Study On Preparation And Characterization Of Ionic Liquids And Their Electrochemistry

Room-temperature ionic liquids or room temperature molten salts are organic salts composed of cations and anions, which are liquid state at a room temperature or near the room temperature. The ionic liquid is the perfect substitute of conventional solvents owing to its wide electrochemical widow, low melting point, neglectable vapor tension and special solubility. The ionic liquids have been widely used in many fields such as organic synthesis,catalyst and separation, electrochemistry and so on.In this paper, the hydrophobic ionic liquids N-butyl-N'-methylimidazoliumhexa- fluorophosphate([bmim]PF₆),N-hexyl-N'-methylimidazoliumhexafluorophosphate ([hmim]PF₆),N-Octyl-N'-methylimidazoliumhexafluorophosphate([omim]PF₆),N-Decyl-N'-methylimidazoliumhexafluorophosphate([Demim]PF₆) were prepared with conventional two-step method. And thire products were characterized by 1HNMR and infrared spectrum. Then the electrochemical widows, the density and the conductivity of these ionic liquids have been determined.The electrochemical behavior of FeCl3 in the five ionic liquids (including hydrophilic and hydrophobic ionic liquid) was studied using cyclic voltammetry measurement. This paper also discussed the effect of the cation and the anion of ionic liquid on the electrochemical behavior of FeCl3. The results indicate that the reduction of Fe3+ was a reversible process and was controlled by diffusion of FeCl3 in ionic liquids. The structure of the cation and the anion of ionic liquid have affect the electrochemical behavior of Fe3+, and the effect of the anion of ionic liquid is much more larger than the cation: when the ionic liquid anion is BF4-, FeCl3 the size of the order of the peak current is [EMIM]BF4ï¹¥[BMIM]BF4ï¹¥[HMIM]BF4. when the ionic liquid anion is PF₆-, FeCl3 the size of the order of the peak current is [BMIM]PF₆ï¹¥[HMIM]PF₆. And when the same ionic liquid cation, FeCl3 the size of the order of the peak current is BF4-ï¹¥PF₆-.Finally, a current oscillatory phenomenon was investigated systematically at the liquid-liquid interface with a three-electrode potentiostat in combination with cyclic voltammetry in this paper. It was related to the concentration of Fe(CN)₆^4-, to the scan rate, to the size of the water drop, and to the supporting electrolyte in the organic phase. We proposed a specific adsorption of ion pair model in the L/L interface system. That is, the oscillation is caused by the forced ion-pair formation at the interface between the negatively charged Fe(CN)₆^4- in the aqueous phase and the positively charged TBA+ or TPnA+ in the organic phase. It is significant for us to understand the chemical oscillation mechanism at the L/L interface and to realize structure of L/L interface better.