Electrochemistry in ambient-temperature chloroaluminate molten salts

Ambient temperature chloroaluminate molten salts are receiving increasing attention as solvents for a growing variety of chemical and electrochemical processes. These systems have considerable interest as intrinsic Lewis acid-base solvents and a great potential in extending the range of media for the study of fundamental aspects of metal-ionic interfaces and synthetic chemistry. This thesis contributes to the use of AlCl₃/EMIC melt system as electrolytes and especially to the features of electrochemical metal deposition/nucleation on various substrates including gold and a novel diamond-like electrode material, nitrogen-incorporated tetrahedral amorphous carbon (taC:N).; The general characteristics of ambient temperature chloroaluminate molten salts, specifically for AlCl₃/1-ethyl-3methylimidazolium chloride (EMIC) are initially summarized, along with the organic synthesis of EMIC and preparation of AlCl₃/EMIC as well. Then, Al underpotential deposition (UPD) and Al/Au alloy formation are investigated on polycrystalline gold in acidic AlCl₃/EMIC melts. The information obtained in this chapter complements that reported for Al electrodeposition on Au in high temperature molten salts. Our results are consistent with the formation of at least two alloys. Fast phase transformation between these intermetallic compounds at room temperature in the Al UPD region is observed. These processes have been further studied with the electrochemical quartz crystal microbalance (EQCM) in AlCl₃/EMIC melts with benzene as a co-solvent. The addition of benzene decreases media viscosity, making it possible to monitor changes in the effective mass of the Au electrode induced by the underpotential and bulk deposition of Al from AlCl₃/EMIC using rather conventional EQCM instrumentation and without affecting the intrinsic electrochemical characteristics of the system.; A new class of electrode material, nitrogen-incorporated tetrahedral amorphous carbon (taC:N) was examined in both aqueous and AlCl₃/EMIC melts.; An unusual behavior of electrochemical metal deposition and dissolution properties on taC:N has been studied in parallel with those at conventional electrodes, along with the corresponding nucleation features at the initial stage of metal deposition process.; It is shown that the electrochemical deposition of Al and Cu on taC:N in AlCl₃/EMIC melts agree well with the instantaneous and progressive three-dimensional hemispherical diffusion controlled nucleation/growth models, respectively, although a slight deviation from the ideal nucleation behavior is commonly observed at very high overpotentials. (Abstract shortened by UMI.)...