Study On Synthesis Of Imidazolium-based Ionic Liquids And Its Application Of Electrodeposition

Because ionic liquids have advantage physical chemistry natures including the wide electrochemical windows and well catalytic performance, it has been got more and more attention by researchers recently. As a effective method to get smooth and well-properties electrodeposit coatings, ionic liquids have become one of the hot research which could be electrodeposited the refractory metal such as W,Al,Ti. Futhermore aprotic ionic liquids will be the favorable electrolyte to electrodeposit aluminum or aluminum-manganese alloy. So in this paper we proceed the preliminary exploration including the synthesis of ionic liquids, electrochemical characteristics of imidazolium-based ionic liquids, the electrodeposition Al and Al-Mn alloy from chloroaluminate ionic liquid, thus the major results are as follows.1. We synthesized ionic liquids focusing on the [EMIM]Br yield with different synthesis methods, and the yield of microwave method can be achieved by 94.2% with 1000 s reaction time. UV spectra and IR spectra comparative study was to identify the structure of [EMIM]Br and AlCl3/[EMIM]Br ionic liquid; UV spectrum showed that imidazole ring and the type of electronic transitions from AlCl3/[EMIM]Br ionic liquid, and IR absorption bands indicated the corresponding structure of ionic liquids. DFT B3LYP quantum chemical method is to explore the reaction mechanism, which followed SN2 reaction mechanism; the density of chloroaluminate ionic liquid were determined by density-bottle, and the density decreases as temperature rising.2. Electrochemical curves of five different ionic liquids were determined by the classics three-electrode system at room temperature. Electrochemical windows showed that scanning speed was no significant effect, furthermore the negative side of the electrochemical potential window was influenced by the difference of anionic Lewis basicity, the open circuit potential of 2AlCl3/[EMIM]Br ionic liquid was measured with Al/Al(â…¢) reference electrode, which indicated that the reduction process of Al(â…¢) followed three electron transfer process combining with the Nernst equation; while the conductivity of ionic liquid was measured by conductivity meter, which obey Arrhenius equation.3. The nucleation process of aluminum was expressed by electrochemistry method. from 2AlCl3/[EMIM]Br and [BMIM]HSO4 ionic liquid. Cyclic voltammograms showed that Al/Al(â…¢) followed quasi-reversible reaction mechanism, furthermore chronoamperograms showed that the mass transfer of Al (â…¢) was diffusion controll process from 2AlCl3/[EMIM]Br ionic liquid; analyses of the nucleation models suggested that the deposition process of aluminium proceed the instantaneous nucleation with diffusion-controlled growth, which was little influenced by overpotential from2AlCl3/[EMIM]Br ionic liquid; the deposition process of aluminium on Cu substrates occurred the underpotential deposition at-255 mV, and the bulk deposition at-590 mV, and chronoamperograms showed that the electrodeposition of aluminium proceeds via an uncertain three-dimensional nucleation model from [BMIM]HSO4 ionic liquid at room temperature.4. The electrodeposition Al and Al-Mn alloy was carried out from 2AlCl3/[EMIM]Br and [BMIM]HSO4 ionic liquid by constant current method. The results showed that current efficiency reaches maximum value 83% at current density of 40 mA/cm2, and aluminum deposition coating was more smooth via the application of potential step methods, and SEM images showed the dense grain at the deposition coating from 2AlCl3/[EMIM]Br ionic liquid; furthermore the dense Al-Mn alloy deposits were obtained from 2AlCl3/[EMIM]Br ionic liquid at 40 mA/cm2; however the dense and continuous grain were obtained from [BMIM]HSO4 ionic liquid at 70 mA/cm2.