,4,8 To elucidate the effect of the positive potential limit on the formation of the surface Pt-oxides, CVs were recorded in TEADHP as shown in Fig. 6, in which the starting potential was kept constant at 0.2 V. The positive potential limit was gradually changed from 1.7 V to 2.5 V, however, the data are shown only in the potential range between 0.2 V and 1.7 V in Fig.…”

“…Both PCILs and APILs are favorable for electrochemical applications due to their electrochemical stability. 8 ILs are regarded as "designer solvents" because specific anions and cations can be used to tailor their polarity, viscosity, and other physicochemical properties [9][10][11] and are becoming increasingly popular as adaptable solvents due to these unique physicochemical properties compared to conventional volatile organic solvents. Therefore, they are enabling advancements in a variety of fields, including energy storage, separations, and bioprocessing, electrochemical sensors.…”