Abstract
The kinetics of the dissolution and deposition of aluminum from a first generation ionic liquid consisting of AlCl3/1-ethyl-3-methylimidazolium chloride (molar ratio 2:1) was studied. Electrochemical impedance spectroscopy shows that the double layer capacitance and the charge–transfer resistance depend on the state of the electrode surface. The impedance spectra are strongly influenced by mass transport. The rate–determining step of the aluminum deposition, as determined from the cathodic Tafel slope evaluated from current step experiments, was found to be either a chemical step, releasing the complexing agent chloride, while aluminum is in the divalent oxidation state (AlCl3
− → AlCl2 + Cl−) or an electron transfer from the divalent to the monovalent aluminum occurring twice for the overall reaction to occur once (Al2+ + e− → Al+). The rate–determining step for aluminum dissolution was found to be the transfer of an electron from elemental aluminum to the monovalent oxidation state (Al0 → Al+ + e−). A linear slope in the low cathodic overpotential region of the Tafel plot suggests a change in the cathodic rate–determining step. The Tafel slope indicates a chemical step, releasing the complexing agent chloride, after the last electron transfer (AlCl− → Al0 + Cl−) to be the rate–determining step for overpotentials below 50 mV. Density functional theory calculations support the proposed reduction and oxidation mechanisms.
Funder
Bundesministerium für Wirtschaft und Energie
Publisher
The Electrochemical Society
Subject
Materials Chemistry,Electrochemistry,Surfaces, Coatings and Films,Condensed Matter Physics,Renewable Energy, Sustainability and the Environment,Electronic, Optical and Magnetic Materials
Cited by
27 articles.
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